Looking to see what the largest tires I can fit with my current setup on the ex. I have 2002 4x4 diesel with x codes up front and 2.5 inch hanger brackets. Rear has modded b codes with 4 inch blocks. Running 2004 18 inch Harley Davidson wheels. Looking for the tallest widest tires. Would like to squeeze 37's on it if possible.

 

I have a 6" lift with 37's and they fit fine, but even with 6" i had to cut a fair amount of front bumper. My tires are 12.5" wide and it comes just barely beyond the body.

With a 4" lift I've heard of people doing it but it's tight, really tight, and expect to cut a fair amount of front bumper off.

It may fit, but you may not want to turn and hit a speed bump at the same time with a 4" lift

 

What gear set did you install ? I would match the tire to the gear set and then trim sheet metal if required.

 

The guy I got my HD rims had 37" tires on them. He was getting rid of them because he was not comfortable with the ride and handling, especially when he was loaded. He upgraded rims and tires and sold them to me. I think the factory rim is 18x7.5 which may be too narrow for 37's.

 

I have 3.73 but it takes a lot of engine to get moving. I'm saving up for 4.50 or 4.88. Probably the latter.

 

I have stock 3.73's. Eventually upgrading to 4.10's.

 

The 04 Harley Davidson rims are 18x8. Currently running 325/65/18 tires on them. Looked good 2 years ago with a 2.5" lift. But now with the x codes and modded b codes it has just over 6 inches of lift over stock height and looks really stupid with small tires.

 

So, to give you an idea how tight things can get, here is a pic of my Ex (which I just snapped out the front window) showing it with a 4" BDS lift running 35's on 18's.



I may be able to shoehorn in 37's, but there would not be much room to spare, especially on the front. The 35's almost hit the body on the back now, with 37's there would need to be some cutting done...

Hope this helps!

 

Personally I wouldn't go bigger then a 305 with the 3.73

 

Based on a power factor or smoking the rear end? I have not had any concerns with power or acceleration. Don't get me wrong 4.10's would definitely come in handy in the mountains pulling my loaded work trailer @ 7-9k lbs, but I've made due with it. Instead of holding 70 I can usually only hold 55-60 on some hills. But most of my driving is flat ground.

 

I have X codes, modded B codes with 305/75's,on 04 HD wheels.

I specifically didn't want 35x12.5 due to width / rub issues.

The rub the spring bad and really inhibit turning radius. They look perfect as far as filling out the wheel well though.

I think with your additional lift the 37 would fit similarly to mine.


But.....I'm HATING the fuel mileage that these tires ate up. Wether in town/feeeway/towing 7k load/ empty etc. Across the board I've lost 3 mpg consistently by hand calculation.

I think a change to 4.56 / 4.88 would serve me and the 6.0 well from the 3.73's.

90% of my driving is in town, ( I live 30 blocks from work....) or heavy towing on the freeway. Both of those would benefit from some deeper gears.


Hopefully this helps some.

 

Based on operating the engine in the optimum rpm range which is going to net you the best mpg, torque on demand and longevity , basically the general drivability of your ex.

Your transmission is also matched to that optimum rpm range and gear selection can be be affected. Again, driveability, longevity and durability will be affected.

Fitting 37s is the easy part making your truck work well with 37s takes a bit more work. Aside from gears I would make sure your steering box , ball joints, tie rod, track bar and unit bearings are all tight, 37s are going to magnify any weakness in the system you may have, Also a good set of shocks and steering damper are key. softer brake pads will help with the loss in braking.

 

That might explain why I've put 2 transmission and 3 rear ends in this truck.

 

Yup,

If you increase the tire size without changing the gear ratio you are putting more stress on the drive train to do the same work, that creates more heat. More heat equals shorter life span. Match the gear ratio to the optimum rpm and your junk works better and last longer.

A better torque converter and additional transmission cooling capacity are also wise investments ..... Even with stock size tires in my opinion.

Like I said, making 37,s fit is the easy part. Making them work as well or better then the factory setup is a bit more work...... But it is doable.

 

But how much are 4.10's going to affect mpg? I get 14 mpg hauling my trailer.