How much caster is too much caster and anyone tried e36 rear shocks on e30?

[Mossman]

hey guys.
Just got my e30 vert back on the road. It was perfectly fine last year, now it's got e36 m3 front suspension/brakes and 318ti rear stuff.

I'm running...

97 m3 control arms
e30 m3 offset control arm bushings
e30 m3 springs with e30 strut hats
and regular e36 bilsteins.

Wheel is pretty well centered in wheel well, but car jerks kind of violently over sharp bumps in the road, and there's tons of feedback through the steering wheel. I don't know what part of my setup I can attribute that to. I think the struts are a little bit weak, so tomorrow I'm putting konis in up front.

My question is, if I redrill my shock towers to use the m3 offset strut hats will I have too much caster? I know what everyone parrots, more caster = better high speed stability but more steering effort. I have power steering so I don't care about the effort, but will running this hacked together bunch of parts mess with the geometry enough to alter my camber while compressing the suspension and stuff like that, or is caster independent? Also how exactly do alignment machines measure your caster, they don't know what angle the strut is at do they?


Also completely unrelated and I will figure out for myself as soon as I roll out of bed tomorrow. I think e36's have more suspension travel in back than e30's and therefore I may have issues with bottoming out, but has anyone run e36 rear shocks on e30's? Obviously the tops are the same cuz you can use the same mounts, I think the bottom bolts are the same, they're adjustable and probably valved better for lowering springs than my fresh stockies I'm running now, so all that I have to worry about is bottoming them out. I'll fully compress them side by side with an oem sport and billy touring rear shock tomorrow to see how much longer they are. But I was just curious if anyone had any input.

Thanks guys
-Sam

[Mossman]

e36 shocks are a couple inches longer both uncompressed and fully compressed. I'm gonna run em with bump stops pretty firm though and see what happens.

[nando]

Have you had an alignment? it will feel like that if you have excessive toe in either direction.

[oekundar]

Mossman,

I'm very interested in your findings....I'm planning on running a similar suspension on my vert as well...I'm guessing that the e36 control arms are plug and play?

[Massive Lee]

I wonder if the problem might not be partially attributed to a lack of caster.

[gearheadE30]

^^+1. Caster helps the car absorb bumps when it is moving at speed. With enough of it, it can also reduce body roll. That's way more than you can dial in, though. does it jerk as in no suspension movement, or as in side-to-side shot strut mounts/ball joints?

[Mossman]

Okay....
So I redrilled the shock towers for the offset m3 top plates. They're about as far back as they can be without the spring/hat rubbing on the back of the shock tower. Car drives SO differently. I had a ton of tools and parts in the trunk so I couldn't beat on it, gonna go do that now. It used to be very willing to turn, especially at low speeds. It felt odd but it would be like you'd turn the wheel a little and the weight of the car would knock the wheel over and it'd turn by itself. Now it's opposite, wheel wants to be centered, it doesn't feel like there's sharp turn in but when you give it some muscle and steering wheel angle it is very planted and the steering is weighted.

Basically it feels less tossable but in reality it might turn a lot better. I eyeballed the alignment again and it's still off a tiny bit by my eye, with a bit of toe out that I can't fix. One of the tie rods is seized up I'm gonna throw e36 units in I think.

I'll take pics of where the strut is located in the tower now and get it on an alignment rack for proper toe and camber/caster #'s ASAP.