tire & axles & lifts, Oh My!

[waynestiles]

I've been trying to read up on the whole tire size/axle ratio/required lift deal for my GW. there is a lot of info here but it is really scattered and some of it is pretty old.
My GW has the standard 2.70-odd axle ratio, which is fine for my highway needs. If I have collated all the scattered bits of info here on the site and understand it properly, it looks like 30 or maybe 31 inch tires are the most that can be accomodated on my factory 15" wheels without at least lifting the body.
As I understand it, going upward in tire size increases the engine effort required to rotate them and so there is a tradeoff between the axle/gear ratios and the tire size. I assume there is a breakpoint point as well between "taller" tires giving slightly increased mileage and speed vrs. the amount of engine it take to roll them---correct?. what about the relationship between "taller" tires and "taller AND wider" tires.

I'm trying to figure out what the practical and reasonable tire limits are for a stock 360 with the 2.70 gearing. I'm willing to make a little body lift if it is beneficial, and in any case I may need to redo tired springs anyway a bit farther down the road. however there is no point in going too big on tires if the gearing won't work it.

[Dmntxn77]

Your gearing is horrible.. You will notice negative effects with any increase in tire size..

When a person gets larger tires, it is common for those tires to be a more aggressive tread. That aggressive tread, along with the larger contact patch, and the increase in height from the larger tires will eat up any mileage advantage you would gain by having larger diameter tires.

As far as tire size in concerned, I had a 4" lift with 31"s, and rubbed pretty bad at flex.

[fulsizjeep]

HAHAHA! I had 2.72 gears on my 88 when I moved to Colorado. And 32s with 4" lift. You can easily go to 32x11.5x15 on the factory 15x7 alloys. There might be a little rub on the front springs, but not enough to get excited about. I pulled a 6x12 Uhaul full of my junk from Florida and the power was awesomely inadequate for the ride. Flatland of FL was not too bad without a load on it. The Rocky Mountains demanded I get 3.73 or lower for life above the tree line.

[Stuka]

32's with no lift? Not without cutting or some lift.

My J10 was a gutless pig with 31's and 2.73's in the mountains, but got 17mpg on the freeways (258). Actually drove it a few times with the 34's and 2.73's. I got into 3rd gear on the HWY, only saw forth on long downhill grades. Moving to 4.56's was great though.

[jkilmer83]

I have 31s on my 76 waggy but not shure the rims are stock. I would love to go to 33's not to hijack here but how much lift would i need?

[jaber]

I got 31's on my gw now. I had to put 2" blocks under the rear to keep the fenders from eating sidewalls. I cant say much about the power issue on this one, it's camed and injected.:thumbsup:

I just got 33-10.5's for my dd J-10. They rub when I stuff a tire. The tired 360 does not like them. She's a real dog with the 2brl motocrap. :cool:


Oh, and 2.72's in the GW and I'm not sure on the truck.

[Casey]

How do you use you're GW? It all boils down to how and where you wheel most, and if you also use it as a daily driver. Then do you have the 2.73 gears or 3.31? The towing package had the 3.31 gears.

I found the 3.31s worked well enough on my old '90 GW with 4" of lift and 31x10.50-15 BFGs on stock wheels. The 31s would've never fit without the lift. The gears were ok with the stock manifold and carb. Once the Edelbrock manifold and 1406 went on it had it's old umph back. Gas mileage was about 11.5 mpg after it was all done. The lift, performance parts, and tires cost about $1800. I did the work in my driveway.

*note the super cool FSJN decal
http://img.photobucket.com/albums/v189/rcasey/FSJ/90gwdone007.jpg

The '88 I had ('Valdez) had 3.73s with the same tires and lift, and the Edelbrock parts + cam. It got 13.5 mpg and would dust a 2003 Yukon in the quarter. :D

Granted if you want more from your wheeling experiences, along with fewer dents. You'll most likely want bigger than stock tires. Which translates to more lift. Then the power will fall from the big tires. You'll need more power, better gearing....you go to bigger rock piles...you'll need bigger axles for the massive tires you're running...

This can easily turn into a pile of junk like the one in my driveway.


my .02...
Slap a set of mud terrains (of your choice) in 235 or 30x9.50-15 on the stock wheels.

Go wheeling and drive to the grocery without worries.


Otherwise...welcome to the madness. http://img.photobucket.com/albums/v189/rcasey/smilies/wife.gif