wheel and tire size question

cr500taco

Adventurer
I am going to be getting new tires very soon,. But just got to thinking. My Tacoma has 31x10.5x15 tires on 7" wide wheels. the wheel width range for the tires is 7"-9". is it better to have the tire on a narrower wheel or wider wheel?

Also, is it better to stick with 15" wheels or get bigger wheels?
 
Last edited:

Ducky's Dad

Explorer
Depends on how you use the truck. Off-road, stick with 15s. Better compliance over obstacles and softer ride because of the taller sidewalls relative to tire diameter. You can improve lateral acceleration on pavement, slightly, by going to a wider rim. Street handling would be improved with a larger diameter wheel if you stay with 31s, but ride quality would degrade slightly and steering feedback and responsiveness would improve. For a trail truck, bigger (diameter) wheels look cool but hurt performance. More rim width is usually a good thing for just about any application, as long as it fits the tire and does not cause clearance problems.
 

cr500taco

Adventurer
Depends on how you use the truck. Off-road, stick with 15s. Better compliance over obstacles and softer ride because of the taller sidewalls relative to tire diameter. You can improve lateral acceleration on pavement, slightly, by going to a wider rim. Street handling would be improved with a larger diameter wheel if you stay with 31s, but ride quality would degrade slightly and steering feedback and responsiveness would improve. For a trail truck, bigger (diameter) wheels look cool but hurt performance. More rim width is usually a good thing for just about any application, as long as it fits the tire and does not cause clearance problems.
thanks for the input. I am referring to off road use. so, it would be best to go with a 9" wheel? In the future I plan on going up to 33x12x15 and those recommend 8.5" to 11" width wheel.

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Ducky's Dad

Explorer
would be best to go with a 9" wheel? In the future I plan on going up to 33x12x15 and those recommend 8.5" to 11" width wheel.
Probably yes. I've never owned a Taco, but 9s are likely a bit wider than most Tacos run with 12" cross section tires. Be careful selecting offset and backspace so that you don't mess up clearance with suspension components or body parts at full lock and full stuff. Too little backspace will put a strain on your steering and suspension. Best advice is usually to keep the new rim centerline within 1/4"+/- of where the stock rim centerline is. I'm running 35-12.50s on 8" on my Dodge and they are fine on those rims. Ran the same size tires on 7.5" with no problems. 12" tires on 9" rims may prevent you from using tire chains.
 

4x4junkie

Explorer
Keep in mind the tire beads generally can slip off easier with a wider rim than with a narrower one when aired down for offroad use.

If you're looking to upsize to 12.50-wide tires in the future, I'll 2nd the suggestion to go with 15x8 wheels.
 

cr500taco

Adventurer
Keep in mind the tire beads generally can slip off easier with a wider rim than with a narrower one when aired down for offroad use.

If you're looking to upsize to 12.50-wide tires in the future, I'll 2nd the suggestion to go with 15x8 wheels.
that makes sense about the tire harder to slip off a narrower wheel when aired down. there seems to be only a few tires available in 33x10.5x15. I am running 31' BFG's right now and BFG's are one of the few that are available in 33x10.5x15. But, I am going to try out Cooper Tires for my next set. if I like them over the BFG's, I am going g to stick with them. but, unfortunately, they are not available in 33x10.5x15. So, I will be stuck with having to get 33x12.5x15. I may be getting set of 31"s for daily driving and and another set of 31's that's more aggressive for off road use when going on trips. So, I will need to get a second set of wheels. the 15x8 will be good, because than I can use them for both the 31"s and 33"s. Just not ready to get 33"s, yet because, I'll probably need to regear and it seems that I need to get wider fenders to run the 12.5 wide tires.

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cr500taco

Adventurer
I went to the trouble of contacting several manufacturers recently when shopping for new wheels in addition to new tires; the tire size I planned to run indicates compatibility with a 6.5" to 8.5" wheel. Customer service was... not helpful. I was summarily told to "only mount tires on approved rim widths" (not the question I asked) and variations of "we cannot make recommendations other than to use approved rim widths" . The question I had asked was how rim width affected behavior within the approved range and what benefit I would gain by running a 7" wide or 8" wide rim (both are within the approved range, and both are readily available rim widths for my application) .

In the end I found absolutely no *authoritative* and rigorous answer on the topic. The general agreement among countless everyday random people on the internet is that a wider wheel (for a given tire, within approved range) will provide quicker response to steering input while a narrower wheel will allow lower air pressures without burping out air at the bead over very uneven surfaces. Nothing backed up by any sort of academic rigor just "common sense" assumptions.

I went with 8" wheels, for 255/80 series tires. Have nothing to compare them with for this particular platform (new truck to me, new kind of truck to me)
that's why I posted here. to get feedback from people who actually use their vehicles they way I plan to, because they know.

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Ducky's Dad

Explorer
Nothing backed up by any sort of academic rigor just "common sense" assumptions.
Lots of this is backed up by reputable magazines and their road/tester-reviewers, some of whom are actual engineers and some of whom actually know how to write. I am not referring to your typical offroad/4WD publication, but to others such as Car & Driver, Road & Track, Motor Trend, AutoWeek, etc. The truck and offroad rags seem to be particularly sloppy in their test practices and writing/editing. The info about steering response, coefficient of friction, lateral acceleration, suspension and steering loads is covered in numerous books on race preparation for various types of vehicles. When I was more serious about this stuff (a long time ago), I used to go to the Millikan Library at Cal Tech to find the articles and papers that were not on the local news stands. The material is out there, is well documented, and can be found if you dig. Most tire company employees don't know much.
 

Happy Joe

Apprentice Geezer
After much research (and more than a little frustration with the supposedly knowledgeable) and after more than a little experimentation on my part;
I found that for non racing dual purpose on and off road use on SUVs, pickups etc. a good way to pick a rim width is to simply measure the tread width of the tire in question (note don't go by the section width, it has no real relation to the tread width between brands) and pick a rim that comes close.
Picking a rim that is slightly narrower can be advantageous if running very low aired down pressures though I haven't had issues (typical air down pressure is in the 7 to 12 psi range, typical highway pressure is in the 24 to 30 psi range).
For example my 12.50 section width tires have a tread that measures in at 9.75 inches so I went with 10 inch rims (I could have gone with 8 inchers but the extra 1/4" of rim has posed no issues on or off road.

Enjoy!
 

cr500taco

Adventurer
I did some more researching online. a couple of websites stated that for off roading it is better to have a narrower tire than wider tire. wider tires are good for deep mud and soft sand.

So, it sounds like, once I am ready to go up to 33"s, it is best for me to get 16" wheels and 285/75/16 tires, instead of 33x12.5x15. It seems that 285/75/16 is a popular size that people are running on their Tacomas and they don't need to get fiberglass fenders, which I think that I will need with 33x12.5x15. Plus the fact of giving me more tire options, since very few tires are offered in 33x10.5x15.

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cr500taco

Adventurer
I did some more researching online. a couple of websites stated that for off roading it is better to have a narrower tire than wider tire. wider tires are good for deep mud and soft sand.

So, it sounds like, once I am ready to go up to 33"s, it is best for me to get 16" wheels and 285/75/16 tires, instead of 33x12.5x15. It seems that 285/75/16 is a popular size that people are running on their Tacomas and they don't need to get fiberglass fenders, which I think that I will need with 33x12.5x15. Plus the fact of giving me more tire options, since very few tires are offered in 33x10.5x15.

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bump for answers to this.

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