Does size matter if weight doesn't really change?

[northshoremb]

Hello I have a 2 Door JL with the 2.0 and has 3.45 gears and everything I read says if you put 35" tires will have hard time hitting 7th and never 8th but to me that sounds stupid as long as you choose 35" with lower weight. Does tire diameter actually change anything if the weight doesn't change like if running a 33" that's say 60# vs a 35" that's 57-60#???? To me I can see if the 35" are 10ply that are 67-72# and the 33" are in the 50's.
Just want to figure this out before I go 35" on the Sport 2 door cause if can't do 35" 6ply that are light I'll just go to 35" on our 2023 Gladiator Rubicon and put the 33" on the 2dr

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[Old Dogger]

There are 3 factors to consider: Tire diameter, weight and roll resistance. Each one plays a part in it.

 

[dstevens]

At 70mph in 8th gear (down a hill presumably) you'll be at 1554 rpm. With a 60lb tire that will be 1554rpm. With a 80 lb tire it will be 1554 rpm. With a 40 lb tire it will be 1554 rpm. Perhaps I don't understand the post, but it seems like you are trying to talk yourself into believing the 3.45 final will be good for 35s. Who knows, preference varies a lot amongst people and some might not have a problem with gearing that tall. Personally I find 4.56 too tall for 35s and that 4.88 or 5.13 would be better.
Rotational inertia is a thing with larger or heavier tires but I only notice that while braking.

 

[Trails]

Hello I have a 2 Door JL with the 2.0 and has 3.45 gears and everything I read says if you put 35" tires will have hard time hitting 7th and never 8th but to me that sounds stupid as long as you choose 35" with lower weight. Does tire diameter actually change anything if the weight doesn't change like if running a 33" that's say 60# vs a 35" that's 57-60#???? To me I can see if the 35" are 10ply that are 67-72# and the 33" are in the 50's.
Just want to figure this out before I go 35" on the Sport 2 door cause if can't do 35" 6ply that are light I'll just go to 35" on our 2023 Gladiator Rubicon and put the 33" on the 2dr

No matter what the weight, a bigger diameter tire is like turning a higher gear. So, to make up for it, many suggest using a "lower geared" (higher number) axle ratio. E.g. A 4.10 is "lower geared" than a 3.45 .

 

[2nd 392]

That 2” in diameter is like having ~.2-.25 higher gears on top of the extra weight and rolling resistance. Would you be happy with ~3.20 gears with heavier, 12.50 33’s ?
IE- 3.73’s with 33’s is about the same overall ratio as 3.45’s with 31’s

 

[northshoremb]

No matter what the weight, a bigger diameter tire is like turning a higher gear. So, to make up for it, many suggest using a "lower geared" (higher number) axle ratio. E.g. A 4.10 is "lower geared" than a 3.45 .

Ok this is the answer I was looking for. Had no idea it changed gearing I was just looking at weight and thinking people generically assume a bigger tire will always be heavier. This is why I asked cause the 35" I was looking at was same weight as the 33" so to me thought wouldn't be an issue. So thank you for clearing that up and will take the 33s off the Gladiator and put on the JL then get 34-35" for the Gladiator

 

[grimmjeeper]

Diameter is about 90% of why you change gears.

Weight (when going bigger) only influences a little. It's why you round up after calculating change for diameter.

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