I have been running SCCA Solo2 autocross for a while but keep coming in second. I need a good tire, slicks, for running autocross. How wide can I go and is a change from my 18" going to make a difference. I am running a stock 2006 with good sticky DOT street tires, everyone else in my class is running slicks. Pleae help me get faster!!!!!

 

This information is written by "staticlag."

- Changing the factory wheels to aftermarket wheels is a very simple to install modification which can drastically increase the performance of the vehicle. This is one of the easiest ways to obtain marked gains with any vehicle. Conversely by adding heavier more fancy looking wheels there is a significant decrease in performance.

Concept:

By adding lightweight wheels you are reducing the weight of the largest rotating part of the drivetrain. Heavy objects have a lot of inertia, inertia is defined by Newton's second law of motion, that objects in motion like to stay in motion and objects at rest like to stay at rest. Heavy objects have more inertia than lighter objects because they have more mass. By reducing the weight of the wheels you are reducing the power that the engine wastes overcoming the wheels' inertia.

How does this apply to the RX8?:

The stock wheels were manufactured at two different facilities they can weigh between 20-22 lbs.

The stock bolt pattern is 5x114.3. Wheels are 18" by 8" wide. Wider wheels can fit wider tires on them allowing for added traction.

A very popular racing wheel is the lightweight Enkei RPF-1 which is 18" by 9.5" wide and a lightweight 18lbs a wheel.

Each brand of wheel has different clearances and different "offsets." Knowing if a particular wheel will fit your car is dependent on the size of your wheel wells, and brake kit. There is no exact way to know if a wheel will fit if the person has no experience with the car or the wheels. Buyer beware when buying from inexperienced salespeople.

Care must be taken when selecting wheels, usually cheaper wheels are manufactured with inferior processes which makes them very prone to denting on road imperfections.

Some people buy wheels solely for looks and not performance. Typically upsizing a wheel (18" to 19", 20", etc) to a fancier variety adds a lot of mass. That gain in mass results in significantly lower performance.

Staggered wheels (making the rears wider than the front) may look cool, but the added traction on one part of the car has a massive negative effect on the handling of this car. Since our weight balance and steering is fairly neutral going staggered is a bad idea.

--- Hope this helped you with "making you faster" and your tires/wheels.

 

It's always down to the tires, and if those guys are shelling out for racing slicks you need to do the same or settle for second.

I've raced Karts, Autoxed, and now track on Hankook ventus v12's.

I get satisfaction from comparing the occasional even car on the track and seeing what tires they're running, but I won't play that Joneses game.

Oh, way back in 1978 I won TTOD at a SCCA autox in a slow RX3 against Vettes, 240z, BMW, and Mazda RX4's (all the good stuff). I had geared the the rear end down from 3.7 to 4.11, and once moving stayed in 2nd the whole time. the tires were Uniroyal Rallye 240 (a good DOT tire somewhat like the Ventus V12's'

I run 225/40r18 which gears down 3.3% which is a hint for you, but slicks are tough to beat even with crap drivers.

 

You may want to read the rules before you consider changing wheels.

 

Yes - and read the Racing forum, which is 90% autocross.