Tire Designations ?

Aspect Ratio - 65 is a percentage of the sidewall measurement. In this case it would be 139.5 MM This is the distance from the bead to the tread face.

R = Radial tire construction.

Changing the aspect ratio changes everything except the rim size.

225/60 R17 = diameter 27.6", Sidewall 5.31", Circumference 86.8" Revolutions/mile 730.3

Hi,

Really good explanation.

Thank you very much.

BTW: Usually safe to go up or down by /5 ? /65 oem to /60, e.g. for new different tires

Bob

--------------------

As long as you keep the speed difference in mind and the load and speed ratings are ok then yes.

They should also say how long the material will last before failing. I recently found out that the material wears out before the tread. For low mile drivers the tread will be fine but the actual tire material is worn and the tires need replacing.

I now buy tires with low tread life ratings for this reason.

A while back, you could see 225/65HR17 . The speed designation. Your not suppose to interchange front back with different speed tires. Lower aspect tires probably don't matter as much as 70 series.

Obviously clearance must be achieved with selected sizes. People try increasing basic tire size if going to lower aspect. Like 235/60 or whatever.

Greg

Speed ratings are still there, sometimes in the sizing sometimes after it. Keep in mind that those ratings are for sustained speed, not occasional excess.

Forgot to mention in the first answer. Sidewall height also has a BIG effect on ride quality and handling. The taller the sidewall the better the ride as there is more area to flex over bumps and road irregularities. However the shorter the sidewall is you get better handling due to the lack of that same flex.

Both have bearing depending on the vehicle you want the tires for.

Tires for your off roading 4X4 will want taller sidewalls for better flex and traction off road. Plus the taller tire gives more ground clearance. The taller sidewall also helps protect the drive train from sudden shocks as they absorb more abuse.

By the same token, the tires you put on your Ferrari will want shorter sidewalls to maximize the lower COG and give you predictable handling.

g wrote: "A while back, you could see 225/65HR17 . The speed designation. Your not suppose to interchange front back with different speed tires."

If, hypothetically, you have T(118mph/190kmh) on one axle and H(130/210) rated tires on the other, what is the danger of that if you never exceed

No real danger.

A higher speed on front will produce oversteer. Generally higher speed rating has stiffer sidewall. Tire pressure will also affect flex.

Greg

There is no danger. The whole "speed rating" thing is a bunch of boy racer nonsense that means nothing to people driving on the highways in anything like a remotely sane manner. Today's tires have a huge safety factor as far as how fast you can safely drive on them. Also keep in mind that the speed ratings were based on tires loaded to at least 85% of their rated load. That's far higher loading then the perhaps 60 to 70% of max load users would typically see.