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Discussion Starter #1
little bit of a backstory on this question -

Saturday I had a go at the Porsche Experience track - where i had a 90 minutes in a 911 GTS with an instructor in the passenger seat.
It was incredible. all I need is $144,000 to buy my own and I'd be totally happy in that car.

I did pretty well on the track - except for a constant "bad" habit I had (my instructor was constantly disappointed in me for this lol) - and I can 100% attribute it to daily driving my 69 coupe.

I was braking way too early and also penciling the brakes.
My braking way to early I understand - I wasn't comfortable driving like the instructor was

However the penciling / pumping the brakes I attribute to my mustangs non ABS

Im running a 17x8" Rim, on a 245/45R17 95Z Nitto INVO tire with factory power brakes
My factory power brakes have NO problem locking up the front wheels - so I'm used to pumping them when I need to stop fast (I'll lose traction if I brake hard under 30 mph)

Whats the weak link here? Is this just how it is for us? I'm assuming ABS isn't really an easy add on, if its even available.
I imagine adding bigger brakes wont solve that either - are better tires the best option?

I thought I got decent ones - what would you guys recommend?
 

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Do you have an adjustable proportioning valve? Might want to add some bias to the rear brakes.

I have to really stomp on my brakes hard to lock them up with the 200 tread wear Falken's. Besides that it stops incredibly quick.
 

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I think your weak link is lack of feel that comes from those power brakes. I have found it much easier to modulate non-power brakes. Meaning that if you jam on power brakes and they begin to lock-up you have to release a bunch more pressure before they actually release which you equate to pumping i think. Not that you couldn't learn it.
Vintage power brakes have never felt linear to me.
 

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Are the brake lines/MC properly bled? I had some air in the lines and had a similar issue where I'd apply the brakes and wouldn't get much stopping at first until I applied a ton of pressure.

Also, any update on your Holley Sniper and getting it tuned?
 

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Discussion Starter #6
Do you have an adjustable proportioning valve? Might want to add some bias to the rear brakes.

I have to really stomp on my brakes hard to lock them up with the 200 tread wear Falken's. Besides that it stops incredibly quick.
this is my proportioning valve - https://www.summitracing.com/parts/clp-pv-2/overview/
I don't believe its adjustable?

I think your weak link is lack of feel that comes from those power brakes. I have found it much easier to modulate non-power brakes. Meaning that if you jam on power brakes and they begin to lock-up you have to release a bunch more pressure before they actually release which you equate to pumping i think. Not that you couldn't learn it.
Vintage power brakes have never felt linear to me.
Definitely agree with you there - I feel like I'm stepping on a piece of wood


Are the brake lines/MC properly bled? I had some air in the lines and had a similar issue where I'd apply the brakes and wouldn't get much stopping at first until I applied a ton of pressure.

Also, any update on your Holley Sniper and getting it tuned?
yeah they were properly bled- im wondering if SS lines would help at all?

ps - I got my Sniper USB cable, but probably wont have time to get to the Dyno till 2019. this holiday season is a bit nuts for me at the moment.
 

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I have that same proportioning valve in my car and it works correctly. I tried the bigger 15/16" rear wheel cylinders to see how they work with Granada calipers in front. That did throw the brake bias off because the rear was locking up early. When I went to the correct 29/32" all was well. If the rear wheel cylinders are smaller, for some reason, it might not be optimal.
 

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Locking the front wheels is desirable, as long as it is predictable. You do not EVER want to lock the rear wheels first. Doing so will instantly turn you from driver to spectator, as the the car spins around.

If the brakes can be applied in a predictable, safe manner without locking unexpectedly, the best thing you can do is participate in an autocross time trial. Completely safe, normally laid out on large parking lot or airport runway. Even if you get in a spin, about the worst you can do is hit a rubber cone. You'll learn a lot about yourself and your car.
 

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there's no secret or magic involved in getting the most out of your, or anyones classic car non-ABS brakes.

1) adjust the proportioning valve so the rears DO NOT lock up before the fronts

2) drive your car and school yourself how much leg pressure is needed at any given speed and on any given surface to lock up the wheels. Back off of that point slightly and you will stopping as well as your car can stop

pumping the brakes, etc. is not a technique that will permit you the shortest stopping distance, ever.

depending on the speed and surface variables, either moderate or heavy STEADY pressure will stop your car in the shortest distance.

Z

in a discussion like this, it bears pointing out that you must have the best friction material. The best is not cheap, and will NOT be whats included with anyones inclusive brake kit. But do you want to save money, or do you want to keep all 4 wheels on the road ???
 

