SPEC Twin Disk Clutch Drag?

[car_craft]

I recently had the SPEC twin disk kit w steel flywheel installed on my e92 m3 6mt.

the clutch is not fully disengaging. since the install i have trouble shifting into gear, any gear, with the engine running. with the clutch pedal fully depressed the car will begin to move when i start to shift into gear, even if i cannot fully engage the gear. none of these issues existed before the install. after about 500miles of driving i brought it back into the shop, they suspected there may be air in the lines and bled the system again, but the issue remains, i have about 1200 miles now on the new clutch and it still drags.

The clutch, flywheel, spring clip, release fork, and pilot bearing are all brand new.

some internets searches have brought up this issue on other cars, mustangs, corvettes, rx8 etc, in all cases it was an aftermarket clutch kit, but not many solutions, some were improper installation, bent forks, others were that the OEM hydraulics could not handle the higher force required to fully disengage some of these aftermarket clutches.

Has anyone had this issue with the SPEC twin disk, or any other aftermarket clutch kit on our cars? Does it get better as the clutches wear?

[rcracin]

No experience with this spec specifically but I'm fairly confident that the pressure plate is no good. Usually it's too short when this happens. A potential trick is putting a washer behind the ball on the pivot arm but it's a little half assed for an m3.

No, it will not get better. Your clutch discs will just wear out prematurely.

I'd go back to OEM. You can try contacting SPEC and getting them to pay for a new installation.

[Melchior]

One or both of the clutch discs are probably installed backwards. They are not perfectly symmetrical and are offset to one side. If they get installed backwards there isn't enough room in the pressure plate to fully disengage.

I haven't worked with this specific clutch but I've seen this on other installs.

[rcracin]

I've seen the backwards clutch disc thing too with other cars.

Either way that thing needs to come apart.

[car_craft]

Thanks for the responses,

I have contacted SPEC but have not received a response from them yet. I will reach out to the shop that did the install, with regard to the possibility that the clutch disks could have been installed backwards.

Was hoping some who had this clutch kit could share their experience with it.

[crypticc]

I recall someone saying same thing in the ****** site and backwards install was mentioned.

Correction: something about the throw out bearing that can be installed in either a low or high position for amount of pedal travel needed to disengage.
Interesting talk was of slippage if the reinstall doesn't match the original, rather than difficulty disengaging. Suggest looking at that other site.

[car_craft]

today the clutch felt fine, no trouble shifting in any gear...

Starting to feel more like an intermittent problem, its been about 2 weeks of city / highway driving since install. maybe just some air in the line. I think i will have it looked at anyway.

[car_craft]

So the clutch hydraulics were bled again, but no change in the clutch feel. I have gotten more used to it though, i have about 2500 miles on now. It only sticks (drags) when the car is stopped, when the car is moving it will disengage perfectly fine and i can shift with very little effort. When it does stick i can shift into a high gear, like 6th, and it will break free, and allow me to shift into any gear like normal. So i think the assembly is disengaging, but maybe the clearance on this kit is very tight, hopefully as it wears in it will stop behaving this way. Many people with aftermarket high torque clutches say this is perfectly normal, but SPEC advertises this as an "OEM feel" and not as a race clutch, although i guess with a 900lb torque rating it is pretty much a race clutch. I would think if something were warped or not installed properly than the issue would be much worse. it sticks about 50% of the time when stopped and like i said shifting into high gear breaks it free. This also makes me think that maybe the first gear synchro is a little weak, the transmission does have 80k miles on it, although this problem didnt exist with the OEM unit. The OEM unit was slipping at high rpm. When driving it it does feel like the OEM unit.

[M3_Dylan]

Do you have a clutch stop installed? I installed my spec super twin 600 miles ago and had to remove 3 washers from my clutch stop. Otherwise I would get the same symptoms as you.

[Move Over]

^ What Dylan said. Clutch was not fully disengaging with all the washers in the clutch stop. Worth a shot.

[car_craft]

no aftermarket clutch stop was installed, just the OEM one.

[car_craft]

It been bled twice since the install, but i guess its possible that there still could be some air trapped in the system.

[Move Over]

Originally Posted by car_craft

It been bled twice since the install, but i guess its possible that there still could be some air trapped in the system.

There's not a whole lot of fluid in the clutch line, but if your brake res is not full it can pull air through.

Are you using a pressure bleeder, or the old school way?

[car_craft]

The shop that did the install bled the lines first after the install and then a second time 2 weeks later, i assume they used a pressure bleeder, but cant say for sure. I haven't attempted to bleed them again (3rd time) my self yet.

When i spoke to SPEC last, they said when they do the install they sometimes file down the edges of the teeth slightly to allow the clutch disks to slide smoothly over the input shaft of the transmission, they said the edge of the teeth could catch any small imperfections on the input shaft. Maybe its a tolerance issue in the clearance. Any way it would be a full days labor just to inspect the assembly, so i have decided give it some time to break in more, if it continues to be an issue after a few thousand more miles, which will be April-May, i might have it pulled apart. I would certainly try another bleed before hand. Was trying to see if there were any simple solutions, or if maybe this was normal until its fully broken in.

[cheetah_e92]

no experience with this although I was looking into getting the Spec twin setup for my E92 M3...so definitely following your issue. Have you tried the suggestion from the two members about shimming the pedal for clutch stop?

In my Honda race car I have a twin disc clutch and had to mess with the clutch engagement and pedal stop which helped a lot similar to your issue...and even worse when car moved forward while staged at the light(drag race car)...

