LS7 Clutch - Pedal Sticking to floor - Slow to return

[olemiss540]

My 400hp LS swapped racecar with T56 (brand new LS7 clutch and flywheel during initial build) has been successfully tracked for about 8 or 10 HPDE weekends now (build thread in the track section).

Just last event started having an issue where the clutch pedal would get sticky and slow to come back up and first/reverse became hard to engage.

I pressure bled but the fluid looked good and no change in pedal stickiness. Was still drivable but want to get issue sorted but honestly don't know much about clutch workings so hoping some advice from experts around here on best places to start.

[E36M3LX]

My 400hp LS swapped racecar with T56 (brand new LS7 clutch and flywheel during initial build) has been successfully tracked for about 8 or 10 HPDE weekends now (build thread in the track section).

Just last event started having an issue where the clutch pedal would get sticky and slow to come back up and first/reverse became hard to engage.

I pressure bled but the fluid looked good and no change in pedal stickiness. Was still drivable but want to get issue sorted but honestly don't know much about clutch workings so hoping some advice from experts around here on best places to start.

sounds like a failing clutch slave cylinder. I would start there.

I'm assuming its an internal slave. If you want to start with something easier and possibly take care of some preventative maintenance, you could consider changing the clutch master cylinder first.

But unfortunately, my money is on the slave failing

[olemiss540]

The slave/TOB unit was brand new 10 HPDE weekends ago, any idea if they are prone to failing under track use?

What about something like this: https://www.risefabshop.com/bmw/48ul...qu3y0evalpmyui

Or should I just still to something like this? https://www.fcpeuro.com/products/bmw...758830#fitment

Is there an OEM replacement considered an upgrade I can use from a different model? I am sorry for the stupid questions I just dont have a good understanding of how clutch systems operate.

Edited to add: Doing some google-fu, came across this: No you will not "need" an adjustable. But be advised, whatever master you install & break in the clutch with is what your stuck with the life of that clutch due to the adjustable pressure plate on it.

So it appears I need to try replacement of the old existing clutch master with an OEM version as a first step.

[octanematty]

Interested to hear how it felt before the issues? what is your current master cylinder?

I'm just about to get my swap running and even though i think my master isn't fully 100% bled, i don't think it pushes enough fluid even once i perfectly bleed it.

I ended ordering a Wilwood 7/8 master 260-13624 which seems a much better fit than the Risefab setup.

[olemiss540]

Worked fine for 2 years with the stock master. No funky release point issues, but I did remove my clutch stop I believe.

[Lantz]

I had a very similar situation but it happened after changing clutches. I have a T56 magnum and went from a single disk to twin disc (both Monster) and I now have some sticking if I remove the pedal return spring (gives better feel on twin disc setups). I went through my setup with Monster and they recommended I install a tick master, although that’s not possible because it’s in my BMW. I designed a bracket to fit a Wilwood master that should solve my problems similar to yours. The Rise product looks nice its just very expensive. This will be similar in design to theirs but cheaper. I dont post on here much anymore but I’ll try to post my results after. My instagram is @Lantz_E39 if you want to follow progress.

Edit for reference: I replaced the stock BMW clutch master and the T56 slave when I changed to the new clutch. Basically every part is new so in my setup it’s pointing to inadequate clutch master cylinder bore size.

[Lantz]

This ended up being a lot more complicated than I thought. The Wilwood doesn’t come with an end, the length is wrong, and the width needs to be machined down. This is my first prototype.

Final product available at www.LantzFab.com

CD8AE64B-6ABF-429F-B827-AE0FC9DD5294.jpg

[HighSpedLowDrag]

How did this end up working?

[Albertan]

I had similar problems with my LS swap. Twin disk Spec clutch. I went with a Tilton clutch master. I redesigned the entire mechanism then also made my own clutch arm etc. Seems I never do anything the easy way. It has been working fine for probably 5 years.