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How much the brakes grab have has a lot to with the material used in manufacturing the brake lining pads and shoes. We went through this all time in the phone company fleet. Some brands were dangerous in the mountains, they would just grab and stop. We finally settled on only using Bendix brake shoes and pads. That was over ten-years ago and a lot has changed since then. The ceramic pads had only been out for few a years. They lasted for ever without wearing out. I'm a big fan of those.

If the pads and shoes get glazed it changes how they grab. It they get a bunch of brake dust in there that has an effect on how they grab. If the rear shoes are not arched to fit the drum that will cause it to not stop as good. I'm puttering around here with an F350 Boom truck I bought to work around the house with. I bought new Motorcraft rear drums and Motorcraft shoes, The arc of the lining is so bad that one third of the shoes does not even contact the drum. They should be re-arched so that 100% of the lining is making contact. This use to be standard when doing a brake job but because of the asbestos lining they outlawed these machines, It was a $5000.00 fine here in CA if you were caught with one in your shop. I have one of these out in the garage I'm restoring right now so I can arc my own shoes. I got it or $100.00 because it was missing a part. Then I found the part on eBay for $20.00.

A lot of time you will do a brake job and it will feel a little spongy for awhile until the shoes and pads seat in. The brake get better the more you drive them.

Brake shoe arcing machine


Then you need to make sure the bore of your master cylinder is compatible with your wheel cylinder size. Ifit has a proportioning valv that its functioning like it should, You never know what has been done to the original engineering when people start swapping parts around? Make sure the correct size wheel cylinders are on the rear.

Also you need to make sure your rear brakes are adjusted up. They are suppose to self adjust but they don't always work. The way you can tell if they are adjusted up is to rapidly step on the peddle twice. The first pump pushes the shoes out and if you step fast enough before the springs pull them back the second pump will get hard with less travel than it normally does. If still feels spongy, you have air in the line, something is flexing, brake hose is bulging. You can clamp off the rubber brake lines to Isolate front brakes from rears or left and right front brakes to see what eliminate the spongy pedal. Its not a good idea because you can damage the hoses. We had special vise grips made for clamping hoses. Internal leaks in the master cylinder can cause it to be spongy.

If you are loosing rear brake fluid it has to be going somewhere. if you do not see any leaks and if its a dual reservoir master cylinder a lot of the time the missing rear fluid will end up in the opposite reservoir through an internal leak. So if one side is loosing fluid and one side is gaining fluid. Its time for a master cylinder. Look at the back of the master cylinder to make sure its not leaking. Make sure you don't have smashed steel line under the car that's preventing the rear brakes from getting pressure.

If brake fluid or gear oil from a leaking axle seal gets on lining it will cause the brakes to lock up. They get real grabby and lock really easy. Its like when you set a glass on a wet table and then its to hard get the glass to release. Nine time outs of ten if your loosing brake fluid and brakes are locking up easily the shoes are soaked. Don't even try to clean them. I have soaked them acetone , stuck them back on and the heat just brings the grease or brake fluid right out of them again. You cannot get it all out of there.

If everything is correct with your brakes and you can lock them up. the only thing you can do is to choose a tire with a softer tread.
 

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Discussion Starter #23
It sounds like you're at a crossroads now. For a lot of the issues you have stayed about poor quality is a good reason to look at aftermarket purpose built parts vs stock replacement. You're using your car more as a DD, I'd say splurge for some new aftermarket parts.

As far as the tires skidding, that's more of a problem with a hard tire. As you stated 15" tire choice is limited. I would say go for 17's. Let's face it, they're the new 15's. This is a very common size, tons of choices at reasonable prices you can get anywhere on the road. Personally I like the 17" American Racing version of the TTD. you can even get it in the ideal 4.75" BS for a 8" wide wheel.

I totally understand your choice for rear disc choice. I think it's the right choice in your case. I couldn't agree more.

Front brakes, well the stock KH is a good set up. Maybe try a different pad. However the big 12" TA brake kit SoT is a awesome set up! With a stickier tire then your current tires, maybe with a 17" tire that's wider you may not be able to lock them up. Anyway with the SoT TA brakes, you'll NEVER have to worry about brake fade or anything else. Not to mention they weigh less then your current set up.

I'm not trying to spend your money but if your proposed upgrades are what you want and in your budget, go fo
Thanks for the thoughtful answer. I'm quite set on the styled steel wheels, and would go with the Legendary 17x7s if I were to move up to 17". They have 4.25" backspace. I'm a little insane so I prefer a narrower wheel and fatter tire, cosmetically. Not sure how that would work on 17s with a narrower sidewall but I guess there's one way to find out.

I've got EBC Reds on the KH brakes up front, so I don't think I could get much better than that. I think if I got an actually sticky tire and resolved my rear brake and/or MC issues, the fronts would do a lot better.

The TA brakes are pretty cool but 2 grand is a LOT for those things! If I was really committed to spending a lot of money I'd go with 17" wheels and big Wilwoods to go with it, I think.

