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Component Matching #5
Page 2
Now that I have managed to turn most of the readers off with my negative comments. For those of you that are still reading this. Here are a few thoughts on selecting tires for your T.R.
The size you select should be the largest tire you can fit both on the stock wheels and in the wheel well. On out cars the largest for the fronts should be 235 x 60 x 15. Some 245s will fit but some will also rub the inner fenders when turning. The largest in the rear is 245 x 60 x 15 for normal highway radials.
For performance tires in the rear, 275 x 50 x 15 or the equivalent cross reference of, 26 x 10 x 15 for slicks will fit but be careful when turning into up inclines such as driveways like mine. The front sway-bar is thicker and stiffer and will cause the car body to be more closely aligned to the attitude of the front wheels. This means that the body will tip or lean and could contact the rear tires in the wheel well. To avoid this try to approach driveways at an incline straight forward rather than at an angle.
Some people use 28 x 10.5 x 15 slicks, these will most likely require trimming of your inner fender lip. The equivalent metric size for the cross-reference is 275 x 60 x 15. The profile number is the only difference and that makes the 2 inch difference in height.
Here’s a little known fact. Take a tread width measurement of an M&H 26 x 10 x 15 DOT and then do the same on a 28 x 10 x 15 DOT. We are talking about the 275 x 50 compared to the 275 x 60. The tread width will be wider on the shorter tire. This indicates to me the potential for better traction due to the wider tread contact patch on the shorter 26 inch tall tire.
When selecting tires make sure you use the proper width wheel. This is something that some have chosen to not do, as evidenced by the number of TRs I see with stock width wheels running tires that I know are designed for wider wheels.
Tires are designed for a specific wheel width. Sometimes there is a range of choices. By choosing the widest wheel in the range you will be getting the best selection. This is because the footprint of the tire is affected by the way the tire carcasses is held or carried in the bead of the rim. Narrower bead separation means the tire is deformed by forcing the bead edges closer together. This means deformation to the original design even if the wheel width is within the spec but on the narrower side.
This effect is greatly increased, if the wheel used is narrower than the rim requirement specs suggested by the tire manufacturer. This forcing the bead edges closer than designed, results in a rolling effect that pulls up on the side edges of the tread contact patch.
The only way to address this condition is to run lower pressure in the tire, which deforms it to an even greater extent causing the sidewalls to bulge out in order to try to get the edges of the tread contact patch to lay flat on the pavement. This is the only thing that can be done to address this condition and is not desirable.
Having too little pressure can cause the sidewall to wear on the pavement and make the tires run hot from flexing more than they were designed to when rolling. Even if you are lucky enough to get the exact amount of air pressure that straddled the fine line between best possible compromise for tread contact and avoiding sidewall contact on a straight forward roll, they will still likely contact the sidewalls to pavement when cornering.
Besides this, the center of the tread patch will be either loaded very lightly or possibly loose contact during certain operating conditions. It also makes the tire more likely to break away from the bead seal when cornering, since it will possibly be riding on the rolled over sidewall, and not have the proper pressure to keep the bead seated.
Besides all of the previously mentioned negatives for this mis-match of components, the tire being under inflated will be very soft and will not feel right, handle or drive well.
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