E30 Zone

Hi can anyone tell me where i can get light weight fly wheels for an e30 318iS?? whats best way to go about it get my one lightened or are they better bought in.

You can lighten an M20 flywheel. Not sure if you also need an M20 clutch to? Think you'll need an M20 starter as well. JBRacing do a lightweight flywheel but they cost a bit http://www.jbracing.com/flywheel-bmw3.php

Most UK IS's were NOT fitted with the dual mass flywheel, you will most likely have the same one that is found on the m40 engines, these can be lightened, have a look in the traders section and get the link to vision racing developments website, they have a write up on there showing how they lightened the flywheel on their IS track project.

Better still the vision build thread.

http://www.e30zone.net/modules.php?name ... c&start=50

About half way down the page.

awesome thanks

It is a strange one. I think its the same with the catalytic converters, some markets had them and fitted some not.

has anyone lightened a e30 325i flywheel? or is it dual mass?

Lightened M20 flywheel, this is under 6kg and is fitted to my M52B28, IMO it is too light for a road car, heel and toe when approaching busy junctions is frowned upon

what i bought for my is


lightened m20 fly,sachs clutch with longer thrust bearing,m40 starter with m20 ring gear fitted.



makes a noticed improvement.

Whats the difference in height of both assemblies fragpie? Doesnt look much at all in that photo

as i understand it most 318iS have the dual fly, its only the very early 89 cars that had M40 ones

dan i never measured it but you need a different thrust bearing to make the clutch pedal sit where it's sposed to apparently,i think it's a 323i one but not sure.

si i've had a few m42's and none had dual fly,they all had m40 ones.
is the dual only on a/c types?

mine is a 91.

Nah, you dont 'need' one, ive always used standard M20 stuff and never had a problem with clutches, it will only be a slight difference anyway

oh i see,well it was inc in the sale so it would've been rude not to fit it

I haven't seen an iS with a dual-mass yet either, only "heard" of people saying there's had one.

I have a 5.9kg M20 flywheel in my car at the moment too... It's not too light at all as I love heel-and-toe anyway so it makes the car even more fun if I "have" to use it.

I used a 325i release bearing too... might put in a 323i one with the new gearbox though when I get the clutch back for it.

was your pedal any lower on the 325i bearing Dave?

When I drove Dafs car with the same flywheel/clutch and 323i bearing it felt the same, couldnt tell at all

DanThe wrote:Lightened M20 flywheel, this is under 6kg and is fitted to my M52B28, IMO it is too light for a road car, heel and toe when approaching busy junctions is frowned upon

Has any metal been taken off the clutch side?

On mine the clutch side just got a light skim, the rear didnt have as much removed as that but not far off.

It was one of Hongkongfuey's

I fitted an M50 JBR ally flywheel to my iS so in theory a normal M50 flywheel will fit without pissing about with starter gears like the M20 flywheel swap.

Mind you, i don't know what the standard M50 flywheels are like with regards to lightening them.

No difference in the clutch pedal as far as I have noticed Mick.


Standard M50 flywheels are dual-mass so that'll be the end to that.
I was going to use an S50 lightweight flywheel from BBB on my car which would mean I could use the M42 starter again but I just getting my old M3 clutch made into a paddle clutch rather than buying a new one and then a new flywheel and possibly still having problems with the clutch as it would be a solid flywheel with a solid clutch.

My fecking solenoid doesn't push out at times which just spins freely. Think I need to tighten the two screws in the body alittle more as at first I had them too tight and it was shooting out but not spinning after swapping the gear over from the M20 starter:roll:

mine sounds like a six pot on turn over


i'll await the abuse now

Funny... people often ask if my car is a 325 when ticking over too and then say, its surely more than 1.8

There's a world of difference between 6 and 4 pot engines, and their flywheel requirements.
A 6 pot can, in theory, be run at a couple of RPM without any flywheel fitted, whereas a 4 pot will just stop with two pistons at TDC and two at BDC after the first power stroke. There's the matter of all the nasty vibrations produced by a straight 4 as well!
The difference between a M40/42 flywheel and an M20 one (never seen dual mass versions either) is much greater than is suggested just by putting them on the scales. A large percentage of the mass of the M40/42 wheel is in the rim, where it has the greatest effect, where the M20 is approximately a uniform thickness all the way out.
A M20 flywheel on a 4 pot is light enough as it comes, IMHO.

True, an M42 flywheel is basically like an M20 fly but with a big dish all around the edge of it.

I know the 4 cylinder needs alot more momentum from a flywheel to carry it between strokes but to be honest, I don't care if the car is alittle less refined if it means the car becomes more responsive and ultimately more fun to drive.
Maybe some people would prefer the opposite and like a very smooth engine but if thats the case just buy a 320i.


However, my car having a heavy 6 speed gearbox... all the extra gears and bigger shafts along with that probably make up for a light flywheel

It's quite correct that all the clutch, shafts in the gearbox, and even the prop. are all part of the flywheel (when in higher gears, at least.)

This thread has inspired me to lighten my flywheel, I have a 325i M20, I also have access to a lathe... is this therefore somthing i can do my self? Has anyone had this done to their 325i?
I need to know which side to remove material off and the where abouts (i.e where shouldnt i). Previsouly there was mention of different release bearings, is this the case with this engine also?

If it goes well, I could offer this service to others.

i'm sure these things need balancing.

JasonR wrote:If it goes well, I could offer this service to others.

Someone's beaten you to it mate. Hongkongfuey (spelling?) already offers these at a pretty decent price.

i'm sure these things need balancing.

I have access to all the kit required to balance it as there is a full time engineer at my place of work. Spoke with an engineer today who has lightened a flywheel before so understand the principle now.

Once i pick up a spare flywheel i'll give it a go and keep you updated.

how do i get hold of this hong kong fuey???? anyone know what he charges??

treeseries wrote:how do i get hold of this hong kong fuey???? anyone know what he charges??

I can't remember exact figures, but it was sensible money we're talking about and on an exchange basis if I remember correctly.
PM him.

Think its only a 100 quid on exchange from him which is reasonable really.

I have my own lathe too and I just take lighten them to how much I want and then get them balanced later on if I just don't get somebody to do the whole job while I can do something else