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Discussion Starter · #1 ·
Hi Folks

Looking at the parts catalogues for the 981, 991 and 991 GT3, I can see we have three parts:

981 355 130 26 - 981
991 355 130 26 - 991
991 355 130 80 - GT3

Anyone seen these to verify any differences?

I'm beginning to think a lot of the 981/991 parts are shared yet are numbered differently. Anyone replaced the Brake Master on their 981?
 

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I forget what the issue was. But the GT3 991 master cylinder has some kind of electronic valve. Or maybe it's the 981 that has it. Either way, they're not interchangeable as it's something I wanted to do.
 

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Anyone replaced the Brake Master on their 981?[/QUOTE]

I used the 991S MC. Same cylinder diameter as the GT3.
 

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I had originally asked BGB to change my MC to a GT3 MC because I wanted a firmer pedal feel. But they found that my stock MC had an extra valve they hadn't seen on other 981's. So there are at least two versions of the 981 MC, and one of them is not interchangeable with the GT3 part...
 

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Discussion Starter · #5 ·
Thanks for all the responses.

Sportwagon - does your car have PTV?
 

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Yes, my car does have PTV. But the question of whether PTV has something to do with the extra valve was pure speculation on my part, which I posted in my BGB build thread.

Maybe John from BGB can chime in. At the time he was building my car, it was the first time he’d seen it. I wanted the GT3 MC because the brakes felt a little soft compared to the S2000, but now that I’ve sold the S2000, the Boxster brake feel no longer bothers me, so I never figured out why MC’s were not interchangeable ...
 

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if you have PTV .. the master cylinder has that extra valve. to activate the brakes. .. if you dont have have PTV. you dont have that valve.

lemon
 

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if you have PTV .. the master cylinder has that extra valve. to activate the brakes. .. if you dont have have PTV. you dont have that valve.

lemon
But then why wouldn't the GT3 MC have this valve?
 

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Discussion Starter · #9 ·
Good stuff! That was exactly the question I was about to ask. PTV Plus is standard on the GT3.
 

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that is a question that been bugging me too.. when i changed to the Rotora Big brakes . The owner of Rotora and I were talking about this. He Opted to use the stock system on board the cayman S. . i don't know if the GT3 has a different system.. it also has the rear steering deal.


Lemon
 

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As does the 991 Turbo, but it shares the same BMC as NA 911's:

991 355 130 26

I'm confused....
Well, at the time BGB ran into this problem with my MC, there were *not* two different 981 MC part numbers. So whatever the physical difference was, it was *not* reflected in Porsche's part numbering system at the time.
 
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