225/50/17 is kinda tall IMO but so is 215/65/15 ,,, But your close in overall diameter with those sizes . I'd go more like 225/45/17
No matter what you have if your wheels are locked your not stopping as fast as possible
especially if your tires UTQG treadware number is rather high
Yep, I pulled up a tire size calculator and a 225/50/17 is nearly the same size as my current 215/65/15 (25.9" vs. 26"). My 215/65/15s fit perfectly with no rubbing issues and I don't even have my fenders rolled. But I also have narrower wheels so who knows what that does to the overall tire shape. At any rate, I think it'll fit... I think.

Hi Kelly....well first thing is do you really have a 1956 9 inch rear? Ford started making them in 1957. Do you happen to know what it's out of? The big bearing rear is found in the larger Ford cars of that era like a Ford Ranch station wagon. I have one out of a 1958 Fairlane and it's a small bearing rear. The brakes on mine were 11x2" and the actual shoes if I remember right were only about 1 3/4" wide. BTW.. those drums are really rare and hard to find. I changed out mine to a F150 size..by using a backing plate from a early 70's F100 and the rest from an F150. The early 9 inch rear that fits in a Mustang is the same width as a 65 Mustang but has 3 inch tubes and no taper at the ends. An early 9 inch is actually a about an 8 3/4 inch gear but a late 9 inch fits in it. That's what I did... put in a late model chunk.
The housing should have 2 dimples and most also had a factory drain plug underneath. My 58 does. Here's a couple of pics. Got any of yours?
As awhtx said, yes I have a '56 rear out of some large station wagon or another. No taper on the tubes, factory drain plug underneath, smooth back.


I have an Explorer rear end with discs. Before the swap, my stock rear drums worked just fine. I can honestly say that after the swap, I can’t really tell a difference in stopping power. Worked well before, works well now.

I’m sure you’re right about fade and weather as far as disc superiority, but I don’t track my car or drive it much in bad weather so that’s not much of a factor.

I did have to go to larger wheels to clear the Explorer rear discs. They too have an internal drum parking brake and that pushes the swept area of the rotor and the caliper out so that my old 14’s wouldn’t fit, and I question if 15’s would clear.

Regarding the larger wheels and new tires, I’m very pleased with that update. The 17” tire selection is great, and my butt dyno tells me I have no negative effects of heavier wheels or lower tire sidewalls. The ride isn’t harsh and the handling is spectacular.

Based on your listed situation, rear discs wouldn’t be a bad thing, but that has more to do with the poor state of your drums and potentially the aging master cylinder than the superiority of discs.
Yeah, I'm not expecting improved braking power from the rear discs over the drums - since my drums are dialed back with a prop valve, I already know that even the drums are overpowered for what is needed on the rear. But I do think that the discs will bring me improved consistency and better parts quality. As you say, the drums are just not in a great state I think. Or the MC. It's hard to say!

What size wheels/tires do you have on your car? I see quite a few people with pretty fat tires on their '65/66, but every car is different of course. I'm trying to get away with not rolling my fenders because I'm afraid I'll crack the billion coats of clear that are on the car.


Hi Kelly... the fact that you CAN lock up the wheels is an indication that you don't necessarily need MORE braking power but, rather, need to transfer more of that power to the pavement... the opposite of losing traction under acceleration.

I fear you might have a bum master cylinder if you have "disappearing brake fluid" without the sign of an external leak. Crawl under the dash and pull back the dust boot where the brake pedal pushrod goes into the firewall and look for signs of leakage there... that's the most common source. Same deal with wheel cylinders... look under the dust boot for signs of fluid. Many years ago I purchased a wheel cylinder hone. I've probably used it a hundred times...enough to replace the stones, anyway. Rebuild kits are still readily available and are cheap.

The biggest problem I see out there, today, is the quality of friction materials. IIRC you run EBC front pads, don't you? They're decent as are Porterfields. I also thing Porterfield makes 10 x 1-3/4 shoes in the R4 spec and, should you think you NEED more rear brake you can always scare up some Aerostar/Ranger 10 x 2-1/2 backing plates and adapt them to fit. While an 11.2 inch front rotor isn't exactly huge by today's standards, it was enough to who down 428CJ's in the day and you CAN get caliper mounts to move up to the D-1 Lincoln/T-Bird versions of the K-H 4-piston and THICK 12 inch rotors.

As far as the pavement goes, it's all tire contact patch and coefficient of friction...which is affected by things like weight transfer/inertia, centrifugal force, etc. A tire with a hard rubber compound that is overinflated with skim along the road surface. Excessive nose dive and transfer of weight from the rear will lessen rear brake effectiveness forcing the fronts to do more work. Nose dive will also change wheel alignment causing dynamic changes in camber and toe that can affect tire contact patch. Don't forget that when you move to a larger front tire that the assembly will not only typically weigh MORE, but that weight will be farther out from the axial center which will INCREASE the inertial forces of the spinning tire so bigger isn't always better.

