Effect of wheel offsets

[IsaacMTSU]

Lean Burn, Thanks for the "Thanks"!

[Frank Lee]

The Bonneville racers are all about this sort of thing... IIRC I saw mention of it in a Hot Rod magazine aero article. There is a sweet spot for how flush the wheels should be from the bodywork... how do we find it? No wind tunnel for most of us; perhaps a yarn tuft test could reveal something but I'm not sure about that as right behind the wheels is a turbulent zone at best anyway. Perhaps there is an article about it and the information it has can be transferred over to your particular car.

I noticed the early 1L prototype had convex rather than flat wheel covers that stuck out a bit more than I would have expected; you can be sure those were fully vetted by the VW aero team.

[aerohead]

Originally Posted by LeanBurn

I was more after whether the air moving down the side of the car would get caught on the wheel well right under the side mirrors or would having the tire more outwards would minimize/eliminate it, not so much how much turbulence the wheel itself created. If it was as the drawing above suggests the "fan-like" turbulence created by the wheel would push the air to more align with the rest of the body side that would be great. If the fan-like turbulence is negligible then there is more of a chance the air gets snagged on the wheel well, creating drag. If the wheel was pushed out to more in line with the body air would have less of a chance to get caught there.

If the car was always in still air the wheel wells would be in train with the side of the car.Momentum would tend to carry the air straight back,although if you've been besides cars in the rain you may have seen air blasting out the front wheel wells as engine compartment air makes its escape from the body.
Observations have firmly established that cars are exposed to some crosswind most days.I believe that the SAE tests with a 7-degree crosswind @ 7mph for 18-wheelers.
In this case,if you're NOT going to cover the openings,then 'flush' wheels would have an advantage,as they would help block the windward transverse vector of the apparent wind which might otherwise trigger flow separation when snagging the trailing leading edge of the wheelhouse(s). 'MOON' -style wheel covers would also help.
Ford Motor Co. discovered a 9% drag savings for their Probe-IV with spat enclosures of the front wheels,which were shielded additionally with an elastic urethane skirts.

[LeanBurn]

I have to admit that due to my main road orientation, location and climate that I often get a crosswind. Often 45deg to nearly parallel to the car. Would the advantage still be applicable as you mentioned?

[aerohead]

Originally Posted by LeanBurn

I have to admit that due to my main road orientation, location and climate that I often get a crosswind. Often 45deg to nearly parallel to the car. Would the advantage still be applicable as you mentioned?

As Frank Lee has touched upon,without a wind tunnel study of your particular Corolla,we're grasping for any public domain data specific to wheel wells.
I've no such documentation.
If you have no plans for skirts,looking at today's hybrids of any make or manufacturer will give some ideas as what you see will have been tuned in the tunnel.
If your wheels are even with the sides of the car it will preclude the future addition of skirts which do not add frontal area.So you'd be limiting future streamlining.
You could work your front wheels through their full range of motion and see if the wheel arches could be choked down or radiussed,which would minimize the crosswind hit.

[Gone2]

I always tend to shy people away from the wheel spacers on cars. If you get the ones that push the wheels an inch or more, they are fine. The cheaper ones that are sold at Pepboy's that slip over the lugs are notorious for causing damage to the lugs and ultimately could cause damage to the vehicle if not monitored closely.

Are Wheel Adapters Safe? | eHow.com

[ProDarwin]

Originally Posted by Sentraguy

I always tend to shy people away from the wheel spacers on cars. If you get the ones that push the wheels an inch or more, they are fine. The cheaper ones that are sold at Pepboy's that slip over the lugs are notorious for causing damage to the lugs and ultimately could cause damage to the vehicle if not monitored closely.

Are Wheel Adapters Safe? | eHow.com

Get extended wheel studs then. Usually about $1 each. Plenty of racers use these spacers with massively wide, sticky tires that put a tremendous load on the hub. They work great.

[F8L]

I've noticed that on the Prius, especially the GenII, the tires are tucked into the wheel well a fair amount. The rears appear more tucked than the front. I'm not sure if this was and intentional design or not. I will look more closely at my new GenIII and see if this is still the case.

[pjbgravely]

Originally Posted by aerohead

,although if you've been besides cars in the rain you may have seen air blasting out the front wheel wells as engine compartment air makes its escape from the body.

Interesting idea but why does my car do it? I have not seen it directly but there is always a dirt line on the side on my car that starts at the top of the front wheel well.

My front wheel wells are sealed completely from the engine compartment except at sway bar. I might try to seal that better and see what happens.

[gone-ot]

...wheels are like arms...best kept "in" not "out" flapping in the breeze.