offset, 5-lug swaps, and scrub radius

[VinniE30]

A positive scrub radius will increase steering effort, and I see a lot of people on here with lower than stock offset wheels, how noticeable is this? Not to mention other effects of changing the scrub radius as it was designed from bmw.

I'd like to eventually get a wider track but can it be done without negatively affecting the scrub radius?
I'm not too familiar with how a 5-lug swap is done, but does this move the steering pivot point (kingpin axis) , therefore allowing you to have a wider track while keeping the scrub radius the same as on a stock e30 or e30 m3? Or would this increase the scrub radius even more, since the hub is being moved farther out but the pivot point does not change?

I'm asking this because I want to get a wider track "the right way" and the thought of increasing track via 5-lug swap vs lower offset wheels and how they would affect suspension geometry came to mind.

[LivingLegend06]

It's generally accepted that the gains from having wider tires and a wider track outweigh the increased scrub and jacking forces from pushing the track width out.

I expect e36 components will change the kingpin axis but using e30 m3 bits wont as the m3 uses the same control arm geometry as the standard e30.

If you start screwing with the suspension geometry you are probably going to male things worse before you make them better unless you already have lots of knowledge and the money for all custom parts.

[VinniE30]

It's generally accepted that the gains from having wider tires and a wider track outweigh the increased scrub and jacking forces from pushing the track width out.

Right, the increased scrub doesn't have to do with traction per say, it has more to do with just what the driver feels, that is, the increased steering effort. Why is this a concern? Because power steering delete. The scrub radius also affects stability under braking.

I expect e36 components will change the kingpin axis but using e30 m3 bits wont as the m3 uses the same control arm geometry as the standard e30.

Interesting. Do you know why this is? That is, how the e36 components are different in that they change the kingpin axis but the e30m3 components don't?

If you start screwing with the suspension geometry you are probably going to male things worse before you make them better unless you already have lots of knowledge and the money for all custom parts.

Right, that's primarily why I'm asking questions like this. Because I want know the best way to increase the track width without messing up things like scrub radius. If for example, the e30m3 5 lug swap increases the offset by 10mm then would this has any advantage in terms of suspension geometry over putting on a 10mm spacer? Obviously you wouldn't do a 5 lug swap just for that but I just want to know how it affects the suspension geometry, in particular, scrub radius.
A lot of great handling cars (see elise, miata, etc.) have high offset wheels for optimal scrub radius(near zero). It seems like running low offset, wide wheels is a bad way to increase track width as opposed to the e30m3 5 lug swap right? Obviously just talking about suspension geometry here not other irrelevant things like cost.

[LivingLegend06]

The kingpin axis is just going to be the line from the outer balljoint on the control arm and pivot point in the strut tower. When you use E36 5 lug you use E36 control arms which are different from E30 arms (I'm not sure exactly how, I know caster is negatively impacted but not sure about the kingpin axis). To properly move the kingpin axis you would need to move the pivot point in the strut tower as well as outer balljoint.

Reinstalling power steering isn't that hard if all your worried about is increased steering effort.

[TobyB]

Because I want know the best way to increase the track width without messing up things like scrub radius.

Then you need to move the effective pivots out with the track. So, hypothetically, you'd
use longer lower control arms and move the top strut mount out as track width increased.

It's quite hard to do.

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