Dual Mass or Single Mass Flywheel

[Casa de Mesa]

Appreciate the insight and perspectives.

Are these dual mass flywheels a failure prone point on the S54? What kind of mileage are people getting from them?

I ask because my E36 M3 (sold) I replaced the clutch at 155k, flywheel was still original. On a racecar, I got 5 seasons out of a 7.25" Quarter Master sintered iron race clutch and aluminum flywheel. That included standing starts, loading on a open car hauler (no winch), extended crawling times through the pits, tech, etc. It finally got overhauled due to a really badly leaking rear main seal but was was otherwise fine.

My point - I'm easy on equipment, this car being no different. I've owned this car for ~40k of its 74k miles. The clutch shit the bed because of the flywheel I'm nearly certain - outer edge wear pattern on the friction material, irregular wear pattern on the flywheel friction surface.

So it has me wanting to simplify a tad. I also don't love the engagement of the dual mass / SAF combo (vague) and reducing rotational weight is huge (up to a point, I know it will introduce other issues if taken too far). Hence my questions around the DMF and my lean towards a SMF.

If that video above is as loud as an SMF on our cars will get, I'm sold. Listened to a few others on the YTub, not bad at all.

[SteelGreyM]

Appreciate the insight and perspectives.

Are these dual mass flywheels a failure prone point on the S54? What kind of mileage are people getting from them?

I ask because my E36 M3 (sold) I replaced the clutch at 155k, flywheel was still original. On a racecar, I got 5 seasons out of a 7.25" Quarter Master sintered iron race clutch and aluminum flywheel. That included standing starts, loading on a open car hauler (no winch), extended crawling times through the pits, tech, etc. It finally got overhauled due to a really badly leaking rear main seal but was was otherwise fine.

My point - I'm easy on equipment, this car being no different. I've owned this car for ~40k of its 74k miles. The clutch shit the bed because of the flywheel I'm nearly certain - outer edge wear pattern on the friction material, irregular wear pattern on the flywheel friction surface.

So it has me wanting to simplify a tad. I also don't love the engagement of the dual mass / SAF combo (vague) and reducing rotational weight is huge (up to a point, I know it will introduce other issues if taken too far). Hence my questions around the DMF and my lean towards a SMF.

If that video above is as loud as an SMF on our cars will get, I'm sold. Listened to a few others on the YTub, not bad at all.

Flywheel should definitely not be wearing before the clutch. Actually the clutch is quite a strong part on these cars. Stock clutch can take well more than 100k+ miles of real abuse

[mrgizmo04]

Whatever you do just make sure either your clutch or flywheel is sprung. If neither a sprung something will break. Believe me I broke shit 2 times before realizing my mistake.

I had solid single mass flywheel with stock clutch and pressure plate. No springs in the setup. Snapped 2 pressure plates!

Yep, something needs to be sprung. Sean just broke his pp at Laguna a few weeks ago and went back to dmf.

https://youtu.be/8YPgO4lzQXc

Sent from my SM-G950U using Tapatalk

[jbfrancis3]

Whatever you do just make sure either your clutch or flywheel is sprung. If neither a sprung something will break. Believe me I broke shit 2 times before realizing my mistake.

I had solid single mass flywheel with stock clutch and pressure plate. No springs in the setup. Snapped 2 pressure plates!

To be clear, either the flywheel or the clutch disk needs to be sprung. Then for the pressure plate, what you often get is unit that eliminates the SAC (self-adjusting clutch) mechanism and folks say this yields more direct engagement.

Certainly never hurts to check or ask the question but a full SMF kit from a reputable name will include a sprung pressure plate. I can see how someone piecing together different setups could create a system where nothing is sprung resulting in damage.

[lapoune]

Have the steel rogue\jb racing on one of my cars and it's annoying at idle, once the car is warm, you have ac on, it's by far the dominant sound coming out of the car. Does make for quick rev-matches though.

I would also be wary of vibration. People point at the porsche GT cars a lot as an oem application but the cars they put the single mass flywheel on are known to have vibration issues (bolts backing out, stuff cracking from vibration). Following generations after the 997 have dual mass flywheels, with special exceptions. For the newest iteration they lightened the dual mass but still didn't go single mass, and you kind of get the best of both worlds.

IMO you need a properly tuned dampener to go with it and be watchful of vibration problems (accelerated bearing wear, vanos bolts etc).

[Mr.wReckless]

Having installed a JB Racing LWFW and Sachs sprung clutch and pressure plate with my manual conversion last year:

I tried both OEM oil and the Redline rattle fix. The redline helped a little, but it still rattles, but now the gearbox isn't the nicest shifting, especially when cold. The rattle in that linked video isn't really giving you the whole picture IMO. To my ears the video suffers a bit from poor audio and I don't think the idle rattle is the worst bit about the SMF, you can just clutch in and the rattle will disappear. The worst of the rattle is when you engine brake in 2nd gear. It really doesn't sound nice at all. If NVH is important then I wouldn't recommend a LWFW, there's no way around the rattle.

That being said, my car is an event/sunday car and not a daily, and it's really nice to drive with the SMF. But if it's your daily I can't recommend a SMF to be honest.

