BryantH

I've read a few suggestions for Cayman S owners regarding swapping their master cylinder with one from a GT3 to improve pedal feel (usually in combination with steel braided brake lines).

Has anyone tried a similar swap with a base Cayman? Obviously the base Cayman has smaller brakes so I'm assuming it has a smaller master cylinder as well. I put steel braided lines on my Cayman and although they've improved pedal feel quite a bit, I prefer as mechanically stiff a pedal as possible.

Does anyone know if the GT3 cylinder would be appropriate or if there's another MC in the Porsche family that would swap in to improve pedal feel?

ECS Tuning

The base model uses the same Master Cylinder as the S, so yes the GT3 Master Cylinder would work on a S. As you mentioned I would also get the SS brake lines for the full effect, for more information Click Here. Let me know if you have any other questions or concerns and I will gladly answer them.

BryantH

Excellent, exactly what I needed to know.

I installed my Steel braided brake lines myself, so I'm moderately handy in a shade tree mechanic sort of way. How hard an install do you think this would be?

I'm guessing it would be something like.

1. Vacuum fluid from brake reservoir
2. Remove reservoir.
3. Remove old master cylinder.
4. Install new master cylinder
5. Reinstall reservoir
6. Full bleed on brakes

With some concern about dripping any brake fluid into the frunk and possibly some potential difficulty in getting tools down to the master cylinder if I'm coming in from the area where the reservoir is mounted.

Am I delusional or is that about it?

BERG

Its a pretty easy swap. I would suggest removing the trunk carpet because you will spill some fluid down behind. To add to the swap think about changing the booster also. There is a number on the booster corresponding to the amount of boost. The lower the number the better. 3.5 = GT3, 5.0 = 09 Cayman (mushy). Much better feel overall. If you do this make sure that the push rod is adjusted correctly or the brakes will drag.

BryantH

Thanks for the tip. Now on adjusting the push rod, is this something that can be done after the brakes have been bled? I'm assuming you'd go to a wheel, try to turn it (cars on jackstands) and if it's stuck you'd walk back around and fiddle with push rod until the tires turned freely. Is that the basic procedure for adjusting the push rod? Or is this something that needs to be done prior to bleeding and requires constant draining/removal, etc or some other painful means to set it correctly?

Also, on another Rennlist post I found these step by step photos

https://rennlist.com/forums/987-981-...-cayman-r.html

Is that the brake booster mounted to the frunk behind the master cylinder and reservoir sticking out of it? I just want to visually understand what I'm looking at.

Is the push rod on the MC or the Booster?

DGH-Fahren

Guys : Here is a slightly different twist to this thread. Porsche spends millions to work out the ABS, Porsche Stability Management (PSM), Automatic Brake Differential (ABD) and Anti-Slip Regulation (ASR) software control algorithms, based on OEM brake hardware.

So, what happens to these functions when GT3 and other non standard parts, such as larger Brembo calipers and rotors are added ??

I suspect that the software needs tweaks that it never gets, and therefore the car will behave strangely at the limits.

I would love to add better calipers, pads and a GT3 master cylinder, but I am leery of the "Law of Unintended Consequences" ... things that your think you know, but really don't, because you have not applied system thinking. In other words what are ALL of the things that will be affected by the swap and does it matter ?

Has anyone out there down this, and then pushed the car to the limits on the track consistently. If so, how did the ABS, PSM, ASR and ABD behave ?

Evidence is appreciated.

Freunde am Fahren !

STLPCA

Re: swapping to a GT3 Master Cylinder.
Collectively there are thousands and thousands of track miles on Caymans with GT3 MC and I've yet to read/hear of any negative consequence (apart from a very few complaints that the pedal pressure is too great - for those the PCCB MC is probably a better choice). My personal experience has been that the GT3 MC has absolutely no impact on any of the electronic systems.

BryantH

Just the master cylinder shouldn't really change anything that the software cares about. The Master Cylinder is what you activate with the brake pedal. I'm pretty sure the ABS system must have it's own secondary cylinder that it actuates. An engineer would have to account for an offline or faulty ABS unit and I would think a part of that would just be keeping the systems separate.

Changing Calipers would be a different story however. Depending on how much fluid is needed to push the pistons it could fundamentally change the brakes for sure. As could possibly a larger radius mounting point to accommodate larger disks (from a software tuning standpoint)

I actually think it's interesting that the base Cayman and S use the same master cylinder. I would have thought the big reds would flow significantly more fluid. But in hindsight I'm guessing Porsche worked to flow similar levels of fluid in the base calipers just to avoid the expense of cascading part changes to swap in the different pads/calipers. Good to know in case any of you S owners every decide to sell a mint condition set of big reds

Are the brembos you are looking at different than the big reds? I think those are from Brembo.

Flybot17

I recently did the GT3 MC swap on my Cayman R. Huge improvement in brake feel at the track. Track braking results in the pedal being just about level with the gas pedal, which makes the heal/toe much easier. Street driving, the brake pedal just feels higher and more firm.

Overall great mod. My only dificulty was bleeding the brakes. It took about 2 lt of fluid to get all the bubbles out. The fronts bled easily. The rears just would not give up the air, even after several ABS stops. I was using a motive bleeder. Finaly got it out using the old two-man method.

OP, dont forget to add "bench bleed the MC" to you list on post #3.