Installed Cobra brakes, still can't stop. Going hydroboost

wytstang · Oct 4, 2010

nmcgrawj said:
I think he was referring to the fact that if you slam on the brakes as hard as possible, the wheels will want to lock up causing the stopping distance to be greater. ABS will fight this, thus making it not as bad. But still not making up for it.

I also sent jason another email asking a few more questions, will report back with details.

The gt and cobra share the same caliper, the only difference is the slightly larger rotor on the cobra. We're only talking .5 difference here (gt 10.5" to 11" cobra) I just don't see this as a problem at all. How can .5 shorter decrease your braking that much?

nmcgrawj · Oct 4, 2010

It's not only the rear. The brake set up on a cobra is set up with a different bias. The GT setup is optimized for it's components....changing some and not all disturb this setup. Thus making it perform worse than just a GT setup alone. You really need to have the bias set for the front and rear brake setup.

Now can anyone prove the bias on the GT and cobra are the same?

I inquired to Jason about their manual brake set up. We got off topic and this is what I discovered. I'm pretty sure MM knows their stuff....and if Jason isn't there in 2011....perhaps this is all bull lol.

1slow95 · Oct 6, 2010

Started on the hydroboost install last night. Got the old MC and PS lines removed. The fittings on the hydroboost lines are all the same so everything will bolt right in. It looks like the hardest part is going to be removing the old booster. Almost had it out, then hit on the valve cover. I should be able to finish it tonight. My batteries were dead in my camera so I'll get some pics tonight.

revhead347 · Oct 6, 2010

I had trouble getting my booster out with the 302 block in there. It's a tight squeeze.

Kurt

Mustang5L5 · Oct 6, 2010

You think it's tough getting that booster out? Try putting it in in a Fox. It's like pushing a watermelon through a straw to get that thing in.

1slow95 · Oct 6, 2010

Just one more line to connect and need to tighten all connections. Two modifications that need done; the upper left(next to clutch cable) hole in the firewall for the booster needs drilled out slightly, and the pedals are different so I had to cut the end off the old booster and weld it to the new one. The hose to PS pump doesn't fit very well, but it'll work for now.

1slow95 · Oct 8, 2010

Well that was a pita, but I can stop now!!! The end I cut off and welded to the new booster gave me all the problems. First it wasn't the right angle so the pedal would stop about 2" off the floor. Then it broke when I put too much pressure on it. After practicing with the welder and going over the manual I fixed the wire speed and heat settings, and got it pretty good but the angle was wrong again. One more try and I had it. It goes to the floor and it held up while I pumped the brakes hard for about 5 minutes.

Took it for a test drive and I can now lock up the front tires! Although I think I get what the problem is with the brake bias because it didn't take much pedal to lock up. May look into that in the future... I'll give it a good test tomorrow when I hit up some back roads, then sunday I'll be at Nelson Ledges road course all day.

1slow95 · Oct 11, 2010

Brakes held up great at the track. I thought they were pretty good, until I rode with my cousin who has the Brembo Cobra R setup. Much better braking with those. I wish they would clear my rims.

Anyways, the pedal is still hard with the new MC and hydroboost but if you push on it it will stop unlike before. Plus I can now get to my #8 spark plug.

revhead347 · Oct 11, 2010

That's awesome. Any chance you can get together a list of the stuff you need to do that swap.

Kurt

1slow95 · Oct 11, 2010

revhead347 said:
That's awesome. Any chance you can get together a list of the stuff you need to do that swap.

Kurt

Hydroboost / SN95 Brake swap / 17x10.5 FR500 rim install with 315 rear tires

All you need is a complete hydroboost setup off a 4.6 Mustang. That includes the booster, MC, and 3 power steering lines. One high pressure line goes from the booster to PS pump, another goes from the booster to the steering rack, and a low pressure line runs from the booster to PS pump then PS cooler to rack.

You also need either a pedal assembly from a 4.6 stang, or cut the end where the pedal attaches off the old booster and weld it to the new one.

95BlueStallion · Oct 11, 2010

nmcgrawj said:
So how much shorter is the stopping distance?

Or are we making statements by the "butt meter".

You're correct in assuming I havent done any Car and Driver braking tests, but you can feel quite a difference between a single piston 10" rotor setup versus a dual piston 13" rotor setup. It would be like doing an H/C/I swap and arguing that there are no power gains if they hadnt dynoed the car. Im not trying to start any bickering, just giving my opinion in the matter was all.

Mike, sorry to hijack, and nice work fabricating a functional setup on your car. Glad it worked out how you hoped it would!

S351Saleen77 · Oct 18, 2010

1slow95 said:
Great info. In my searches before buying the brakes I found many people reported the stock MC and Cobra brakes worked fine, and many others that said it was much better with the Cobra MC. I figured I'd try it and buy the MC if I needed it.

This is what I have read also so I left the GT master cyl on #58 when I swapped to 14" 4 piston Alcons. On #58 It had stock GT brakes and I put 14" Alcons on the front and 13" rear rotors and left the GT Master cyl. It dosen't stop quite as well as #77 but I figured it was the pad material. The car does stop better than stock, and with no master cyl swap. It has a great pedal feel also.

