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Charter Member
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Discussion Starter · #1 ·
Does anyone have a source for flange brackets that will accept Cobra calipers for 13" Cobra rotors to run on the rear? Several of us just got back from an open track event at Gainseville, hosted by DSCC. MAN what a blast!!, but need more brakes.
Thanks,
Richard Bailey
 

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Pro FFR Builder and Moderator
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You would be better off going with a wilwood 4 piston rear system instead of a 2 piston system like the PBR fronts.
 

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Gordon is right on. My Wilwood 4-piston Dynalite II calipers really work great. Especially when paired with the Superlite-6 6-piston calipers on the front.

2FAST
 

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FFCobra Craftsman
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I have Cobra R brakes from Disc Brakes R Us. 13" on front and 11.5" on rear, drilled and slotted rotors, Hawk pads, standard power booster, IRS, Tbird Spindles, Cobra hubs, pin drive, Compomotive HB, and John Lisman brackets to mount rear caliper brackets. I believe I bought brackets through Richard Oben at North Cobra. It looks like he does have a less expensive option available.

http://www.northcobras.com/catalog/brakes/brakes.htm
 

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David - excuse my ignorance, but what are pad knock-back issues?

I have 4 pistons on the rear, and haven't experienced any problems. are you describing the condition where the pads wear unevenly? If so, I'm using differential bore calipers, and don't have that problem.

If it's something else, I'm interested to hear of their problems.

Craig
 

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FFCobra Fanatic
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820 Posts
richard

i have the cobra rotors all arround with wilwood 4 piston calipers front and rear. the pistons of the front calipers are bigger than the ones on the rear(1.75 vs 1.38) and i have exellent brakes. the brackets i made up of steel with a good grider, band saw and a drill press. no big deal. you are welcome to see my car at any time. i did go up your way for abacoa this month and i'll probably go again for the one in march. maybe we can meet there. let me know if you are going. you can tell your brother chris to go too.

cheers

luis lopezFFR4031
 

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Craig,

Pad knockback occures when the axle/flange/bearings flex small amounts. A mm of flex in this area is amplified greatly at the outer edge of the rotor.

What is happening, is your fixed caliper does not float. As your corner under very high G loads, your axle/flange/bearings flex and the rotor presses against the pad and pushes the pistons in. When you come to the next corner, you will have a very long pedal while you push the piston back out to make contact with the rotor.

You wont see this happen on cars driven on the street. You wont get enough grip in most cases.

It is a VERY real problem with sticky DOT R tires or slicks when cornering over say 1.2 G's.

Mark Jones and Dave M both have this problem along with a number of folk we race with.

The only real cure is floating rotors, and they are noisy and expensive.

David
 

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Dave-

Would a residual valve eliminate the problem?
 

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2Fast,

A residual pressure valve will not help if the rotor is indeed pushing the pistons into the caliper. The pressure from that happening would be more than the 2 psi or 10 psi valve.

I think it is worse for solid axle cars with c-clips, but you are running a 9 inch with no c-clips, so you might be o.k.

Craig
 

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David - thanks for the info. I'm only playing around with rock-hard street tires, so I haven't yet experienced any problems. I'll now know what the problem is if my pedal goes long with slicks!

Thanks,
Craig
 

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David is correct, I have the Willwood 4 piston rear and 6 piston front (now 4 piston in front). With street tires you will never notice it but side load from the slicks will deflect the spindles enough to push back the pistons, this causes the brake pedal to nearly go to the floor after a high G turn! Residual valves help a little but not enough.

The brakes look cool though when your not moving!

Mark
 

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Feng Shui Master
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1,224 Posts
David Borden, We have had the problem with pad knock on vehicle with c-clips. Originally we used a Chevy 10 bolt and at about 1.0 G with disk conversion we had enough movement to hear the thunk on deceleration, We thought the problem was a worn rear axle assembly, we changed to a 12 bolt w/ c-clips and after a while we had the same problem (mostly because we took that long to sort the handling issues) after two more seasons we went to a Ford 9" with large bearing ends., Mosier axles, Stainless Steel brand 4 piston aluminum calipers. We now have no more thump. I can not tell you that it is gone forever, but its helps. Good luck,
 

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408 Freak
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I personally think that 13" rears are WAY too much. Up front I think that would be fine, but I wouldn't go more than 12" out back. Why do so many people use Wilwood stuff here? I have heard too many thing about them toasting Dust Seals and having too much Caliper flex. I would much rather have the Stoptech front brakes, or the '00 Cobra R Brembos. Does anyone know of anyone running these brakes? They are much better in the brake department than Wilwoods IMHO. See rear brake material here....

http://www.corral.net/forums/showthread.php?s=&threadid=344187

Jon

[ February 27, 2004, 01:21 AM: Message edited by: Jon B. ]
 

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Jackal,

C-clips might be part of it. Especially if the clutch packs are not shimmed tight and allow for a bunch of movement of the axle.

IMO, it may be that C-Clip axles dont have a pressed on bearing like the ford 9inch does. The axle is allowed to bow with the bearing being the fulcrum point.

The big nine inch bearings use press on tapered bearings like you said, and act just like the IRS Hubs and bearings with the additional help of the axle being much larger and reducing flex.

If I were to build a solid axle track car, that originally came with c-clips, I would seriously look at converting it to the 9inch bearing ends for sure.

David
 

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Pro FFR Builder and Moderator
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Dave, you are right about the posi not shimmed tight enough. It is more likely that the stock axles flex a lot. I use many wilwood brakes kits and I don't have the kick back problems that some seem to be experiencing.
 
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