Tire theory

[surfingcrna]

Just wanted to make sure I understand the effects of changing rim size.

As long as the overall diameter remains unchanged, no changes to the mechanics of the truck need to be done if you change rim size correct?

For example:
285/45r22 changed to 280/55r20 yields a 0.1% difference. A couple sources list < 0.5% difference is preferable.

I also included a pic I found with a larger difference just to verify the idea.

 

[Edwards]

In terms of speedometer/odometer all you care about is overall diameter. In terms of other things it's a turkish garage sale.

If you get too much offset or too wide a tire, mileage goes down due to wind resistance.
If you raise the truck too much due to lifts or taller tires mileage goes down.
If you get heavier wheels (very easy to do unless you spend $$$ on lighter forged wheels) mileage goes down along with HP/torque because you are now having to spin more weight.

 

[Phoon]

As long as all 4 tires are the same outside diameter on a 4x4 vehicle you are golden. You can throw 35" tires on a stock truck and not do anything mechanically as long as they physically fit on the truck.

It will just change the way it drives a little, and throw off your speedometer as the effective gear ratio has been changed. A bigger tire travels further on one full revolution than a small tire.

 

[surfingcrna]

Thanks. I was trying to increase my available options being that is seems there's not many choices for the 22 inch rims. Wasn't planning on lifting and it seems I had to adjust the tire calculator to a smaller width to maintain the <0.5%. I was even able to go to an 18 inch rim by choosing 275/65r18 though I have no clue what that would look like on a truck. And I was trying to keep the speedometer correct. Just a way to sort out the theory in my head

I've read more side wall looks better but can give you a bouncy ride, though maybe if you have the pressure a little higher that might help.

 

[Edwards]

Thanks. I was trying to increase my available options being that is seems there's not many choices for the 22 inch rims. Wasn't planning on lifting and it seems I had to adjust the tire calculator to a smaller width to maintain the <0.5%. I was even able to go to an 18 inch rim by choosing 275/65r18 though I have no clue what that would look like on a truck. And I was trying to keep the speedometer correct. Just a way to sort out the theory in my head

I've read more side wall looks better but can give you a bouncy ride, though maybe if you have the pressure a little higher that might help.

More side wall looking better is subjective. Find what you like. Taller tires (more sidewall) do ride softer but can also prevent popping a tire on the highway (ask me how I know). Lower sidewalls give more control and road feel but at the risk of tire/wheel damage.
A whole other ball of wax is going XL or D/E load range. The higher up that path you go the stiffer the ride will be. You need to decide what trade off between tire indestructibility vs. nice ride.

You'll notice the hardcore off road guys going 18" wheels and the street crowd (forgive the generalizations) going for the 22". I'm sticking with 20" because it still gives more sidewall than my MB E550 had. Rides awesome, looks good to me, and handles my off road adventures beautifully.

 

[surfingcrna]

More side wall looking better is subjective. Find what you like. Taller tires (more sidewall) do ride softer but can also prevent popping a tire on the highway (ask me how I know). Lower sidewalls give more control and road feel but at the risk of tire/wheel damage.
A whole other ball of wax is going XL or D/E load range. The higher up that path you go the stiffer the ride will be. You need to decide what trade off between tire indestructibility vs. nice ride.

You'll notice the hardcore off road guys going 18" wheels and the street crowd (forgive the generalizations) going for the 22". I'm sticking with 20" because it still gives more sidewall than my MB E550 had. Rides awesome, looks good to me, and handles my off road adventures beautifully.

Thanks for the info.

Which 20in do you run?

 

[Edwards]

Just the standard 20" on the Limited. I bought the truck as I liked it and plan to run the ORP Falken's until I need new tires. They are exceeding my expectations.

 

[surfingcrna]

Do the towing specs change based on different tire dimensions or is more based on tire construction?

 

[Billet1500 4x4]

Do the towing specs change based on different tire dimensions or is more based on tire construction?

they change based on dimensions. A load range E for one size will be different than a load range E in a different size tire. Look for the number and letter that accompanies a tire. Like 113T this is how you compare apples to apples. the number is the load range, google load range chart and the number corresponds to a load rating for the tire in pounds. the letter is the speed rating google speed rating chart and the letter will have a MPH with it. Factory 20's are 113T so as long as the tire you're looking at is 113 or higher you're golden. It's also a good indicator of how stiff the tire will feel. higher number stiffer ride. Tires with 2 numbers are common in the LT sizes the higher number is load rating at max inflation pressure the other number is for a lower inflation pressure given by the manufacture don't hold me to this but i think it's at 75% max inflation but I could be wrong all tire manufactures have this info on their web sites. You might see LT 305/55R20 123/119T Load E 10 ply as an example.

 

[surfingcrna]

Thanks that's what I was looking for. Appreciate it.

 

[Billet1500 4x4]

Thanks that's what I was looking for. Appreciate it.

No problem, that's what these forums are all about.

 

[surfingcrna]

I ran into one more thing. When looking at wheels there were 2 offsets listed and both were supposed to be compatible according to the website. As I understand the offset is how far away from the center of the tire the mounting hub is. If that's the case how can +19 and +1 both fit? Wouldn't that large of a difference make the tire run on one side or the other?

I posted an example pic

 

[Billet1500 4x4]

I ran into one more thing. When looking at wheels there were 2 offsets listed and both were supposed to be compatible according to the website. As I understand the offset is how far away from the center of the tire the mounting hub is. If that's the case how can +19 and +1 both fit? I posted an example pic

You can fit anywhere from +20 to -44 , positive numbers mean the hub face will be that many mm away from the center of the wheel towards the outside of the wheel, negative numbers are that many mm from the center towards the inside of the wheel. Larger negative offsets push the wheels out side of the fender wells.giving the truck a more aggressive stance, you can go to custom wheel offsets web site and look at the ram gallery to get an idea of how different tire and wheels will look on your truck. They will post the tire size rim size and offset typically

 

[surfingcrna]

Perfect thanks again