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Discussion Starter · #1 ·
This post is directed toward folks that have been using the Cobra rotor conversion on 1965-73 OE drum hubs.

Looks like the hub hole dia. of the Cobra rotor is larger than the O.D. of the hub snout. This would mean the rotor is installed on the studs and not hub-centric.

Here is a picture of a non-Cobra rotor sitting on the O.D. of the hub snout:
http://www.streetortrack.com/files/vmf/hubcentric.jpg

Anybody experience any vibrations/issues at high or steady speeds from the rotor hanging off the studs and not centered on the hub hole? Can anybody explain why this gap is or isn't a problem?

If the O.D. of the rotor stud holes are pretty tight to the studs, the rotor isn't going to go anywhere. The only issue I can think of is if there was a lot of slack in the rotor stud holes. Then the rotor wouldn't be centered and during installation would sit lower, meaning more of the rotors weight would be hanging down. This 'lop-sided mass' would probably cause vibrations at speed.
 

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I imagine this would be a big problem and unacceptable. This front or rear? I'm not familiar with your specific problem, but I installed SN95 discs on the back of my 8.8, and haven't used it yet, but I have the same problem you're describing, and I think someone else I read somewhere had the problem and had to machine up some hubcentrics. I'll be doing that out of some steel pipe or something when I get that far.
 

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Discussion Starter · #3 ·
JohnnyK said:
I imagine this would be a big problem and unacceptable. This front or rear?
Front. I'm noticing all the folks doing the Cobra front rotor swap and using their stock hubs. From all my measurments of rotors and hubs, the OE hubs look a good but smaller than the hub hole in the Cobra rotors.
 

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Shaun said:
This post is directed toward folks that have been using the Cobra rotor conversion on 1965-73 OE drum hubs.

Looks like the hub hole dia. of the Cobra rotor is larger than the O.D. of the hub snout. This would mean the rotor is installed on the studs and not hub-centric.

Here is a picture of a non-Cobra rotor sitting on the O.D. of the hub snout:
http://www.streetortrack.com/files/vmf/hubcentric.jpg

Anybody experience any vibrations/issues at high or steady speeds from the rotor hanging off the studs and not centered on the hub hole? Can anybody explain why this gap is or isn't a problem?

If the O.D. of the rotor stud holes are pretty tight to the studs, the rotor isn't going to go anywhere. The only issue I can think of is if there was a lot of slack in the rotor stud holes. Then the rotor wouldn't be centered and during installation would sit lower, meaning more of the rotors weight would be hanging down. This 'lop-sided mass' would probably cause vibrations at speed.
This is the same thing I ran into with the (rear) brakes when I was designing the rear disc setups I was working on. There was a good bit of slop around the wheel stud holes of the rotors. This meant everytime you did a brake job, rotated the tires, or if you just took the wheel off and put it back on, the rotor would shift slightly each time. Without the rotors being centered, the slight movement of the rotor in relation to the axle (or front spindle hub), meant the brake pads would not be tracking in the exact same plane on the rotor's friction surfaces each time the wheel was removed/replaced. Centering ring example on rear: http://www.ultrastang.com/images/2006/v6gtsn95reardiscs0460ms.jpg

When I was piddling with the front brakes on my '68, I used a centering ring on the hub to keep the rotor from being reliant on the wheel's studs: http://img179.imageshack.us/img179/7280/g2con68003tk3.jpg

http://img221.imageshack.us/img221/5664/g2con68006yd7.jpg
 

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Discussion Starter · #8 ·
ultrastang said:
Shaun said:
This post is directed toward folks that have been using the Cobra rotor conversion on 1965-73 OE drum hubs.

Looks like the hub hole dia. of the Cobra rotor is larger than the O.D. of the hub snout. This would mean the rotor is installed on the studs and not hub-centric.

Here is a picture of a non-Cobra rotor sitting on the O.D. of the hub snout:
http://www.streetortrack.com/files/vmf/hubcentric.jpg

Anybody experience any vibrations/issues at high or steady speeds from the rotor hanging off the studs and not centered on the hub hole? Can anybody explain why this gap is or isn't a problem?

