Performance Difference between 10.5 inch and 9.5 inch wheels

[DougKTexas]

Hi
I am looking into 9.5 inch (235) tires. I live in the Texas Hill Country and driving the hills at highway speeds is a real challenge. Plus I really like the skinny tire look...

My FJ60 has a H55F 5 speed transmission with an OME lift and currently has 31/10.50r15 tires.

Has anyone gone from 31/10.50r15 tires to 235/75r17 tires? Is there a performance gain from going with narrower tires?

thanks
Doug

 

[klinetime574]

I doubt there would be a seat-of-the-pants observable notice in performance by reducing the width of the tire by an inch. There may be a reduction in weight per tire which could help. Check manufacturer specifications to know how much weight you will be reducing, if any. Also a narrower tire should wander less, think about a 12.5" wide meaty tire compared to a 9.5".

I wouldn't really say my 60 has trouble on the hills in Texas with a 4 speed. You must have some more weight on your rig? Or I just accept the speed haha

I would say that if you like the look, do it. Post pics

 

[Skniper]

It's my understanding that wider tires equal greater rolling resistance...more surface area, more friction, more mass. More power and gas consumption. How much?....dunno.

Riding a skinny tire road bike and riding a fat tired mountain bike on pavement are vastly different experiences, takes a lot more work to push fat tires.

 

[klinetime574]

@Skniper This is true.

Will it be noticeable on the gas gauge? Maybe. "Performance" Mine makes me smile so that's all that counts.

 

[Elbert]

in a 60...doubt performance is part of the equation...

 

[Heckraiser]

Yes it's skinnier, and the tire itself will likely be lighter. However a 17" rim is heavier (assuming same style/material). Moreover, a 17" rim places the rotating mass farther from the center of the wheel, creating essentially the same effect as additional weight when it comes to acceleration and braking. I think think this would offset the reduced rolling resistance of a 1" skinnier tread.

My guess: zero noticeable difference.

 

[DougKTexas]

On the Jeep JK we went from 305 to 285 tires, the 305 where on the Jeep when we purchased it. There was a noticeable difference in the accelerate between the tires. Everything else stayed the same. But that is a 2008 Jeep. Not a classic FJ60.....

 

[Output Shaft]

Skinnier tires of the same diameter do have a lower rolling resistance compared to wider tires, but they won't do anything for acceleration. A 10.5" tire at 50 psi probably has the same rolling resistance as a same diameter 9.5 inch wide tire at 35 psi or so (just a guess).

Decades ago, I experimented with 31/12.5/R15 tires (for baja sand driving) and they were the worst road tire I had ever driven.. (compared to BFG AT). Way too much rolling resistance.. but they were crap tires anyway. Got horrible mileage.

If one really wants to enjoy not suffer as much while driving a FJ60 on paved hills with the stock 3:73 gears, the easiest solution is to mount a second set of wheels... some dainty 235/75/R15's.

Yep, those dinky 28.9" tires are the ticket in the hills. The truck accelerates, shifts and stops so much better with the smaller DIAMETER tires. And the shift from 2nd gear to 3rd is no longer like climbing Mt. Everest with the H55F.
Too bad those tires look painfully small and pretty much blow off road on anything but graded dirt roads.

"Some guys" own two sets of wheels/tires: 235/75/R15 (28.9") street tires (max rated at 50psi) and larger 31/10.5/R15 AT (or MT) or bigger. They drive the dinky tires around town cuz they really like the way the car drives with them... especially up hills and when up-shifting while driving up hill...and also for the braking. For off-roading adventures, they swap and mount the bigger tires.

Other than that, changing the diff gears will get the engine where it should be with 31" tires in the hills, but that's a Whole Nuther Can-O-Worms

 

[Honest Don]

Adding a "Mark's" header helped out quite a bit with my 60's highway abilities. It may be something to look into for your situation.

 

[Elbert]

I don't see any performance gain going to a narrower tire on the 60...as the question is posed. Sure if the size (diameter) of the tire changed from present to smaller diameter then some increase in power might be observed. If all things stay the same and you just go to a narrower tire...then essentially you are in the same state (all things equal).