How and why to photograph your tire sidewall info

I recently received this comment/message/question about tire sidewall info:

A material list on the tire sidewall? I’ve never seen this. It sounds like FDA package list of: flour, corn syrup. Reading black bumps on black might work in ideal lighting, but I have trouble finding the max PSI.

I replied with this:

The list of materials and the max load numbers are easily seen molded on the sidewall of all tires per Federal Regulation for the last 30 years. The US-DOT specified  size, location and content are as seen in the attached examples. These pictures were taken with natural lighting and not even in direct sunlight.

To read letters molded on your tire sidewall, you might find it easier if you get out your phone aka camera and snap a couple of pictures of this important information.

I suggest you wash your tire sidewall with soap and water and snap pictures of three areas with the tire in full sunlight. Here are examples from three different tires:

 1. The complete DOT serial

NOTE: You should confirm all your tires have the same serial number. If not, get a picture of each serial number.

 

 

 2. The tire max load information

 

 3. The tire material list

Note on “Max psi”: You should focus on the “Max Load” and understand that the tire is only rated for that load when the tire is inflated to the stated PSI, and the inflation is checked at ambient temperature. The “Max psi” IS NOT the highest level of inflation a tire can tolerate. Undamaged tires can tolerate much higher PSI when warm from running.

Keep in mind, if you have the tire sidewall info handy in a photo or on your phone, it will be much easier for you than if you have tire problems in the middle of the night and don’t know what tire you need for a replacement.

 

 

 

 

 

 

Can you really tow your trailer at almost 90 mph?

 In September 2024 I wrote about the operational limits on ST-type tires. I suggested that the published 65 mph speed limit was a realistic compromise. But apparently many people think they can get tires with some “magic” rubber in them so they can safely drive faster. Therefore, I am again writing about the “speed rating” of ST-type tires.

 

In the U.S., “speed rating” is really a measure of tolerance for high heat and is based on a test with speed increasing every 10 minutes until the tire fails. In Europe, Asia, and the rest of the world, they do not offer an ST-type tire because their speed tests are more realistic and stringent.

When radial ST-type tires were introduced to the U.S. market some 45 years ago, they were given a higher load capacity rating than a same-size LT tire. However, the trade-off was stated in the industry standards books as having a max operating speed of 65 mph, with load and inflation adjustments required if operating above 65 mph. With 50 years of tire design and testing under my belt, I know of no “magic” rubber that will deliver greater load capacity for a given size and inflation without some trade-off.

Five variables for operation speed

There are only five variables that control operation speed: size, load, inflation, speed and the ability to be rated for operation with passengers in the vehicle. So, unless you invent some “magic” rubber, you are limited by physics.

Yes, materials have improved over the last 45 years after the switch to radial construction, and we have seen improvements in tire performance. But have you ever asked why a company can make a tire of the same physical size and same load capacity at a given inflation and somehow make one tire carry significantly more load than the other without some trade-off in operation speed?

 If I had invented some “Super Magic Rubber” for ST-type tires that gave them “Super Strength,” why wouldn’t I put the Super Rubber in the other tires I make and sell and take over the worldwide tire market? Any company can ignore reality and make a marketing decision and claim a “Speed Rating”.