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Discussion Starter · #1 ·
I'm not sure if this is just bad driving on my part but:

I was trying to do some fast startoffs, but the first time i tried it i let off the clutch at about 1500-1800, and press the gas to hard and obviously got wheel spin. The second time i tried it I tried to be a bit more careful. but once i let the clutch go it seamt as if the car was going nowhere. The revs were high, the clutch was not depressed, and the speeds were low, and I'm pretty sure the wheels were not spinning. I'm pretty sure all the power was going in to the clutch. Would this be considered a slipping clutch? I dont notice the clutch slipping at any other times during normal driving, but for that moment it seamt as if the clutch was partially engaged but i was not engaging it, I think i even changed it to second and it was still doing the same until i let off the gas a bit, but i emphasis i dont think the wheels were spinning. Sorry for my ignorance, I am by no means an experienced race driver, and dont catogorize myself at one, but i do know my limits, and I do know I cannot get good startoffs
. The DSC was off also. O and of course there was a burning smell afterwards, I dont think it was the Wheels
. fortunate for my clutch, I dont do this everyday
.

fas
 

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Yep. That was a slipping clutch all right. Don't do that again
I had that happen twice, and it weakened my clutch enough that it began to slip on it's own, when fully engaged. Made the car undrivable, and I had to have it replace at around 8000 miles. Also, what's happening there is the pressure plate is spinning at high rpms against the flywheel, but is overheated and isn't gripping. This caused my flywheel to warp slightly, with heat distortion.

If, when you say you "tried to be a bit more careful", you meant that you 1) applied >4k rpm or so on the gas, and 2) "eased" the clutch out over the course of two or three seconds -- that's something you shouldn't do. It just takes the engine's power and dumps it into the clutch, not letting it do proper power transfer. This causes it to heat up and fail.

Never "ease out" the clutch on the M5 while apply lots of rpm, or power-shift when going uphill (which puts more strain on the clutch -- that was the problem I had with mine). Match the revs with what the wheels want in the gear you're going into, and drop the clutch fairly quickly. The car has too much weight for a slipping (half-engaged) clutch to move quickly without overheating.

If it happens again, I'd get the clutch checked or replaced before it starts slipping too badly. There's rumor of an upgraded Z8 clutch that's available for M5's with clutch problems, but BMW's never admitted publicly to that.

How to get a good launch (imho):

1: rev to about 2k rpm, ease out the clutch (about 1 to 1.5 seconds) while applying gas to about 3.5k.
2: floor it and shift from 1st into second at about 6500k. You want to shift a little early out of first, because you don't want to hit the rev-limiter, and engine rpms are ahead of the tach a little bit
2: when you shift into second, just drop the clutch (release it very quickly, less than 0.5 seconds). Ease off the gas just a little bit when you do this, to get a good rev-match. If you keep it floored, you'll get too much wheel-spin into second (which is really cool and impresses onlookers, though). If you ease off too much, you'll get pitched forward a bit and maybe get some wheelspin from engine breaking.
3: Shift from 2-3, 3-4 in the same way, but at about 6800 rpm. It's usually all over well before you need to get out of 4th


I am by no means an expert driver either, but I'm trying to grow my skills to match my car
Enjoy!

-Wolf
 

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Discussion Starter · #3 ·
wolf,

thank you very much for your input. May i ask did the clutch get replaced under the warranty?

fas
 

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Discussion Starter · #5 ·
wolf,

thank you once again for the info, i'm sure my bmw dealer will probably give me a hard time until i make a fuss about it. It's good to know that it was covered for other people.

regards,
fas
 

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During Spartanburg performance school there is an acceleration exercise.
All they are concerned with burning clutches and wearing tires - so technique they offer is:
slowly increase rpms/same pace - release clutch up to the point there car starts moving - no tire spinning. Then drop clutch and floor gas.
Next gear - drop gas, press clutch, shift, drop clutch, floor gas. Repeat for next gears - if desired (track there is to short to go to 3rd and above - for this exercise).

For optimal acceleration - you can try to have a very little tire spin - both times - when start and from 1-2nd (don't know optimal rpms though).


Just my $0.02 = 0.05DM

Vas
 

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I've read on another site that some BMW clutch use a hydraulic valve to slow the engagement, intending to smooth shifts. The result was burned clutches.

