All Things Mk5 > Performance Modifications
TT-RS/Golf R master cylinder
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
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