Geo

Fergit it. You're going to get smart-assed comments anyway.

Since you always post cool pix, often rally cars, I figured I should post a rally car gone straight.....

Scott at Team Harco

Blasphemy!!! Next thing you know we'll be seeing WRXs and Evos on the track! Oh...wait.....too late.

Scott at Team Harco

Kevin,

Welcome to Rennlist. This is a great place.

No you're not likely to notice the difference between a 7" or a 7.5" inch rim. The larger rim will permit the installation of a slightly larger (wider) tire.

Regarding tire questions: The Tire Rack has a very useful technical section. Here is the link to their explanation of tire sizing.
http://www.tirerack.com/tires/tirete....jsp?techid=46

Hunt around for more tech topics. If you don't find the answer to a particular question - you can always bring it here. If we don't know the answer - we can always make something up.

Litespeeds

Wow, I didn't think this thread will spark so much information. I understand about unsprung weight and I know it is very important for both acceleration as well as handling and even braking.

The main thing to consider is if this is going to be a track only car or a car that I will be driving to and from the track. After going to Thunderhill on Tuesday with the Lotus club, I got the chance to drive my friend's Spec 944 and it was alot of fun. The more I think about it, I don't think I will ever race in the Spec 944 group. I don't think I have it in me to push any car to its near limits. My decision will be to probably keep my rear torsion bars stock and upgrade around that with shocks, springs and swaybars.

At the same time, I will have to weigh the 15x7 phone dial wheels with Toyo RA1 tires to see what the exact weight is and compare that with the 18" wheels and Pirelli Corsa tires and see how much difference it really is before I make my final decision. Thanks everyone for posting.

shepcam

I have the Boxster S 17"s and they give a firm ride but handle well with the low profile tires. I had to get rid of those ugly 15"s!!!! I dont plan to track the car anyway so performance was not a big issue.

Geo

If you're not racing, just get whatever pleases you. Even if you're going to the track, don't worry about equipment making you faster. If you want to go faster, work on the driver.

Matt H

That is because they do not use things like sidewall stiffeners, etc. The tires are made JUST for the track, on the street they are very prone to damage. If you have ever picked up the rear wheel from a funny car you know how light a wheel and tire combo can be (can be lifted with two hands quite easily, probably throw your back out since it is so much lighter than it appears).

It is not made by any manufacturer and I dont think there is a RMA spec for it (no RMA spec, no buildly tire). I can check if you care.

The single most important difference, and it is a big one, is that you are better able to use a 225/45R17 on the 7.5" wheel. This will make the stagger from front to back less and it is a HUGE plus. If the 235/35R17 is mounted on a 7" wheel, I would not want to drive it. That tire is oversized for the wheel.
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M758

When I stated in autocross in 1998 and DE in 1999 I never figured I would ever race either. I figured 1-2 events per year in my stock 951 on street tires would be enough.

You can see where that lead to.


BTW.... the 225/50 on 15x7 wheels is one of the cheapest tire/wheel combo you can get for the 944. My guess it you can easily spend 75 to 100 less per tire than you can with 18" or even 17" wheels. Plust using the same size tire on all corners allows you to rotate all 4 tires to maximize tire wear.

A DE car on RA-1 can probalby last one full season on one set of tires at $130 each or so. Food for thought.

Dave in Chicago

I second Joe's "one season on RA-1" comment. That's been my experience through last year (many DE days) and this year (DE + Club Racing). Both seasons ran me through a set. I still have enough for a bit of track time now if I can finish my brake rebuild work in time.

RA-1's may not be the fastest in Club Racing, but I find them to be just about the PERFECT DE tire.

They will make noise a bit (not too surprising at the limit), wear well, appear to be tough enough for street use, and have usable tread in the wet (but don't expect them to resist hydroplaning like a really good street tire - they won't).

I buy RA-1's at www.frisbyracetire.com.

Geo

Agreed, the RA-1 is not the fastest race tire, but our philosophy was, when we have gotten everything else out of the car and/or all that was left for us to get to the front or as close as possible was the 1-2 seconds we could get from Hoosiers, the RA-1 was just fine and we'd sink the savings back into car development. I imagine I will run them for a while on my ITS 944 until I can justify the faster tires. It's not like we're running pro races.

blindeye

This is my 83. I really liked the black contrast of the cookies but hated the cookie cutters. I kept them in great condition. But wanted to update the look. Found some 17" Cups. Yoko ES 100 225/45 front and 255/40 rear. Street only use. The high profile 215/60's rode smoother, softer and quieter. They took bumps in the road better. The 17 ride rougher but grip better. Car cornes better than it did with the stock 60's. Since its not a 0-60 car, at least as a commuter car, accel isnt that important - if there is a difference. And if you wanna make up any of the difference, remove your inflatable spare. The 60's did tend to float down the road. You could release the steering wheel and it would go straight down the road. With the lo porfile 17's, they tend to track and turn quickly according to what they come in contact with in/on the road. Cant let go of the wheel or I'd be off and onto the street in no time. Love the new look. Car looks 10 years newer. Thinking about painting the spokes on the Cups black for the contrast. Do what you want to your car. You have to drive it. You have to live with it. Personalize it so that YOU are happy with it. For the Porsche purist, the Fuchs cant be beat. But for stylin', the 18" Turbo Twists look like they were made specifically for the 944. Love that look, but the Cups dont suck either.

Here are a couple of links to calculate tire differences... They all seem to vary in their calcualtions.
http://www.dakota-truck.net/TIRECALC/tirecalc.html
http://www.web-cars.com/math/tiresize.html
http://www.1010tires.com/TireSizeCalculator.asp
http://www.net-comber.com/tirecalc.html
http://www.geocities.com/vipervenemgts/tire_calc.html

Litespeeds

Car looks great with the 17" cups. The 1st picture shows a larger wheel gap and the 2nd picture looks like you lowered the car a little.

I have already calculated the tire sizes and the stock 15 x 7 with 215/60/15 tires has an overall diameter of 25.16. If I go with an 18" wheel the front tire will be 225/40/18 with an overall diameter of 25.08 and the rear tire will be 265/35/18 with an overall diameter of 25.30.

The formula is tire width (215) multiply by ratio (.6) divided by 25.4 multiply by 2 and add rim size (15) and you will get the overall tire diameter.

By going with this combination, the speedometer will be just about the same as stock and the handling should be more precise with the ultra low profile tires. I am sure the car will suffer in acceleration but the only way is to borrow my friends set of wheels and put them on my car and see how they look and drive. That is the best way to do it before I make my final decision.

I guess if I really wanted to, I can have a street set of 18" wheels and tires and also a dedicated track set with the 15" phone dials. Just depends upon how much money I want to put into this car.

kevincnc

Thanks Scott- that is exactly what I was looking for-
Kevin