Bushing/Mount Material & Brands

[TostitoBandito]

I'm starting to look into scoping out bushings and mounts to refresh my M3 with. My car is daily driven, but also tracked (HPDE) during the summer. It already has a Ground Control street/track suspension with 440/550 spring rates, to give you an idea of my current NVH tolerance level for street driving. It's stiff for sure, but not overly noisy or obnoxious IMO (just don't ask my wife). All my existing bushings are in ok shape as far as I can tell (none are falling apart), but are OEM/rubber with a few likely being original to the car.

Anyways, I'm looking into doing:

• Rear subframe
• Diff mounts
• FCAB's
• Trans mount
• Possibly motor mounts

I already have newish poly RTAB's and will soon have new poly sway bar and camber arm bushings (since they come with those items). Anything else obvious I'm missing?

Materials. Options include OEM/rubber, 70A, 80A, 95A, 75D/Delrin, and solid/aluminum. For my application, what are your opinions on what I should do? Should everything be the same, or should certain places be stiffer or softer than others? My inclination is that 75D or solid are probably not a good idea for a street car, but that I also probably want avoid the softer poly and do something like 95A to put up with track driving without deforming (if not using rubber).

Also, are there certain places where it pays to still use rubber even if I'm using poly elsewhere? I figure motor mounts might be one place where softer is probably better.

Lastly, what is the current brand preference for poly? AKG, UUC, Powerflex, etc...

Looking forward to everyone's thoughts.

Thanks!

[TheJordanWhitte]

In my experience finding something that is an OEM+ ends up being the best for a daily.

I would check out revshift, I have their motor and trans mounts and they're great for a little added stiffness and mostly better quality but they feel just like OEM.

[LockDots]

The harder anything is the less slop and cushion there will be in terms of noise vibration and shock.

Personally I'm going with AKG 95A bushings in the RTAB, Rear Subframe, Diff, and FCAB. Everything else I'm keeping OEM. All the ball joints and bushings I'm replacing are being swapped for Lemforder replacements including the Motor Mounts. The transmission are being slightly upgraded using E21 transmission mounts with aluminum cups. Should help stiffen up the driveline/transmission without adding significant NVH.

That being said most of the harsh NVH comes from the motor and transmission so choose your mounts wisely.

[rajicase]

I wouldn't use AKG subframe bushings they are horribly designed..

[LockDots]

I would have liked to see them with a metal sleeve but at the same time it allows the bushing to compress and nicely fill the "holder" and sit itself nicely against the body. I haven't had a chance to drive on them yet but I expect to retorque them and use some loctite on them to be safe.

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[mitch500]

I went with all oem rubber on my recent suspension rebuild. To much BS with poly that I've been digging up on the forums lately. Mine lasted 150k miles so might as well last another with the oem.

Like lots of people said, do you think the ltw was ripping around the ring with poly? Doubt it.


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[LockDots]

Also true, but it would also offset the cost of producing poly just for that variant.

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[TostitoBandito]

So from what I gather the AKG bushings lack the metal sleeve that the Powerflex and Revshift bushings seem to have? Does this make it more difficult to properly torque them or more likely for them to deform?

[LockDots]

So from what I gather the AKG bushings lack the metal sleeve that the Powerflex and Revshift bushings seem to have? Does this make it more difficult to properly torque them or more likely for them to deform?

That's a touchy question and the answers are fairly 50/50.

Some people say it's harder to torque, others say they torque fine after letting them settle in order to retorque. I know a handful of people who've tried them and love them so I'm giving them a shot. At this point I can have the diff and subframe out in an hour or two so if I end up wanting to change them it's not that big a deal for me.

[pbonsalb]

That's a touchy question and the answers are fairly 50/50.

Some people say it's harder to torque, others say they torque fine after letting them settle in order to retorque. I know a handful of people who've tried them and love them so I'm giving them a shot. At this point I can have the diff and subframe out in an hour or two so if I end up wanting to change them it's not that big a deal for me.

I have a set for my E90M3 waiting for me to install. Due to the lack of sleeve, the torque spec is lower than stock. Its on the AKG website. If you are compressing until a steel or aluminum sleeve contacts metal, then you are transmitting more noise. Probably not an issue, but I think that was AKG's idea. They do sleeve their diff bushings, but those are somewhat isolated by the subframe bushings at one end and the guibo at the other end.

[TostitoBandito]

I've decided on 95A Revshift bushings for the subframe, diff, and FCAB (already have poly RTAB). I'm gonna replace the engine and transmission mounts with OEM rubber. I'm also going to do all 8 ball joints on the car at the same time, so it should be a fun winter project. Will give me an excuse to do a bunch of other PITA things up front too, like drop the oil pan for a gasket/pump/nut/pickup/baffles, and maybe a UUC SSK and/or Z3/E46 steering rack as well.

[bigpuppy]

I know you've already decided, but, I've been running the Treehouse Racing FCABs for probably 6+ years without issue. I felt like they added some crispness to the steering without much increase in NVH. I installed them when I installed my Z3 steering rack so it's difficult to tell exactly which item did what but, turn in is definitely improved and the sublte shaking under braking is gone.