Greg

[Sered]

I had the Spec twin p-trim on mine and never had your issue. I think the TOB is configurable and maybe you got it installed it in the wrong position. Mine disengaged exactly in the middle of pedal travel. I also had a UCP installed with a clutch pedal stop.

Never once had a problem as you describe.

[car_craft]

Originally Posted by cheetah_e92

no experience with this although I was looking into getting the Spec twin setup for my E92 M3...so definitely following your issue. Have you tried the suggestion from the two members about shimming the pedal for clutch stop?

In my Honda race car I have a twin disc clutch and had to mess with the clutch engagement and pedal stop which helped a lot similar to your issue...and even worse when car moved forward while staged at the light(drag race car)...

Greg

So yesterday i decided to remove the OEM clutch stop completely, which is just a thin plastic shim only about 2mm thick, much thinner than most OEM aftermarket clutch stops. Its a small change but it did help reduce the drag and the transmission shifts smoother, and not having as much trouble from a stop.

[car_craft]

Originally Posted by Sered

I had the Spec twin p-trim on mine and never had your issue. I think the TOB is configurable and maybe you got it installed it in the wrong position. Mine disengaged exactly in the middle of pedal travel. I also had a UCP installed with a clutch pedal stop.

Never once had a problem as you describe.

I dont know how common this issue is, there are people like you that have no problems with this kit, and others that have similar experience to mine, even on other non-bmw applications using this same clutch kit.

I do think part of my issue still could be related my transmission synchro for first gear, because i never had a problem shifting into high gears from a stop. the first gear synchro sees the most wear and tear, and like i said the car has 82k miles on it now. So this could be making a subtle issue more pronounced. And air in the lines is still a possibility.

I think i will call SPEC again to ask about the TOB, i have heard other people say that it could be installed different ways, but i would like to confirm this with SPEC before i blame the installers. The install was done by Turner Motorsports and i find it hard to believe they would install a clutch incorrectly.

[Sered]

Originally Posted by car_craft

I dont know how common this issue is, there are people like you that have no problems with this kit, and others that have similar experience to mine, even on other non-bmw applications using this same clutch kit.

I do think part of my issue still could be related my transmission synchro for first gear, because i never had a problem shifting into high gears from a stop. the first gear synchro sees the most wear and tear, and like i said the car has 82k miles on it now. So this could be making a subtle issue more pronounced. And air in the lines is still a possibility.

I think i will call SPEC again to ask about the TOB, i have heard other people say that it could be installed different ways, but i would like to confirm this with SPEC before i blame the installers. The install was done by Turner Motorsports and i find it hard to believe they would install a clutch incorrectly.

I doubt its a synchro issue. You should have zero drag as the clutch should be completely disengaged. Mine is fully disengaged at even 3/4 travel and I had a huge clutch stop. I bet money that its either a disc install backwards or a TOB issue.

[car_craft]

Originally Posted by Sered

I doubt its a synchro issue. You should have zero drag as the clutch should be completely disengaged. Mine is fully disengaged at even 3/4 travel and I had a huge clutch stop. I bet money that its either a disc install backwards or a TOB issue.

I spoke to SPEC yesterday. And they said the following are generally the cause of problems with this kit.

1. Because there are 2 disks that have to be aligned perfectly and the fact that the alignment tool is not perfect, it is pretty common for the second disk to be slightly out of alignment. and as the input shaft of the transmission slides through the teeth of the second (misaligned) disk, the teeth of the second disk can score and scratch the splines on the input shaft. This causes that second disk to not slide smoothly over the spline, and it can snag on the spline and cause drag, making it very hard for the synchro to engage the gear. Ideally it should slide smoothly across the input shaft and there should be no drag at all (as quoted above). This is a common problem on any assembly with more than one disk. He said its actually very difficult to get them aligned perfectly the first time. The bell housing should slide smoothly onto the block if they are aligned properly. if the second disk does score the input shaft, he would take a file and clean up the burs, and then reassemble, until there is no drag.

2. TOB - some throwout bearings have a high and low setting (some dont), the difference achieved by installing it 90deg rotated from the other which puts the arm either closer or further away from the spring fingers, this sets the engagement point. The OEM TOB that came out of my car seems to have only one setting, in other words rotating 90 deg will not change the distance between the clutch fingers and the TOB release arm. I dont remember what the one in the SPEC kit looked like, so i cant say if it had 2 settings or not.

3. Weak cylinders, old hydraulics may not be able to handle the extra force required to disengage a high torque clutch assembly. Some fluid can leak passed the piston reducing the pressure applied to the TOB release arm.

4. Air in the lines.

He didn't seem to think that backwards disks were a likely cause, he emphasized 1) and 2) as being the most likely culprit. Depending on the application you may be able physically view the clutch assembly through an access in the bell housing, if so then you can easily troubleshoot the cause of the drag, you can measure the distance the TOB moves for example. But on the e92 m3 there is no way to see into the bellhousing, unless you drill a hole and insert a camera.

[rcracin]

Go back to oem and all your problems will be solved. Not even kidding. I wouldnt want to deal with this headache.

[car_craft]

Originally Posted by rcracin

Go back to oem and all your problems will be solved. Not even kidding. I wouldnt want to deal with this headache.

lol, after going through this i would have to agree. I went with this kit because it was the only reasonable alternative to OEM for this car. Since i have an 08, getting a new OEM clutch means a new DMFW as well. The SPEC kit was half the price of the OEM option. At this point i would rather just get the SPEC kit to work instead of spending more money on an OEM unit. Alternatively others haven't had any problems at all.