Questions About Tires/Rims/Size

[Kalal92]

I don't know much about tires and the different sizes i've got 15's on my Comanche it's a 86 2.5 4speed 4x4. Is there a limit to what size I can go before having issues? Just a thing I'm not too familiar with. Thanks

 

 

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[mikekaz1]

the bigger you go the worse your gas mileage gets.   that being said, many people can go up to a 31 inch tire without too much issue if at all.   you have somewhere around 27/28 inch now

[Eagle]

You don't have "15s." 15-inch only tells the diameter of the steel (or alloy) wheel rim, it doesn't tell the width (depth) of the rim or the size of the tire.

 

The photo shows that you have 235/75-15s. That means it's a 15-inch wheel. The cross-section width of the tire at the widest point is 235mm (about 9.25 inches), and the height of the tire on one side of the rim is 75% of the cross-section width (235x.75 = 176mm or 6.94 inches). On factory wheels, 235/75-15 is the largest size tire you can run without the tires hitting bodywork somewhere. You have aftermarket rims, which probably move the tires farther out (away from the vehicle centerline) than factory wheels, so you may already have some interference.

 

The largest tire size from the factory on an MJ was 225/75-15.

[HOrnbrod]

you have somewhere around 27/28 inch now........

 

Actually he is right at a 29" tire (28.9") now.

[Marine1Texas]

I am not sure if you have a manual or auto.

I think the 2.5 was 4.10 rear end . if you have the 4.56 I have numbers for that too.

235/75r15 is 28.9 but basically a 29inch tire

 

Check this link out to my blog http://vitha.us/blog1/2016/08/22/jeep-tire-to-trans-and-rear-end-gear-ratio/

It gives how bigger tires work to lower final ratio to the rear gear and the trans. I have most of all Trans and final gears listed

I have listed each trans as it works with each of the available rear gear ratio's

It shows you how rpms move to each gear at a speed with changing of tires up and down

[Eagle]

I am not sure if you have a manual or auto.

I think the 2.5 was 4.10 rear end . if you have the 4.56 I have numbers for that too.

 

When mated to the 4-speed manual the 2.5L usually had 3.55 gears.

[Marine1Texas]

ok noted. I only have the information put on the spec page to go off and did not see that. However I do have listed the AX5 and AX4 with the 3.55.

 

I use the 31/10.5r15's with AX15 with 3.07 in diff on my 88MJ with 4.6. feels like the 87 with smaller 235/75r15s because the extra power of the 4.6

on my 87 I use 235/75r15's with AX15 with 3.07 in diff with 4.0. When I put the 31's on the 87 4.0 I had to down shift on some hills on highway.

When I ran the 235/70r15's on the 87 4.0 it was very very peppy but noticed the ride was rougher.

[mikekaz1]

 

you have somewhere around 27/28 inch now........

 

Actually he is right at a 29" tire (28.9") now.

 

right! its the 225 that's the 27/28.

[Marine1Texas]

I think your max would be a 31 inch on your 2.5L AX4. However you will notice some lag on the hills. at 55 mph with factory size tires your at 2369 rpms. With your current 235's your at 2270 Rpms. If you go to say 31x10.5r15s you will be at 2117Rpms.

 

I think it all comes down too what you going to use it for. If your going to off road bigger and wider the better. If your going to just do a small bit of off-roading but with highway driving 235/75r15 (9.3wide x 28.9 High) at perfect in my mind. If your not going to offroad and mainly use for highway I would go for best economy with width 235/70r15 (9.3wide x 28 High) or 225/75r15 (8.9wide x 28.3 High).

[Eagle]

 

 

you have somewhere around 27/28 inch now........

 

Actually he is right at a 29" tire (28.9") now.

 

right! its the 225 that's the 27/28.

 

 

225/75-15 is 28.3" diameter.

 

205/75-15 is 27.1" -- maybe that's what you're thinking of.