I wonder if this has been the cause of some M5 clutch failures.
 

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it's official, my clutch is completely screwed up. A while ago i tried to launch the car with 5 people in it, let clutch out at about 2,000 rpm, nothing but slippage. Months later i'm doing an acceleration run, clutch slips going into second, and third. It seems all that valve does is burn the clutch rather than just let it grab. It is unfortunate this car has such a huge flaw. My BMW rep told me he had heard nothing about slipping clutches, this was a couple of months ago. But then again he also didn't know anything about the innaccurate temperature gauge. Never the less he was a nice guy and helped me out. I'm just upset BMW doesn't keep their people informed. I will bring my car to the dealer shortly to get a new clutch.
 

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I've just had my second service and had the clutch replaced for the first time. I had experienced the spinning of the clutch whilst stationary trying to get a quick start with 4 large passengers on board back when the car had 10,000km on it. From then on, it was never the same feeling as though there was always some amount of slippage under heavy load.

My M technician ordered one of the new clutches for me and it was fitted and the flywheel machined. When I got it back, there was an enormous shudder in the car, both at idle and under acceleration. So back to the dealer I go - after 3 hours on the diagnostic machine (which picked up another separate minor fault!) they decided that the flywheel must be out of balance and so ordered a new one.

Got the car back with new flywheel and voila! all problems solved.

The new clutch feels quite different, taking up close to the floor and is lighter in feel than the previous one. I certainly notice the difference in takeoff and under load in the 4th gear overtaking speeds - obviously mine was always slipping under these circumstances.

An important message for you - my M technician put the clutch down as "shuddering" when I booked it in and not "slipping" - apparently if it is slipping BMW can ask you to contribute or pay for the clutch, whilst if it is "shuddering" it is a pure warranty question. Nice blokes, my dealer here in Australia!

So now I'm happy after 50,000km of driving with new clutch, new flywheel and no more slipping / shuddering. Wonderful car!

Andrew E
 

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I've been to Spartanburg this week. This technique (quoted below) isn't just being recommended - THIS IS THE ONLY PROPER CLUTCH TECHNIQUE.

If you get your foot to the floor before you've ensured that the clutch is fully engaged, you're asking to burn up your clutch in short order. As the Spartanburg exercise proves, it is possible to get very good fast launches and upshifts without excessive clutch slipping. The instructors there told us that LOTS of people who came to the course had pretty bad clutch technique. It's easy to understand why - in most cars, you can get away with it for a long time - because those engines just don't develop any torque at low RPM.

Once again - rev to NO MORE THAN 1500 RPM - then release the clutch at the same time as your roll on the throttle - clutch should be ALL the way out before you get to 2000 RPM. By the way, it is perfectly OK (although SLOWER) to induce a bunch of wheelspin. You just wear out the tires, not the clutch. But if you let the engine run at a different speed than the transmission, that poor old clutch absorbs all the difference - and with 400HP it just ain't gonna handle it. Period.

Your 1-2 shift must also ensure that the clutch is fully engaged ASAP. This is easy - if you intend to accelerate hard, just move the lever and get the hell off the clutch pedal right away. If you're not in such a hurry, use a gentle right foot until your left is all the way up.

I talked with several drivers at the course this week who have what I consider to be good clutch technique. One guy has 20,000 miles on his car already. Not a slipping clutch among us. Sorry, guys - I'm more convinced than ever: if your clutch slips, it is almost undoubtedly your fault. So when you get the replacement, learn how NOT to slip the clutch except as described above.


Originally posted by lokhankin:
During Spartanburg performance school there is an acceleration exercise.
All they are concerned with burning clutches and wearing tires - so technique they offer is:
slowly increase rpms/same pace - release clutch up to the point there car starts moving - no tire spinning. Then drop clutch and floor gas.
Next gear - drop gas, press clutch, shift, drop clutch, floor gas. Repeat for next gears - if desired (track there is to short to go to 3rd and above - for this exercise).

For optimal acceleration - you can try to have a very little tire spin - both times - when start and from 1-2nd (don't know optimal rpms though).


Just my $0.02 = 0.05DM

Vas
 
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