Tire Diameter vs Weight and Their Affects on Performance

[CreepyCrepe]

Hey all,

I have a 4dr 2023 2.0L Willys Sport with the unfortunate 3.45 gearing and I'm trying to do some research into new tires. I realize that any additional tire diameter or weight will negatively impact the acceleration and braking, but does one have a greater affect than another? An example would be the two tires below:

• Toyo Open Country A/T III
  • Tire Size: 34x10.50R17
  • Load: D
  • Diameter: 34"
  • Width: 10.5"
  • Weight: 55lbs
• Hankook Dynapro AT2 Extreme
  • Tire Size: 295/70R17
  • Load: E
  • Diameter: 33"
  • Width: 11.5"
  • Weight: 61lbs

Would the diameter of the taller, lighter tire be worse than the weight of the shorter heavier tire or vice versa? I'm just looking to min/max my performance while maintaining the 3.45 gearing. Thanks in advance!​

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[AcesandEights]

Those are not the circumferences.

Maybe look at revolutions per mile. Really though, you're considering different things when looking at "diameter" and weight. They have different impact/effects on different things. So, which of those things is most important to you?

 

[CreepyCrepe]

Those are not the circumferences.

Maybe look at revolutions per mile. Really though, you're considering different things when looking at "diameter" and weight. They have different impact/effects on different things. So, which of those things is most important to you?

Sorry diameter. Big dumb. Screwed that up throughout.

Well, tire diameter changes your ground clearance at the expense of your final drive ratio while weight would change your unsprung weight and would have to overcome more inertia in starting and stopping. Just trying to gather which affects performance more and learn a bit.

 

[bjm00se]

As a general rule:

If you don't regear, diameter will have a bigger impact, because it's changing your final drive ratio.

If you do regear correspondingly, then diameter's no longer a consideration and weight becomes the bigger consideration.

However, even this is an oversimplification, as a larger diameter tire of the same weight will have more angular momentum for a given rotational velocity. But none of us jeepers can calculate that; our brains explode if we try.

 

[azwjowner]

The 34x10.5R17 will be by far the better performing tire. Diameters on the vehicle will be very close for those tires because the 34 is a 33.5" and from memory 295/70/17 is something like 33.3". But an inch narrower tire weighs less and gives better handling on-road. D rated instead of E rated means the ride is much softer and not as harsh.

 

[CreepyCrepe]

None of us jeepers can calculate that; our brains explode if we try.

Hell some of them mix up diameter and circumference.

 

[HungryHound]

FYI.... C = π d

 

[CreepyCrepe]

FYI.... C = π d

So a C load tire is like a D load tire with pie. Got it.

 

[CreepyCrepe]

The 34x10.5R17 will be by far the better performing tire. Diameters on the vehicle will be very close for those tires because the 34 is a 33.5" and from memory 295/70/17 is something like 33.3". But an inch narrower tire weighs less and gives better handling on-road. D rated instead of E rated means the ride is much softer and not as harsh.

So would you choose a similarly weighted load c 285/70r17 or the 34x10.50? Given the price of a lot of Rubicon take offs, the difference in price could be applied to a better lift to make up for the .5" or less difference.

 

[azwjowner]

So would you choose a similarly weighted load c 285/70r17 or the 34x10.50? Given the price of a lot of Rubicon take offs, the difference in price could be applied to a better lift to make up for the .5" or less difference.

Well you're talking to the guy who started the pizza cutter tire thread, so I'd go with the 34x10.5 because I like the looks & narrow performance. But you are correct, it's about a 0.7" difference (the 285/70 is a 32.8" tire) and you only get half of that difference as increased ground clearance (so only 0.35"), so given that Rubicon take offs are so much cheaper, they are clearly the cost-effective way to go. Plus they are lighter, so they'd have better acceleration/braking performance. You can get 0.5" Teraflex spring spacers for less than $100.

 

[Tncdrew]

3.45 gears suck! 'Nuff said ?

 

[The Last Cowboy]

With tall tires and numerically high gears, think of it as always fighting the big chain ring gear on a bicycle. The larger the tire, the harder to get moving or go uphill.

34” is about as far as I’d push it. But even the 3.45s aren’t ideal for 32” stock tires. 3.74s would have been a better choice for Jeep to have made.

 

[CreepyCrepe]

3.45 gears suck! 'Nuff said ?

Yeah, I often go back and forth about the cost of a regear in comparison to just getting some Rubicon take off axles. That may be a question for @chevymitchell (and one he may have answered already as well)

 

[CreepyCrepe]

Well you're talking to the guy who started the pizza cutter tire thread, so I'd go with the 34x10.5 because I like the looks & narrow performance. But you are correct, it's about a 0.7" difference (the 285/70 is a 32.8" tire) and you only get half of that difference as increased ground clearance (so only 0.35"), so given that Rubicon take offs are so much cheaper, they are clearly the cost-effective way to go. Plus they are lighter, so they'd have better acceleration/braking performance. You can get 0.5" Teraflex spring spacers for less than $100.

I do like the looks/thought of the 34x10.50 though, especially in the Toyos.

 

[Tncdrew]

Yeah, I often go back and forth about the cost of a regear in comparison to just getting some Rubicon take off axles. That may be a question for @chevymitchell (and one he may have answered already as well)

I hear ya!
I have the 3.6L/8-spd here. 4.10 wasn't enough for me. Re-geared to 4.56 (Chevymitchell did the work).
Absolute perfection (gearwise IMO), with 285/75-17's.

Couldn't be happier.

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