Rock Toy

First is you have to check your speed with GPS to make sure you are actually doing 65 mph.
Having the correct speed is the most important factor in figuring rpms. The next is having the correct tire height not the tire size. As in a 225x75 r15 is 28.3 inches tall and a 35/12.5xr15 BFG KM2 is 34.8 inches tall
Do you now have the 4.56 gear ratio? If not what is it?

Hoooper

did you do any conversion to figure out if your speedo is correct? If you have not corrected your speedo and you are 4.56 gears on 32s and AX-15, your speedo will read high

smoothlandin

I corrected my speedmeter with a new gear, I put the 4.56's in, and I checked the speedo with gps and its dead on. I will measure my hankooks when I can. So my tach is off or my tires measure out bigger?

Rock Toy

65 mph x 4.56-1 differential ratio x 336 x .79 OD transmission ratio / 37.5 tire height = 2098 rpm

65 x 3.90 x 336 x .79 / 32 = 2103

The closest I can come trying to figure out what you have going is with a 37.5 inch tall tire, or going with a 3.90 differential gear ratio.

Mine is 65 x 4.88 x 336 x .79 / 34.8 = 2419 rpm

smoothlandin

I appreciate the help. Now I have to figure out why my tach reads like 400 less than it should? Faulty ground? Maybe I should ask this somewhere else

96rokee

i have my fenders trimmed and folded to the maxxx.
when my tire is tucked its pretty close i dont have pics of it tucked
but you can eyeball the line of where the fender ends and see that 35s would most likly rub

gvns8

If you are going to be doing trails like the Rubicon, I would definitely go for the 35's. You can get by on 33's but why not go for 35's which would be a much better tire size for the trail and give you better rpm ranges on the road (just carry extra shafts). I have 33's and feel like a little more clearance would make a big difference and plan to go to 35's soon.

96rokee

with the pics i posted do you guys think 35s would tuck in there without rubbing
or would i have to tub it?

ct67_72

I dont know why you keep talking about tubbing it. There are plenty of people running that setup. as a matter of fact a friend runs 3" lift with 35's.
Here is mine again with another shot.


worst case you set up some bumpstops in the back.
personally, I flex it hard, check clearances, and hit stuff with a big *** hammer until it clears. I will probably add bump stops to be safe, but its just fine.

96rokee

haha i think you have convinced me..
now i just gotta wait till my next paycheck and ill be rollin on fresh tires lol

knightrohulk

I run these bump stop plates in the rear:

http://jeepin.com/features/dpg_bumpstopplates

I also run an extended rubber bump stop on the top to go along with these plates. I have cut my rear fenders also. I have run 35 x 14.5 Pit Bull tires with a 4.5" lift and no trouble. I don't know why you think you need to tub it.

ct67_72

I'm gonna make a set just like those. My springs are super flexy and they will inverted just like the are talking about on that site.

mikeXJ1020

35s!!!!

thebe001

Nice looking set up man. What width rims are those in the pic... 8"? I really want to try mouting some 35" KM2s to my stock 7" alloys. I am running 33"x10.5" KM2 with 2" spacers they don't have many miles left and are staring to look small under the old XJ.

XJlimitedx99

This thread is 4 years old.

12.5" wide tires on a 7" wheel is pushing it.