R32 GTR clutch master cylinder adapters

[weikleenget]

Hi again all, I’ve tried doing some searching on the topic but couldn’t find the answer I’m looking for.

 

I deleted my clutch booster because it had an air leak and was squealing like a hog, and now my clutch has very poor pedal feel and the friction zone is way too small, so I believe I need a bigger diameter clutch master cylinder to compensate for not using the booster. I found a Wilwood option that’s 3/4” for a good price and will fit my 3AN clutch line, but all the firewall adapters I see online such as RB factory or Chase Bays are listed as RWD only (GTST/GTS). Link below.

https://rbfactory.shop/products/nissan-to-wilwood-girling-clutch-master-cylinder-adapter

My question is if these adapters will also fit a GTR, and if anyone has experience using a 3/4” CMC without the booster, my clutch is a Nismo coppermix twin plate.

 

Thanks, always appreciate the advice!

Edited November 27, 2024 by weikleenget

[GTSBoy]

I've not looked at a GTR without the booster there. Is the hole and mount on the firewall not just the same as GTSt? I would have expected it to be. Nissan don't change panel stampings if they don't have to, and you'd think they'd just order/design the booster to mount to the same place.

[Duncan]

Yeah 4wd (boosted) has a recess in the firewall for the booster, and 2wd is flat - the example in the link shows the flat surface.

When you deleted the booster, did you just attach the factory slave cylinder directly to the recess in the firewall with no adaption?

 

[weikleenget]

51 minutes ago, Duncan said:

Yeah 4wd (boosted) has a recess in the firewall for the booster, and 2wd is flat - the example in the link shows the flat surface.

When you deleted the booster, did you just attach the factory slave cylinder directly to the recess in the firewall with no adaption?

 

We just disconnected the vacuum line if I remember correctly, booster is still there. Is there a rebuild solution for the booster or a different adapter that will work for GTR chassis?

[r32-25t]

There are adaptors that allow you to delete the booster and use an s15 clutch master cylinder. 
 

if you want to keep the booster they are still available brand new 

[GTSBoy]

And boosters can be rebuilt by the same sort of brake shops that will rebuild a brake booster.

[weikleenget]

12 hours ago, r32-25t said:

There are adaptors that allow you to delete the booster and use an s15 clutch master cylinder. 
 

if you want to keep the booster they are still available brand new 

I saw the s15 version but will it be enough force for my clutch? I guess just repairing the booster is the best option 

[GTSBoy]

5 hours ago, weikleenget said:

I saw the s15 version but will it be enough force for my clutch? I guess just repairing the booster is the best option 

Dude - we all run massive clutches on the original non-GTR master on everything other than a GTR.... The boost was never required.

[weikleenget]

4 minutes ago, GTSBoy said:

Dude - we all run massive clutches on the original non-GTR master on everything other than a GTR.... The boost was never required.

Is the problem that we just disconnected the line, does it need to be plugged? I’d rather not buy another master cylinder

[GTSBoy]

No, you don't want to plug the vacuum line, as that will turn that side of the booster into an air spring and probably make it feel worse.

I'm not saying that the GTR master itself doesn't need a booster. I haven't paid attention to the GTR one to know what size it is cf the non-GTR ones. But when you think about it - they have to do the same job, which is to move a little slave piston a few mm to do what it is supposed to do, and that final action is the same on all the cars. So, it is very unlikely that the GTR MC is any different than the others, because it has the same pedal stroke and the same output requirement. The booster just makes it feel easier.

I'd suggest you probably have an actual hydraulic problem. It's totally common on these old shitboxes.

[r32-25t]

6 hours ago, weikleenget said:

I saw the s15 version but will it be enough force for my clutch? I guess just repairing the booster is the best option 

I’ve got one on mine and it’s fine, 

[weikleenget]

2 hours ago, GTSBoy said:

No, you don't want to plug the vacuum line, as that will turn that side of the booster into an air spring and probably make it feel worse.

I'm not saying that the GTR master itself doesn't need a booster. I haven't paid attention to the GTR one to know what size it is cf the non-GTR ones. But when you think about it - they have to do the same job, which is to move a little slave piston a few mm to do what it is supposed to do, and that final action is the same on all the cars. So, it is very unlikely that the GTR MC is any different than the others, because it has the same pedal stroke and the same output requirement. The booster just makes it feel easier.

I'd suggest you probably have an actual hydraulic problem. It's totally common on these old shitboxes.

What could be causing my clutch problem besides a bad master or slave then? Both those parts are new 

[GTSBoy]

Poor bleeding. That stupid damping loop in the plumbing that should be completely replaced with a braided hose. Just the first 2 that come to mind.

[joshuaho96]

8 hours ago, GTSBoy said:

Dude - we all run massive clutches on the original non-GTR master on everything other than a GTR.... The boost was never required.

Not required but appreciated. Super Coppermix Twin even the non-competition model feels like the pedal is noticeably heavier than stock which was pretty well judged IMO. I'll be swapping in the Nismo operating cylinder soon to see how that feels. 

1 hour ago, GTSBoy said:

Poor bleeding. That stupid damping loop in the plumbing that should be completely replaced with a braided hose. Just the first 2 that come to mind.

Personally I haven't felt anything that justifies replacing the damping loop, at least compared to more modern stuff where the clutch delay valve is actually quite noticeable.

[GTSBoy]

1 minute ago, joshuaho96 said:

Personally I haven't felt anything that justifies replacing the damping loop,

Some of them keep working fine. 9 out of 10 of them end up causing an absolute misery bleeding the system and get thrown on the workshop floor in a tantrum and never thought about again because they were never really needed and just added crap to the car that we could have done without. Same-same with HICAS, A-LSD, and various other stupidities that over eager 10x engineers thought we had to have.

[weikleenget]

10 hours ago, GTSBoy said:

Poor bleeding. That stupid damping loop in the plumbing that should be completely replaced with a braided hose. Just the first 2 that come to mind.

I replaced the whole clutch line with the chase bays braided hose, I think it removes that loop, is it the short hose that comes immediately off the slave or is there a drawing in the manual to find what you’re referring to? It was just re-bled when I upgraded to the nismo slave, old slave worked fine but I thought that might help, didn’t change a thing. It’s like the first half of the pedal is pushing air and then when it finally actuates the master the friction zone is tiny. Makes it practically impossible to launch the car

[Duncan]

OK, that is a helpful description, because that sounds exactly like a bleeding issue in the clutch....these are hard to bleed manually even when the damping loop has been removed.

I'd suggest bleeding again....start by filling the master cylinder up and opening the bleed nipple. Come back and check every now and then that the master cylinder is not empty. Let it gravity bleed for a few hours and see if that improves