Help! i need a new clutch!

[///Harlis]

As per title, i need a new clutch. I was quoted $590AU for an OEM replacement. But i'm not sure if it will hold my future power needs. In the next 6 months i am going to supercharge me M42 with 6-7psi. so what i want to know is..

1. How much torque can the stock clutch take? will i even need a performance one?

2. Who makes a performance clutch for M42's. Any big brands that may be in Australia? (don't want to order from the states).

3. Is an E36 M42 clutch the same as an E30 M42 clutch?

If they are the same clutch and i find one online for the e36 318is (as more aftermarket parts are available than e30 318is's) should i be okay getting it? oh and has anyone had any experience with those gripforce F1 clutches on ebay?



Thanks in advance!

[Hodge]

First off, do you have an E36 or an E30?

If you have an E36 with the Getrag 250G transmission you can use just about any E36 clutch and flywheel combination.

I have the UUC 11.5lbs flywheel, E34M5 Clutch, and E36M3 pressure plate (also known as UUC Stage 1) and I love it. But you also should have the E36M3 slave cylinder so your pedalis so hard to work.

If you have an E30, I believe you can modify the M20 clutch assembly to fit your M42, gaining a lighter flywheel in the process (which is a good thing on these motors). But I do believe this also requires that you modify your starter as the teeth are different on M42 flywheels compared to M20 flywheels. There should be a nice write up on here about the conversion.

[///Harlis]

Oops sorry, i have an e30. i'd rather not do the M20 flywheel conversion. it vibrates enough as it is. But if i cant figure out what to do i'll have to do it i guess. im sure they make aftermarket clutches for the M20.

anyone have any idea about the torque the stock one can hold?

[peerless]

The stock M42 has 2 flywheel variety's available. Both a single mass and a dual mass. I can't give you figures on what amount of torque each one would take. I would say the single mass to be the winner, although dual mass is used most frequently in deisel applications where torque is always a factor.

The tech sheet on a dual mass claims to be non-resurfacable. This is not true, but you will need to find a specialist to do it properly. I have spent alot of time comparing M42 to M20 flywheels and weights.

Enjoy:

I keep hearing about this M20 conversion so I decided to do some research into what the real advantage was.

Flywheel weights
------------------
5/90 US 318is M42 5sp. A/C. Originally Twin Mass 21 21 1 223 550 12.250kg / 27lbs
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3/89 European 318is M42 5sp. NON-A/C. Single Mass 11 22 1 739 315 9.9kg / 22lbs
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3/90 US 325is M20 5sp. A/C. Single Mass 11 22 1 706 573 8.5kg / 19lbs
________________________________________________________________

Clutch Kit weights (Includes Clutch Cover, Disk, Throw-out bearing)
-------------------
5/90 US 318is M42 Dual Mass 21 21 1 223 571  5kg/11lbs
3/89 European 318is M42 Single Mass, 21 21 1 223 570  5.6kg / 12lbs
3/90 US 325is M20 Single Mass, 21 21 1 223 102 6.98kg / 15lbs
_________________________________________________________

Combined weights as rotating assembly
-------------------------------------------
5/90 US M42 Dual Mass. 17.25kg / 38lbs
3/89 Euro M42 Single Mass. 15.5kg / 34lbs
3/90 US 325is M20 Single Mass 15.48kg / 34lbs
____________________________________________

Total weight savings of M20 single mass to M42 single mass  0 lbs.

_________________________________________________________

With the M42 specific flywheel you can use a M42 starter. No need to change the starter pinion gear as required with the M20 conversion. This can be a problem if your starter shits the bed at the track or some parking lot. You can go to a parts store and buy a starter and throw it in the car. What if the car changes ownership and the new owner takes it to a shop and the tech is scratching his head why the new M42 starter doesn't work.

In regards to cost I have broken that down as well. Here the M20 conversion does have and advantage. M20 single mass flywheels are plentifully available in the US. These can be found used in mostly good condition for $50-100. The Euro M42 single mass flywheel is not a common item here in the states so they most likely would be purchased new. Pelican has them for $323. We purchased ours through a private party for $200 shipped, new in the factory BMW box. I haven't checked my dealer pricing yet.

Price Comparison (new parts, pelican parts for pricing)
______________________________________________
5/90 US M42 Dual Mass,  Flywheel $685 Clutch Kit $209 ($894)
3/89 Euro M42 Single Mass, Flywheel $323 Clutch Kit $230 ($553)
3/90 US M20 Single Mass, Flywheel $367 Clutch Kit $216 ($583)

Total Cost saving of M20 vs M42 flywheel conversion using new parts, none, it would cost $30 more. But again that using new flywheels and as mentioned before the US single mass flywheels are fairly plentiful in good used form.

Also as one last note of interest, the M42 single mass because of its design leaves a LOT of meat that can be milled off for a very good weight savings, maybe more so then the M20?.

A nice trait of the M20 is it has more surface area. M42 215mm/8.46" to M20 228mm/8.97" diameters. Thats 13mm/.500" (1/2") difference. For the forced induction guys, thats a good thing.

Well that about wraps up my research on the subject. I hope you find it useful and informative.

If you see an error in what I researched please point it out and provide references to included information. Something of this nature needs to be correct.

Part numbers and weights where provided by bmwfans.info

M42 single mass advantages:

Lighter weight over the dual mass unit and just as light as the M20 conversion.
Use factory M42 starter with no modifications
Use factory clutch kit complete
Uses factory length flywheel bolts
All parts readily available.

Disadvantage:
Cost involved in acquiring single mass flywheel
====================================

M20 single mass conversion advantages:

Lighter then M42 dual mass, but same weight as M42 single mass.
1/2" more clutch surface diameter for improved load capacity on high HP M42's.
Less cost for flywheel as they are plentiful used in good condition.
All parts readily available.

Disadvantages:
Must purchases additional throw out bearing as the M20 bearing is too short. (323i)
Must use modified flywheel bolts
Must use spacer in back of flywheel for proper spacing
Must modify existing starter and install M20 pinion gear

For complete M20 conversion instructions and modifications read here,  http://www.blackforestindustries.com/m20flywheel.htm

M42 single mass flywheel setup:



M42 Dual Mass flywheel setup: