Wheel Offset - what does it do?

[Rondo]

I have 2 sets of wheels for my old FF. The offset in one set is 12 mm a wheel less than the other - so total difference in the track width of the car is of ~25MM...1 inch. So track width " greater. I have always used them for different types of tires so no back to back comparison. I never paid attention to which set was installed when I set the car up EXCEPT ride height which is different for the different tires as overall tire height is different

My question - aside from track....what's the effect on the suspension geometry and therefore performance and ? Should I feel it (if I would is an entirely different subject....buns of steel!) Should I go wide or go home??

Perhaps there is a thread on this.....just point me please

Thanks all as always for your thoughtful responses!

[Purple Frog]

My question - aside from track....what's the effect on the suspension geometry and therefore performance and ? Should I feel it?

The answer: It depends.

Seriously, you might not get much response because so few of us know how to answer. It involves a lot of math, etc. Its in that rare atmosphere that folks like Steve Lathrop dwell.

My normal kneejerk reaction would be "wider is better". But, most of us would not feel it.

[David Ferguson]

Backspacing differences at the front will change the Scrub Radius. Here are a couple of threads on this topic:

https://www.apexspeed.com/forums/sho...t=scrub+radius

https://www.apexspeed.com/forums/sho...t=scrub+radius

https://www.apexspeed.com/forums/sho...t=scrub+radius

There are lots more in my search for "scrub radius"

[ChristopherBernard]

Wheel offsets, tire diameter and adjustments to your ride height will all change your instantaneous centers, roll centers and even roll axis.
Not possible to determine full effects without "doing the math". Plotting it all out either manually or with a suspension program.
Lap times would at least be an indicator of final results.

[alangbaker]

Wheel offsets, tire diameter and adjustments to your ride height will all change your instantaneous centers, roll centers and even roll axis.
Not possible to determine full effects without "doing the math". Plotting it all out either manually or with a suspension program.
Lap times would at least be an indicator of final results.

I think you might be overthinking this a bit.

Wheel offset is not going to change your instantaneous centres, roll centres, or roll axis enough to notice; certainly not a change of less than half an inch.

[t walgamuth]

I am sort of a traditionalist. I remember when I learned that the Indy cars of the fifties all ran narrower track at the rear. I was told they handled better that way. They also cornered at the speedway with the tail hanging out enough to be seen on film. Watching a front engine roadster hang it out there always makes my hair stand up on my neck.

I always wish for a narrower track on the rear for that reason. In autocross of course a narrower rear end allows you to drive closer to the cone too. Then too a spacer making the front wider will at least also give more leverage on the spring effectively softening it and thus should result in more grip.

I have always tried to make my tracks narrower in back, using spacers on the front and or different offsets.

The present van Diemen has not been touched for track and it handles really well. It is adjustable with air pressure enough to satisfy my desires.

No science more complicated than that, and whether the handling feels better or not.

I always strive for neutral handling.

[BorkRacing]

Wheel offsets, tire diameter and adjustments to your ride height will all change your instantaneous centers, roll centers and even roll axis.
Not possible to determine full effects without "doing the math". Plotting it all out either manually or with a suspension program.
Lap times would at least be an indicator of final results.

Ron,

With the risk of the wrath on this website (since I never won the Runoffs), I will agree with Chris.

Having run a Crossle' 32,35,40 and 55 through my suspension program (from University of Buffalo's Race Vehicle Dynamics) I can say minor changes sometimes have major effects. Will they affect our driving/lap times? Depends on your ability, the condition of the rest of the suspension and track conditions.

Crossle's were designed very well, up to the 55f after which their designer left to form his own company. Yours is a 62f or around that era If I remember correctly. So how good John Crossle was with his slide rule I am not sure.

In.the 55f and earlier cars, minor variance from standard has some very big effects on roll centers, scrub radius etc. to the effect of moving roll centers out 300 feet and 10 feet high. Makes for an interesting drive to say the least.

But unless we put your car through the suspension program I can't say exactly in what way increasing front track will lead you

Rob.