Big Brakes - Master Cylinder & Rear Bias?

[Westyfield2]

Ignoring all the threads about "Standard callipers are fine", "Wilwoods bend", "I wish I could afford APs"... lets just say you've got 4pots and they're AP/Brembo/Compbrake/HiSpec/Wilwood/whatever.

I've seen comments a few times about pedal travel being rubbish & needing different master cylinder, and other things about bias needing changing.

What's the truth and what's the myths?

 

[sam JFM]

I use a standard cup master and it's fine - different but fine

 

[MG cup]

Same.

​197 Brembos and fine on Cup.

 

[Craig.]

197 brembo's on a Ph1 with standard master cylinder & mines fine.

 

[Sam@NP]

Wilwood midlights were fine with standard master cylinder

 

[theo_tl]

172 ph2 standard master cylinder & Clio V6 Ap calipers, I have`t felt any change of pedal travel.

 

[BIGASH]

My alcons are fine with standard 172 cup master cylinder but had never ending issues with the standard 182 cylinder and ABS system

 

[Cup_Phil]

I can never understand why people panic and think the master cylinder needs swapping
It doesn't - standard cup master cylinder is fine

90% of the people I've spoken to over the years who've fitted 4pots then complained the pedal travel is too far just simply don't know how to bleed 4pots properly

 

[Westyfield2]

Thanks all. Wonder where the myth of "You must change the master cylinder otherwise instant death" came from then!

My alcons are fine with standard 172 cup master cylinder but had never ending issues with the standard 182 cylinder and ABS system

Oh... Not heard that one before, other than people getting air in the ABS and needing to clear it out with RS-Tuner/Clip. What was up with it?

 

[BIGASH]

Oh... Not heard that one before, other than people getting air in the ABS and needing to clear it out with RS-Tuner/Clip. What was up with it?

I don't know in all honesty but the company that used to run my car tried everything and couldn't fix it. Basically the ABS kicked in too early so you would be nicely modulating the pedal and then suddenly ABS would kick in.

All I'm trying to say is if going to all the expense of fitting 4 pots then get rid of the ABS I find it much easier drive now.

 

[GodSpeed]

I don't know in all honesty but the company that used to run my car tried everything and couldn't fix it. Basically the ABS kicked in too early so you would be nicely modulating the pedal and then suddenly ABS would kick in.

All I'm trying to say is if going to all the expense of fitting 4 pots then get rid of the ABS I find it much easier drive now.

A bit suprised by that aswell, my Brembo 197 calipers will go on in two weeks with std 182 main, So I guess Ill have to hope for the best then.

 

[MartinR]

Great my brembos are going on soon too hope the ABS doesn't interfere to much

 

[Westyfield2]

Be interested to hear how you get on GodSpeed & martin182 .

Unless the pistons of BIGASH's Aclons use way more fluid than any of the other 4pots people use, I'd be tempted to say he was just unlucky... Surely there must be others still running with ABS/ESP without switching to the 172 Cup setup?

 

[Sam@NP]

ABS was not effected by my 4pots (wilwoods)

 

[MG cup]

I wouldn't be surprised if it was something to do with the wiring on James's car.

 

[BIGASH]

I wouldn't be surprised if it was something to do with the wiring on James's car.

This^^^^

I just didn't want to start a bashing against the company involved.

 

[Sam@NP]

This^^^^

I just didn't want to start a bashing against the company involved.

​Because gent.

 

[Paris 182]

i know is an old thread. but i need your advice.
after fitting the brembos i have a lot pedal travel. all 4 nipples were bleeded 4 times and no air bubbles coming out but still the pedal has a lot of travel. what i do wrong?
Thanks

 

[JB21]

i know is an old thread. but i need your advice.
after fitting the brembos i have a lot pedal travel. all 4 nipples were bleeded 4 times and no air bubbles coming out but still the pedal has a lot of travel. what i do wrong?
Thanks

No need to bleed the lower nipples, just bleed the upper one at a time. Try gravity bleeding for a minute or 2 and then have someone pump the pedal whilst you open and close the nipple. If that doesn't work then you may have air within the abs pump, if so go out and find a dirt path or patch of grass and fire the abs off 4-5 times to get rid of any air and then re-bleed as above.

 

[Paris 182]

No need to bleed the lower nipples, just bleed the upper one at a time. Try gravity bleeding for a minute or 2 and then have someone pump the pedal whilst you open and close the nipple. If that doesn't work then you may have air within the abs pump, if so go out and find a dirt path or patch of grass and fire the abs off 4-5 times to get rid of any air and then re-bleed as above.

im really sorry. i haven't explain correctly. I haven't touch the lower nipples. i said 4 meaning the 2 top on each caliper.
could you please tell me if i have to do the bedding process now that i have the pedal travel or i need to do it when the pedal is normal?

 

[JB21]

If the pedal is normal then no need to bleed again, but if your getting extended travel then there's air in the system which need to come out. Try this first though...with the engine off try pumping the brakes 2-4 pumps and see if the pedal goes solid, if so then turn the engine on and the pedal should go lose again, this will tell you if there's an issue with the brake booster or master cylinder if it the pedal doesn't go hard with engine off, if ok then proceed the re-bleeding.

Good luck.

 

[Paris 182]

thanks mate

 

[mikekean]

Depends on the size of pistons in the calipers, 197 Brembo's piston size designed to run with a servo setup. The 197 does run a bigger master cylinder but the size difference is fairly small so thats why when fitted to a 172/182 they work with no issues. Now if you go and buy a set of AP calipers with pistons sizes aimed at being used with a bias pedal box this is when you start to get a long pedal and need a larger master cylinder to compensate. Generally though if the calipers are fitted with dust seals this normal means they are designed for a road application i.e. servo setup and will work just fine on most master cylinders, although that is a pretty crude rule of thumb.

 

[Paris 182]

Thanks guys. Sorted.
I took my car to Mike at Rentech here in Portsmouth. Excellent service. Pedal is back as normal. Brake fluid replaced and bleeding.

 

[chaski]

Thanks guys. Sorted.
I took my car to Mike at Rentech here in Portsmouth. Excellent service. Pedal is back as normal. Brake fluid replaced and bleeding.

Just adding information here.

I bled my brakes twice and still had a soft pedal. I then bled them in this order after suggestions from a mate:

Rear N/S
Front O/S inner then outer
Rear O/S
Front N/S inner then outer

I'm not sure if the order had anything particularly to do with it, but I do think bleeding the rear calipers helped for sure. I was surprised to see a fair bit of air come out the rear pipes. Pedal was perfect after.