If the O.D. of the rotor stud holes are pretty tight to the studs, the rotor isn't going to go anywhere. The only issue I can think of is if there was a lot of slack in the rotor stud holes. Then the rotor wouldn't be centered and during installation would sit lower, meaning more of the rotors weight would be hanging down. This 'lop-sided mass' would probably cause vibrations at speed.
This is the same thing I ran into with the (rear) brakes when I was designing the rear disc setups I was working on. There was a good bit of slop around the wheel stud holes of the rotors. This meant everytime you did a brake job, rotated the tires, or if you just took the wheel off and put it back on, the rotor would shift slightly each time. Without the rotors being centered, the slight movement of the rotor in relation to the axle (or front spindle hub), meant the brake pads would not be tracking in the exact same plane on the rotor's friction surfaces each time the wheel was removed/replaced. Centering ring example on rear: http://www.ultrastang.com/images/2006/v6gtsn95reardiscs0460ms.jpg

When I was piddling with the front brakes on my '68, I used a centering ring on the hub to keep the rotor from being reliant on the wheel's studs: http://img179.imageshack.us/img179/7280/g2con68003tk3.jpg

http://img221.imageshack.us/img221/5664/g2con68006yd7.jpg
Thanks for the info/pictures. I just wonder what the folks using the Cobra rotor conversion bracket kits are using for centering rings? If they are not using anything how are they centering the rotor? Are they getting any vibration when driving when not using any rings?
 

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JohnnyK said:
Can't it just come tumbling out then?
Nope. The ring has a small ridge on it that keeps it from sliding out once the rotor is in place and the wheel bolted down.
 

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Shaun said:
ultrastang said:
Shaun said:
This post is directed toward folks that have been using the Cobra rotor conversion on 1965-73 OE drum hubs.

Looks like the hub hole dia. of the Cobra rotor is larger than the O.D. of the hub snout. This would mean the rotor is installed on the studs and not hub-centric.

Here is a picture of a non-Cobra rotor sitting on the O.D. of the hub snout:
http://www.streetortrack.com/files/vmf/hubcentric.jpg

Anybody experience any vibrations/issues at high or steady speeds from the rotor hanging off the studs and not centered on the hub hole? Can anybody explain why this gap is or isn't a problem?

If the O.D. of the rotor stud holes are pretty tight to the studs, the rotor isn't going to go anywhere. The only issue I can think of is if there was a lot of slack in the rotor stud holes. Then the rotor wouldn't be centered and during installation would sit lower, meaning more of the rotors weight would be hanging down. This 'lop-sided mass' would probably cause vibrations at speed.
This is the same thing I ran into with the (rear) brakes when I was designing the rear disc setups I was working on. There was a good bit of slop around the wheel stud holes of the rotors. This meant everytime you did a brake job, rotated the tires, or if you just took the wheel off and put it back on, the rotor would shift slightly each time. Without the rotors being centered, the slight movement of the rotor in relation to the axle (or front spindle hub), meant the brake pads would not be tracking in the exact same plane on the rotor's friction surfaces each time the wheel was removed/replaced. Centering ring example on rear: http://www.ultrastang.com/images/2006/v6gtsn95reardiscs0460ms.jpg

When I was piddling with the front brakes on my '68, I used a centering ring on the hub to keep the rotor from being reliant on the wheel's studs: http://img179.imageshack.us/img179/7280/g2con68003tk3.jpg

http://img221.imageshack.us/img221/5664/g2con68006yd7.jpg
Thanks for the info/pictures. I just wonder what the folks using the Cobra rotor conversion bracket kits are using for centering rings? If they are not using anything how are they centering the rotor? Are they getting any vibration when driving when not using any rings?
In the Mustang Steve Cobra kit, there are no rings. Only the wheel studs.
 

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ultrastang No. It's a machined piece of 6061-T6 aluminum. It just simply slips into the center of the rotor. [url said:
http://www.rosehillperformanceparts.com/images/R_1.JPG[/url]
Ultrastang,
Thanks for the Link. I used Crown Vic rear discs, and have the same situation. I've been pondering what if anything to do about it. Do you know if the rings are deep enough to center the wheel, also?. According to Rosehill's site, not having them is only a problem if the wheel is removed often, but it seems unsound to me, anyway.
 