Some things to digest, anyway.... I'm not convinced that most brake "upgrades" are really upgrades that are needed, other than replacing existing parts that are adequately designed by may be worn out or poor quality.
Right, and that's what kind of got me onto the 17" wheel/tire track. I want something that is actually sticky and has great wet AND dry performance. There doesn't seem to be a lot available in a 15" anymore that prioritizes those three things.

I will check my MC. The wheel cylinders have leaked under the boots in the past multiple times (replaced multiple times). I haven't had good luck with new Wagner wheel cylinders at all, between them leaking and them having badly machined bleeder screw threads, so I am about done with them. I'd rather put a top-quality part on from the get-go then spend a lot of time trying to fix something that's brand new that shouldn't need to be fixed!

Yes, EBC up front so I don't think my front brakes are really an issue. I know at least that the fronts should be operating at 100% capacity, were they not hindered by the rest of the system having air in it. I can bleed all air out no problem, rotors are true, pads minimally worn and properly bedded in. I think they are probably fine and I'm not that interested in upgrading them unless they prove unable to stop whatever tire I put on the car. But I'd like to make a point - while the KH brakes did stop a 428CJ back in the day (and they still do now), the problem is that all other modern cars have so much BETTER braking power. People are constantly slamming on the brakes at the very last minute because their cars are equipped to stop on the head of a gnat, and I'm afraid that one day I won't be able to plan for that and I'll end up stuffed in someone's trunk. This is a case of wanting to be towards the front of the pack in a braking arms race, if you will.

Fortunately, I don't get much nose dive at all with Jane. I keep a lot of weight in the rear (misc road trip stuff I'm too lazy to unpack, full size spare, toolkit, etc.) and I think that helps. She stops pretty level front to back. Or maybe I just don't get nose dive because I skid before I have time to really get a good bite into the road!

I autocross with the stock rear drum brakes with no issues. You have a problem with your brakes but the rear brakes being drum isn’t the problem.
Yes, I agree. But swapping out old drums for new drums, vs drums for discs, is a fairly minimal price difference, and at this point I'm afraid of all drum wheel cylinders!
 

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Kelly, I think your money is best spent on just better tires. I don't have to tell you the ones that will transform your car, you've read my posts enough to know my feelings on the best 15" tires.

You can get that set of Avons and spend less than the big brake kits you are considering.

Aside from that, buy some Porterfield R-4s rear brake shoes and have the drums turned so they are perfectly round.

Z
 

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Not clear on what you were saying about the tires/wheels.
Just that they have more weight farther out to the edges, more inertia to stop and more effort needed to get them spinning. Not worth really worrying much about I guess, but its there and will be another negative within the "friction circle"(googly it) of these light-ish cars. (Theory substantiated by Porsches braking and handling better with 18" wheels opposed to 19 or 20:))

Hard to completely blame the wheel cylinders, 80-20, 60-40 who knows but the one i did about a month ago that i finally discovered had a funk load of rusty fluid on the pistons where it was leaking. didn't drive much last year because of paint so maybe H2O settled in the area and killed it. Find the recent DOT 5 discussion, LOL!
 

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I had a set of Firehawk GT's on one of my 2nd Gen RX7s. They were plenty sticky and I had to get pretty stupid to get them to bark at all. That being said, the 8YO BFG T/A's that came on Vickie's 65 had become so stiff they barked in a parking lot just turning down an aisle. Start with the wheels and rubber and see if your condition persists. As a tire hardens, it gets very sensitive to air pressure. Lower the air pressure by 3-4lbs and see if they suddenly become very chatty. Definite sign of a hard tire. Especially in a long sweeping turn.
I personally am not a fan of the 17's. It's a looks thing and I'm firmly old school on that. Too many cars looking like the Hot Wheels from the 80's+. At some point I feel I will have no choice though.
 

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Thanks for the thoughtful answer. I'm quite set on the styled steel wheels, and would go with the Legendary 17x7s if I were to move up to 17". They have 4.25" backspace. I'm a little insane so I prefer a narrower wheel and fatter tire, cosmetically. Not sure how that would work on 17s with a narrower sidewall but I guess there's one way to find out.

I've got EBC Reds on the KH brakes up front, so I don't think I could get much better than that. I think if I got an actually sticky tire and resolved my rear brake and/or MC issues, the fronts would do a lot better.

The TA brakes are pretty cool but 2 grand is a LOT for those things! If I was really committed to spending a lot of money I'd go with 17" wheels and big Wilwoods to go with it, I think.


Yep, I pulled up a tire size calculator and a 225/50/17 is nearly the same size as my current 215/65/15 (25.9" vs. 26"). My 215/65/15s fit perfectly with no rubbing issues and I don't even have my fenders rolled. But I also have narrower wheels so who knows what that does to the overall tire shape. At any rate, I think it'll fit... I think.


As awhtx said, yes I have a '56 rear out of some large station wagon or another. No taper on the tubes, factory drain plug underneath, smooth back.



Yeah, I'm not expecting improved braking power from the rear discs over the drums - since my drums are dialed back with a prop valve, I already know that even the drums are overpowered for what is needed on the rear. But I do think that the discs will bring me improved consistency and better parts quality. As you say, the drums are just not in a great state I think. Or the MC. It's hard to say!

