over tightened wheel bearings affecting mileage

[lonelydriver]

Did my knuckle job 2 months ago and was wondering if my poor mileage is due to possibly over tightening the wheel bearing preload?

It's a 88 fj62 w/ the 3fe and i'm getting about 12 mpg with mostly highway.

-Regards
-Kevin

 

[ballardcruiser]

Were you really getting better MPG before the rebuild? That sounds about normal for me.

 

[lonelydriver]

i hit about 15mpg i believe once w/ stock tires but didnt really drive it too much b4 the tire upgrade to 33's and knuckle rebuild. I know these trucks don't get great mileage, but every bit helps.. especially here in LA where the gas prices really hurt.

The nice truck nods I randomly get make it worth it though.

p.s. I do calculate the tire increase to calculate the mileage.

I multiply the miles on the trip odometer by 1.14 use that to divide from the gallons from the pump. Does that sound correct for a 33 inch bfk ta/ko upgrade?

 

[Pluton]

It is possible that the 33's on stock axles would lower the mileage, especially in city driving. But, like the other guy said, 12 mpg is not out of the realm of "normal"

 

[krzyabncanuck]

I would use a GPS to figure out for sure. But think about the wider tire you are trying to move also, along with it being taller. If you are really worried about gas mileage sell it to me.

 

[ballardcruiser]

I'd consider all of the above, but I don't think your wheel bearings are playing a role in the mpg. Are you worried that you overtightened them somehow? Did you not use the fishscale method and all that?

I'd think if the bearings were having a big effect on the engine efficiency, you'd have other indicators. For starters, the hub would be fairly hot to the touch after driving a while from all the friction.

33"s and 12 mpg seems about average to me, though. I really wouldn't expect or hope for much more. Keep it tuned up and drive conservatively and you'll save as much as gas as humanly possible.

 

[Heartworm]

our calcs agree

I have a FJ60 with 33X9.5s and your adjusment factor and mine are real close. However, I use the figure 0.865 and divide it into the originally calculated mileage. Incidentally, my overall mileage over 3000+ miles is 15.34 mpg (standard shift difference?).

 

[Cruiserdrew]

If they were tight enough to decrease gas mileage, you would have burned them up long before now. It takes just 5 minutes to check the adjustment anyway. Just re-check and then you'll know.

 

[lonelydriver]

Is there a way to check it without removing the caliper? I assume the brake pads increase the resistance of the hub to turn. Is there a general test I can perform , maybe jack up the front and see how difficult it is to turn the tire.

I did the hubs with the fishscale a while ago, but thinki might have overtightened them to maybe 15lbs of preload.

Am I just paranoid?

-Kevin

 

[lonelydriver]

I'm not sure if this is a good way to tell that the wheel bearings are overtightened, but the lug nuts are hot after driving. I can probably keep my hand on the lugnut for maybe 5 seconds before it gets uncomfortable.

I know it's vague but any suggestions would help.
-Kevin