On #77 It came with 13" Alcons up front. It stops incredible, I know the pads are really really soft and dust a lot, they are Pagid made in Germany. I have no idea if Saleen swapped the GT master for a Cobra, I assumed he left it alone. The Alcon 4 pistons have more area than the stock single but everything works great! Maybe Saleen did swap master cyl?

Here is a MM&FF article where they put just the front 14" Alcons on a Cobra. They don't talk about changing the master cyl even though the piston area will be different between the 4 piston Alcons and the 2 piston Cobras.
Alcon/Roush Brake Upgrade - One Brake Coming Up! - Muscle Mustangs & Fast Fords Magazine

I'm glad it worked out for you! I like how it frees up alot of room! And the #8 spark plug!

.

Mustang5L5 · Oct 18, 2010

S351Saleen77 said:
Here is a MM&FF article where they put just the front 14" Alcons on a Cobra. They don't talk about changing the master cyl even though the piston area will be different between the 4 piston Alcons and the 2 piston Cobras.
Alcon/Roush Brake Upgrade - One Brake Coming Up! - Muscle Mustangs & Fast Fords Magazine

.

With 4 piston brakes, since the pistons are pushing against each other, you only factor one side into the equation in determining caliper piston surface area. So you would calculate the area of 2 of the pistons on the same side and compare to the 2 piston cobra calipers.

I do not know the sizes of the pistons of the 4-piston Alcons. I do know that the 4-piston Cobra R Brembos are VERY similar to the 2-piston cobra brakes, so an MC swap is not required with those calipers.

To be frank, the guys at MM&FF, as smart as they are, are not engineers. So just because they didn't swap the MC, doesn't mean it's not required. it could be something as simple as they overlooked it, or they just didn't feel like it. Of course, i'm not claiming to be any sort of brake design engineer or anything like that, but i do know a bit about hydraulic systems. Reducing or increasing the size of the slave cylinder (the caliper) has a huge effect on effort the master cylinder needs to exert.

The vast majority of guys with 94-95 GT's and Cobra brakes that i know...never swapped the MC. Some complain about the feel...some live with it. There is a very technical arguement as to why they should swap to the 15/16" or 1" bore MC's. It's also fairly easy to do.

S351Saleen77 · Oct 28, 2010

I don't know the size of pistons in the Alcon calipers but they look to be much larger than the Cobras which is probably why I have nice pedal effort instead of a hard one.

I am going to be putting the new Ford Racing cobra calipers on a Fox Saleen which came with a SVO master cyl and Lincoln front and rear disks. The SVO master cyl is even a bigger bore than the SN95 gt's so I will probably do a swap for sure on that. I heard that if I use the 93 Cobra 1" bore then the low fluid warning will work again, I guess it's unhooked with the SVO unit.

89oem · Nov 8, 2014

Interesting, so with hydroboost and 93 cobra calipers how would the braking be?

The '93 Cobra used 60mm front calipers and 45mm rear calipers, im unsure of hydroboost MC size.

What is the calculation you use? @Mustang5L5

Thanks!!

90lxwhite · Nov 9, 2014

Mustang5L5 said:
You think it's tough getting that booster out? Try putting it in in a Fox. It's like pushing a watermelon through a straw to get that thing in.

That's what she said.

Mustang5L5 · Nov 10, 2014

89oem said:
Interesting, so with hydroboost and 93 cobra calipers how would the braking be?

The '93 Cobra used 60mm front calipers and 45mm rear calipers, im unsure of hydroboost MC size.

What is the calculation you use? @Mustang5L5

Thanks!!

It would be like downsizing your master cylinder slightly and increasing the power available.

The with few ford models that shared same brakes, ford upsized the MC a 1/16" to compensate.

So if you were to toss hydroboost on with no other changes, you would find your braking power has increase.

Now, not necessarily a good thing if just touching the pedal barely locks up your wheels at 60MPH.

Without knowing the exact combo, it's hard to make a recommendation. Really there is no need to swap to hydroboost when there are a number of vacuum boosters available and downsizing your bore size 1/16" or so would make a pretty big impact in itself.

89oem · Nov 10, 2014

Thanks, I appreciate the reply here and on my thread, sorry to double ask, thought it went well here...
Have to go hydroboost for my coyote swap due to space I had manual brakes as a teen and no thanks for that again.... Sounds like Im heading into experiment land, I'll determine HB MC size and post up in my other thread

Installed Cobra brakes, still can't stop. Going hydroboost

wytstang

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nmcgrawj

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1slow95

revhead347

Apparently my ex-husband made that mistake.

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That is…until I whipped out my Bissell

1slow95

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revhead347

Apparently my ex-husband made that mistake.

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95BlueStallion

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S351Saleen77

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Mustang5L5

That is…until I whipped out my Bissell

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89oem

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Mustang5L5

That is…until I whipped out my Bissell

89oem

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Installed Cobra brakes, still can't stop. Going hydroboost

Mustang Master

Advanced Member

Apparently my ex-husband made that mistake.

That is…until I whipped out my Bissell

Apparently my ex-husband made that mistake.

My assy trans to myself

Member

That is…until I whipped out my Bissell

Member

Mustang Master

I'm kind of a She-Man

That is…until I whipped out my Bissell

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