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Old 11-01-2003, 08:30 AM   #1
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Here are a few helpful links of interest:

What does offset mean?

Offset is the relation between the mounting surface of the wheel (the pad that mounts on the hub) and the centerline of the wheel. This keeps everything centered in the wheel well. The higher the offset number, the more it pushes the wheel/tire toward the suspension of the vehicle, the lower the number, the more it moves everything out toward the fenders.

How tires work, construction, etc.

Wheel fitments:

There are a lot of factors that go into a wheel fitment. These include (but are not limited to) bolt pattern, offset, center bore, and load rating. The shape of the inside of a wheel can be an issue on vehicles with larger brakes. If a car has been lowered or has coilovers that will change the wheel fitment as well. These changes will require a test fitment on the car where you have access to the vehicle and the tires/wheels. That's the only way to know for sure if it works. We have to do this for every wheel we sell on the stock vehicle setup. That way we can guarantee they fit and with what tire size.

Please don't ask me for fitment information on a wheel we don't sell. You need to check with the vendor selling that wheel for the correct fitment information. It's not that I'm trying to be crappy, it's that I have no way to tell if they will fit or work safely. It's sort of like asking a Volvo parts department if a wiper switch off a Camaro can fit on a Volvo and what would be involved in making that work. You need to go to the vendor selling that item. If they are selling that wheel for your vehicle, they should have test fit information about which tire size/s work right? No one else is going to be able to tell you what will fit without access to the wheel, tire, and vehicle. If they can't tell you what tire size to run, that tells me they have never test fit them on the vehicle. If that's the case, how do they even know the wheel fits?

Wheel weights
Provides a great collection of wheel weights by diameter, but does not tell you weights by width(so it may be off on certain wheels because of width differences)...still a good 'rule of thumb' type guide to what wheels are worth buying for weight saving purposes.

More wheel weights and specs
Like the site above, provide lots of usefull wheel information, weights, bolt patters, finishes, etc.

Tire pressure info
How to set your "Base" tire pressure(see below for more information as to why thats important) for performance, and howto read a load index, tire sidewall, etc.
Good posts about suspensions and wheel tire package affects on track handling.

Tire Inflation Tips for Road or Autocross Racers

1. Inflate your tires to your desired pressure(IE 30-32psi baseline usually).
2. Mark each tire from the outer edge of the treadblock(outside edge blocks) to about 1" down the sidewall of the tire. I suggest using a white grease pen.
3.Do your lap, run, etc.
4. Check to see how much of the grease mark has worn off.
-if LESS than 1/4" is worn off, deflateyour tires a few PSI
-If between 3/8" and 5/8" is worn off, remark the tires.
-if MORE than 3/4" is worn off, inflate the tires a few PSI.
Remark the tires and write down the PSI you set them at. Idealy you'd get about 1/2" rollover during hard cornering, maximising contact patch. You may notice different tires(Front to rear usually) require different settings of air pressure to run effectively, thats fine just adjsut them and keep checking.

Trouble shooting tire symptoms at the track
Troubleshooting Tire Temperatures
Reading - Handling problem - Reason

All tires too hot - * - Compound too soft for track and ambient temperature conditions.

Front tires too hot - Understeer - Front tire pressures too low.

Rear tires too hot - Oversteer - Rear tire pressures too low.

Inside edges too hot - Too much body roll - Too much negative camber or too much toe-out.

Outside edges too hot Too - much body roll - Too little negative camber, too little toe-out or too much toe-in or wheel width too narrow for tire width.

Center of tread too hot - * -Tire pressure too high.

Edges on too hot - * -Tire pressure too low.

All tires too cold - * - Compound too hard for track and ambient temperature conditions or car not being driven to limit.

Front tires too cold - * - Inadequate load on front tires.

Rear tires too cold - * - Inadequate load on rear tires

Remember to set your cars pressure back to normal after the event if you use street tires(street tire class, etc).
You'll probaly noice quite the improvement in cornering using this method....
Tire Maintanence Tips and General Information
Tire Terminology
Directional- The tire has to rotate in one direction, in respect to the vehicle. Directional tires generally feature swept back tread blocks, and use this design for better water traction. Directional tires will have a "rotation" or "direction" arrow specifying how it should be sitting on the wheel and car.
Asymetrical- The tires tread is different from side to side, and MUST have one side of the tread design/tire facing out, the other facing in. A few tires feature this design, it serves the same purpose as using a directional tread, buy lends itself to larger tread blocks overall(generally speaking).
Tire Care
Rotation- Rotate your tires, supposing they are the same size front and rear, every 4,000 to 6,000 miles. The harder you drive, the earlier you should rotate them, and vice versa. If you have a directional tire, you can only move the tire/wheels front to back, and can't switch sides without dismounting the tires. If you have excessive allignment problems(negative camber), I would reccoment dismounting the front tires, and swapping them side to side before the rotation, this will help even out the wear pattern that you see so often(inside edge worn out too early). If you have asymetrical tires, you can rotate the tires any way you want, but I would recommend a modified cross roatation. The front tires go to the opposite corners, while the rear go straight up(IE LR tire is LF, but LF tire is now RR.), this wont avoide the edge wear(since the tire can only have one 'outward' side) but it will help extend the life a little bit by avoiding repeditive suspension stresses(wear patterns). All other tires you can rotate as you want, ususally front to back, as normal.
Tire Inflation
See above post and FAQ link about tire pressures. Check your tire pressure at least once a week when the tires are cold (before you drive on them in the morning) to make sure you aren't running one under-inflated. It's important to remember, for every 10 degree change in ambient temp outside, you will gain or loose 1 psi of pressure in your tires. If the outside temp drops 20 degrees, you will loose 2 psi. If you park in a heated garage in the Winter, this can lead to a dramatic drop in pressure when you get the car on the road. You have to bump up your pressure to make up for that change!
Stages of tire wear
Most tires start with 10-11/32" of tread all across the tread blocks. In between the trad blocks you should see some little "bridges" of rubber, those are "wear bars" once a tire's tread is worn to those, its time for replacement(most wear bars are at 2/32"). After the wear bars, you will hit "secondary rubber", which is a rubber cap below the main tread carcass, you will know it by a slight discolloration compared to the regular tread rubber. After that, you'll hit your cords, or the inside of your tire...we all know what that is. Check your tires wear every week(with your tire pressure), and at worst every month, and be sure to cheack the inner and outside edges for odd wear, just because the middle of the tread is fine, doesnt mean the tire is.

other links soon, keep checking back.
Your personal contact at The Tire Rack
1-877-522-8473 ext# 313
fax# 574-236-7707

Last edited by Grant@Tirerack; 11-01-2003 at 11:46 AM.
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