7 series bushings???

[ahlem]

I was addressing the shake at 45mph issue and found a receipt for installation of 7 series bushings in the front control arms about 75k miles ago. It appears that the control arms were replaced at that time. Will my Bavarian Auto replacement 5 series bushings conflict with this? Should I get 7 series bushings instead? There are adjustable camber plates and a Racing Dynamics sway bar under there.

[xspeedy]

You are probably referring to the thrust arms. The 7 series bushing is an "upgrade" to the thrust arm to extend service life as the thrust arm bushings are a weak spot in the front end. You can replace the bushings or you can actually order new new control arms with the 7 bushings pre-installed. BMW (bmaparts.com) has Lemfoerders (OEM) like this. The arms aren't terribly expensive. To answer the question, I think either bushing will fit the thrust arm, but the 7 version will last longer.

[BigKriss]

the m5 bush will last longer again and is the same shape as the other mentioned.

[632 Regal]

go M5 bushing and no need to worry of blowing them the first time you need to slam the brakes... dont ask, I know.

[xspeedy]

Is the M5 bushing really the way to go? I have heard that stronger bushings can be too hard and cause more burden on downtsream components causing other problems.

[BigKriss]

who told you this?


Is the M5 bushing really the way to go? I have heard that stronger bushings can be too hard and cause more burden on downtsream components causing other problems.

[xspeedy]

who told you this?

I don't recall now, as it has been a while. It was someone knowledgeable as I remember. It did make sense to me though, as the bushing is there to provide some absorption of the braking forces.

I guess the question is one of the purpose for the thrust arm bushings to begin with. Why wouldn't we just put rocks in there if harder is better. I'm guessing if we stiffen the bushes, the load must be carried forward to something else.

The M5 may have harder bushings, but maybe it has stronger downstream components as well to support them?

[BigKriss]

its your money and your call, but I would still purchase the m5 bushes. they are a harder rubber but still have gaps there for movement. the 7 series bushes are harder than the stock items, so if your worried about failure about other components why not just install the stock bushes again.

cheers


I don't recall now, as it has been a while. It was someone knowledgeable as I remember. It did make sense to me though, as the bushing is there to provide some absorption of the braking forces.

I guess the question is one of the purpose for the thrust arm bushings to begin with. Why wouldn't we just put rocks in there if harder is better. I'm guessing if we stiffen the bushes, the load must be carried forward to something else.

The M5 may have harder bushings, but maybe it has stronger downstream components as well to support them?

[xspeedy]

its your money and your call, but I would still purchase the m5 bushes. they are a harder rubber but still have gaps there for movement. the 7 series bushes are harder than the stock items, so if your worried about failure about other components why not just install the stock bushes again.

cheers

Thanks. I was asking about the M5 ones because when I did mine a year or so ago, the 7 ones seemed the popular choice, and BMA had the arms with them already pressed in. If the M5 ones are the popular upgrade and there are no issues, I'll do that when I'm done with these. I don't want to have to do that job again.

[xspeedy]

By odd coincidence, Mike Miller responded to a question in the new (March) issue of Roundel regarding bushing options for thrust arms on an E46.

He basically says to stay away from polyurethane bushings as they are too hard for the street. He also says that firmer bushings aren't really the answer as they are less compliant and more likely to break on poor roads like what we have in the US. Rather, larger bushings are better to offering longer life.