Went from 18s to 17s...realignment needed?

AmBo said:

Hey, just put on my snow tires (17" Chrome Bullitts) from my 18" chrome saleens. I got an alignment when I went to the 18s, but now do I have to get another one?

My car seems "wobbly" at high speeds but idk if it's from not having 18x10s out back or the alignment. WHatever it is, it scares the piss out of me...

Oh, also, snow tires have no traction and it sucks...I'm so spoiled by my KDW2s...

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Scrub radius is the distance between where the SAI intersects the ground and the center of the tire. This distance must be exactly the same from side to side or the vehicle will pull strongly at all speeds. While included angle problems will affect the scrub radius, it is not the only thing that will affect it. Different wheels or tires from side to side will cause differences in scrub radius as well as a tire that is low on air. Positive scrub radius is when the tire contact patch is outside of the SAI pivot, while negative scrub radius is when the contact patch is inboard of the SAI pivot (front wheel drive vehicles usually have negative scrub radius).

If the brake on one front wheel is not working, with positive scrub radius, stepping on the brake will cause the steering wheel to try to rip out of your hand. Negative scrub radius will minimize that effect.

Scrub radius is designed at the factory and is not adjustable. If you have a vehicle that is pulling even though the alignment is correct, look for something that will affect scrub radius

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When you turn the steering wheel, the front wheels respond by turning on a pivot attached to the suspension system. Caster is the angle of this steering pivot, measured in degrees, when viewed from the side of the vehicle. If the top of the pivot is leaning toward the rear of the car, then the caster is positive, if it is leaning toward the front, it is negative. If the caster is out of adjustment, it can cause problems in straight line tracking. If the caster is different from side to side, the vehicle will pull to the side with the less positive caster. If the caster is equal but too negative, the steering will be light and the vehicle will wander and be difficult to keep in a straight line. If the caster is equal but too positive, the steering will be heavy and the steering wheel may kick when you hit a bump. Caster has little affect on tire wear.

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AmBo said:

Yea, I think I need another alignment *sigh*

I went from 18x9/18x10 to 17x8s all around...

Thanks for the info

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tomustang said:

tires balanced?

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AmBo said:

VERY possible! :Zip2:

And droptop, I think you're right...I want my fatties back.

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