[TostitoBandito]

I know you've already decided, but, I've been running the Treehouse Racing FCABs for probably 6+ years without issue. I felt like they added some crispness to the steering without much increase in NVH. I installed them when I installed my Z3 steering rack so it's difficult to tell exactly which item did what but, turn in is definitely improved and the sublte shaking under braking is gone.

I assume you mean these:

https://store.vacmotorsports.com/tre...rms-p1927.aspx

Looks like a cool product/idea, but as far as I can tell they don't make them anymore. I'm curious what the benefit of these are over the standard lollipops with poly FCABs in them. These are also poly so the bushing feel should be similar to any poly FCAB, but I'm not sure what the different housing design does for the car.

[blckstrm]

I know you've decided on a course of action, but I'd consider where your "line" is and think about motor mounts.

I did Vorshlag motor and tranny mounts (the softer ones) and it definitely moved the car significantly down that NVH continuum between a street car and a race car. However, I can also say that motor mounts are the one thing that has had the single greatest impact on the feel of the car. Connecting that 330 lb hunk of iron firmly to the car (rather than using the "waterbed" approach) impacts both the power delivery and the handling feel to a surprising degree. Clutch uptake changes, you get a more direct feeling when shifting, more immediate response to throttle, and then the way handling changes for the better is also a surprisingly stark improvement from stock.

There have been more than a few changes that moved my car further down that slippery slope toward race car than I really wanted for the relative benefit they provide, but that was NOT one of them - I'd do it again tomorrow, and would honestly be the first thing I'd do on a new car.

[propcar]

information and feedback is all over the place.

I've heard comments that going all aluminum in the subframe is fine and causes minimal NVH increase. And then there's another side that will say that's insane.

[TostitoBandito]

information and feedback is all over the place.

I've heard comments that going all aluminum in the subframe is fine and causes minimal NVH increase. And then there's another side that will say that's insane.

From what I've gathered on this, NVH is tolerable if you go stiff/solid on the diff OR subframe but not both. The diff is the noisy part and it's double isolated with its own bushings inside the subframe which also has bushings. As long as there's some dampening in either the subframe or the diff bushings, that won't all be transmitted into the body.

I think this is why you see people running solid diff bushings who say it's ok and people running solid subframe bushings who say it's ok. I don't think any of them actually run solid in both places at once.

As for motor mounts, yeah it's definitely a slippery slope. My car rides significantly more aggressive than stock with its stiffer linear springs, but it's still pretty civilized as a daily driver. I don't want to push it to far over the edge. That said, I'll do some more reading on the poly motor/trans mounts. I still think I'll end up doing rubber, but if it makes a difference like you said then it's probably worth at least thinking about some more. What type of poly were those Vorshlag mounts, 80A or 95A? It looks like their current options are 95A or solid motor mounts and 80A, 95A, or solid trans mounts. Revshift also makes similar motor/trans mounts in both 80A and 95A.

[blckstrm]

From what I've gathered on this, NVH is tolerable if you go stiff/solid on the diff OR subframe but not both. The diff is the noisy part and it's double isolated with its own bushings inside the subframe which also has bushings. As long as there's some dampening in either the subframe or the diff bushings, that won't all be transmitted into the body.

I think this is why you see people running solid diff bushings who say it's ok and people running solid subframe bushings who say it's ok. I don't think any of them actually run solid in both places at once.

As for motor mounts, yeah it's definitely a slippery slope. My car rides significantly more aggressive than stock with its stiffer linear springs, but it's still pretty civilized as a daily driver. I don't want to push it to far over the edge. That said, I'll do some more reading on the poly motor/trans mounts. I still think I'll end up doing rubber, but if it makes a difference like you said then it's probably worth at least thinking about some more. What type of poly were those Vorshlag mounts, 80A or 95A? It looks like their current options are 95A or solid motor mounts and 80A, 95A, or solid trans mounts. Revshift also makes similar motor/trans mounts in both 80A and 95A.

Vorshlag recommends red motor (95) with orange tranny (80) mounts for something still street driven, and that's what I've got. I don't think you'd dislike it - I didn't feel like it was enough harsher to complain about, but my wife didn't like the change (though she wasn't driving, either). I will say I'd go back to a factory dual mass flywheel / clutch setup - the lightweight stuff is just too far across the line for me. But I'd do Vorshlag motor mounts the day I got a new car.

[propcar]

what LTW flywheel did you go with though?

[blckstrm]

what LTW flywheel did you go with though?

UUC / M5 combo. I may trade with a friend who has pullies and go back to stock on the flywheel.

[TostitoBandito]

I may have to give the poly mounts a try then.

The Vorshlag mounts are a fair bit spendier than the others I see (like twice as much). Revshift's look more or less the same except that they embed the metal end caps within the bushing material, supposedly to keep the ends from separating from the poly under load.

