Wheel/Tire idea

[kevinthenerd]

Often the problem with modifying ride height in the suspension is to restore the proper geometry (especially camber), and this step is often overlooked by those who just slap lowering springs on their car. I got to thinking about something, though. Another way to lower the center of gravity of a car is to put smaller wheels on it, and with no change to the springs, it wouldn't change the suspension geometry (but it might change the optimal geometry, though, which is something I'll have to investigate on paper some more). Smaller wheels also simulate a shorter gear ratio, and they provide less rolling inertia. Do people sell aftermarket rims that are something like 10 or 12 inches in diameter but that are really wide?

The only problems I can see (that aren't already associated with a lowered ride height) is that you're going to have difficulty fitting the suspension uprights and brakes into the smaller area, and the spedometer will have to be adjusted. You'll also have problems scaling bumps, so ride comfort will suffer. The tires will have less time to cool, but increased width would more than make up for this because a wide tire uses its patch more efficiently. Other than that, it seems like a cheap modification for what you'd get.

[TheSilentChamber]

Its not really going to change alot other than the fact you'll look like a mexican. The center of gravity will be lower, but your still riding on squishy suspension.

[kevinthenerd]

Originally Posted by TheSilentChamber

Its not really going to change alot other than the fact you'll look like a mexican. The center of gravity will be lower, but your still riding on squishy suspension.

You don't think it'll help acceleration in underpowered cars?

[Moppie]

Most cars come with the smallest size wheel that will fit the car, the rest come with bigger wheels in order to use lower profile tyres.
While a lot has to do with image, the lighter wheel and lower profile tyre will also offer greater benifits to performance than useing a smaller wheel and tyre.

I do know of people who use smaller wheels on race cars, but they tend be a last ditch effort, after lower suspension has been fitted, along with shorter gear ratios etc, to get that little extra bit of potential performance out of the car.

[TheSilentChamber]

Originally Posted by kevinthenerd

You don't think it'll help acceleration in underpowered cars?

Accelleration on take off or wanting to pass someone on the highway doing 75?

[Rufe]

A couple of issues to consider...

1. smaller tire, less air in tire, less load rating.
2. smaller diameter, wears much faster, overheats easier.

You are correct in wanting to lower the CG. But do not overload the tires in the process.

[mazdatech177]

yeah, youll probably end up smoking the wheel bearings prematurely, and as was stated above... itll look freakin' retarded

[Rufe]

Originally Posted by kevinthenerd

... increased width would more than make up for this because a wide tire uses its patch more efficiently. ....

Can you explain your reasoning a bit more on this point.

Additionally, performance is a balancing act. Add here, take away there.
Have to agree with you in theory, a smaller tire diameter is like getting free power (better acceleration), however, you lose gas mileage, top speed and tire wear.

If you are running a quarter mile, you can tune the car with gearing to get peak engine power at the end of your run. Peak HP does little good if you can't get the engine into that rpm range in time.

[Black Lotus]

Originally Posted by kevinthenerd

but it might change the optimal geometry, though, which is something I'll have to investigate on paper some more----.and they provide less rolling inertia. Do people sell aftermarket rims that are something like 10 or 12 inches in diameter but that are really wide?---- but increased width would more than make up for this because a wide tire uses its patch more efficiently. Other than that, it seems like a cheap modification for what you'd get.

You sound like you want to go to REALLY small dia. stuff, so I'll put in my two bits worth.
If you keep the same offset rims, you retain the same suspension geometry from the front plane view as well as the side plane view. If you change the rim offset, the geometry as view from the front plane changes and everything is up for grabs. If your car is FWD, you HAVE to carefully consider the rim offset.
Were you to find some rims with the same offset, the smaller overall dia. tires could cause you some stability problems. You lose some of the "pneumatic trail"--wider tires have a different contact patch than narrow tires. Their footprint is shorter, as viewed in the side plane. This fore and aft length is called the Pneumatic Trail as opposed to the mechanical trail associated with caster, kingpin offset, etc.
Both trails are associated with the tire wanting to run straight even if disturbed by a side force or steering input.
The pneumatic trail is the "real " feel you get at tire breakaway and the steering will get heavier then lighter feeling as the tire starts to slide. With mechanical trail, the steering just gets heavier and tends to swamp out what the tire is trying to tell you. I suspect that you would end up running more caster to regain directional stability, then have a loss of steering feel as a byproduct.
Then again your car may be so slushy feeling no matter what you do, that my little contribution here is completely redundent.
But hey, you have to consider all the angles.
As a final point, do not underestimate the importance of "looks" and "style".

[kevinthenerd]

Originally Posted by Black Lotus

As a final point, do not underestimate the importance of "looks" and "style".

Yeah... totally ghetto Mexican

[drdisque]

90% of the time smaller wheels won't clear the stock brakes.