I seriously disagree.. maybe on a NA car but the turbo has the power to push the 18's. The speed you gain in the corners is greater than that which would be lost in rolling resistance (rotational mass is irrelevant). I've run various sizes on 944na's and 944T race cars and if you are tracking the turbo, put more rubber under it. If someone is slower around the track on a turbo due to running 18's, they are not leaning on the tire enough...

Stay off the brake, it slows you down

 

do you have actual empirical evidence to support your opinion? every professional article and review i have read points to bigger wheels = slower car. i'd be interested in a side-by-side dyno of the same car running two different sized wheels.

i think the ideal setup is the smallest wheel possible with the widest tire possible.

here's some reading;
http://money.cnn.com/2004/12/15/pf/a...ay_big_wheels/

http://www.nerocam.com/SCC_TAP.asp

http://grassrootsmotorsports.com/art...heels-fortune/

http://www.tirerack.com/wheels/tech/...jsp?techid=108

http://www.edmunds.com/insideline/do...ticleId=104526

http://www.rqriley.com/suspensn.htm

 

I'm speaking from my own experience & from others that have gone this same route. If your running a 951 w/ gobs of hp, u may not notice much of a difference, hence u have the extra hp to turn the 18's. If your running a close to stock 951 w/ maybe a chip & exhaust upgrade, you will notice a difference.

 

I am speaking from my own experience as well. Sorry, I'm not much of a forum racer and was just trying to give my view which is empirical, but not purely scientific, because I am basing it off my personal trials, errors, and successes. The dyno comparison would be of no real help because peak horsepower would not change, only the curve and even then would require an EXTREME difference in weight (from a larger wheel) to have enough effect for a comparison. In a true evaluation of this argument you must consider all the variables at hand and in what sort of venue you are exercising them.

For road racing, the most important consideration in this argument would be the wheel size (and chosen tire) and it's effect on gearing. Different tracks will benefit from different gearing and one way to change that in a stock class is overall circumference of the tire. Now then again you must consider how wide your wheel is and it's effect on the tire you have chosen and even then a healthy difference in air pressure can produce a .5 mph difference at any chosen reference point. Turbo cars are extrememly picky about where the power is made so if you have lost time on your lap, try and look at your shift points. Did you know that a 944 Turbo's horsepower curve drops off after about 5400 RPMs? Unless you are climbing a hill at your shift point, try short shifting your car. This took me a while to figure out and once I did, everyone thought I had close ratio gears because I would shift before them and pull away.

You must consider that Hoosier makes only so many tire sizes and a stock offset will only accommodate so many sizes without protruding beyond the line of the fender. Think about contact patch and how it changes with the weight transfer through a corner. A 17 which is a taller tire than an 18 will have a rounder profile which arguably creates a smaller contact patch under severe cornering with the proper camber angle. You can go on and on introducing one variable after another. If you think they are faster, run them. If you find different, sell them and buy 18's. I'm not an engineer so if I wasn't winning races and I thought it was my wheels, I might try 17's.

Thanks for the suggested readings but I'll stick with what I've got.

 

4 Porsche Fuchs with brand new Hoosier rubber - $1,000 obo

Rims – 16” x 8” Porsche Fuch rims – great shape no pits.

Tires – brand new P225/50 ZR 16 A6 competition road racing tires – list price $219 + tax & shipping.

Stored in a cool dry place away from electricity – perfect condition.f

Just put these in the FS section if anyone is interested.

 

Smaller wheel = less weigh but if weight is the same then less side wall = a more responsive steering up to a point of course. so if you buy a really light 18 inch wheel that is lighter then the stock or the same weight you should get better response from the 18". if you look hard enough you can get some light wheels. CCW is a good place to start

 

I'm amazed that folks are dismissing the issue of weight in racing.

The nickles and dimes those that think 17's 18's help, are wasting that much more on braking. Rotational mass DOES matter.

There is a reason f1 runs 13's, there is a reason NASCAR runs 15's.

I'm sure this is all about looks and the driver weighs 250lbs anyway, so it's really not an issue, but if you are a true time is everything racer, saving weight is as if not more important than horsepower.

 

heheh amen to that, flyinbrian !

people love their bling-bling...

 

Depends on the size of your pocket. There are plenty of 18's that weigh less than 17s

 

Well the guy who posted this question doesn't seem to care anymore, but for the hell of it...

I am running 2001 carrera wheels on the street and track. 18x8 and 18x10's, only because I can get tires for free(and they look nice). Once I started going to the track I noticed how much I hate these big wheels. First off the rear tires are way too big for my near stock car. I dont have enough adjustment to compensate for the grip in the rear so I have lots of understeer. I have also noticed a difference in accel and braking. So depending on the setup one is running, the 18's may have an advantage. I also have had rubbing problems on mine. Ive had to roll fenders, cut wheel well's, adjust rear ride hight.

The pricing on 16's look like they are cheaper and I plan on buying some nice comp tires for my stock 16's when i get some more money. And keep the 18's for the street

 

You're right. The 944 Turbo S is gone and now replaced by a 996 running 18s.

 

Very nice. I hope to one day be able to replace or add on to my Porsche collection with a newer 911. Keep the 944 all track