bigger tires on the 1HDT

[scuba steve]

Hey mudders,
Have any of you rode stock 31" tires and moved up to 35" tires and noticed a significant change either for the worse or better in mileage...i know you have to take into consideration the speedo correction, but with all that aside any improvements or not and also if anyone has a manual tranny that has had this experience if they would like to comment.
Any feed back helps.
Cheers,

 

[lumpy70]

My buddy has an HDJ81 with the manual and he's running 35's. His mileage is so-so. He wants to move to 37's to get his revs down some more.

On his truck he is running close to 2700 rpm at 120 kph. Mine is the automatic and I'm running 31's for now, and I am at 2350 at 120 kph. I'm going to get me some 33's and that should bring my revs down to a nice 2200 rpm.

Obviously if you put on bigger tires they are heavier and have more drag so mileage is a balancing act with your revs.

Confused?

Craig.

 

[Tapage]

I was in 285 and then swap to 315 .. sure you feel the drag and resistance .. but the look worth !

If you wanna go better, swap your 4.11 to 4.88 in auto .. and 4.56 in a manual much more if you do lot's of HW cruising ..

 

[lumpy70]

Don't you mean down to 3.73's? Putting in higher axle gears would increase your highway revs and therefore your mileage.

Better for low end wheeling but awful for high speed.

Craig.

 

[Tapage]

yes .. you will lower your rpm at HW speeds .. ut increasing the effort on the engine ..

Our engines are not that powerfull .. like a cummins engine or V8 ford 7.3 ..

then if you go from 31" to 35" with the same R&P you will found yourself running at lower rpm only in downhills .. any other situation will requile shiftdown to keep the same speed with decreasing mpg and engine performance ..

 

[wussyPup]

I have 2 sets of wheels/tyres for my '90 HDJ81. I get about 30% more km per tank when using the Toyo M55 LT255/85R16, E rated, 10 ply tyres instead of the BFG 35x12.50R15, C rated set.

 

[dieseldan]

I went from 33" MT's to 35" AT's with the stock auto - my temps climbed some on long hills and the shifting pattern changed - really didn't see much noticable difference in mileage. Soon after the swap I had the Aussie Tranny installed and no more temp rise, smoother shifting. I spoke to a guy in N.Van running an FZJ80 on 35's/manual tranny and he's had no issues in 5 years+. Going to depend on how you drive and if you tow much or not. I'd certainly re-gear if going to 37's but 35's seem ok.

 

[shromani]

I have 33x13.5R15 Toyos on with my Auto and stock gears (see pic in sig). I get around 18mpg in town. I truck doesn't seem sluggish, though it's not peppy.