is there such a thing as rear tire scrub radius on an IRS?

[abadsvt]

I was curious if there was such a thing as rear wheel scrub radius since there is no steering. I have always associated it with the front suspension and never thought about the rear. If there is scrub does the same rule of under than 2" is ideal? Thanks

[astroracer]

Scrub radius has nothing to do with steering (of course they are interelated). The scrub radius is a product of the King Pin axis and the wheel/tire centerline or contact point at ground level. IRS have a scrub radius. Even solid axles have a scrub radius, it's just not really taken into account because it is moot.
Mark

[ace_xp2]

Whether or not it matters probably depends on how much caster and/or spindle axis inclination and bumpsteer there is on the spindle. You get the car to drop on toe in and lift on toe out if you've got scrub + bumpsteer + caster in sufficient quantities, I'd think that for the values of steer you might find useful it should be a small effect, but it may show up in the handling. If there's spindle axis inclination you'll get steer lift, which should raise cg and so increase load transfer on that end, again probably a small effect.

[David Pozzi]

There is rear scrub as a function of the linkage geometry & roll center location. Wheel offset won't significantly affect it.

[ace_xp2]

He was talking about scrub radius, not side scrub.

[abadsvt]

Thanks guys for the replies! I love that semi deep dish wheel look but trying to find a happy medium with looks and performance. I was thinking about running a 20x12 with a 6-7" backspace on a c5 rear suspension. I was trying to do research on the affects of a larger scrub radius on the rear suspension but really didn't find much anywhere. Just the front suspension. You think I would notice major performance issues if I went that much backspace? My chevelle will hopefully be driven on the rack once in a while but mostly street. Thanks

[astroracer]

6" or 7" of backspace on a 12" wide wheel puts the mounting flange right about in the middle of the wheel... Not a bad place to be actually. Keeps loads down on the spindle bearings. Now, if you're talking only 3" or 4" of backspace that will overload the spindle bearings and start causing problems in a short time.
Mark

[Mateospeed]

To answer your question, yes, my definition, there is such a thing as a scrub radius on rear suspension. I would think with minimal toe in/ toe out, the effect would be minimal, since there is no steering. As others have stated, I believe the concern when considering backspacing/ offset on wheels is the balance of load on your wheel bearings. Best of luck!

-Matt