I have mixed and matched my brake parts and the brakes feel like crap. I'm pretty sure I have a s5 turbo booster(not 100% on which booster I have) on a 7/8" master cyl. And it feels mooshy with long and soft pedal travel.

I would like to buy the correct 15/16" mc. But first I would like to make sure I do have s5 turbo booster. Are there any psysical features or part # attached that would help identify which one I have?

Also if it is an s5turbo booster, I would have the option of going with a 929 1" or turbo 15/16". Help me figure it out.

 

pics! the S5 T2 booster is funny looking, and takes a master cylinder that isn't compatible with the other FC booster.

 

I won't be near my car till the weekend. Its at parents house.
Could you try describing the difference.

Thnx.

 

they look the same, they just have a different way of attaching the master.

i looked for pics, but didn't find any S5 t2's in the engine bay pics thread

 

Here's a pic from an s5 turbo model with ABS (the ABS is what determines which booster and MC the s5 models have). As you can see the booster is smaller in diameter, deeper, and has a different master cylinder that is stepped on top.



The ones on all the other FC's are a standard rectangular MC with a flat, large diameter booster.

 

I've been looking through tons of pictures. I never found a clear picture but, I think, I know what you mean about the s5 mc. It seams the reservoir of the s5 turbo mc is different in shape. Is this what you meant?

What about the booster?

 

Is English your first language? I don't think the description I gave could be improved upon, at least without a better picture.

 

kinda sounds like air in your brakes and you need to bleed your brakes simple job really

 

...the 929 master is always and option ;-) infact I may have one for sale soon.

 

you can't run a 7/8" BMC with an S5 turbo booster. the plunger is different.

S5 turbo booster is dual stage diaphragm, it's pretty easy to spot.

Here is a picture of a single stage and a dual stage booster (not rx7, but it's the same thing)

 

English is not my first language and your description can , in fact, be improved as it was the reservoir that's stepped not the Mc it self . Haha.

I have recently searched a lot on fc brakes and I am aware which mc and boosters need to be used together. I just needed to know which parts I have to make the appropriate decision.

Also. My brakes have been bled over 6 times and the pedal feel is garbage. Its travels like a clutch.

 

That's an intentional design decision by Mazda, not a hardware failure or installation error.
Some development driver/engineer preferred the "soft" pedal feel which is the result of the small booster/MC combo.

I think you're wasting time trying to meld different boosters and MCs (been there, done that, spent a fortune on brake fluid).
Just find a car with the 1" bore master (lots of Hondas, Nissans, etc.) or (ideally) a Subie 1 1/16" setup and grab the whole booster/MC combo. This eliminates the hassle of setting the booster pushrod>MC clearance and is basically a bolt in proposition.

 

7/8" non-abs FC BMC and booster vs. 1" 929 BMC w/ dual stage booster:

 

You realize you're telling this to people who have functional braking systems, right? So is it more reasonable to assume that 1) every FC has crappy brakes and we all just fail to speak of it, or 2) something is wrong with your specific brake system or bleeding procedure?

 

I would not call a properly functioning FC's brakes "rock solid" but I would in no way describe them as deficient or of poor design, either. The only vehicle I've driven with a "stiffer" brake pedal is my denali after I swapped in the hydroboost system from an escalade (which uses power steering line pressure from the PS pump to drive the brake booster assist).

 

Nor would I.
Like I said, the pedal "feel" was an intentional design choice which can be changed with various other boosters/MCs but I've never claimed that doing so will improve actual braking distances. It very well may but I've no data to back up such an assertion.

 

My brakes have always felt mushy, initially it was the busted ABS system. Then after after that was bypassed, i suspect the worn out components combined with the booster (which might be is ABS specific) provided less than confidence inspiring performance.

However I will soon be replacing everything except the booster/master and the hardlines, so I hope that will make a big difference. I've got a 929 booster/master that I would like to install, but I'll try a MC brace first to see what kind of difference that makes after the system is bled and bedded.

 

I swapped out my entire S5 Turbo ABS setup to non-abs S4, swapped in non-abs hardlines, booser, and BMC... and added a BMC brace, and I still don't like the brakes, nor to fellow racers that have driven my car.

next step that I'm currently in the middle of is swapping on the 929 BMC+Booster with an wilwood adjustable prop. valve... (and swapping brake pads). Hopefully it doesn't suck....

Frijolee (ronin speedworks) says they work pretty amazing....
http://www.norotors.com/index.php?to...54583#msg54583

 

Well, considering how terrible my brakes are currently that's bound to be an improvement. I cut , bent, and re-flared the ABS lines instead of finding non-abs versions but I doubt that accounts for the difference in performance.

I was actually considereing the Ronin Caliper/rotor upgrade and figured the 929 MC/Booster should go on at that time, but if the brakes feel as bad as you describe I guess I'll have to add it sooner.

 

Thanks for posting that side by side picture. That really helps. I am now pretty sure I have all non turbo parts. S5 non turbo booster with s4 7/8" mc.

More info:
I have also replaced my s4 tII abs brake system for a a non-abs s4 4 pot brake system. It used to work nice and it did have that semi mooshy feel which I though was awesome for braking in the wet. But now it is way worse. And it gives me absolutely 0 confidence during breaking. The car is simply not drivable at a track right now just because of brakes. Pedal Feels dead like a clutch then it just brakes hard with no warning no pedal feedback. Clokker. This was described in one of your brake mc/booster related threads.

Since I now know the parts I have, this weekend I will buy a fresh 7/8"mc and bench bleed it real good and just try to get it somewhat normal. I'm done wasting my time. It time to drive!

Thanks for all the help fellas.

 

Yes, and IIRC, that's when I stopped mixing/matching cylinders and boosters and started grabbing both from the same donor.

 

Ok. I have had it!! New s5 n/a 7/8" MC, bench bled, and bleed system till no bubbles. It feels the exact same. Its atleast 2-3 inches of dead pedal travel then you feel a tiny feedback and blam! they engage. They are also very weak. I accelerated in 1st gear and jumped on the brakes full force and they did not lock up, not even close. I have the worst fc brakes in history!! Im about to give up.=/

 

have you tried adjusting any of the adjustments?

 

I have not. The need of special tools has kept me from adjusting the booster rod. And I'm not sure how adjusting the pedal rod works.

 

Assumibg i have seized hardware or calipers. What would happen if you tried to bleed the brakes with old seized hardware or seized caliper piston. My rear calipers have been on the car since 05' when I got her. I Have only done pads a couple of times and never lubed or serviced the hardware on rear calipers. No calipers are stuck clamped on the rotors though. Can calipers seize in an unclamped position.

I hoping I have a seized caliper or something and its not allowing me to bleed the system properly. Just to be clear I have no leaks on master cyl, factory prop. Valve , nor the rear calipers "T". I have also visually inspected all calipers while mounted for leaks. This weekend I will be removing them all for a closer look.

Question is, will brakes bleed correctly if a caliper is seized.