Positive offset rims vs. Negative

[bestclimb]

Originally Posted by AntiochOG

Thanks for elaborating bestclimb. I am aware of the relationship between scrub radius and wheel offset. However, wouldn't the effect of this only be seen in a dynamic driving situation and not when the car is stationary, i.e. on the alignment rack. The face of the wheel should be parallel to the hub regardless of how much or little it is offset.

You got it. The car is aligned on the rack, or pads or garage floor. The proper amount of toe is put in, then when you are driving down the road the extra (or lack of) scrub radius adds or removes some toe that is not accounted for.

one reason why FWD cars tend to have small scrub radius is the thrust and drag of acceleration and braking can cause a slight toe in under acceleration and toe out while braking.

[niky]

Apart from alignment issues, your major worry really will be that the tires or rims will rub on inboard suspension components because of the difference in offset. Spacers should minimize both issues quite nicely, but again, be sure you have enough thread left on the stud to hold the wheel on properly.

[Occasionally6]

In addition to the effect on dynamic tracking (toe) the change in offset will mean the track is altered. A narrower track (more negative offset) means the roll centre will be higher and the jacking (lifting) component of the cornering force higher (= bad).

The effects may not be the same front and rear. That will alter the weight transfer distribution, which is the basis of tuning handling on a 4-wheel vehicle. At best, the result will be unpredictable.

The change in offset will alter the loads on the wheel bearings.

Even small changes (like < 1/2") in wheel offset can lead to things like wheel shimmy (feels like out of balance wheels).

Using spacers to get back to the standard wheel offset solves some (most) of the problems but loads the wheel differently to its design load.

I really don't like altering wheel offsets from the factory specification. Surely there's an alternative.

[hat_man]

Thanks for all the good information. Asking questions here is one of the main reasons I come here. So much good information here given in a way that makes it easy to understand.

If I were to do this then it sounds like I would have to go with wheel spacers to keep the offset the same and I would still benefit from the weight savings. As for loading the wheel differently I really don't know what that means but the original car these might come from has a slightly heavier (approx 100 lb) curb weight difference. That and I don't ever engage in any "spirited driving" and very rarely accelerate hard or brake hard except for children and wildlife. I drive about as boring as my life is.

[justme1969]

Look that above is all mostly true but you need to know specifics here so call your local wheel shop and ask how much offset you can use straight up.
They know and will ask if car is lowered or about engine mods etc. Get the rite facts dont guess. seen a lowered car crash from the large tires offset out thing because they guessed and when brakes applied hard instead of anti locks the wheels contacted rear of fender locking down and taking away all steering.