Tire size inquiry

[PunkChachi]

I just had my trans rebuilt due to it just becoming total crap. Also while I was in there I had my differentials regeared to 4.11 from the stock 3.73. Right now I have 265/75r16's on there and I am looking at maybe dropping down a little. I was looking to buy new rims because mine look like crap, flaking and chipping of the overcoat.

I was trying to figure out what the advantages, if any, there are of changing rim size. I think the "Sport" model comes with 15" rims and is geared in 4.10. So if I had 15" rims with overall tire height of 30" and 16' rims with overall tire height of 30", is there a difference in performance gained from one over the other? The only thing I can think of is that the 15" rims would be lighter so the engine might not have to work as hard to turn them. Not sure if that would be a noticeable difference though.

Also I thought I would get better gas milage with the regearing. Maybe its a different problem causing the bad mpg but I went from 11mpg to 12-13mpg city after the regear. Anything anyone could tell me on this would be awesome, thanks!

Before I buy new rims I'm going to strip my spare and prime it, paint it with some matte black. If it looks decent just going to do that to all my rims. I've been taking pictures and I'll post them when I finish the spare, few days hopefully.

 

[tommudd]

I just had my trans rebuilt due to it just becoming total crap. Also while I was in there I had my differentials regeared to 4.11 from the stock 3.73. Right now I have 265/75r16's on there and I am looking at maybe dropping down a little. I was looking to buy new rims because mine look like crap, flaking and chipping of the overcoat.

I was trying to figure out what the advantages, if any, there are of changing rim size. I think the "Sport" model comes with 15" rims and is geared in 4.10. So if I had 15" rims with overall tire height of 30" and 16' rims with overall tire height of 30", is there a difference in performance gained from one over the other? The only thing I can think of is that the 15" rims would be lighter so the engine might not have to work as hard to turn them. Not sure if that would be a noticeable difference though.

Also I thought I would get better gas milage with the regearing. Maybe its a different problem causing the bad mpg but I went from 11mpg to 12-13mpg city after the regear. Anything anyone could tell me on this would be awesome, thanks!

Before I buy new rims I'm going to strip my spare and prime it, paint it with some matte black. If it looks decent just going to do that to all my rims. I've been taking pictures and I'll post them when I finish the spare, few days hopefully.

NO KJ ever came with 15 inch wheels
Only KJ that came with 4.10s was the gasser 4 bangers
As far as difference between 15s and 16s is the sidewall height ( which is not much )
A 30 inch tire is a 30 inch tire just the wheel size is different
245-75-16s would be good or the 265-70-16 is a bit wider but same height as the 245-75-16s
245-75-16 is 30.4 inches tall
255-70-16 is 30
265-70-16 is 30.6
31-10.50-15 is 30.4
so pick your poison:icon_lol:

Depending on how you drive, terrain , city/ highway all affects the mileage
As far as in town I never pay any attention, longer trips and all highway I pull 21-22 with my 04 lifted over 4 inches and running 4.10s/265-75-16s

 

[PunkChachi]

Thanks man, I went back to the site I was reading from and I misread what it had said about stock tire size.

Gas milage has dropped over the years, I use to get 21-22 highway now I get maybe 15 highway. I thought it was due to gearing/tires/bad catalytic, over the years I went from stock tire size --> 235/75r16 --> 3" lift --> 265/75r16 --> 4.11 gear ratio, trans rebuild --> replacing both catalytic converters --> K&N Cold Air Intake. Any other ideas about mpg decline? I also change plugs regularly and last September replaced all 4 O2 sensors.

This is a bit off topic but do you know why the 4 cylinder is gear in 4.10 and not the rest of them?

 

[dude1116]

This is a bit off topic but do you know why the 4 cylinder is gear in 4.10 and not the rest of them?

Because the motor can't get out of its own way.

 

[tommudd]

Because the motor can't get out of its own way.

Thats pretty much it, motor didn't have enough to pull the KJ around. They installed them to get the CAFE numbers up but in reality the 4 cyl didn't do any better than the 6

 

[CactusJacked]

Also I thought I would get better gas milage with the regearing. Maybe its a different problem causing the bad mpg but I went from 11mpg to 12-13mpg city after the regear. Anything anyone could tell me on this would be awesome, thanks.

A regear gains you less mpg than you think it might. Part of the taller tire gas mileage discrepancy is simple math due to the speedo/odometer calibration being off. With taller tires, the Jeep is traveling a further distance (more miles) than what the odometer is registering. For instance, with combination driving (stock gearing), my gas used to "assumed mileage traveled" says 14 mpg. But when readjusting to actual miles traveled, compensating for the taller tire size, my true mpg is 15.3.

 

[dude1116]

A regear gains you less mpg than you think it might. Part of the taller tire gas mileage discrepancy is simple math due to the speedo/odometer calibration being off. With taller tires, the Jeep is traveling a further distance (more miles) than what the odometer is registering. For instance, with combination driving (stock gearing), my gas used to "assumed mileage traveled" says 14 mpg. But when readjusting to actual miles traveled, compensating for the taller tire size, my true mpg is 15.3.

This is what makes me not want to punch myself in the face when I get 16mpgs. I just think in the back of my head "It's ok. You're probably getting about 17mpgs."

 

[krisP]

i wish i could just drive other KJs that have the different tire sizes and heavier wheels so i could experience how much/what the power loss feels like, some say a certain tire size they can barely notice and others with the same set up act like its terrible.

 

[tommudd]

i wish i could just drive other KJs that have the different tire sizes and heavier wheels so i could experience how much/what the power loss feels like, some say a certain tire size they can barely notice and others with the same set up act like its terrible.

From experience
I went to the 265-75-16s a week before I did the gear swap
Around town not awful but noticeable for sure
But out on the open road it was a huge PITA. It was always shifting back and forth, would drop 2 gears to get up small grades, ran hotter , etc
Now once you got up over 78-80 you could maintain that but it was hard explaining to the nice officer why you were going that speed
Anything under that and you had to have the OD off all the time. Drove 7 hours to go wheeling one way with the OD off, like I said huge PITA
Of course some just don't want to admit it helps:happy175:
BUT ask those who have and they'll tell you
Like John3:17, TwoBobs to name a couple
Of course I've built a lot of 4X4s and regeared everyone of them
My 03 will be getting 4.10s with 30 inch tires even

 

[krisP]

I'm not debating the fact that there would be some significant power loss, just wish i could see how it feels for myself without spending 1000 on tires just for the sake of me being curious :ROFLJest:

 

[PunkChachi]

Idk if I misconstrued what I said. When I regeared mine 3.73 to 4.11 with 265/75r16 I did notice a great change in acceleration and general cruising on highway. It just wasn't as great a change as I thought it would be, kinda built it up in my head I guess.

 

[tommudd]

I'm not debating the fact that there would be some significant power loss, just wish i could see how it feels for myself without spending 1000 on tires just for the sake of me being curious :ROFLJest:

Borrow a set and run them down the road, don't have to go far