Regards

[Casa de Mesa]

Thanks again for the further replies. This is exactly the kind of feedback I was hoping for and appreciate the detailed responses.

For those of you that have the RE Steel ( jbfrancis3, lapoune ), how long have you had the setup on the car? The vibration issues rattling other stuff loose, is that really a thing with the steel flywheel (opposed to alu)?

I'm leery to put a dual mass back in only for the fact that this one last 74k miles. And for the last 5-8k miles, it's shifted like crap. Plus I have never liked the engagement of the stock setup, and I've already removed that fitting thing on the clutch line (name escapes me at the moment...). Perhaps the balance I'm looking for is a stock DMF with a non-SAF clutch. Like the Sachs performance clutch.

But having driven cars with lightweight flywheels, it's such a different experience. It's like changing from a stock seat to a race shell - it completely changes the dynamics/experience of the car.

However... I'm not willing to sacrifice durability. It's the primary reason for me looking away from the DMF to a single chunk of mass. While this car isn't a daily, and I don't mind some NVH, it don't want to replicate the mess I created with solid diff bushing. That kind of NVH is terrible, those things are coming out.

[lapoune]

Not long enough to form a conclusion. Also not a street car which should help keep it out of the range these harmonics are usually present. Was extrapolating based on experience with other platforms (which could very well not apply here).

Assuming the pairing is fine in this case, to me it still wouldn't be worth it on a street car, too noisy for very little gains.

[Arith2]

Strangely enough, my JB aluminum flywheel doesn't vibrate at idle. It only vibrates between 1k and 2k rpm. With stock bushings everywhere, I could barely tell it was there. Now I have solid subframe bushings and poly diff bushings. I hear it through my diff for sure. There is chatter on decel as well.

[digger]

best bet for a SMF is an OEM cast iron flywheel from early M5 or similar as im sure it could be adapted. Could keep full weight or give it a small diet.

[Mr.wReckless]

Thanks again for the further replies. This is exactly the kind of feedback I was hoping for and appreciate the detailed responses.

For those of you that have the RE Steel ( jbfrancis3, lapoune ), how long have you had the setup on the car? The vibration issues rattling other stuff loose, is that really a thing with the steel flywheel (opposed to alu)?

I'm leery to put a dual mass back in only for the fact that this one last 74k miles. And for the last 5-8k miles, it's shifted like crap. Plus I have never liked the engagement of the stock setup, and I've already removed that fitting thing on the clutch line (name escapes me at the moment...). Perhaps the balance I'm looking for is a stock DMF with a non-SAF clutch. Like the Sachs performance clutch.

But having driven cars with lightweight flywheels, it's such a different experience. It's like changing from a stock seat to a race shell - it completely changes the dynamics/experience of the car.

However... I'm not willing to sacrifice durability. It's the primary reason for me looking away from the DMF to a single chunk of mass. While this car isn't a daily, and I don't mind some NVH, it don't want to replicate the mess I created with solid diff bushing. That kind of NVH is terrible, those things are coming out.

IMO the SMF doesn't make noise all the time like solid bushings in the subframe would. It chatters a bit at idle, though you can change the idle speed and get rid of the worst of it, or just clutch in and get rid of all the idle chatter whilst holding the clutch pedal. The main noise and rattle from the SMF happens (for me at least) whilst engine braking in 2nd gear, otherwise the noise and rattle isn't that noticeable, normal cruising etc IMO there's no more noise than a DMF.

That being said I haven't heard of DMF's regularly failing, it's 2 pieces so of course there is the chance of wear and tear to get the better of it, but unless you abuse the clutch pack or get unlucky with a lemon DMF then I don't see how it would fail within the first 100k sensibly driven miles.

Regards

[oceansize]

IMO the SMF doesn't make noise all the time like solid bushings in the subframe would.

Solid subframe bushings don't make any appreciable noise and the majority of us have moved to solid subframe (and rtab) bushings for this reason, however solid diff bushings will noticeably increase diff whine within the cabin all day every day.

[Syfon]

Found this. Is this pretty representative of the sound?

https://youtu.be/5T82OHRbB1o

If so, that's COMPLETELY liveable. For me, that's not bad NVH.

Here you go. Video of the rattle in macca's drivethru.

https://www.youtube.com/watch?v=R71mMKJg0GU&ab_channel=Syfon

[Mr.wReckless]

Solid subframe bushings don't make any appreciable noise and the majority of us have moved to solid subframe (and rtab) bushings for this reason, however solid diff bushings will noticeably increase diff whine within the cabin all day every day.

Thanks, think I meant solid bushes for the diff in my comparison.

Regards

[Casa de Mesa]

Here you go. Video of the rattle in macca's drivethru.

https://www.youtube.com/watch?v=R71m..._channel=Syfon

Thanks for that very much. That's louder than the first vid I linked. You have a sprung clutch?

EDIT: the answer is yes.

In reply to what clutch to pair with JB Racing Aluminium Lightweight Flyhweel - Phill @ Bimmerworld recommended the Clutchmasters FX100 (Sprung Hub). This is what I'll be installing.