Is a brake master cylinder bigger on a sti 4pot brakes than a WRX?
 

Hi i had a bit of a bump about two years ago and we had a bit of a problem with the brakes were the pedal would drop to the floor and when pumped the brakes would firm up again.

This was solved as there was a hair line crack on the disc..so the fronts were changed....the first thing we did was change the brake master cylinder but the code on it was different...the brakes ave never been the same so we thought it was the front calipers so refurbs them and added braided hoses and motul fluid...got all the air out but still *crap...

when i drive the car and i brake the brake pedal pressure is there and when pumped straight away the pedal goes firmer. i have reason to believe that the brake master cylinder may be smaller that that of a sti.

could anyone please assist. thanks

I asked the same question, as i was looking to upgrade my wrx to an sti if there was any difference.

i was told that up to newage they were all the same. However if you speak to Ian Godspeed im sure he will confirm it

cheers dazza for the reply, my brakes are crap at the moment. do you know or if anyone else if the kevlar pads need warming up before they work properly?

really need to know because i can stick the old master cylinder back on.

I would expect that a 2 pot master cylinder will be different to a four pot item, as it has to move more fluid...

IMHO

dunx

P.S. For a 2 pot to Brembo swap, it would be very likely to need a Newage master cylinder.

Mine didn't, and has been no problem.

98 UK car to Godspeed front Brembos and STi rear Brembos.

Jeff a 98 car would have 4 pots anyway...

dunx

I haven't heard that you need to upgrade the master cylinder when going from 2 pot to whatever (as have 8 pot now) does anyone have a definant answer to this? as any difference. MY97

Yes there is a difference, as std an early 2 pot cars has a 25mm cylinder fitted, later 4 pot cars have the bigger 27.##mm version.

I did the change on mine (fitted an STI8 cylinder)

By fitting it you increase braking feel no end. A must IMHO.

My brake pedal travel is terrible going from 2 pots front and 1 at rear, to just Subaru 4 and 2. Got myself an STI 7 master cylinder to fit, which cost me £6.50 :lol1:

Is it just a straight swap?
Also from which STi onwards should be the better one

Any of the 4 pot equiped ones fit upto STI8, but I would assume the later ones are similar but I cant confirm that.

mines an 98 v4 turbo 2000 and has two pots as standard,does anyone know if that would be the 25mm or the later 27mm master cylinder,thanks

Does the servo need replacing or does the master cylinder bolt to the 2 pot servo?

Hi guys just thought id update on the progress.

The sti comes with a larger master cylinder as i have recently found out.

On the sti master cylinder just below the front of it it is marked as: -

1 1/16.

I think on the wrx it is just one but you can find out but looking at it with a mirror just underneath the front.

dexster81 you just need to add on the sti master cylinder as servo doesnt need changing.

Could anyone on here who has a turbo 2000 or a wrx classic confirm the master cylinder size by looking underneath the front with a mirror would be interesting to see if its smaller and confirm.

thanks guys for the replies.:thumb:

On the UK 2000 MY97 Terzo it has a 1 so does that mean the STi brake servo will NOT fit
or is the 1 and the 1 1/16 just the size of the master cylinder and not the hole it is having to go in on the servo

No mate, 2-pots front, single sliding caliper at the rear, 98 August car.

IIRC, 4-pots arrived with the 99 cars........

You dont need to touch the servo at all

dexster81 that is great for getting that info for us fella, thank you.

This is all aspect answers our questions, firstly the master cylinder on a sti is larger in internal as 1 1/16, the wrx, turbo 2000 etc will have a smaller one that has 1 printed on it.

In my opinion all that needs changing is the mc and not the servo.

This thread is proof that we can work tgether to get a resolution which i think is great.:luxhello:

Or if you used the search function you would find its already been covered LOL ;)

Sorry to resurrect this old thread, but does this mean if the master cylinder is replaced with a sti, this will improve the brakes?

Also will it fit?

Does anybody know if a new age WRX has the same master cylinder as an STi?

interested in the same thing...if the hawk wrx has the same master cylinder as the hawk sti

Hi Jay

I don't think WRX have same Master Cylinder as STI and yes if you are running Brembo from STI I would upgrade yours Master cylinder to STI one

I think John Felstead has have on this bit more information

Hope this help

Thanks,Jura

Not sure who that is :lol1:

I'm sceptical about this. Can anyone say for sure, 100%?

Hi there

Please have look on those threads

http://forums.nasioc.com/forums/showthread.php?t=958909

http://forums.nasioc.com/forums/show....php?t=2054265

http://forums.nasioc.com/forums/show....php?t=1456630

I'm pretty sure John Felstead covered this over here and 22b

https://www.scoobynet.com/scoobynet-...rt-brakes.html

http://bbs.22b.com/forums/showthread...-pot-330mm-kit

Hope this help

Thanks,Jura

Thanks Jura.

Sounds like it's the same but the brake booster is different according to one of those NASIOC threads.....

Never heard of him either.


Newage WRX are different size master cylinder to an STi. (25.4mm WRX, 26.99mm STi)

The man himself! :D

I have read a lot of stuff over the last couple of days suggesting that the 05+ WRX is different, but not the ones before that....

Apparently the size is stamped on it but I've not had a chance to look at mine yet.

Just checked my manuals (which are the US/Canada market but are often the same as EU)

The MY04 (which is MY03 to the EU market) has the same size master cylinder on the WRX and STI at 26.99mm

The MY06 (which is MY05 to the EU market) has the sizes I posted earlier.

Looking at the line pressures, either the brake pedal has a different ratio on the WRX and STI or the brake booster spec is slightly different.

At 66lb of pedal pressure the early Newage WRX has 1323psi line pressure, the STI has 1209psi line pressure.

The later spec Newage WRX has 1450psi, the STI has 1209psi line pressure, which ties in with the cylinder sizes being different.

Now if you are running the WRX 4 pot brake you are going to need a higher line pressure to achieve the same clamping rate at the pad as the STi Brembo 4 pot because the piston surface area is much smaller.

Thanks John for clarifying this,I've been not sure but I've read yours older threads

Thanks again,Jura