[NoLastName]

I've tried many different bushing materials in different places over the years. To qualify my input here, I have a low threshold for NVH on a street driven car. I like street cars to be smooth. An M3 with all new stock bushings feels awesome to me as a daily driver. Having said that, over 8 years my M3 has transitioned to 100% track duty with a full cage and full spherical bearings in the suspension. While I tolerate a lot of NVH on track I really, really hate it on the street.

So... I'm not a huge fan of poly where there needs to be a real mechanical pivoting motion. Over time it creaks and binds when asked to perform a hinge action over and over (like FCABs and RTABS). In short, poly IS NOT maintenance free when used for FCABs, RTABs or any suspension pivot. You'll have to periodically disassemble mechanical joints where poly is used to clean and re-lube them. And just because a poly bushing isn't creaking doesn't mean it isn't binding. Poly tends to be extremely high friction when the grease gets pushed out or washed out over time with street use (which does happen). On the other hand, I think poly is fine for static bushings like rear subframe and diff mounts or engine & transmission mounts where some vibration absorption is desirable but no mechanical movement is required.

If I were to build a dual duty car now based on my experience - to give ok track performance and not go overboard with street NVH I'd use:

• Stock dual mass flywheel and clutch (DMF actually makes a big difference in overall NVH on these cars, yet doesn't make a massive difference in lap times)
• Soft poly engine mounts
• Soft poly transmission mounts (with an isolated mount design, not straight bolt-through)
• Soft poly rear subframe bushings
• Stock OEM rubber diff mounts
• Stock OEM rubber RTABs with limiters
• Stock OEM rubber FCABs (this is a tough one because I notice a big difference in braking stability on track using delrin FCABs - but they can be clunky on street. I might actually use them on a street driven M3 though)
• Stock OEM rubber rear suspension bushings - except for OEM sealed spherical bearings where rear control arms attach to the trailing arms.
• Don't go too aggressive with camber plate design (I have GC race plates - while they're nice and solid for holding alignment the spherical bearings are too noisy for street use)

The biggest change in NVH that I always notice comes from transmission mounts. The more solid they are the more you'll hear and feel gearbox operation. There's some tradeoff there though, as you want to prevent money shift potential... it's a real possibility on track! Keeping the engine and transmission stable in cornering helps avoid that situation.

[propcar]

On the subject of FCAB, turner now has a greasable monoball FCAB. And there's a couple of RTAB's out there too.


https://www.ecstuning.com/b-turner-m...t/019891tms~a/

[pbonsalb]

Have you tried using an 850 rpm idle, raised in the tune, with the LTW flywheel? Have you tried a slightly lighter flywheel, like the one piece chromolly as opposed to the lighter one piece aluminum?

[blckstrm]

I've tried many different bushing materials in different places over the years. To qualify my input here, I have a low threshold for NVH on a street driven car. I like street cars to be smooth. An M3 with all new stock bushings feels awesome to me as a daily driver. Having said that, over 8 years my M3 has transitioned to 100% track duty with a full cage and full spherical bearings in the suspension. While I tolerate a lot of NVH on track I really, really hate it on the street.

So... I'm not a huge fan of poly where there needs to be a real mechanical pivoting motion. Over time it creaks and binds when asked to perform a hinge action over and over (like FCABs and RTABS). In short, poly IS NOT maintenance free when used for FCABs, RTABs or any suspension pivot. You'll have to periodically disassemble mechanical joints where poly is used to clean and re-lube them. And just because a poly bushing isn't creaking doesn't mean it isn't binding. Poly tends to be extremely high friction when the grease gets pushed out or washed out over time with street use (which does happen). On the other hand, I think poly is fine for static bushings like rear subframe and diff mounts or engine & transmission mounts where some vibration absorption is desirable but no mechanical movement is required.

If I were to build a dual duty car now based on my experience - to give ok track performance and not go overboard with street NVH I'd use:

• Stock dual mass flywheel and clutch (DMF actually makes a big difference in overall NVH on these cars, yet doesn't make a massive difference in lap times)
• Soft poly engine mounts
• Soft poly transmission mounts (with an isolated mount design, not straight bolt-through)
• Soft poly rear subframe bushings
• Stock OEM rubber diff mounts
• Stock OEM rubber RTABs with limiters
• Stock OEM rubber FCABs (this is a tough one because I notice a big difference in braking stability on track using delrin FCABs - but they can be clunky on street. I might actually use them on a street driven M3 though)
• Stock OEM rubber rear suspension bushings - except for OEM sealed spherical bearings where rear control arms attach to the trailing arms.
• Don't go too aggressive with camber plate design (I have GC race plates - while they're nice and solid for holding alignment the spherical bearings are too noisy for street use)

The biggest change in NVH that I always notice comes from transmission mounts. The more solid they are the more you'll hear and feel gearbox operation. There's some tradeoff there though, as you want to prevent money shift potential... it's a real possibility on track! Keeping the engine and transmission stable in cornering helps avoid that situation.

That's about exactly how I have my car set up, except for the flywheel (which I do feel crosses the line, so I'm in total agreement) and swapped hats vs camber plates (which will be a nice upgrade when I do them).

It's great around town and can hang at the track, even if it's not the fastest.