Bump steer in lowered E30s?

[LateFan]

Does a lowered E30 produce bump steer? Either in the tie rod / control arm angles, or because of the semi-trailing arms in the rear?

I'm talking a mild drop - H&R sport springs, E90 drop hats.

[JGood]

Yes, there is a bump steer curve. There will not be a significant change to the static position of that curve with a mild drop.

[LateFan]

Thanks.

It has an E36 rack with proper spacers and E36 tie rod ends.

What might cause a slight steering dart to the right on compression, and left on rebound? Causes a little s-curve "wiggle" on big dips or bumps. It self-corrects quickly, more annoying than dangerous. It was pronounced when we brought it home tired, way less now with rebuilt suspension.

Can't tell if there might be a bend in a trailing arm, or if it's in the steering. It feels a bit light in the steering to me. Alignment numbers are within range, although the negative camber is increased with the drop. It has all new OEM rubber bushings, generic shocks from PO.

[e30davie]

Years ago i measured the bump steer on my old corolla with a conglomerate of suspension parts. I took the spring out and put it all back together, attached a straight edge to the wheel with a laser pointer attached. I then put a bit of board a known distance in front of the laser pointer and took the suspension through its motion and marked it out on a bit of paper. Bit of maths gives you an idea of the bump steer.

if you are interested in bump steer its doing it its worth it for the learning exercise. However gotta keep in mind where the suspension is in its normal operation and weather a bit of bump steer actually matters. rear of the e30 is known to toe in when lowered, which is "bump steer" but this also gives stability so it might be a good thing.

In an ideal world you'd want minimal toe change in the area of the arc that is always used. But you will always get some steering effect as suspension works in arcs.

[LJ851]

What are your caster settings?

[LateFan]

[ATTACH]123820[/ATTACH]

[LateFan]

Does anything there catch your eye as off?

[LJ851]

Does anything there catch your eye as off?

Not really, it all looks pretty OK.