Rear subframe bushings & rear differential bushing/mounts

[Thunderguts]

Originally Posted by asbrr

I think I'd recommend you swallow the big one time labour cost and do full bushings if you're planning to keep the car a long time - otherwise it will always be in the back of your mind I feel. I've had 2 piece Whitelines in my car for over 100K kms and they are fine/no issues so far.

Yep, I'm looking at the 2-piece Whitelines on FCP right now and putting together a cart...

[MightyMouseTech]

Originally Posted by Thunderguts

So here's my bushing question: how do inserts rank in stiffness next to a replacement bushing?

So lets say you added Powerflex Black Race inserts to your stock bushings. How much softer is that then 2-piece Yellow street full poly bushings? There's still a lot of rubber in the stock bushings so I'm not sure how much difference a black insert makes over a yellow insert and how that compares to a replacement 2-piece bushing.

Is a stock bushing with a yellow street insert going to be stiffer than an M3 bushing?

I'm reevaluating my options. The inserts are cheap enough that I may try the black race inserts with the stock bushings. If I don't like them, I can always replace the full bushing later. For the other bushings, I think I prefer to go with the M3, especially the differential bushings.

I have tried both. My 135 has M3 bushings, my winter E90 has Whiteline inserts. The M3 bushings are definitely stiffer, and transmit LESS noise than the inserts.

[Thunderguts]

Originally Posted by MightyMouseTech

I have tried both. My 135 has M3 bushings, my winter E90 has Whiteline inserts. The M3 bushings are definitely stiffer, and transmit LESS noise than the inserts.

I'm going with my instincts and getting the M3 bushings. Most of the other options are just compromises for installation ease and I don't want to compromise. I plan to own the car for at least another 20 years so I want to get it right. I know they can be installed without completely removing the subframe and I aim to test that.

[PcarDefector]

Originally Posted by Thunderguts

Yep, I'm looking at the 2-piece Whitelines on FCP right now and putting together a cart...

LOL, I'm doing the same. Was going to get the kit and the RSF bushings (not just the inserts) but and I'm confused about what bushings to get. Whiteline seems to have alternate parts for the same bushing replacements.

[PcarDefector]

Originally Posted by asbrr

I think I'd recommend you swallow the big one time labour cost and do full bushings if you're planning to keep the car a long time - otherwise it will always be in the back of your mind I feel. I've had 2 piece Whitelines in my car for over 100K kms and they are fine/no issues so far.

That's about 10 hours of labor!

If you were to stagger the installation into 3 stages, which group of bushings would you do in each.

I'm trying to balance my budget on a mild track/street car build and have to balance the budget on other parts like wheels, tires, oil coolers, data acquisition, etc.

[PcarDefector]

Originally Posted by MightyMouseTech

I have tried both. My 135 has M3 bushings, my winter E90 has Whiteline inserts. The M3 bushings are definitely stiffer, and transmit LESS noise than the inserts.

When you refer to inserts, you're referring to one that ill the "void" and not the one below?

https://www.whiteline.com.au/product...DT917&sq=13853

[asbrr]

Originally Posted by PcarDefector

When you refer to inserts, you're referring to one that ill the "void" and not the one below?

https://www.whiteline.com.au/product...DT917&sq=13853

Correct - those are replacements, albeit 2 piece, but full replacements (it's the ones I have).

Inserts look like this:

https://www.whiteline.com.au/product...DT918&sq=13854

[Petro135]

I was just looking at these. Im going into the rear end doing some work soon, and was going to go with the m3 next to try. But these have me thinking.
https://www.fcpeuro.com/products/bmw...hoCzy0QAvD_BwE

[MightyMouseTech]

Originally Posted by PcarDefector

When you refer to inserts, you're referring to one that ill the "void" and not the one below?

https://www.whiteline.com.au/product...7&sq=13853

Correct.

[MightyMouseTech]

Originally Posted by Thunderguts

I'm going with my instincts and getting the M3 bushings. Most of the other options are just compromises for installation ease and I don't want to compromise. I plan to own the car for at least another 20 years so I want to get it right. I know they can be installed without completely removing the subframe and I aim to test that.

Yes, I was able to do mine without completely removing the subframe, just need to lower it enough to fit the tool above the bushings. Get the proper tool for pressing the bushings in and out will make it significantly easier.

[asbrr]

Originally Posted by PcarDefector

That's about 10 hours of labor!

If you were to stagger the installation into 3 stages, which group of bushings would you do in each.

I'm trying to balance my budget on a mild track/street car build and have to balance the budget on other parts like wheels, tires, oil coolers, data acquisition, etc.

