Rear Sub Frame Bushings Advice

[hunginator]

Hello,

I've been hearing a lot of mentions about how the RSFB should be one of the first 'mods' to make on our cars. I don't know too much about these things. I tried to do a search in the suspension forums and couldn't find anything.

What is the benefit of upgrading the RSFB and which ones should I get?

My 135i is my daily driver but I also like to drive spiritedly when I get the chance or when I come across a nice twisty road.

My car will see the track maybe once or twice a year.

Thanks in advance!

[desertman123]

My car might not ever see the track and I benefited from the RSFB upgrade.

The stock bushings have a lot of voids in them, and in turn this makes the rear end a bit sloppy. When you go over a bump, the front feels fine but the rear just feels vague. Also on cambered roads I noticed it shifts side to side a bit.

Depends how much you wanna spend. The Whiteline inserts solved my issues for daily driving, and they were $40 and installed in an afternoon with no special tools. Powerflex also makes some inserts.

If you really wanna solve the issue, you can get M3 bushings, but you'll need the bushing tool and the parts are more expensive.

Personally, I'd save the cash and just get the inserts if its not gonna see much track time.

[John_01]

If you car is only used for daily driving the upgrade is still worthwhile.
It makes the cars steering more precise. Even when driving very gently, there is still an effect where the stock subframe bushings will deform and steer the rear of the car due to any small loading. The rear steering effect partially stays in that position until the car hits a bump then straightens up a bit more.

If you push the car around corners, I found the stock subframe bushings make the car seriously unpredictable and loose and its actually unsafe IMO. Braking stability is also affected, which is especially bad if you use the car on a track.

[hunginator]

Thanks for the advice. In that case, how much of my daily driving comfort would be compromised with installing 'upgraded' RSFB?

And on another note, as my car is completely bone stock, are there any other suspension upgrades that 'should've been like this from factory' I should look into?

I noticed under spirited driving at certain corners, that the 135's factory suspension setup is set to understeer BIG TIME. In some corners, the car juts PLOWS!

[f87CSdrifterential]

N55 6MT FBO 80k
non run flats (Michelin PSS)
never track the car
OEM M Sport shocks & springs

I recently installed (2 weeks ago) WhiteLine inserts along with F&R 1M arms/ECS sway bars & trailing arms/UUC tranny mounts. Obviously I can't pin point exactly what made the most impact to the handling, but prior to the install my concerns were the snap back when stepping the rear out around a corner, the squishy non run flat roll into corners, and the squirrelly rear end under hard acceleration.

While I have only put a few hundred miles on the car, I can feel a huge improvement in all areas. I feel like I have gained horsepower because it is making it completely to the ground now instead of getting lost in the loose rear. Everything feels much tighter and I am pleased with the results, much more redefined and "on rails". I eagerly await coil overs as my next suspension upgrade.

[John_01]

Originally Posted by hunginator

Thanks for the advice. In that case, how much of my daily driving comfort would be compromised with installing 'upgraded' RSFB?

And on another note, as my car is completely bone stock, are there any other suspension upgrades that 'should've been like this from factory' I should look into?

I noticed under spirited driving at certain corners, that the 135's factory suspension setup is set to understeer BIG TIME. In some corners, the car juts PLOWS!

My E82 and E90 have both been upgraded M3 rear sub frame bushings. For a completely stock car there is a small increase in harshness from installing these. Especially when the rubber is freshly installed and not broken in. If you have any other suspension mods or changes on the car already, you probably won't experience any downside or loss of ride quality caused by the subframe bushings alone as the difference from stock is not very big. I can't say about the 2-piece polyurethane bushings, but that is something you can investigate.

M3 front arms and tension struts are a popular upgrade which improves front end grip because it adds negative camber. You can search the forums for more info. Its also quite common for people to upgrade springs and dampers. If you are getting the bushings installed by a shop, you should do any other suspension install such as rear springs and dampers at the same time. The car will need wheel alignment afterwards too.

If you are looking at a street oriented setup to achieve both comfort and handling, then a Front sway bar upgrade is quite useful. There's countless threads about this on the forum.

