TT-RS/Golf R master cylinder

[DFish]

Pagid 421's. Nice from cold and work well around Donington Park. :)

Fish

[jimk04]

Hey Bruce you dont need to keep quoting those figures on all your posts!

[DaveB@Vagbremtechnic]

Errr...just for the record the TTRS MC is quite different from the Mk5 GTI

To think its like for like just bigger would be a mistake.

Also Golf R gets the 23.8MC and 57mm pistons

[the bruce]

Right, just measure one side of a fixed caliper when you compare it to a sliding caliper.

I will remove the ''on the edge'' remark on the next addition. Of course it does make a difference
if the MC is 22.2 mm or 23.8 mm and if stock calipers are 54 or 57 mm with ABS software and
booster matched to this.

There are two basic points (and that's not all):

1. Hydraulic adaption - that's what we already talk about. Influences both brake distribution and
pedal effort + travel.

2. Keep in mind most BBKs also provide a larger arm ratio through larger rotors, a better pressure
distribution through stiffer calipers and more pistons and sometimes a higher friction coefficient
which also changes brake balance.

That's why I'd prefer the smaller piston area of a Stoptech ST40 or the Boxster calipers. Almost
same balance as stock, but much better (stiffer) feel, controlability and modulation.

[drsilviuro]

How about CP5200 (4 pot)?

[DaveB@Vagbremtechnic]

Piston sizes on their own don't tell the full story, hydraulics theory states that for a given seal drag the smaller piston will deploy first, the smaller piston will give bite with the bigger piston doing the work.

The 993/996T has 36/44 which is a big split in piston sizes designed in by porsche to give feel with power, I'd be very surprised if your car has a 22mm MC

You only count half the pistons and normally -0%\+7-8% over OEM works

Another example of the numbers not telling the whole story is the rear 4 pot kit we've just put on the TTRS, the single piston surface area is exactly the same as the 4 pots we've fitted but we're having huge non tangible benefits in pedal feel and modulation reported. That's with a bigger disc and pad. A smaller pad is more on and off than a larger pad which for a given pad surface area an give more modulation for a given pedal travel.

Race teams can tune their brakes for different drivers by speccing the Calipers with different piston sizes.

There's also huge amounts of adjustments required for the different jobs....the 370mm rotors AKS are selling at the moment are straight off a Focus world rally car on a Tarmac stage, soon as the car is in the woods they'll put a 310mm brakes on with 16/17" wheels where they'll be a dabbing the brakes whilst keeping the momentum...

Subscribe to race tech magazine there's some ace brake related articles in there 3/4 times a year....they did a full write up on F1 brakes last year....amazing what they get out of a 280mm disc and a tiny 6 pot

[DaveB@Vagbremtechnic]

I wouldn't get hung up over 7/8/8.7.

If I had a polo R it'd get 315x28mm 2 piece bolted fronts with some CP5200 4 pots, Rs14s if I could afford it or M1155 if I couldn't...Id chuck some Mk4 R32 rears on but with the upgrade bracketry to 284mm on the rear. Some 16" track wheels on second hand track rubber

Was a bit surprised you didn't go for it tbh. Those 323x28mm discs you're running are bloody heavy for what they are. They're straight off a Mk1 Cupra R. That said Im glad I didn't it a load of R&D into those cars as they haven't been the GTI killer they were going to be....its given a new lease of life to the Mk4 kits which I'm stocking less and less

[the bruce]

some more:


piston area



1. stock front:


O2 RS/Golf/GTI - Ate FN3 54 mm: 2290 mm²

S3/R32/R - FNRG 57 mm: 2552 mm²



2. aftermarket - fits properly:


AP Racing 6-pot CP7068 (355x32 ) > 2350 mm² (special version of CP7040-caliper for Golf V/VI, Scirocco etc.)

AP Racing 6-pot CP5570: 27.0 + 31.8 + 38.1 > 573 mm² + 794 mm² + 1140 mm² = 2507 mm²

Boxster: 40 mm + 36 mm > 1257 mm² + 1018 mm² = 2275 mm²

Boxster S: 40 mm + 36 mm > 1257 mm² + 1018 mm² = 2275 mm²

993 Turbo: 36 + 44 mm > 1018 mm² + + 1520 mm² = 2538 mm²

Brembo GT 'A-caliper': 40 mm + 36 mm > 1257 mm² + 1018 mm² = 2275 mm²

Stoptech ST-40: 38 mm + 34 mm > 908 mm² + 1134 mm² = 2043 mm²

Mov'it:

4s2 - 36 / 44 = 2538 mm²
4s3 - 36 / 44 = 2538 mm² (u.a. als VAG-Kit mit 322x32er Scheibe, geht unter 17")
4m6 - 36 / 44 = 2538 mm²
6m1 - 28 / 32 / 38 = 2554 mm²



3. aftermarket - mismatch:


Forge: 707 mm² + 1046 mm² + 1164 mm² = 2917 mm²

Mov'it:

4s4:  40 / 44 = 2777 mm²
4s5:  38 / 46 = 2796 mm²
6m3:  30 / 34 / 38 = 2749 mm²


Brembo 8-pot RS4/R8/Gallardo: 28 + 28 + 32 + 32 mm > 2840 mm²

Brembo 8-pot RS6 : 4192 mm²

996 Turbo: 40 + 44 mm >  1257 mm² + 1520 mm² = 2777 mm²

Q7/Touareg/Cayenne (there are 3):

34/36/38 mm : 907.920 + 1017.876 + 1134.115 = ~ 3060 mm²
32/36/38 mm : 804.248 + 1017.876 + 1134.115 = ~ 2956 mm²
30/34/38 mm : 706.858 + 907.920 + 1134.115 = ~ 2749 mm²



4. master cylinder:


- 22,22 mm >  388 mm² (some Golf V, evtl. some Scirocco etc.)

- 23,81 mm >  445 mm² (Golf V R32, Golf V GTI, Golf VI GTI, Golf R, Scirocco 2.0T + R)

- 25,40 mm >  507 mm² (RS3 + TT-RS)



5. rear:


GTI/RS: C38 > 1134 mm²

S3/R32/R: C41 > 1320 mm²

Movit 4m1: 28 / 30 = 1323 mm²

Movit 4m2:  28 / 30 = 1323 mm²



Pi * Radius² = area