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Discussion Starter · #12 ·
ultrastang said:
Shaun said:
ultrastang said:
Shaun said:
This post is directed toward folks that have been using the Cobra rotor conversion on 1965-73 OE drum hubs.

Looks like the hub hole dia. of the Cobra rotor is larger than the O.D. of the hub snout. This would mean the rotor is installed on the studs and not hub-centric.

Here is a picture of a non-Cobra rotor sitting on the O.D. of the hub snout:
http://www.streetortrack.com/files/vmf/hubcentric.jpg

Anybody experience any vibrations/issues at high or steady speeds from the rotor hanging off the studs and not centered on the hub hole? Can anybody explain why this gap is or isn't a problem?

If the O.D. of the rotor stud holes are pretty tight to the studs, the rotor isn't going to go anywhere. The only issue I can think of is if there was a lot of slack in the rotor stud holes. Then the rotor wouldn't be centered and during installation would sit lower, meaning more of the rotors weight would be hanging down. This 'lop-sided mass' would probably cause vibrations at speed.
This is the same thing I ran into with the (rear) brakes when I was designing the rear disc setups I was working on. There was a good bit of slop around the wheel stud holes of the rotors. This meant everytime you did a brake job, rotated the tires, or if you just took the wheel off and put it back on, the rotor would shift slightly each time. Without the rotors being centered, the slight movement of the rotor in relation to the axle (or front spindle hub), meant the brake pads would not be tracking in the exact same plane on the rotor's friction surfaces each time the wheel was removed/replaced. Centering ring example on rear: http://www.ultrastang.com/images/2006/v6gtsn95reardiscs0460ms.jpg

When I was piddling with the front brakes on my '68, I used a centering ring on the hub to keep the rotor from being reliant on the wheel's studs: http://img179.imageshack.us/img179/7280/g2con68003tk3.jpg

http://img221.imageshack.us/img221/5664/g2con68006yd7.jpg
Thanks for the info/pictures. I just wonder what the folks using the Cobra rotor conversion bracket kits are using for centering rings? If they are not using anything how are they centering the rotor? Are they getting any vibration when driving when not using any rings?
In the Mustang Steve Cobra kit, there are no rings. Only the wheel studs.
So has anyone using this kit noticed any issues like vibration etc.?
 

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ultrastang said:
Sorry to block your vibration question Shaun, but Steve which front hub is that? The bearing portion looks more 'square' than the drum hubs I'm familiar with. Is that an aftermarket piece or the '68 disc hub? Steel or aluminum?

I'm not too familiar with the '68 disc setup to know if those were integral hubs cast into the rotors or two piece construction.
 

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Dang...didn't even think about that.

How well does the rotor fit on a stock Mustang Cobra hub? Anybody got one they could look at and let us know?

I too would like to hear if anyone running the MS front Cobra kit has had any problems.

Nate
 

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Dennis Harrelson said:
ultrastang No. It's a machined piece of 6061-T6 aluminum. It just simply slips into the center of the rotor. [url said:
http://www.rosehillperformanceparts.com/images/R_1.JPG[/url]
Ultrastang,
Thanks for the Link. I used Crown Vic rear discs, and have the same situation. I've been pondering what if anything to do about it. Do you know if the rings are deep enough to center the wheel, also?. According to Rosehill's site, not having them is only a problem if the wheel is removed often, but it seems unsound to me, anyway.
This is a Crown Vic setup I had experimented with a good while back. The centering rings work with it too, if you have pre-'74 axles ['74-up have the correct (larger) axle registers to fit the hole of the Crown Vic, SN95, & Mk VII rear rotors] :
--Without the centering rings, this is what your C-V setup looks like: http://img255.imageshack.us/img255/520/crownvictoriareardiscbrxp5.jpg

This is what the Crown Vic setup looks like with the rings:
http://img80.imageshack.us/img80/1754/crownvictoriareardiscbrac6.jpg

Rosehill Performance Parts is owned by my friend and business asscociate, Glen Buzek. These rings come in all our rear disc conversion kits, but we've also sold quite a few of the rings by themselves to people doing rear disc conversions.
 

