Sprung clutch disc for 6 speed conversion??

[IainP]

I think I had something bookmarked on my old phone, it’s not transferred and can’t find the answer with search with search.
I’m changing to a lightweight flywheel later in the year, from the blurb I need an M3 cover.
Also changing to six speed, obviously different splines, I’m pretty sure I saw someone do the same and sourced a sprung center clutch disc. Stupidly (there’s a surprise), I forgot to note the the source, or make/type of disc.
Would anyone be able to enlighten me, or point me in the direction of the relevant thread?
Cheers

 

[Dino D]

I was wanting to do a lighter fly wheel but ended up with a single mass but the same weight which I think was 8kg.

I got it from these guys https://rtsperformance.co.uk/

they do not do lightweight flywheels for 6 cyl BMW as they’ve seen to many problems with damages to gearbox and drivetrain- they strongly advised against it.

that and the fact that their kit was about £400 ish vs many more £££ for the light weight swung it for me.

they make the parts locally so if you already have a flywheel I guess they could sort you out a clutch.

The M50 manifold, M3 headers (exhaust manifolds), 200cell cat and full exhaust and vicious fan delete and remap mean my single vanos revs up really well now.
Would love to try a light flywheel but bottled it when I heard what they said.

are you doing it to a 6cyl or 4cyl ?

 

[Pingu]

Damage to the gearbox and transmission is caused by fitting single mass flywheels and being too harsh when using the clutch. The dual mass flywheel absorbs the rotational vibrations. If you are not mechanically sympathetic, and you engage the clutch too fiercely, the gearbox will "snatch" and be damaged.

I have a lightened single mass flywheel and the only problem is the gearbox chatters. This will reduce the life of the gearbox, but I think the increased performance is worth it.

Despite thinking that a six cylinder engine revving at 1000 rpm is actually doing a constant speed, it is actually being "kicked" 50 times a second. It slows down between kicks. It is this constant kicking that causes the chatter.

The weight of a lightened clutch is irrelevant. The important thing is where that weight is positioned. Google "mass moment of inertia" for an explanation. A lightened flywheel has more mass at the centre compared to a standard flywheel, even though they may both weigh the same.

I don't know why you would need a different cover, other than to fit the six speed gearbox. I'm pretty sure the six speed box is longer, so you will need a shorter propshaft. I wouldn't just get a flywheel. I'd get a flywheel kit consisting of a flywheel, cover, clutch friction plate and release bearing. You will also get a pilot bearing in the kit, but I've never changed one. I would also change the release arm and convert the clutch slave cylinder rubber hose to a stainless steel braided hose.

A dual mass setup has an unsprung friction plate. You must not use this friction plate on a single mass setup. The only rotational absorption in a single mass setup are the springs in the friction plate.

 

[Lee]

I think I had something bookmarked on my old phone, it’s not transferred and can’t find the answer with search with search.
I’m changing to a lightweight flywheel later in the year, from the blurb I need an M3 cover.
Also changing to six speed, obviously different splines, I’m pretty sure I saw someone do the same and sourced a sprung center clutch disc. Stupidly (there’s a surprise), I forgot to note the the source, or make/type of disc.
Would anyone be able to enlighten me, or point me in the direction of the relevant thread?
Cheers

You'll be looking for Dino's build thread where we converted his 2.8 to a 6 speed. Gearbox was 110mm longer so we had the prop shaft shortened, and shortened the linkages for the gear selector aswell. Good memory you'll need to move up to a 22 spline disc.

#ZedShed - Dino’s Track toy 2.8 (6-Speed Gearbox Conversion) | BMW Z1 Z4 Z8 Z3 Forum and Technical Database - ZRoadster.org

 

[Delk]

Has anyone actually had issues with the gearboxes from lightened single mass flywheels or is it just rumours from someone trying to sell thier product?

Reason I ask is there are a whole raft of people running these set ups in E36 and E46 cars and I have never heard anything about it from them.

I ran a lightened flywheel with sprung disc for years without issue. Now I have a twin disc clutch from Hopwood to handle the power and mate up a 6 speed from an E46. The twin disc clutch is inherently not light but its also single mass with unsprung discs.

 

[Andyboy]

It's nonsense.

Every E36 325i built - apart from very early 1991cars - had not only a single mass flywheel but the same Getrag 250G gearbox was used in the 316i, 318i and 320i. Early ones used the bigger ZF box as used later on in the 328i, Z3 2.8 etc. I've never heard of one breaking.

You can break anything if you put your mind to it but realistically, it's not going to happen.

 

[Pingu]

Has anyone actually had issues with the gearboxes from lightened single mass flywheels or is it just rumours from someone trying to sell thier product?

Reason I ask is there are a whole raft of people running these set ups in E36 and E46 cars and I have never heard anything about it from them.

I ran a lightened flywheel with sprung disc for years without issue. Now I have a twin disc clutch from Hopwood to handle the power and mate up a 6 speed from an E46. The twin disc clutch is inherently not light but its also single mass with unsprung discs.

The problem is the noise (chatter). As said, you can break anything. If you just dump the clutch, you can break the gearbox, whereas a dual mass flywheel would probably protect the 'box.

As I said earlier, the weight of the clutch is irrelevant. An F1 clutch pack is like a bean can, compared to a Z3 clutch that is like a pancake. The F1 pack is probably heavier to lift, but will have a much smaller mass moment of inertia.

The flywheel has three purposes. It absorbs engine vibrations, transfers rotation from the engine via the clutch plate to the gearbox, and it holds the teeth the starter motor engages. The less material between the edge of the clutch plate and the starter ring, the better.

The cover just holds the clutch friction plate to the flywheel.

This is from when I fitted my lightened clutch...

Lightweight flywheel & shift pins - w/ Feedback + Video - zroadster.net

www.zroadster.net

There's also this nice little gif on Wikipedia (they all weigh the same, the one closest to the camera has most of its mass in the centre)...

 

[Delk]

Fully understand dumping the clutch and destroying things. Dual mass flywheels are made more to reduce in car vibration and make life more plush.

Not many people are harder on gear boxes then the boosted drift crowd. They don't like the smaller getrag in the 3 series as it fails more often. The ZF holds up well and they put a lot of abuse into them. I don't know of anyone who has broken a box without abusing them really badly.

 

[Lee]

Agree with what Andy says above, fitted many single mass flywheels with no issues.

Also fitted quite a few to zeds including my own.