What size wheels/tires do you have on your car? I see quite a few people with pretty fat tires on their '65/66, but every car is different of course. I'm trying to get away with not rolling my fenders because I'm afraid I'll crack the billion coats of clear that are on the car.



Right, and that's what kind of got me onto the 17" wheel/tire track. I want something that is actually sticky and has great wet AND dry performance. There doesn't seem to be a lot available in a 15" anymore that prioritizes those three things.

I will check my MC. The wheel cylinders have leaked under the boots in the past multiple times (replaced multiple times). I haven't had good luck with new Wagner wheel cylinders at all, between them leaking and them having badly machined bleeder screw threads, so I am about done with them. I'd rather put a top-quality part on from the get-go then spend a lot of time trying to fix something that's brand new that shouldn't need to be fixed!

Yes, EBC up front so I don't think my front brakes are really an issue. I know at least that the fronts should be operating at 100% capacity, were they not hindered by the rest of the system having air in it. I can bleed all air out no problem, rotors are true, pads minimally worn and properly bedded in. I think they are probably fine and I'm not that interested in upgrading them unless they prove unable to stop whatever tire I put on the car. But I'd like to make a point - while the KH brakes did stop a 428CJ back in the day (and they still do now), the problem is that all other modern cars have so much BETTER braking power. People are constantly slamming on the brakes at the very last minute because their cars are equipped to stop on the head of a gnat, and I'm afraid that one day I won't be able to plan for that and I'll end up stuffed in someone's trunk. This is a case of wanting to be towards the front of the pack in a braking arms race, if you will.

Fortunately, I don't get much nose dive at all with Jane. I keep a lot of weight in the rear (misc road trip stuff I'm too lazy to unpack, full size spare, toolkit, etc.) and I think that helps. She stops pretty level front to back. Or maybe I just don't get nose dive because I skid before I have time to really get a good bite into the road!


Yes, I agree. But swapping out old drums for new drums, vs drums for discs, is a fairly minimal price difference, and at this point I'm afraid of all drum wheel cylinders!
I hear ya on the 15 inch tire choices... I think I'd probably go with 18 inch.... I have 18's on the Magnum and there are lots of choices... 225/60R18 Yokohama Avid's now... probably the best tires I've had on it since new... came with Continental, replaced with Coopers, then Michelins... the Coopers were okay, the Michelin's plain sucked...way too stiff.
 

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For most spirited driving, the KH with EBC should do the job, I think major concern is MC and leaking fluid, AND old tires. In my much younger days I did a lot of hard driving with stock KH and stock pads and my problem wasn't initial stopping, it was fade after I had stood on them a few times. If I had EBCs then, I bet it would have been pretty killer, at least for the day (late 70s).
Having said that, since I am shooting for much better braking, I stepped up to 17s for the handling and to clear bigger brakes. Since my setup uses SN95 spindles, I used Cobra brakes with EBCs on the front. Like you, I figure that will allow me to fix them fairly quickly with factory stuff if need be.
 

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Well, I'm gonna go with a dead master cylinder just to be different. If you take the top off the master cylinder you will likely find (as I did on mine) that when you hit the brakes and watch teh reservoirs, you will see a beautiful fountain bubble up in the rear circuit, its gonna make a mess so do it slowly or paint eating fluid will go everywhere. Its not working and teh pressure is going back into the reservoir instead of going to the rear wheels. This is why you can't get the reservoir to seal and where your fluid is going. The fountain stresses the MC seal. I bet you are locking up the front wheels and the rears are doing little to nothing. I had the exact same problem and was stunned at my car in autocrosses when the rears were actually working correctly. The car also stopped nose diving when I hit the brakes.

If you decide to put disk brakes in the back, make sure you install a proportioning valve on the rear circuit so you can dial back the rear circuit. It is very dangerous for teh rear brakes to lock up first which initiates a spin. Assuming you stick with teh KH fronts, you have to set the proportioning valve manually and will end up nominally where TEH REAR BRAKES CANNOT ADD MORE BRAKING THAN THE STOCK DRUM BRAKES as the engineers designed your balanced system. Note the irony here...

One way to get away with slightly better brakes in the rear is to add a later model proportioning valve, I installed one from a 1986 T bird 2 door in my car. I believe Mustangs started adding these somewhere in the early 70s. These delay the full pressure to the rear circuit for a microsecond so as you stomp the brakes and the car nose dives so the unweighted rears won't lock up, as the car settles back, the rears get full pressure. You can then go to the larger 2.25" or 2.5" (CRS here) rear brakes (a common upgrade to put drums and backing plates from early station wagons) and/or try Porterfield brakes in the rear.

Edit: Check the clearance between your drums and the backign plate, you may already have the right backing plates for teh larger drums

As for wheels, more rubber is mo better. There is a large class of us running 225s on 16s (me) and 17s by 8" wheels. I like the 16s because they are baby bear just right, still enough meat to be a nod to old school with a nod to more modern and you get some nice response in turns from the shorter side walls. 225-50-16s or 225-45 17s, all teh cool after market wheels are 8" wide. I have a volvo with 17s and as a daily driver, I do not like them. They are a rougher ride as you loose the pillow effect of a 15" / 16" - 65 /50 aspect ratio tire. For a true road warrior like you, I would seriously consider this. Go drive some 225 45 17 X 8 s on a like weighted car and see what you think.