[f87CSdrifterential]

This is a great thread about installing the inserts and some feed back.

http://www.1addicts.com/forums/showthread.php?t=875885


Down the road when I have done all other performance mods (coil overs/clutch/LWFW/Turbo) I will most likely do the M3 bushings.

[desertman123]

Originally Posted by hunginator

Thanks for the advice. In that case, how much of my daily driving comfort would be compromised with installing 'upgraded' RSFB?

And on another note, as my car is completely bone stock, are there any other suspension upgrades that 'should've been like this from factory' I should look into?

I noticed under spirited driving at certain corners, that the 135's factory suspension setup is set to understeer BIG TIME. In some corners, the car juts PLOWS!

Next to no NVH increase. The feeling over bumps doesn't increase, it just becomes more defined. Check out the camber alignment pin delete. Super simple and it improves turn in a little bit. That IMO is how the whole car should've been from the factory.

[vtl]

I've got Nolathane 49202 bushings in my car which are identical to the Whiteline KDT917 (both owned by the same company)

Heres a thread on my impressions and DIY:
http://www.1addicts.com/forums/showthread.php?t=1158856

Forget the inserts, do the job properly and install the replacement ones, I believe the inserts make the stock bushings thicker and the subframe is mounted further from the body as well.

NVH does increase and is pretty harsh on runflats. Normal tyres it'll be completely fine.

[desertman123]

Originally Posted by vtl

I've got Nolathane 49202 bushings in my car which are identical to the Whiteline KDT917 (both owned by the same company)

Heres a thread on my impressions and DIY:
http://www.1addicts.com/forums/showthread.php?t=1158856

Forget the inserts, do the job properly and install the replacement ones, I believe the inserts make the stock bushings thicker and the subframe is mounted further from the body as well.

NVH does increase and is pretty harsh on runflats. Normal tyres it'll be completely fine.

On a 128 I'd say the inserts are fine but I imagine the 135 guys would benefit a bit more, with how much more torque is put through the chassis. That looks like a pretty easy job too, but what's stopping you from drilling a hole thru the old bushing and cutting it out?

[MightyMouseTech]

They make a HUGE difference. No downside at all IMHO.

The original bushings are as stiff as marshmallow.

[asbrr]

Another thought on the comfort side of things as that seems to be a concern - part of the reason BMW went with these crappy bushings is to try and soften the blow the run flat tires introduce due to the stiff sidewalls.

So if you were to upgrade your subframe bushings (I also recommend replacing the entire bushing rather than just doing the inserts), replace the run-flats while you're at it. You will actually have IMPROVEMENT in ride comfort from the run flat change, and any small NVH increase from the subframe bushings (it's very small if any) will be negated by that change also.

Short answer, do it, and get rid of the run flats while you're at it, then enjoy.

[hunginator]

Thanks everyone. This answers all of my questions. Will be buying some new bushings

[houtan]

Originally Posted by vtl

I've got Nolathane 49202 bushings in my car which are identical to the Whiteline KDT917 (both owned by the same company)

Heres a thread on my impressions and DIY:
http://www.1addicts.com/forums/showthread.php?t=1158856

Forget the inserts, do the job properly and install the replacement ones, I believe the inserts make the stock bushings thicker and the subframe is mounted further from the body as well.

NVH does increase and is pretty harsh on runflats. Normal tyres it'll be completely fine.

+1. The work between inserts and the whiteline or nolathane is very similar since they are split into 2. I would rent the tool from hpa and do the job once.

[slonik]

we use aluminum solid bushes on a lot of cars (e8x/e9x), most of them everyday use.

[vtl]

Originally Posted by desertman123

On a 128 I'd say the inserts are fine but I imagine the 135 guys would benefit a bit more, with how much more torque is put through the chassis. That looks like a pretty easy job too, but what's stopping you from drilling a hole thru the old bushing and cutting it out?

Drilling/cutting it out i've never tried, pulling it out with a tool is pretty quick work with an impact gun, takes about 30 seconds or so to draw out the bushing if everything goes well and nothing breaks.