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4 wheel disc's
4 or 6 piston calipers
all stainless braided flexible hoses front and rear
race quality grooved rotors
carbon fiber metallic track pads
adjustable proportioning to set the proper bias for the track and your tires
track capable tires


might have to get a more modern power brake system with a slave reservoir
maybe a better pedal architecture

all the above is probably on the GTS and most other modern cars capable of that sort of perfomance



All that would probably improve your car's braking significantly but you still need to also address your front to rear weight bias and probably suspension to prevent roll and front end dive which is inherent in these cars unless you re-design the suspension.



A 911 Carrera GTS probably has the front to rear weight sorted out pretty well. An old mustang, probably not so much. I think the GTS also has an optional rear steering feature for the track.
 

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Hummmm.... if the PO doesn't have a proportioning value to the rear brakes the he's getting full pressure to the rear without lockup. That suggests either that the MC isn't working correctly or the rear brake cylinders are too small in diameter limiting the braking force.
In any case, if you're locking up the front brakes then the tires are the weak point... "better" brakes won't do anything. But power brakes do have less "feel" which reduces the driver's ability to modulate the brakes.
 

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Yea, if your locking the fronts first, an adjustable proportioning valve is the last thing you want, its only going to make things worse if you put it on the back and its a bandaid on these cars if you have to put one on the front. I'm not saying you want the backs to lock first, that's dangerous but you need to ascertain just how well your rears are working. I had a similar problem and discovered that my rear circuit wasn't working. THe fluid was just geisering into the master from the rear circuit. I put a new master in and added an 1986 OEM delay type of proportioning valve for the rear circuit along with a residual valve for the drums and it changed everything. My fronts no longer lock up nearly as easily because the rears are now pulling their own weight. The OEM proportioning valve reduces the impulse to the rear for a microsecond as the car weights forward to keep the rears from locking then gives full pressure as the car settles so they pull their full weight without over powering the fronts. The residual valve holds the shoes against the drums lightly so they actuate immediately instead of delaying till the shoes hit finally. With the rears pulling their own weight, the car doesn't nose dive nearly as much and I'm much faster on the Autocross courses being able to wait just a little longer before braking and the car is less unsettled going into the corner so I can hit them harder. Its great!

Balancing the brakes through the full braking cycle of slamming on through steady state braking is non trivial and something that is engineered carefully on OEM cars. Do some reading on the components of modern brakes short of the ABS function - its a system level thought process in order to be done right. There isn't a catalog part that will solve the problem unless your really lucky.

Modulating to emulate ABS is a slow way to brake, a keen foot knowing exactly how much it has before the fronts lock is the best braking scenario. ABS is an engineering approximation since the technology to brake on the edge without locking up is not financially feasible yet. Just go to an autocross and see the difference in your times.
 

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My 2¢ , If you want to increase your braking without a suspension re-design
1) Tires, those Nitto's don't appear to be a top-tier performance tire, The Michelin's are very good, I have the previous version Super Sports on my Boxster, or if you're really commited Bridgestone RE-71R's.
2) Tire camber can reduce straight line braking, especially with low profile tires. I didn't see how much static camber you are running, or what suspension modifications you've made to change the camber curve.
3) Driver inputs, as Dobro mentioned, it also matters how you apply the brakes. Jabbing the pedal can "shock" the tires, causing premature lockup. Also mentioned, lockups and pumping the brakes are not good for stopping distances, they are a recovery technique for when you've made a mistake.
 

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Discussion Starter #17
My 2¢ , If you want to increase your braking without a suspension re-design
1) Tires, those Nitto's don't appear to be a top-tier performance tire, The Michelin's are very good, I have the previous version Super Sports on my Boxster, or if you're really commited Bridgestone RE-71R's.
2) Tire camber can reduce straight line braking, especially with low profile tires. I didn't see how much static camber you are running, or what suspension modifications you've made to change the camber curve.
3) Driver inputs, as Dobro mentioned, it also matters how you apply the brakes. Jabbing the pedal can "shock" the tires, causing premature lockup. Also mentioned, lockups and pumping the brakes are not good for stopping distances, they are a recovery technique for when you've made a mistake.
yeah im pretty set on upgrading to the michelins.

I'm assuming SS brake lines wont improve the terrible power brake pedal feel?
 

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I'm assuming SS brake lines wont improve the terrible power brake pedal feel?
I'm not sure on that one in regards to a vintage Mustang. I know on my truck I didn't notice any difference with SS brake lines, though I do consider a quality braided brake hose to be a safety upgrade, and it certainly can't hurt pedal feel.
 

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Discussion Starter #20
I'm not sure on that one in regards to a vintage Mustang. I know on my truck I didn't notice any difference with SS brake lines, though I do consider a quality braided brake hose to be a safety upgrade, and it certainly can't hurt pedal feel.
yeah on my street bike SS brake lines made a VERY noticeable difference vs rubber for the brake lever feel - but probably because they're not "powered"
 
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