One last edit: If you stay with 215s, I don't think the contact patch, stopping power, for 15s vs 17s will be any different since the tire diameter of all the wheels is nominaly the same due to the aspect ratios going down. You have to go wider to get more contact patch. New tires will stop better as softer rubber will grab better...

Good luck,

M
 

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If you can lock up all the wheels now, all you need is a bigger contact patch and stickier rubber, IMHO your brakes are fine.
My 68 convertible has 15" wheels, 215-60 front, 225-60 rear BFG Radial T/A's. Fully loaded with my wife and two weeks worth of gear it stops just fine, even in panic situations of which I have had my share, wet and dry.
I used to change rubber every 5 years regardless of mileage when we were driving to 3-4 MCA shows every year from Canada. Old tires are not your friend!
 

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One way to get away with slightly better brakes in the rear is to add a later model proportioning valve, I installed one from a 1986 T bird 2 door in my car. I believe Mustangs started adding these somewhere in the early 70s. These delay the full pressure to the rear circuit for a microsecond so as you stomp the brakes and the car nose dives so the unweighted rears won't lock up, as the car settles back, the rears get full pressure. You can then go to the larger 2.25" or 2.5" (CRS here) rear brakes (a common upgrade to put drums and backing plates from early station wagons) and/or try Porterfield brakes in the rear.
If Ford's "proportioning valve" in the 80s did what GMs metering valve always did, it should delay the front pressure momentarily. The reason for this is excess front disk brake wear could occur in low-speed easy driving situations because the front brakes will do almost all the braking. In high-speed aggressive braking, the metering valve probably doesn't matter. For a grandmother who never drives over 25 MPH, it will prevent premature pad wear. See the link below. 1. Proportion pressure front and rear 2. 10 psi. residual check valve 3. Metering valve to apply pressure to the rear brakes before the front brakes 4. A brake warning light to detect a loss in pressure https://www.classicperform.com/Instructions/PDF/PVK.pdf
 

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Before I swapped wheels and tires, I would replace the MC as suggested. I assume you are using a dual bowl. I would also install a good proportioning valve if you haven’t. Make sure the system is balanced and bled properly. Test.

If the above doesn’t yield comfortable results, I would consider two options. One as Z suggested the P R4-S rear shoes. Be sure to buy them from someone whom will work with you like John at ORP. I say this because Mark and I both tried the R4-S shoes on our cars yielding the same results. The rear wheels would not turn with the wheel lug nuts torqued. Both sets were sent back to Porterfield for proper arching to the exact specifications of newly turned new drums. No change. So I throw that out as a caution. The other option would be upgrade to the larger 11 1/4” rear drum kit that John sells. Test.

If the above doesn’t yield comfortable results, I would do as Z suggests and get AVON tires. If you haven’t priced them, they are expensive and don’t last long. I know you like to take long trips so this may not be a viable option. Although it would keep the correct wheels on your car...which is the reason I concur with his suggestion.

After that, I guess your stuck with bigger wheels and tires...and bigger brakes if you desire.
 

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Hi Kelly, late to the party but here are some random ideas.
1. You didn’t indicate which wheel(s) is(are) locking up when you stand on the brakes. The reply may lead one to an answer.
2. You stated that you “have two right side backing plates.” It seems to me that the plates are different (mirror images) for a reason. Could this be causing the “wrong” rear to lock up prematurely? Could it cause the self-adjusting feature (if they have one) to grenade the brake?
3. Have you tried a premium parts’ supplier (i.e., NPD) for your wheel cylinders?
4. I will assume that you have a residual pressure value in the rear circuit.
5. I might try a set of high-performance tires first (yea, they don’t come in RWLs but sometimes we have to sacrifice).
6. I’ve also considered going to 16 (perfect size) or 17 wheels to expand the tire option dilemma. One “problem” I see with 17” wheels is that the brakes look ridiculously small behind them (might not be an issue with your steel wheels). So, going to a larger diameter wheel/tire leads to $$$ spent for larger brakes. Vicious circle.
7. Getting new front brakes with aluminum calipers and hats might offset any increase in 17" wheel mass/inertia.
8. With the bigger diameter rear drums you might be overpowering the rear tires. There are a large number of wheel cylinder diameters, so maybe getting ones a size smaller would result in a better front/rear balance? I assume your left and right are the same size.
Charlie
 

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FWIW, my Mach 1 has the KH, non-power discs up front and drums at the rear. The pedal is rock-solid and the car stops very well. I got all my brake components from Dan at Chockostang, but he's longer selling the drum kits. Too bad, it was a really nice drum kit. No leaks.

I have purchased drum brake rebuild kits from NAPA which were good quality, but that was several years ago; and maybe that's what you're running now.
 

