Euro924S2

Hi Guys. I'm upgrading the brakes on my 924 (together with an M90 supercharger) to the 4 pot Brembo's from a 944S2 / turbo.

My question is, what master cylinder should I use with them given I wont be installing ABS? Do any of the cars fitted with these calipers come without ABS? ie early 944T? I presume all the S2's and 968 etc had ABS as standard?

Cheers, John.

Ps, I've been reading this forum for years, but not needed to post before now as I normally my question has been asked a load of times before!! This time though, whenever someone thinks of upgrading their brakes they get the same message over and over - new fluid, new pads, overhauled calipers! 300bhp doesn't look cool with rear drums though!!!

mattipuh

the one cylinder that goes well to non ABS 944 is such where there's a "bolt" between front and rear brake cylinder. the cylinders that does not have the bolt there, are for ABS. This can be found in WSM.

for instance, this one goes well with non ABS.




non ABS brake cylinder





brake cylinder for ABS cars

Euro924S2

You my man are a genius!

Annoyingly I have the non-bolt, therefore ABS MC.

Can you explain the difference between them? ie why the ABS one wont work properly etc. (I like to understand theses things if I can!)

I don't suppose you have a porsche part number for the non-abs version do you so I can get one ordered.

Cheers, John

Euro924S2

Don't worry about the part number, I just bought one off ebay for £25 used but looks in good condition!

If you have a link to the outlets / lines to make sure I plumb it in correctly that would be very helpful!

I'm presuming the 2 ports opposite one another go to their respective front wheel and the single port, furthest from the booster, goes to the rear and is split left and right?

Should there be a proportioning valve in the system too?

Many thanks,
John

Dimi 944

I don't have ABS on my 1986 944 NA and my master cylinder has no bolt.

Euro924S2

hmm, that's a pity! Thought I had it cracked! Although, maybe I don't need to change it which is less work.

Dimi, is it an alloy MC you have, or steel?

Euro924S2

According to Lindsay racing, the bolt theory holds true! the 944T is listed for bolt version 944-355-011-01 but says ' not for cars with ABS'.

951-355-011-01 is the non bolt version and is for 87 cars onward but says nothing about ABS.

Anyone else able to weigh in on this? Especially anyone who has upgraded their 944 to the brembo brakes and what MC you used?

mattipuh

its shown as a picture in 944 WSM, i can shuffle if I remember when at laptop. it works such as if theres no bolt, cylinder waits the other cylinder (front) to close before it adds full pressure to rear cylinder. I havent dismantled any cylinder but I asked this from Porsche mech when was pondering the same stuff few months back.

there might be cylinders that work also that dont have that bolt ( for instance we used one 19.1/19.1 cylinder last year that worked ok), so its not black and white. but this should be certain with the bolt ones.

yes, paired goes to front and single to rear line..

Euro924S2

Thanks. that interesting to hear.

After a bit of googling, it seems that bolt is the stop for the intermediate piston and just part of this cylinders design. The stepped bore is different in this pre 87 design, compared to the later post 87 design.

Searching the WSM I found the info in the attachment, but basically the front bore is the same, but the rear bore is smaller in the pre-87 (visible bolt) and so will give higher rear line pressures with the same pedal force, compared to the later (no bolt) design.

WSM also says the post-87 MC can't be rebuilt, but the rebuild process is well described for the pre-87.

Either way, I'm not sure my reading explains why one is ABS and the other non-abs but I'll change it and see what difference it makes!

mattipuh

yeah, it's a it strange. it seems in abs type brake cylinder there's "central valve" involved..
here's some pages from WSM.




abs type





non abs type

mel_t_vin

The '86 951, with no ABS, used the same MC as the '87-'88 924 and the '83-'86 944. Namely, 944.355.011.00 [Girling] or .01 [ATE].

Use either one of those, along with the rear 5/18 proportioning valve [928.355.305.01], and the corresponding Girling/ATE booster, to match.