5 Lug swap issues - brakes grabbing & little travel - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 10 Old 06-27-2009, 10:29 PM Thread Starter
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5 Lug swap issues - brakes grabbing & little travel

Finally getting my car on the road and having issues. First there really doesn't appear to be a lot of pedal travel...maybe two inches. I have not measured, but there is very little travel at all. Driving slow, the brakes grab very bad, they are very very touchy. While driving at faster speeds I can not get them to lock up or even come close to locking up. With something like a panic stop, they just slow the car done with not hint of lock up any place. And I mean slow down, they really do not want to stop more than a nice steady pace even when mashed down.

All the parts are new cobra front/rear set up, 93 cobra MC & brake booster. MM proportion valve and eliminator. Only real deviation is I had to add a washer to the rear brake brackets to center the calipers on the disc.

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post #2 of 10 Old 06-28-2009, 03:34 PM
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Not enough M/C rod?

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post #3 of 10 Old 06-30-2009, 07:54 PM
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Hello Icey101. The larger '93 Cobra booster is a tight squeeze into the Fox cars. The snout on the booster that goes through the firewall is plastic and can easily crack during installation if any force was used. You might try disconnecting the vacuum line to the booster and see if your condition is similar. If so, you probably have a cracked booster. That would be my guess.

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post #4 of 10 Old 07-01-2009, 03:05 AM Thread Starter
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That is very possible, I had to use alot more force than I wanted to installing it.
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post #5 of 10 Old 07-01-2009, 09:40 AM
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If the booster is fine, and its a possible M/C rod adjustment, which direction would you want to adjust the rod?

I'm hoping its not a booster issue, my car is doing the same thing, and BOY that was a PITA to install.

My brakes aren't touchy, just not much travel, and a firm pedal. I'm going to re-bleed the system and put some GOOD pads on it to replace the $25 Autozone specials I installed to get the car on the road.

1989 GT- Prowler Orange Pearl
Engine:
331, AFR 185, FTI cam, 90mm LMAF/30 lb, TFS-R intake, BBK LT's, X-pipe, Spintech mufflers
Suspension:MM: TA, PHB, Rear LCA's, C/C Plates, H&R Race Springs, Bilstein HD's, SFC's, Moser 28 splines, 3.73's, Cobra brakes,10th Anniv. Cobra wheels

Last edited by Stang Man; 07-01-2009 at 10:21 AM.
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post #6 of 10 Old 07-01-2009, 11:42 AM
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mine couldnt lock up at all when i first installed it but after re-bleeding the system a couple times and getting out there and driving it a while everything firmed up and drives great. I'm using an SN95 MC and stock fox booster.

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post #7 of 10 Old 07-01-2009, 01:36 PM
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Quote:
Originally Posted by Stang Man View Post
If the booster is fine, and its a possible M/C rod adjustment, which direction would you want to adjust the rod?
There is some tech on MMs site regarding the adjustment.

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Originally Posted by Stang Man View Post
My brakes aren't touchy, just not much travel, and a firm pedal. I'm going to re-bleed the system and put some GOOD pads on it to replace the $25 Autozone specials I installed to get the car on the road.
In your case, it sounds like the M/C is not sized properly for the calipers being used (long/soft pedal M/C is too small; short/hard pedal M/C is too large). This assumes the rest of the brake system is working properly (i.e., no seized pistons or partially operable components).
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post #8 of 10 Old 07-01-2009, 03:15 PM
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Quote:
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There is some tech on MMs site regarding the adjustment.



In your case, it sounds like the M/C is not sized properly for the calipers being used (long/soft pedal M/C is too small; short/hard pedal M/C is too large). This assumes the rest of the brake system is working properly (i.e., no seized pistons or partially operable components).
I followed the MM tech I got when I installed everything, wasn't extremely precise, however.

I'm running the '93 MC and Booster, with SN-95 Cobra fronts and rears. Was running stock booster with '93 MC and it was STIFF, finally got the Cobra booster to fit and it softened up a little bit.

1989 GT- Prowler Orange Pearl
Engine:
331, AFR 185, FTI cam, 90mm LMAF/30 lb, TFS-R intake, BBK LT's, X-pipe, Spintech mufflers
Suspension:MM: TA, PHB, Rear LCA's, C/C Plates, H&R Race Springs, Bilstein HD's, SFC's, Moser 28 splines, 3.73's, Cobra brakes,10th Anniv. Cobra wheels
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post #9 of 10 Old 07-01-2009, 08:10 PM
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Quote:
Originally Posted by Stang Man View Post
I followed the MM tech I got when I installed everything, wasn't extremely precise, however.

I'm running the '93 MC and Booster, with SN-95 Cobra fronts and rears. Was running stock booster with '93 MC and it was STIFF, finally got the Cobra booster to fit and it softened up a little bit.
Don't know what to say. I was very skeptical of how my pedal would feel using the SVO M/C (1-1/8" piston), stock 86 booster and my 99+ front cobra calipers (40mm twin pistons) and Turbo Coupe single 45mm rear caliper. Everything I read indicated using the SVO M/C would result in a very hard pedal; it didn't. In fact, the feel is similar to my stock 01 Cobra. It's easy to modulate, firm but not hard and locks when pushed to the limit. Very "factory" feeling. If you have a "hard" pedal with a short travel, then the evidence would suggest a smaller M/C piston is needed regardless of what others are using. With that said, confirm your components. Just saying they are "Cobra" leaves a lot of unanswered tech on the table. What are the piston sizes of your calipers and what is the piston size of your M/C?

Last edited by qtrracer; 07-01-2009 at 08:12 PM.
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post #10 of 10 Old 07-02-2009, 09:52 AM
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Don't know what to say. I was very skeptical of how my pedal would feel using the SVO M/C (1-1/8" piston), stock 86 booster and my 99+ front cobra calipers (40mm twin pistons) and Turbo Coupe single 45mm rear caliper. Everything I read indicated using the SVO M/C would result in a very hard pedal; it didn't. In fact, the feel is similar to my stock 01 Cobra. It's easy to modulate, firm but not hard and locks when pushed to the limit. Very "factory" feeling. If you have a "hard" pedal with a short travel, then the evidence would suggest a smaller M/C piston is needed regardless of what others are using. With that said, confirm your components. Just saying they are "Cobra" leaves a lot of unanswered tech on the table. What are the piston sizes of your calipers and what is the piston size of your M/C?
The front calipers are actually Mach 1 fare.

The MC is a '93 Cobra unit, 1" bore.(if I remember correctly).

I'm going to re-bleed the system and go with better pads, as well as adjust the prop. valve.

Brakes work GREAT, no complaints about that, just not used to the pedal thats all!

Arron


1989 GT- Prowler Orange Pearl
Engine:
331, AFR 185, FTI cam, 90mm LMAF/30 lb, TFS-R intake, BBK LT's, X-pipe, Spintech mufflers
Suspension:MM: TA, PHB, Rear LCA's, C/C Plates, H&R Race Springs, Bilstein HD's, SFC's, Moser 28 splines, 3.73's, Cobra brakes,10th Anniv. Cobra wheels
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