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Discussion Starter #35
Kelly, I think your money is best spent on just better tires. I don't have to tell you the ones that will transform your car, you've read my posts enough to know my feelings on the best 15" tires.

You can get that set of Avons and spend less than the big brake kits you are considering.

Aside from that, buy some Porterfield R-4s rear brake shoes and have the drums turned so they are perfectly round.

Z
Yep, knew you'd chip in with exactly this recommendation! IIRC, a set of Avons is what, $1400? I'm not considering any big brake kits... I'm considering small rear discs, to circumvent the drum problems, and I'm considering swapping to 17" wheels and tires. A set of 17" wheels and tires will run me less than 1 set of Avon tires, even with the added cost of the silly stick-on white letters!! And given that a set of Avons will last me a year or less, I'd be shooting myself in the foot financially to run those.

A better view of the cost of your tires vs. 17" tires over 5 years of driving:
Year # ----- Avon cost ----- 17" cost
....1.... ----- ...$1400... ----- ~$1400 (up front cost including new wheels)
....2.... ----- ...$1400... ----- $0 (still on 1st set of tires)
....3.... ----- ...$1400... ----- $0 (still on 1st set of tires)
....4.... ----- ...$1400... ----- $500 (new tires at 45000 miles)
....5.... ----- ...$1400... ----- $0 (still on 2nd set of tires)
-------------------------------------------------------
.......... ----- ...$7000... ----- $1900

Running the Avons is absolutely, positively not going to happen!

I had a set of Firehawk GT's on one of my 2nd Gen RX7s. They were plenty sticky and I had to get pretty stupid to get them to bark at all. That being said, the 8YO BFG T/A's that came on Vickie's 65 had become so stiff they barked in a parking lot just turning down an aisle. Start with the wheels and rubber and see if your condition persists. As a tire hardens, it gets very sensitive to air pressure. Lower the air pressure by 3-4lbs and see if they suddenly become very chatty. Definite sign of a hard tire. Especially in a long sweeping turn.
I personally am not a fan of the 17's. It's a looks thing and I'm firmly old school on that. Too many cars looking like the Hot Wheels from the 80's+. At some point I feel I will have no choice though.
Yes, my current tires are really hard, even though they never squeal. It is pretty interesting when you hammer the throttle and the car just skates around with no sound from the tires at all! I usually have them inflated to 30 psi, a couple psi below spec.

Agree with your sentiment on the 17s. Looking at my photoshopped version of the 17" wheels/tires though, I think I could be ok with them as long as they retain the old school styling. Fitting a 50 series under there would go a long way to retaining the more muscley look.

I hear ya on the 15 inch tire choices... I think I'd probably go with 18 inch.... I have 18's on the Magnum and there are lots of choices... 225/60R18 Yokohama Avid's now... probably the best tires I've had on it since new... came with Continental, replaced with Coopers, then Michelins... the Coopers were okay, the Michelin's plain sucked...way too stiff.
Yes, I saw that the Yokohama Avids got great reviews! They are available in a 17" and they were top of my list if I do make the swap. Glad to hear that you like them!

Well, I'm gonna go with a dead master cylinder just to be different. If you take the top off the master cylinder you will likely find (as I did on mine) that when you hit the brakes and watch teh reservoirs, you will see a beautiful fountain bubble up in the rear circuit, its gonna make a mess so do it slowly or paint eating fluid will go everywhere. Its not working and teh pressure is going back into the reservoir instead of going to the rear wheels. This is why you can't get the reservoir to seal and where your fluid is going. The fountain stresses the MC seal. I bet you are locking up the front wheels and the rears are doing little to nothing. I had the exact same problem and was stunned at my car in autocrosses when the rears were actually working correctly. The car also stopped nose diving when I hit the brakes.

If you decide to put disk brakes in the back, make sure you install a proportioning valve on the rear circuit so you can dial back the rear circuit. It is very dangerous for teh rear brakes to lock up first which initiates a spin. Assuming you stick with teh KH fronts, you have to set the proportioning valve manually and will end up nominally where TEH REAR BRAKES CANNOT ADD MORE BRAKING THAN THE STOCK DRUM BRAKES as the engineers designed your balanced system. Note the irony here...

One way to get away with slightly better brakes in the rear is to add a later model proportioning valve, I installed one from a 1986 T bird 2 door in my car. I believe Mustangs started adding these somewhere in the early 70s. These delay the full pressure to the rear circuit for a microsecond so as you stomp the brakes and the car nose dives so the unweighted rears won't lock up, as the car settles back, the rears get full pressure. You can then go to the larger 2.25" or 2.5" (CRS here) rear brakes (a common upgrade to put drums and backing plates from early station wagons) and/or try Porterfield brakes in the rear.