Might be possible with a reciprocating saw but the rubber is so stubborn I wouldn't want to try it.

[dbronnik]

Originally Posted by hunginator

Thanks everyone. This answers all of my questions. Will be buying some new bushings

Originally Posted by slonik

we use aluminum solid bushes on a lot of cars (e8x/e9x), most of them everyday use.

+1 on using solid bushings, no increase in NVH. I used delrin/aluminum ones from Alekshop: http://alekshop.com/products/aleksho...ngs_bmw_e9x_m3

[bNks334]

Just did the bushings. I used the Whiteline KDT917 kit. They are definitely an upgrade over the M3 bushings and they are cheaper. #1 improvement is that when I hit bumps while turning the rear no longer bounces around. It's a nice subtle improvement all around in handling.

Forget renting a $200 tool. Go to harborfreight and buy a propane torch for $14. A tank of gas costs ~$4. Lower the subframe half way at all 4 corners. Then work one corner at a time lowering each corner completely and then re-installing as you go (this prevents the subframe from shifting). It took me HOURS to get lined back up since I mistakenly took out all 4 bushings. At least leave both rear partially threaded while you do the fronts and vice versa.

Place a large socket between the bushing and the car. Jack the car up as close to that bushing as possible and let the weight of the car push the bushing out. Some extra weight in the trunk helps. This is where the torch helps as well. Use a medium flame to slowly (2-3minutes) heat the metal sleeve. Use some tinfoil to protect vulnerable pieces of your car. The bushing will start sliding right out with 0 effort! It works.

[Dackelone]

Dackel's replacement of rear suspension OE bushings with M3 ones…
http://www.1addicts.com/forums/showt...frame+bushings


I would go with the 1M/M3 bushings(RSFB). They really do not ride much harsher than stock bushings. But they do not allow the rear axle to move around like the OE bushings do. Gone forever will be that rubber band effect when you get on the gas in a corner!

I am still VERY HAPPY with my M3 bushings. Our cars should have come with it!! The ride is great, yet the control is there when you throw the car into a turn or drive at high speeds. I really like them.

The best way I can describe the difference is you will no longer feel like the rear end is held in place with rubber bands. When you drive down the road and run over a manhole cover... you won't have to counter steer as you run over the manhole cover. Its really worth the time and money!!

Dackel

[SkullV]

My 135i will never see anything but the street so I went with the inserts as they were cheap and easy. No regrets at all. If I was going to track the car I would have gone with solid aluminum bushings, but I have other toys for that .

[dojk]

Hi,
What do you mean the subframe has to be aligned?
How do I know it's aligned?

Thanks.

Originally Posted by bNks334

Just did the bushings. I used the Whiteline KDT917 kit. They are definitely an upgrade over the M3 bushings and they are cheaper. #1 improvement is that when I hit bumps while turning the rear no longer bounces around. It's a nice subtle improvement all around in handling.

Forget renting a $200 tool. Go to harborfreight and buy a propane torch for $14. A tank of gas costs ~$4. Lower the subframe half way at all 4 corners. Then work one corner at a time lowering each corner completely and then re-installing as you go (this prevents the subframe from shifting). It took me HOURS to get lined back up since I mistakenly took out all 4 bushings. At least leave both rear partially threaded while you do the fronts and vice versa.

Place a large socket between the bushing and the car. Jack the car up as close to that bushing as possible and let the weight of the car push the bushing out. Some extra weight in the trunk helps. This is where the torch helps as well. Use a medium flame to slowly (2-3minutes) heat the metal sleeve. Use some tinfoil to protect vulnerable pieces of your car. The bushing will start sliding right out with 0 effort! It works.

[houtan]

Originally Posted by dojk

Hi,
What do you mean the subframe has to be aligned?
How do I know it's aligned?

Thanks.

No it doesn't. When you reinstall and tighten the subframe bolts, there are pieces that will guide it to the original position. You will see once you remove it.

Old but really good thread with install tips throughout: http://www.1addicts.com/forums/showt...=802595&page=2