How much of a difference does offset make?

[Wreckerboy]

Wheels sticking out beyond the body work hurts your aero, and your brake cooling. Not many people realize the later.

Please explain this, as I am not following the logic. TIA.

[Rabbit07]

One other compromise here is Scrub Radius. Don't forget that!

On the Areo and Brake Cooling, the air gets disrupted with the rolling tire. If the Tire/Wheel is tucked the air moves past it on the outside aiding in evacuating the hot air from the brakes.

[ShelbyRacer]

Chris,

I'd actually think that having the face of the wheel roughly even with the body of the car is best for evacuation. Having the fast moving air provide the low pressure would induce the best airflow, providing you have a high pressure area as a source. Having the wheel tucked in would tend to generate a turbulent null (cowl induction anyone?), which would provide pressure much closer to atmospheric, probably tending towards a back flow to the underside of the car. Again, all this depends on the aero package as a whole...

[shwah]

One other compromise here is Scrub Radius. Don't forget that!

On the Areo and Brake Cooling, the air gets disrupted with the rolling tire. If the Tire/Wheel is tucked the air moves past it on the outside aiding in evacuating the hot air from the brakes.

Which is why you should use the air dam allowance to cover as much of the wider track tires as possible.

I have taken the widest track I can get approach. 1" spacers in the front with ET13 wheels vs. stock ET35. My car is lb/hp challenged for my class, which is pretty much a momentum class anyhow - so I tend to choose trade-offs in favor of cornering.

The scrub radius stuff is a valid concern, but IMO when you are working the tire at an appropriate slip angle, it is less of an impact than when there is static friction between tire and road. Bump steer probably causes more issues...

[Flyinglizard]

Scrub only counts when both front tires are on the ground.

[quadzjr]

Scrub only counts when both front tires are on the ground.

I think we should assume that atleast for the majority of the time we plan to keep the front tires on the ground.

[shwah]

I think we should assume that atleast for the majority of the time we plan to keep the front tires on the ground.

You would be surprised how often they are not.

More importantly how often the inside tire has very little load and thus very little friction to share with the rest of the situation.

At least if you are running a solid diff.

[Flyinglizard]

Chris has it. If you are going fast with a locked diff, the car is like a two wheeled device. The inners are off of the ground. MM

[betamotorsports]

Track is one of the components of lateral load transfer. Its far more important then 1.2 lbs of unsprung weight.