Anti-sway - No way

[mjfeeney4]

Recently replaced the front swaybar links on my 91 525i, to correct a "thunk" whan going over bumps. The thunk noise is gone and the front suspension seems OK.

Now I'm noticing a sway which is not really bad, but anyonying especially at speeds above 50 MPH. Suspect that the subframe mounts are shot, but not sure that this would cause a swaying feeling. Springs are original ( 161Kmi) and struts are 5 years old and have about 60Kmi. Any suggestions?

[George M]

If you are referring to rear sub frame bushings being shot...not a big contributor to swaying. Aside from sway bars and modest contribution due to spring rate...the shocks on your car are a major factor. Would say that stock shocks typically will go about 80k miles on these cars prior to replacement...some run them to over 100k miles....so you are getting close if you want ideal performance. Other thing you can do is opt for thicker sway bars front and rear...at some compromise to ride quality...but not as much as opting for stouter shocks to control sway in corners.
HTH,
George

[Bill R.]

thing that he's referring to swaying back and forth as he drives down the road.... Kind of like accerating with a 500hp 2500lb car on a wet road... where the rear end wants to move from side to side... If the subframe bushings are gone it will want to do this causing you to make steering corrections more often than not.. It makes it feel like you punched it on a dirt road with bald tires...only not quite that exagerated. If you ever drove a muscle car with a broken leaf spring mount you'll know the feeling.. Thats the first thing i would look at is the subframe mounts just to see if they are shot.... If he's talking about sway as in body roll going around corners then I'm all wet..

If you are referring to rear sub frame bushings being shot...not a big contributor to swaying. Aside from sway bars and modest contribution due to spring rate...the shocks on your car are a major factor. Would say that stock shocks typically will go about 80k miles on these cars prior to replacement...some run them to over 100k miles....so you are getting close if you want ideal performance. Other thing you can do is opt for thicker sway bars front and rear...at some compromise to ride quality...but not as much as opting for stouter shocks to control sway in corners.
HTH,
George

[632 Regal]

George, there has been mention on here about the different part numbers on the sways such as the alloys being used while the diameters stay the same.

Would you know of a way to find out which are worth swapping into out cars to stiffen the corners?

Seems like a mystery to me and I havent found any sort of ratings on the different sways.

[black_bird_blue]

There's a bit of a problem here with terminology; one man's sway is another man's wander is another man's weave is another man's....

If you can't feel the car running out of travel when you run it over some large, long undulations and it doesn't skitter wide if you corner over a rippled surface, your dampers are probably fine. Forget the idea of bouncing the corner of the car to see if the dampers work, you can't put enough force in and it only tests one speed.

My experience with wandering cars is that it can have a lot to do with the rear of the car.

Having said that, you did check the alignment of the car when you swapped the sway bar bushes, didn't you? That would be the place to start, I think.

Damian

[tim]

Black Bird- please post a pic of your ride. I've never seen a '96 540it (or any '96 for that matter), but I want one!

PS, I agree with Geo. I just changed my rear shocks recently and did the sway bar links at the same time. wow.

[black_bird_blue]

Black Bird- please post a pic of your ride. I've never seen a '96 540it (or any '96 for that matter), but I want one!
.

Sadly it's not a real "96" as you use the term, in Europe we just use the year the car was sold. BMW's habit is to keep selling the old estate alongside the new saloon for about a year, so it's just an ornery E34 wagon. These runout models are usually good buys because they get laden with everything to sweeten the deal. The only thing non-standard about mine is that it has the E39 wheels on it (along with the spacer ring-things) but otherwise it's rather dull, I'm afraid...

I try and drive it interestingly to make up for its dullness...
Damian

[George M]

Agree with Damian...depends on the terminology...what is meant as to sway..if sway is used synonomous with wander or if used in proper context...have to believe the latter unless told otherwise however...so likely isn't rear end bushings if we are talking body roll. And Jeff...no matter how scientific you are, you can't really infer how any bar either front and/or back will perform. The thing about alloys is..it mostly affects yield strength and not modulus of elasticity which influences torsional rates...how bars work when being loaded. As a general guideline...bigger is stiffer :-)...but you know that. The best way to determine the best combination is anecdotally from this board...what people have tried and like. Suspension engineers can't effectively computer model sway bars...only establish a baseline to work from...the rest is prototype and test. Keep in mind all cars would run big bars if there weren't a downside in NVH...there is brother....so bigger isn't necessarily better on the street....why I run the stock bars on my 7...for as hard as I push it...which is above the norm...the car handles beautifully and has a great ride.
The archives has I am sure great testiments as to what people like best...BMW Motorsport M bars should be given careful consideration as generally the factory knows best.
HTH,
George

[George M]

You may be right Bill...also Damian's impression as well. Poster still hasn't weighed back in to set the record straight...lol. BTW...I removed my subframe mounting plates on my 150K mile E-32 to have a look at the sub frame bushings...had the car up in the air recently and decided to rotate the tires. Used a breaker bar and as Ed mentioned, the 22 mm locknuts weren't too bad to get off...I used a breaker bar instead of air. The bushings are still intact and concentric but there is cracking around both spars that comprise the interior of the bushing so as expected, they need to be replaced. Perhaps we will rekindle the subframe bushing tool buy in the spring with a small group of guys which will make transfer of the tool more managable from a time standpoint.
Would still like to have the tool end up in your tool box.
George