It's a lot but my shop didn't charge me anywhere near that much. I pre-assembled the front struts, and the put them in along with the rear springs/shocks, new RSFBs, brake lines (since you're lowering the subframe a bit at the rear, you likely have to disconnect them so might as well swap em) and I think I was around 7 hours total IIRC...not small but it was all sorted in one shot.

[PcarDefector]

Originally Posted by asbrr

It's a lot but my shop didn't charge me anywhere near that much. I pre-assembled the front struts, and the put them in along with the rear springs/shocks, new RSFBs, brake lines (since you're lowering the subframe a bit at the rear, you likely have to disconnect them so might as well swap em) and I think I was around 7 hours total IIRC...not small but it was all sorted in one shot.

Thanks for the info.

Where did you get the work done and what was the rate? PM me the info if it's not appropriate here.

[TimCSquared]

The Whiteline Bushings are currently on sale for $100 at Prothane.

Just installed these. Love em.

https://www.prothanesuspensionparts.com/kdt917

[fast1eddy]

Originally Posted by TimCSquared

The Whiteline Bushings are currently on sale for $100 at Prothane.

Just installed these. Love em.

https://www.prothanesuspensionparts.com/kdt917

That's a smoking deal. I'd highly recommend these especially at that price.

[asbrr]

Originally Posted by TimCSquared

The Whiteline Bushings are currently on sale for $100 at Prothane.

Just installed these. Love em.

https://www.prothanesuspensionparts.com/kdt917

That is 100% a fantastic deal...anyone looking for RSFBs should jump on this, it's a steal!

[asbrr]

Originally Posted by PcarDefector

Thanks for the info.

Where did you get the work done and what was the rate? PM me the info if it's not appropriate here.

PM sent!

[gjm120]

Originally Posted by asbrr

That is 100% a fantastic deal...anyone looking for RSFBs should jump on this, it's a steal!

Ordered! Not sure when I'll get around to installing. Inserts have been in for only about 3,000 miles, but, couldn't resist.

[Thunderguts]

Ugh! This is a tough call. For $100 and a couple hours of installation it's a hard deal to pass up. I still want M3 bushings, but these are tempting for a year or so.

[gjm120]

Originally Posted by Thunderguts

Ugh! This is a tough call. For $100 and a couple hours of installation it's a hard deal to pass up. I still want M3 bushings, but these are tempting for a year or so.

Just curious why you think the M3 bushings are better (or why so much more expense better)?

I'll tell you my only reservation with solid bushings - will they put more stress on the subframe than it's designed to take? I feel the poly will have an ever so slight amount of give vs Al, but still more than rubber.

[Thunderguts]

Originally Posted by gjm120

Just curious why you think the M3 bushings are better (or why so much more expense better)?

I'll tell you my only reservation with solid bushings - will they put more stress on the subframe than it's designed to take? I feel the poly will have an ever so slight amount of give vs Al, but still more than rubber.

That's the kicker. M3 bushings are 4x the cost of Whiteline bushings on sale.

Two reasons I prefer the M3 bushings and neither one is based on any evidence.

1) I can't shake the idea that 2-piece poly bushings will eventually squeak and also wear out. This is based on old experience from the 90s.

2) In general BMW knows what it's doing. Parts may fail due to a bean counter's pfennig pinching, but their engineers are smart fellows. They designed the 1M and M3 suspensions to work as a complete system (granted not in our cars exactly). The subframe was designed with a certain amount of deflection built into it and all the trailing arms and control arm bushings are appropriately strengthened as well (another mod I will eventually make). If you remove all deflection from the subframe, all forces are then transferred to the smaller trailing arm and control arm bushings. That can't be good for them. On a smooth track, I wouldn't see a problem, but in the real world with potholes and other imperfections, I think it's better to go with what BMW intended as a high-performance suspension. I just think for a street car, as a whole, the suspension will work better with M3 bushings all around.

[tracer bullet]

Originally Posted by Thunderguts

1) I can't shake the idea that 2-piece poly bushings will eventually squeak and also wear out. This is based on old experience from the 90s.

Same here. "Window weld", inserts, other methods to fill motor mounts and so on all led to failure. Complete replacement was the only way to go.

That said, the 2 piece versions that have half the bushing above and half below, are interesting. But supposedly* the M3's can be put in w/out totally dropping the subframe, so that feature (top & bottom halves) perhaps isn't a big deal after all.

* I had my local indy specialist do it. I'm generally a DIY'er but w/ a little kid and no time I was not getting into this one.

[Petro135]

Originally Posted by Thunderguts

Ugh! This is a tough call. For $100 and a couple hours of installation it's a hard deal to pass up. I still want M3 bushings, but these are tempting for a year or so.

I was also going to either go m3 or solid rsfb to replace my inserts. But for $100 i ordered these. Cant beat that deal!!!!