Scrub radius help

[ChrisD]

Following on from this thread: http://www.ft86club.com/forums/showthread.php?t=84079

Quick bit of background:

• Lowered the car, now want to bring the wheels out so they're roughly flush with the bodywork.
• Car will be used for road, track days and drift events.
• Currently on stock wheels (17x7) and stock sized tyres (215/45/17).

I want to bring the rear wheels out by about 20mm, the front's I guess could come out by a bit as well but they don't seem to look as "sunken in" as the back. So I've found a few wheels that are 0.5 inches wider and have an offset about 13mm less than stock, so that extra width combined with the offset should give me 19mm of extra poke if I understand this correctly (because 0.5 inches is 12mm, so half that on each side means 6mm extra on the outside).

Assuming that is correct, my problem is that most of the wheels I find in the right size only come in one offset so I would have to have the same on all 4 wheels, meaning the front offset is going to get changed too. So I think this will then mean it gives it more positive scrub radius... but I'm not sure how much extra is enough to cause any problems. Everywhere I have found online just seems to say "you don't want excessive positive or negative scrub radius" but they fail to say what is classed as excessive and what is ok so I have no idea if changing the offset by 13mm is an issue or not.

So my question is basically: how important is it to try to keep the front's offset the same as it would be stock so that the scrub radius stays the same? Should I only be looking for wheels that I can get in two different offsets so that I can have the rear's poke enough but keep the front's offset roughly as they were stock, or am I not going to notice any problems if I just get et35 offset (13mm less than stock) on all 4 wheels?

[cjd]

Sort-of answered in your other thread, but...

keep wheels and tires the same front and back for the best performance (as far as I've ever read... )