Scrub radius

[Tristan]

I aim looking at buying a 2000 big butt Kia sportage and have got a question or two.

One thing that is currently causing me a problem is finding wheels for one. This is what I have found.
Standard offset = 45mm
Standard Rim size = 15x6
Hub = 108mm
Studs = 5 by 5.5
You can fit 15x7 and 15x8 (bronco, cj jeep, Suzuki) wheels and these wheels have 0 offset
You can put 30x9.5 with 2inch lift no problem
You can fit 31x10.5 with triming

Now I have Questions. I enqiured about some wheels (white steel 8 spoke) and was told no can do. I then asked for Bronco 15x7 and was told that the offset change would effect the scrub radius in a major way and make it uncontrolable if i look a wheel up in the wet. Is this the case?

I thought that the increase in track would be a good thing. I have also think by looking at diagrams about scrub radius that if you change the offset in the way above it may be corrected by increasing the rolling diameter. Is this the case?

A lot of people appear to run 15x7, 15x8 and 30 or 31, do you have any problems or changes?

Finally can you run 16x7 and 255/70r16? It this a good option?

Many thanks Tristan

[-Scott-]

I have also think by looking at diagrams about scrub radius that if you change the offset in the way above it may be corrected by increasing the rolling diameter. Is this the case?

Yes. But the angle between the axis of your ball joints and the centreline of the wheel is quite sharp - so you need to increase OD by 3 or 4 times the change in offset. So, to correct a 45mm change in offset, you'd need to increase your OD by more than 6 inches. I've increased OD by 3 inches, with a 10mm offset change.

[FireTruck]

Most 4wd's have a pretty large negative scrub radius. As long as everything is balanced and working (ie. tyre pressure is the same side to side, same wheel width and offset both sides, same tires, both brakes working, etc) you shouldn't see much of a difference.

Alot of cars are designed these days with a small positive scrub radius - but few serious 4wd's are. As always its a compromise... you modify the car, you should modify your driving style to suit.

S.

[Tristan]

Thank you for the reply I am still looking in to solutions to my problem. Also what effect might changing the scrub radius have on a vehicle.

[lay80n]

Thank you for the reply I am still looking in to solutions to my problem. Also what effect might changing the scrub radius have on a vehicle.

Make the steering more heavier, and car cause tyre wear basically. Due to the increased radius, tehre is more leverage to work against you at the wheel, hence why the dude you spoke to said that it woulf gith back more if you lock a wheel etc.

Layto....