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Applejack said:
ultrastang said:
Sorry to block your vibration question Shaun, but Steve which front hub is that? The bearing portion looks more 'square' than the drum hubs I'm familiar with. Is that an aftermarket piece or the '68 disc hub? Steel or aluminum?

I'm not too familiar with the '68 disc setup to know if those were integral hubs cast into the rotors or two piece construction.
All the '65-'73 Mustangs [that came from the factory with disc brakes] had hubs that were pressed into the rotors. The Mustang IIs, Mavericks & Granadas had the one-piece castings.

The hub that was picured on my '68 was from a '70 Mustang. I later changed it to a '65 V8 hub because there's a 1/4" greater [outboard] offset to the '70 hub which pushes the rotor further out.

Difference in two hubs shown here:
http://img229.imageshack.us/img229/4471/6570hubs001ax6.jpg
 

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Discussion Starter · #17 ·
ultrastang said:
Applejack said:
ultrastang said:
Sorry to block your vibration question Shaun, but Steve which front hub is that? The bearing portion looks more 'square' than the drum hubs I'm familiar with. Is that an aftermarket piece or the '68 disc hub? Steel or aluminum?

I'm not too familiar with the '68 disc setup to know if those were integral hubs cast into the rotors or two piece construction.
All the '65-'73 Mustangs [that came from the factory with disc brakes] had hubs that were pressed into the rotors. The Mustang IIs, Mavericks & Granadas had the one-piece castings.

The hub that was picured on my '68 was from a '70 Mustang. I later changed it to a '65 V8 hub because there's a 1/4" greater [outboard] offset to the '70 hub which pushes the rotor further out.

Difference in two hubs shown here:
http://img229.imageshack.us/img229/4471/6570hubs001ax6.jpg
Interesting. I have drum hubs from both pre-70 years and 70-73 years. The following picture shows the same variance in height but when the races and bearings are installed, the front side of the plane where the studs are installed ends up being in the same spot.

http://www.streetortrack.com/files//vmf/IMG_5511.jpg

Are you saying that the disc hubs were different?
 

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ultrastang said:
This is a Crown Vic setup I had experimented with a good while back. The centering rings work with it too, if you have pre-'74 axles ['74-up have the correct (larger) axle registers to fit the hole of the Crown Vic, SN95, & Mk VII rear rotors] :
--Without the centering rings, this is what your C-V setup looks like: http://img255.imageshack.us/img255/520/crownvictoriareardiscbrxp5.jpg

This is what the Crown Vic setup looks like with the rings:
http://img80.imageshack.us/img80/1754/crownvictoriareardiscbrac6.jpg

Rosehill Performance Parts is owned by my friend and business asscociate, Glen Buzek. These rings come in all our rear disc conversion kits, but we've also sold quite a few of the rings by themselves to people doing rear disc conversions.
Thanks for the reply. The question is do the rings locate the wheels (assuming they are large holes also) in addition to the rotors? From your second pic it looks like the answer is no.
Thanks again,
Dennis
 

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I'm not sure if this answers your question, but looking on the Vintage Venom website at the cobra disk conversion the kit includes a spacer that is both hub centric to the drum brake hub and the center hole of the brake rotor. The correct dimensions are machined into the spacer so everything fits together centered on the hub, with the rotor snuggly over the spacer's hub. I don't know if the cobra kit you're looking at includes a spacer like the Vintage Venom kit, but I imagine the hub fit issue would have to be addressed in a similar manner. I don't think a lug centric fit on the rotor would be stable enough for safe braking.
 

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Discussion Starter · #20 ·
Rickmaan said:
I don't think a lug centric fit on the rotor would be stable enough for safe braking.
This is what I was hoping for some clarification on.

Lets say, just for instance that the lug holes are such that they fit the holes in the rotor within the same tolerance as a hub hole design. With 5 lugs at 90ft-lbs what would be the difference?
 
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