After searching long and hard to find the right tire size and rim combination i kept running into different types of construction on the tire and reasons why tires fall off of beads, etc. Leaving me pretty frustrated.

It's only after reading semi-extensively into suspension dynamics that i've come up with a way of choosing tire and rim size depending on your application.

In all applications having less unsprung weight is an advantage.

Unsprung weight is the weight from the coils down. (Brakes, tires, rims basically.)

The reason this matters is because it effects the way your shocks and coils respond too going up and down. Obviously more weight equals more work for the shocks and springs coming down, more force coming into the system.

Less unsprung weight means better response out of your coils and springs. (They will hit the ground faster and stay on the ground better.)

This is why i'm guessing offroaders pick small wheels and attach large tires to them.

This advantage is two-fold. With the tire being larger, along with say a bias-ply construction, the tire, being rubber and air has a better chance to conform to the environment under it. Also reducing unsprung weight with smaller wheels and less material in the tire.

So the first step to increasing offroad performance would be reducing unsprung weight and getting a larger diameter tire.

For on-road performance unsprung weight still applies but different dynamics come into play. The stiffer the entire system, and the lower the center of gravity, the better. This is why larger, lighter weight wheels hold really small tires on them. More rubber and air = less stiff.

So the lighter the wheel the better no matter which way you look at it. (You also have to keep in mind strength though.)

So for you guys who want pure offroad performance in your tires and rims. Pick the smallest diameter rim possible witha bias-ply tire.

For the most of us that take our rig offroading once in a while if at all ever. A Radial all-terrain tire coupled with a slightler smaller rim than 20" is a better choice.

This isn't complete, and please add/critique/contribute to this so we can have a general reference point for the best tire and rim size for what you want to do.

(UNless all you care about is looks then none of it really matters.) i want both, looks and functionality so if i can spend the same amount or even less money and make my truck ultimately safer, more functional and looking good i'll be happy.

 

interesting stuff on unsprung weight! Nice to have someone actually looking stuff up instead of just asking!!

I would say you are right on track!

 

Tis why I've always said that I wished 15" wheels would fit on my truck and why I've posted 3,818 times about choosing a 17" instead of a 20" or larger on a 4x4...

 

yes the 15 or even 17 will be much better for performance, im a sucker for the larger wheels, and quite frankly wish i went with 22's....maybe one of these days lol. that was a nice tid bit of info you found and what a NICE change of pace that is to actually see someone do their homework!! :thumbsup:

 

i like this thread, its the function over form thread. the thing is unsprung weight is really only taken into consideration when your dealing with racing or performance related w/e. Most people will change wheels and tires for looks and function, and then will throw in price.

good write up though

i just picked up a set of 20s with 34" tires on monday off craigslist

 

Thanks guys for the positive replies.

I was surprised at how complicated this type of thing can get. There's all kinds of different factors like the offset and inset of the wheel, and all kinds of markings on the wheels that help you match them to different sizes which wheel/tire places don't want you to know.

I wish I did due diligence before I purchased my sound equipment.