Brake master cylinder replacement questions

[jake_zx2]

Hey guys, upgraded my front calipers to PP Brembos and about to hit a track day, so wanted to make sure to also add the PP master cylinder along with them. I’m trying to remove the stock one, but the area is too tight. Would you guys remove all the lines in the way? Remove the ABS module altogether? Also, the clutch hydraulic system isn’t tied into the brake hydraulics, right? It has its own separate system that won’t need bled after replacing the brake master cylinder? Thanks for the help!

Sponsored

 

[BmacIL]

No need.

 

[jake_zx2]

No need.

Mind elaborating a bit? No need for what? Bleeding the clutch?

 

[BmacIL]

Mind elaborating a bit? No need for what? Bleeding the clutch?

Changing the MC.

 

[CrazedAntelope]

No need.

I agree. I just did the upgrade from 4 piston to 6 piston brembos and everything seems to be working fine without upgrading the MC. I am going to a trackday in 2 weeks so we'll see if there are any issues.

I had heard from Terry at Vorshlag that a master cylinder was needed. I have a brand new GT-PP cylinder in box but I didn't want to risk getting air bubbles in the ABS system, so I chose not to replace it. The master cylinder will sit on the shelf for now.

 

[BmacIL]

I agree. I just did the upgrade from 4 piston to 6 piston brembos and everything seems to be working fine without upgrading the MC. I am going to a trackday in 2 weeks so we'll see if there are any issues.

I had heard from Terry at Vorshlag that a master cylinder was needed. I have a brand new GT-PP cylinder in box but I didn't want to risk getting air bubbles in the ABS system, so I chose not to replace it. The master cylinder will sit on the shelf for now.

Not only does it work, I did the math to prove it. It works very well on track.

Vorshlag had issues because they ran way too aggressive of a rear brake pad on the car.

 

[jake_zx2]

Changing the MC.

I had heard from Terry at Vorshlag that a master cylinder was needed. I have a brand new GT-PP cylinder in box but I didn't want to risk getting air bubbles in the ABS system, so I chose not to replace it. The master cylinder will sit on the shelf for now.

Yep, Terry went to a track day with PP calipers and stock MC and had brake pressure issues all day. replaced MC and didn’t have any issues again. PP MC has a larger piston that matches the flow required for the extra brake capacity

but really, that wasn’t the question here. I’m too far along already, so there’s not much sense in putting the stock MC back on

 

[BmacIL]

Yep, Terry went to a track day with PP calipers and stock MC and had brake pressure issues all day. replaced MC and didn’t have any issues again. PP MC has a larger piston that matches the flow required for the extra brake capacity

but really, that wasn’t the question here. I’m too far along already, so there’s not much sense in putting the stock MC back on

And if you actually do the math you know it's not real. There is less total piston area with the 6 piston calipers than the base. All changing the MC does is change the force requirements for creating the same pressure. Verified with BillyJ and several others.

 

[jake_zx2]

Okay, well like I said, it doesn’t really matter because I already have the old MC pulled and the new one sitting right beside it ready to go on, so now all I need is to receive the information I’ve asked for

 

[BmacIL]

You should not need to bleed the clutch hydraulic system as long as you don't let the feed line drip dry. It's best to pre-bleed the MC before you install on the car, and then quickly change the lines over. ABS module should not need to be touched. The other thing that made probably the most significant difference to VM's results was the booster change. It has higher assist level than the base.

 

[mikeD4V]

Not sure if you're done but I'll put this here in case someone searches for it later. Put some shop towels under the booster because fluid will spill into the frame channel, on the head, and the headers. Pull the the silver L shaped bracket holding the lines on from the stud on the booster to finally release it. The bracket comes off with force by wiggling it while pulling toward the front of the car. I'ts tight under/back in there and hard to reach but it will come off. The stud is threaded and the bracket hole has little lips holding it onto the threads. Bench bleed the new master if you can before installation. No need to fiddle with the ABS. Reuse the black rubber piece on the clutch nipple to secure the clutch line. As mentioned already, keep the clutch line up and away while doing the swap. It will be messy.

For anyone searching this later, the auto GTPP master does not have the clutch nipple so you can use a remote reservoir for clutch fluid. This can help prevent clutch friction material from coming up the clutch line and negatively affecting the master.

S550 GTPP master swap by MikeD, on Flickr

Sponsored