GT3 master cylinder on the cheap?
Discussion
I've read that fitting a GT3 brake master cylinder to a 996 C2 will give a noticeable improvement to brake feel and peddle action. This is something I'd like to try next time I'm having my brakes looked at.
Genuine items are pretty pricey: http://www.design911.co.uk/fu/prod129444/Brake-Mas...
I've heard that there's an Audi item that's identical apart from the fact it's made of cast iron rather than alloy. It's for a 1.8T car, amongst others. On eBay it's here: http://www.ebay.co.uk/itm/Brake-Master-Cylinder-10...
Question is: What's the part I can order from GSF if I'd rather get it with one of their discounts? I think it's this one, but can anyone confirm: http://www.gsfcarparts.com/652vg0500?
With this weekend's offer it gets another 35% off the price, but is it the right one? They seem to be available with or without Audi's ESP - I'm guessing I want without?
Thanks.
ETA, sauce: http://www.911uk.com/viewtopic.php?t=104878&si...
Genuine items are pretty pricey: http://www.design911.co.uk/fu/prod129444/Brake-Mas...
I've heard that there's an Audi item that's identical apart from the fact it's made of cast iron rather than alloy. It's for a 1.8T car, amongst others. On eBay it's here: http://www.ebay.co.uk/itm/Brake-Master-Cylinder-10...
Question is: What's the part I can order from GSF if I'd rather get it with one of their discounts? I think it's this one, but can anyone confirm: http://www.gsfcarparts.com/652vg0500?
With this weekend's offer it gets another 35% off the price, but is it the right one? They seem to be available with or without Audi's ESP - I'm guessing I want without?
Thanks.
ETA, sauce: http://www.911uk.com/viewtopic.php?t=104878&si...
Edited by IknowJoseph on Saturday 14th November 00:09
I presume that VW AG decide that they need a master cylinder built to specified dimensions, to move a known amount of brake fluid about, and design one part to fit all the cars they make. The Audi ones get cast in something heavy and the GT3 ones are a bit more fancy, otherwise it's all the same. Still, if it's enough to operate the brakes on a 2 tonne barge it should stop my little C2 OK 
Thanks for the TRW tip, I'll have a look.
Thanks for the TRW tip, I'll have a look.
Just to check?.
http://www.ebay.co.uk/itm/PORSCHE-911-Brake-Master... (only one I can find in the UK)
And all I do is get them swapped over and the brake pedal feel will improve? (CR is the vehicle being fitted to)
http://www.ebay.co.uk/itm/PORSCHE-911-Brake-Master... (only one I can find in the UK)
And all I do is get them swapped over and the brake pedal feel will improve? (CR is the vehicle being fitted to)
To the OP,
The 996 C2 uses a 23.8mm piston in its MC, the GT3 uses a 25.4mm piston. Note also that the GT3 uses less boost assist (3.15 v 3.85).
Changing to the larger MC will require more pedal force to achieve the same line pressure. Changing the booster will further increase the amount of effort required on the pedal.
The 997 GT3 MC will also fit though you may require new hard lines from the ABS to the MC to be made. It will depend on the fitting size on your current lines. You may be able to use an adaptor as an alternative but making new lines would be my preferred choice. The larger size of the 997 GT3 MC will further increase pedal effort you need to provide to achieve the equivalent line pressure.
For the poster asking about the Cayman. If you use the search, I posted some calculations on % change in effort swapping MCs on the Cayman. As per above, the 997 GT3 uses a 27mm diameter master cylinder which will increase the pedal effort you need to use to achieve the same line pressure.
Slightly off topic but a contributor to the soft brake pedal issue on the later cars, including the Cayman R is the increased booster assist Porsche used. While the MC will increase pedal effort and improve things, reducing the booster assistance would also be a positive move.
On the steel braked cars, the booster has a 5.00 boost assist, while the booster is 4.50 on the PCCB cars AFAIK. Compare this with the 3.85 assist on the 996/986 (and 3.15 on the 996 GT3) mentioned earlier. Thats a 30% increase in brake assist between a steel braked 996/986 and an equivalent 987/997.
How interchangeable the boosters are is something I don't know. I don't have a Cayman etc. If I had I would have pulled that stuff off and worked out what would go on in its place.
The 996 C2 uses a 23.8mm piston in its MC, the GT3 uses a 25.4mm piston. Note also that the GT3 uses less boost assist (3.15 v 3.85).
Changing to the larger MC will require more pedal force to achieve the same line pressure. Changing the booster will further increase the amount of effort required on the pedal.
The 997 GT3 MC will also fit though you may require new hard lines from the ABS to the MC to be made. It will depend on the fitting size on your current lines. You may be able to use an adaptor as an alternative but making new lines would be my preferred choice. The larger size of the 997 GT3 MC will further increase pedal effort you need to provide to achieve the equivalent line pressure.
For the poster asking about the Cayman. If you use the search, I posted some calculations on % change in effort swapping MCs on the Cayman. As per above, the 997 GT3 uses a 27mm diameter master cylinder which will increase the pedal effort you need to use to achieve the same line pressure.
Slightly off topic but a contributor to the soft brake pedal issue on the later cars, including the Cayman R is the increased booster assist Porsche used. While the MC will increase pedal effort and improve things, reducing the booster assistance would also be a positive move.
On the steel braked cars, the booster has a 5.00 boost assist, while the booster is 4.50 on the PCCB cars AFAIK. Compare this with the 3.85 assist on the 996/986 (and 3.15 on the 996 GT3) mentioned earlier. Thats a 30% increase in brake assist between a steel braked 996/986 and an equivalent 987/997.
How interchangeable the boosters are is something I don't know. I don't have a Cayman etc. If I had I would have pulled that stuff off and worked out what would go on in its place.
Edited by fioran0 on Saturday 21st November 01:39
With the MC off, the booster itself is simple to swap.
I don't know about alternative parts. There are plenty of other boosters around with lower ratios that is for sure, and trying one from the earlier 9X6 cars would be my first approach. They may well just bolt right on without any fuss. The parts list for some of the 9X7 cars showed 9X6 numbers once.
It is going to take an owner with some spanners and some problem solving capabilities to sort it out I suspect (if indeed it can be). As I previously mentioned, had I owned one I could have told everyone the answer; whether that turned out to be a part that fitted or simply a reply that nothing would. I don't however so cannot help other than to point it out.
Changing the MC is a straightforward method to improve the, quite frankly crap, pedal on the 9X7 cars. I absolutely see why owners change it. The point was simply to mention that the bore diameter is not the sole reason. The 986 boxster runs the same MC bore as the later spec boxster when on steels for example, but there is no comparison between the two in terms of pedal feel.
I don't know about alternative parts. There are plenty of other boosters around with lower ratios that is for sure, and trying one from the earlier 9X6 cars would be my first approach. They may well just bolt right on without any fuss. The parts list for some of the 9X7 cars showed 9X6 numbers once.
It is going to take an owner with some spanners and some problem solving capabilities to sort it out I suspect (if indeed it can be). As I previously mentioned, had I owned one I could have told everyone the answer; whether that turned out to be a part that fitted or simply a reply that nothing would. I don't however so cannot help other than to point it out.
Changing the MC is a straightforward method to improve the, quite frankly crap, pedal on the 9X7 cars. I absolutely see why owners change it. The point was simply to mention that the bore diameter is not the sole reason. The 986 boxster runs the same MC bore as the later spec boxster when on steels for example, but there is no comparison between the two in terms of pedal feel.
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