symptoms of bad steering rack?

[matt0300]

Its not hard to turn. Just when I hit bumps it jumps to one side or the other. New tierods CABs and CA. When I'm just sitting in the car there is a tiny bit of play in the wheel and when I jiggle it left to right I hear a clunk noise. Can someone chime in with possible problems. Thanks.

[jeffnhiscars]

the clunk when not moving could just be the taking up of slack in the system since you replaced the usual suspects or could be the coupling. If its lowered you could be getting bump steer. Search for it.

[immajackuup]

Its not hard to turn. Just when I hit bumps it jumps to one side or the other. New tierods CABs and CA. When I'm just sitting in the car there is a tiny bit of play in the wheel and when I jiggle it left to right I hear a clunk noise. Can someone chime in with possible problems. Thanks.

i have the same problem too.

the clunk noise is coming from the firewall where the steering shaft pass through.

just found out you have to tighten the big nut under steering column.

more info

http://www.m42club.com/forums/showthread.php?t=7728

[matt0300]

Well when I had my friend jiggle it u could hear it coming from the rack but again it could just be the extra slack. Thanks for ur guys replies if u have any other suggestions let me know.

[matt0300]

And it does sound a lot like bump steer. How do u correct it?

[jeffnhiscars]

And it does sound a lot like bump steer. How do u correct it?

I'll try to explain it as best as I understand it. When you lower your car your change the relationship between the control arm and the tie rod away from parallel (or close to it). When the car is in transition (ie cornering) these 2 parts, if off plane, will respond differently so if you hit a bump, it will generate disproportionate feedback tot he steering wheel as if the car is trying to steer itself...ie bump steer.

I didnt know I had bump steer until after I upgraded to an e36 rack and cured it, by inadvertently compensating for the lowered car by putting the spacers above the rack (as opposed to the often recommended bottom placement).

I took the pic after the rack swap and you can see that the tierod and control arm are pretty much parallel. Now when I hit THAT bump at 50mph on the interstate on ramp the car is rock steady.

Bump steer 101 as I know it.

[Sagaris]

I will share my steering geometry picture because putting the spacer UNDER the rack is what fixed mine.

Spacer ABOVE rack (bad geometry)


Spacer BELOW rack (better geometry)

[jeffnhiscars]

I will share my steering geometry picture because putting the spacer UNDER the rack is what fixed mine.

Yours is shinier than to say the least. I tried to put the spacers underneath and there was no way to get the rack up that high without it hitting the pan. Keep in mind that thats an M10 and the rack I removed has a steel tubular body rather than cast aluminum so maybe it mounted differently in the beginning.

Honestly, I never thought about angles at all til after it was all done so i just got lucky in eliminating the bump steer I had for 7-8 years even though I didnt know I had it til it was gone

[matt0300]

Thanks for all that info. I'm about to swap my steering rack and see if that does it.

[Jaxx_]

not bump steer in the sense that you're thinking. Steering wheel shake is not normal.

[jeffnhiscars]

I was looking at the pics posted by Sagaris & myself & I realized that his wheels were turned slightly whereas mine we dead ahead which perfectly illustrates how bump steer can occur. The outer ball joint and the tie rod rotate on different axis' so that as you turn the wheel, your toe & camber will also change. Thats why the angle in his "after" pic is noticeably different from mine.

Now imagine the wheel turned even further with a corresponding increase in that angle. As you turn, the ability to keep the knuckle stable is reduced so when you hit a bump its shakes. Think about carrying a heavy object above your head with your arms extended at 45 degrees, then again with your arms at 90.

Bump steer 301 !!

[Sagaris]

I think the discrepancy in the angle is more-so due to the fact that my car is sitting on the ground and yours is in the air with the suspension at max. travel.

[jeffnhiscars]

I think the discrepancy in the angle is more-so due to the fact that my car is sitting on the ground and yours is in the air with the suspension at max. travel.

That's part of it for sure as well as different suspension components etc. Suspension geometry seems to be part art part science, so every bit helps. Thanks.

[benz-tech]

I just installed my e36 rack and split the shims top and bottom. I will put it on the alignment rack next week and determine once and for all what is the best combination to eliminate bump steer and will post the results. In the past I had my Datsun 510 down to under 15min toe change for the full range of suspension motion, not an easy task.

Side note: E36 rack FTW! Best $40 bucks I ever spent at a pick-n-pull.

[jeffnhiscars]

I just installed my e36 rack and split the shims top and bottom. I will put it on the alignment rack next week and determine once and for all what is the best combination to eliminate bump steer and will post the results. In the past I had my Datsun 510 down to under 15min toe change for the full range of suspension motion, not an easy task.

Side note: E36 rack FTW! Best $40 bucks I ever spent at a pick-n-pull.

The alignment rack will help set your toe which will change when you move the shims..and of course its the only adjustment you can make (absent camber plates). Seems to me though, that evaluating the impact on bump steer while on the rack all you can do is eyeball the relationship between the tie rod and CA.

Interested in your conclusions, since Im about to swap the e36 rack and tie rods from my 318i coupe to my 325i Cabrio.