# Industry standard question about tires **URL:** \ **Category:** Factual Questions\ **Created:** [July 13, 2009, 8:52pm UTC](https://boards.straightdope.com/t/industry-standard-question-about-tires/502899 "2009-07-13T20:52:48Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![mazinger\_z](https://avatars.discourse-cdn.com/v4/letter/m/5f9b8f/32.png) [@mazinger\_z](https://boards.straightdope.com/u/mazinger_z)\ **Post date:** [July 13, 2009, 8:52pm UTC](https://boards.straightdope.com/t/industry-standard-question-about-tires/502899/1 "2009-07-13T20:52:48Z")
If I wanted to know where to find industry standard definitions about tires, e.g. treads, sizes, weights, names and definitions (like definition of a tire cover is xxxx; definition of a tire patch is xxxx, treads are yyyy, and steel belted radial means zzzz), where would I look? Thanks in advance. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [July 13, 2009, 9:10pm UTC](https://boards.straightdope.com/t/industry-standard-question-about-tires/502899/2 "2009-07-13T21:10:40Z")
Tire size is given by a number like P225/50R16. P means passenger vehicle (T is temporary, C is commercial, LT is light truck, I don’t remember the rest). 225 is the tire width, in millimeters. 50 indicates the sidewall height as a percentage of the width (I don’t know why they do it this way instead of just giving it a height, but they do). In this case it would be 50 percent. R is radius, so R16 means it fits on 16" rims. Can’t help you with the rest, sorry. ---
**Author:** ![mazinger\_z](https://avatars.discourse-cdn.com/v4/letter/m/5f9b8f/32.png) [@mazinger\_z](https://boards.straightdope.com/u/mazinger_z)\ **Post date:** [July 13, 2009, 9:18pm UTC](https://boards.straightdope.com/t/industry-standard-question-about-tires/502899/3 "2009-07-13T21:18:30Z")
> [@engineer\_comp\_geek](#): > > Tire size is given by a number like P225/50R16. > > P means passenger vehicle (T is temporary, C is commercial, LT is light truck, I don’t remember the rest). > > 225 is the tire width, in millimeters. > > 50 indicates the sidewall height as a percentage of the width (I don’t know why they do it this way instead of just giving it a height, but they do). In this case it would be 50 percent. > > R is radius, so R16 means it fits on 16" rims. > > Can’t help you with the rest, sorry. That’s good so far. Is there a place where all this is written down? I know there’s something for what I’m looking for with regards to electricians and code, and such. I am curious if there is something associated with tires. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [July 13, 2009, 9:21pm UTC](https://boards.straightdope.com/t/industry-standard-question-about-tires/502899/4 "2009-07-13T21:21:47Z")
I found these Googling under _automobile tires specifications_: [http://www.offroaders.com/tech/AT-MT-Tires/tire-tech.htm](http://www.offroaders.com/tech/AT-MT-Tires/tire-tech.htm) [http://www.howstuffworks.com/tire.htm](http://www.howstuffworks.com/tire.htm) (go through all seven parts) …and this Googling under _automobile tires construction_: [http://en.wikipedia.org/wiki/Tire](http://en.wikipedia.org/wiki/Tire) I’m sure much more is available by Googling. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [July 13, 2009, 9:32pm UTC](https://boards.straightdope.com/t/industry-standard-question-about-tires/502899/5 "2009-07-13T21:32:30Z")
> [@engineer\_comp\_geek](#): > > R is radius, so R16 means it fits on 16" rims. No, R is Radial construction. 16 (all by itself) is the **diameter** (not radius) of the wheel, and thus of the hole in the tire, in inches. So yes, it fits a 16" rim. ---
**Author:** ![Dog80](https://avatars.discourse-cdn.com/v4/letter/d/6bbea6/32.png) [@Dog80](https://boards.straightdope.com/u/Dog80)\ **Post date:** [July 13, 2009, 10:12pm UTC](https://boards.straightdope.com/t/industry-standard-question-about-tires/502899/6 "2009-07-13T22:12:42Z")
> [@engineer\_comp\_geek](#): > > 50 indicates the sidewall height as a percentage of the width (I don’t know why they do it this way instead of just giving it a height, but they do). In this case it would be 50 percent. Pure racing tires (ie. non DOT-approved) usually have overall diameter in mm as the second number. For example, 245/620/17 (roughly equivalent to 245/40/17). I guess they do it that way because it is easier to calculate how a specific tire size will affect the final drive ratio.