shaving a flywheel

[Digitalwave]

The average shaved M20 flywheel goes from 19-20 lbs to down to 13-15 lbs. The difference of 5-6lbs is VERY noticable, as it would be in the 5-6lbs additional difference from a shaved M20 flywheel to an aluminum one.

[sweetride01]

Is it somewhat comparable to adding hp?

[Digitalwave]

You could say that, since you are minimizing driveline loss.

[MrK]

How about just swapping the flywheel for one from an e21? Anyone know if that would work?

[Berlin]

what about m42 flywheels

[AdironRider]

M42 flywheels are the heavist at almost 28 lbs. You can swap in a m20 flywheel/ clutch and modify the starter and you should be money.

[ACHTUNG]

I just had aprox. 5lbs removed from my flywheel. It weighs aprox. 13lbs now.

[Ali//325i]

Ya My flywheel comes in at 12 lbs exaclty and was balanced and resurfaced at the shop i took it to. I could have gone lower but he said he wanted to keep it streetable at 12. My car runs great and i never have to use the brakes around town. They sent me a dual mass flywheel when i ordered it and i ended up getting it lightened, balanced, and resurfaced for less than it cost to buy a brand new flywheel.

-Ali

[aTron12]

A little late here.. would you guys say that 15lbs is a good, safe weight to aim for? I am going to have this done next week since my flywheel is going to a machinist anyway.

[idanity]

12 is the sweet spot for steel flywheels.




and the disc side




lets also talk about minimum thickness

4cyl. engines
84-85 = 23.5mm (.925 in)

6 cyl. engines
1984 = 25.0 mm (.984 inches)
1985-1990 = 32.0mm (1.26o inches)

open the Bentley to section 4 and page 58 to see the "a-step" cut (flange height)


weight can be ultra light, but remember to consider the warping.
steel is more durable than alloy, but my rule of thumb (or writs) is
never machine a flywheel thinner than the pressure plate (which would be hard to do)

when they machine it, also request all edges be rounded out.
also ask about the flange height (if they know, bmw doesn't specify what would reduce pedal throw to the point of not ever releasing the disc, and to perfectly release it at its minimal throw)
this is where experience comes into play.

ask you local track.
luckily, when i brought mine in, i already asked around, called around,and when i deliverd the f.w. i found 5 different posters of e30s...
thats a score.

to add.
if you can afford it, have your p.plate balanced to your flywheel when its all done.
they will have to mark both f.w.and p.plate so you can re-align them when you install it. but its worth it.

have fun.

[idanity]

iwoops, didn't realize this thread was ressurected from almost 20000years ago.

[sweetride01]

Haha, it seems so.

I got mine taken down to about 12 pounds, it's great now. Revvs so quickly :-D

[aTron12]

Any negatives from going down to 12lbs? I have read that it is possible to throw one's idle off if the flywheel is shaved down too much. I'm thinking about going to 15lbs unless anyone thinks I should just go for lighter. I drive an '88 325is--daily driver. Thanks!

[sweetride01]

Yes, it does make the idle a little less predictable. In fact, with my Jim C chip and Schrick 284/272 cam, the idle is quite rough, and if I run with the AC on, the car can stall when I depress the clutch (the revs drop too quickly). But I'm sure that with a stock cam, this would not be a problem.

[aTron12]

That is helpful. So maybe I will stay at 15lbs in hopes of finding a good balance between performance and stability. I am running a stock cam...