Edit: Check the clearance between your drums and the backign plate, you may already have the right backing plates for teh larger drums

As for wheels, more rubber is mo better. There is a large class of us running 225s on 16s (me) and 17s by 8" wheels. I like the 16s because they are baby bear just right, still enough meat to be a nod to old school with a nod to more modern and you get some nice response in turns from the shorter side walls. 225-50-16s or 225-45 17s, all teh cool after market wheels are 8" wide. I have a volvo with 17s and as a daily driver, I do not like them. They are a rougher ride as you loose the pillow effect of a 15" / 16" - 65 /50 aspect ratio tire. For a true road warrior like you, I would seriously consider this. Go drive some 225 45 17 X 8 s on a like weighted car and see what you think.

One last edit: If you stay with 215s, I don't think the contact patch, stopping power, for 15s vs 17s will be any different since the tire diameter of all the wheels is nominaly the same due to the aspect ratios going down. You have to go wider to get more contact patch. New tires will stop better as softer rubber will grab better...

Good luck,

M
I do get a bit of a fountain, but it's fluid not bubbles. Always kind of thought that was normal as long as there weren't air bubbles coming with it. Hmm. That does sound like exactly my problem though! Do you have any recommendations for a good brand of MC? Both disc/drum and disc/disc, if you've got em. Currently I have a '74 Mav 15/16" disc/drum master. Bought it brand new from... you guessed it, the parts store. Ugh!!!

Yes, I already have a prop valve in the rear lines. Those 11" drums would kill me if I didn't have one! The later model prop valve is an interesting idea - though my car doesn't really nose dive in a hard brake.

Based on tire size calculators, I think I could run a 225/50/17 tire on a 17x7 wheel. That would give me exactly the same tire height as my current 215/65/15s. So maybe I would still get the pillow effect. I've got reasonably upgraded suspension (Bilstein shocks, new GT springs, roller spring perches, new reworked UCA/LCA, adjustable shocks in rear) which may also help me out. But yes, it certainly won't be as cloud-like as my 65 aspect ratio 15" tires!


Before I swapped wheels and tires, I would replace the MC as suggested. I assume you are using a dual bowl. I would also install a good proportioning valve if you haven’t. Make sure the system is balanced and bled properly. Test.

If the above doesn’t yield comfortable results, I would consider two options. One as Z suggested the P R4-S rear shoes. Be sure to buy them from someone whom will work with you like John at ORP. I say this because Mark and I both tried the R4-S shoes on our cars yielding the same results. The rear wheels would not turn with the wheel lug nuts torqued. Both sets were sent back to Porterfield for proper arching to the exact specifications of newly turned new drums. No change. So I throw that out as a caution. The other option would be upgrade to the larger 11 1/4” rear drum kit that John sells. Test.

If the above doesn’t yield comfortable results, I would do as Z suggests and get AVON tires. If you haven’t priced them, they are expensive and don’t last long. I know you like to take long trips so this may not be a viable option. Although it would keep the correct wheels on your car...which is the reason I concur with his suggestion.

After that, I guess your stuck with bigger wheels and tires...and bigger brakes if you desire.
Yeah, all of the fiddling around with drum parts is the reason that I am considering swapping to discs. It is hard to get the specs on a disc wrong! No worrying about shoe fitment, bad arches, bad wheel cylinders, yada yada... I just don't see a reason to stick with the drums. Stopping power will be the same with a properly built drum or disc, but the drums will require a lot more work to get working as they should.

As you say, the Avon tires would not work for me. I put a price breakdown of the yearly cost of Avons in my response to him above!

Hi Kelly, late to the party but here are some random ideas.
1. You didn’t indicate which wheel(s) is(are) locking up when you stand on the brakes. The reply may lead one to an answer.
2. You stated that you “have two right side backing plates.” It seems to me that the plates are different (mirror images) for a reason. Could this be causing the “wrong” rear to lock up prematurely? Could it cause the self-adjusting feature (if they have one) to grenade the brake?
3. Have you tried a premium parts’ supplier (i.e., NPD) for your wheel cylinders?
4. I will assume that you have a residual pressure value in the rear circuit.
5. I might try a set of high-performance tires first (yea, they don’t come in RWLs but sometimes we have to sacrifice).
6. I’ve also considered going to 16 (perfect size) or 17 wheels to expand the tire option dilemma. One “problem” I see with 17” wheels is that the brakes look ridiculously small behind them (might not be an issue with your steel wheels). So, going to a larger diameter wheel/tire leads to $$$ spent for larger brakes. Vicious circle.
7. Getting new front brakes with aluminum calipers and hats might offset any increase in 17" wheel mass/inertia.
8. With the bigger diameter rear drums you might be overpowering the rear tires. There are a large number of wheel cylinder diameters, so maybe getting ones a size smaller would result in a better front/rear balance? I assume your left and right are the same size.
Charlie
Not late to the party at all! Responses:
1. I'm not sure which wheels are locking up. It's either all 4, or it's the front 2. It's not the rear two, because it's not trying to swap me end-over-end. I think it's all 4, because the car is not nose-diving heavily.
2. I don't think so, as the hardware is correct for both drums - just one of the backing plates is wrong. Functionality is likely equal between the two because the car doesn't kick to one side or the other under heavy braking. BUT the shoes are slowly carving away at a bump on the wrong backing plate. I would assume that if they continue digging a groove, eventually they would get bound up and not want to expand properly due to being stuck in the groove. But that's all speculation.
3. I have not! I checked and they seem to use Raybestos and Centric brand. Maybe worth looking at.
4. I do not, and only recently became aware that I should have one.
5. No matter what size, high performance tires just don't come in RWL anymore. The problem is finding an actual high performance tire in a 15" size. I find it hard to trust a lot of review sites as TireRack has the BFG Radial TA listed as a "high performance" tire and it CERTAINLY is not!
6. Agree that 16" is a better size than 17", but tire options are also limited in 16s. Happystang recently pointed out to me that 16" wheels interfere more with the front suspension on an early Mustang than 17" wheels do - something about the 16" wheels not clearing balljoints, while 17" do so you can run more backspace and tuck your tires in better. The styled steel wheels I want to get do not have that big open-spoke look, fortunately - I really don't like that look on an early Mustang, especially with tiny brakes as you say!
 

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I do get a bit of a fountain, but it's fluid not bubbles. Always kind of thought that was normal as long as there weren't air bubbles coming with it. Hmm. That does sound like exactly my problem though! Do you have any recommendations for a good brand of MC? Both disc/drum and disc/disc, if you've got em. Currently I have a '74 Mav 15/16" disc/drum master. Bought it brand new from... you guessed it, the parts store. Ugh!!!
Fountain - no bubbles that's what I'm talking about not good, Sometimes a tiny squirt initially but as you continue to push, it must stop - there should be nothing. I actually went to a ranger master but I'm not really crazy about it. I'll do something else next time. Let us know what you decide and how it works...
 

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I would just go to new shoes (Porterfield R4-s) and turned drums before investing in a rear disc swap. You already know the braking benefit of rear discs is negated by the lightness of our vintage Mustangs over the rear wheels. There is some ease of service with the discs, but that's not a deal breaker imho.

If it turns out you still are wanting to go to rear discs after trying the Porterfield shoes, I'm sure they would sell in a heartbeat on the forum classified. I put them in my K code and immediately had to modify my "normal" breaking pressure

Z.

PS I knew the 15" Avon's would be panned as too expensive, but had to put it out there. For many, the 20,000 mile replacement schedule would not be on the same timeline as it is for KellyH, and thereby have a greatly reduced cost per year.

Personally, I gave up beef, pork, and all processed meats, and lived on a lunch of peanut butter w/ apples; dinner-ed on pinto beans / rice for a year in order to afford my Avons. But I'm given to extreme behavior(s).
 

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If you can find some original wheel cylinders with the correct bleeder holes they can be bored out and stainless liners installed. You'll never have to buy another wheel cylinder.

And I know of a shop in Waco that can arc your shoes to fit your drums if there's no shop in Austin that does it.
 

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As I see it, there is no specific benefit to keeping drums on the rear, other than that I have them on there already. It bothers me that I would need to modify any off-the-shelf parts to keep these drums functional in the future - boring out / rebuilding brand new wheel cylinders, rearching brand new shoes, turning drums (FWIW, I did have my drums turned a few years ago), etc. - just to get "good enough" performance in return. I do not want to have to worry about braking on my daily driver, anymore, period. So I think that my decision has finally been made there, after many years of bitching about the brakes.

I've done some more research on the 17x7 wheels. First of all - Autoworks Restomod did an episode on the Magnum 500 version of this wheel by the same manufacturer. They compared the 17" wheel+tire to an original 15" wheel+tire and found that the 17" package is actually lighter by 4 lbs, because the wheel is aluminum alloy! So that was good to find out, considering that many of you brought up the problems that adding unsprung weight could cause. Were I to switch, I would be reducing unsprung weight by around 16 lbs.

I'm most concerned about the backspacing and fitment of these things. My 15x6" wheels, with 4.00" backspacing and 215/65/15 tires, just barely clear because they are tucked in pretty perfectly. 225/50/17 tires should be just a little shorter than the old tires and so should fill up the wheelwell perfectly, just as the old tires did, but I'm afraid that they won't tuck right and may not clear. I've tried a few offset calculators and they all seem to give me different answers so who knows. Maybe I'll start a thread to see if anyone around here has those wheels (or equivalent) on their cars right now without issue.
 

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I'm most concerned about the backspacing and fitment of these things. My 15x6" wheels, with 4.00" backspacing and 215/65/15 tires, just barely clear because they are tucked in pretty perfectly. 225/50/17 tires should be just a little shorter than the old tires and so should fill up the wheelwell perfectly, just as the old tires did, but I'm afraid that they won't tuck right and may not clear. I've tried a few offset calculators and they all seem to give me different answers so who knows. Maybe I'll start a thread to see if anyone around here has those wheels (or equivalent) on their cars right now without issue.
The difference in tire height is near negligible at only 3mm. But the 225/50's will protrude outward three times that distance, a full 9mm (3/8") further than what you have now, and you say you're barely clearing as is. I'd call that a roll of the dice with both aggravating and monetary implications. Even if someone pops up and says that combo works for them, their car may not sit like yours does stance-wise which is visibly lower than stock.
 

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