How much of an increase in mpg can I expect with overinflated tires?

[Jim Dunlop]

Can anyone comment on whether it's better, on a front-wheel drive car for example, to run the front tires a couple PSI lower than the rears? For me, it's a cheap way (along with removing the spare/jack/carpet from the trunk) to give the car an aggressive stance. However, I wonder if making them all the same pressure, or running the fronts higher than the rears, would be best.

[lca13]

>>ernie: skeptical about dbl psi/half rr claim.

Inversely proportional makes sense, but not linearly and not with a 1x1 slope, if nothing more than because drive train resistance is not affected by tire pressure. Max mpg gain is probably when you start really slipping in the corners, and max mpg loss is probably when intitial resistance is "much" larger than actual rolling resistance. In either case, your tires may not last very long :-)

[GasSavers_Minger]

I'm still stumped as to what I should set mine as, both the manual and tires say a max of 35...maybe I'll try 40 next time I fill up?

[McPatrick]

I have 50 psi in 35 psi tires and they work great. It's up to you of course, but just to show you what's possible. And you will be able to tell the difference in your mpg...

[GasSavers_Minger]

Alrite, thanks. I just wasn't sure how much of a max before say, the tires gave out or soemthing.

Yeah, I'm one helluva newb, but I want to get bac into the 40's again...got htere once (370/8.8mpg) but all the others have been in the 36 range...what's weird is that its the same trips, over and over again...oh well.

[rvanengen]

Just a $0.02 worth...make sure your tires are in good condition, and if you really pump up the tires, consider getting them balanced after inflating.

One of our cars, the tires need to be balanced and it got MUCH worse after over-inflating...and the other car, nearly lost the tread due to separation...not sure if it was due to the inflation, or junky Michelins??

[jadziasman]

Very good point about tire condition. All four of my tires are new (or practically new). And - to my surprise - the VX Enkei wheels are holding the pressure rather well. I just added a few psi to them today exactly 1 week after the initial overfill. Just as the bad guy Emile in the classic film Robocop says when he fires the mini cannon for the first time - I LIKE IT!!!!

[GasSavers_Minger]

Hmm...just went from 35 to 43, maybe will go higher, but I think I feel it taking longer to slow down... but the rides a little harsher, but its all good =]

[jandree22]

I'm a member of the don't-exceed-sidewall-spec group. The owners manual is a suggestion based on estimated load in the car. There's leeway built in for people that load their car full of other people and misc. heavy cargo. That's why it's safe to screw around with that number.

The sidewall is the max pressure that the specific tire manufacturer determined is safe. Basically the point where they shed liability if the tire blows up while you're inflating it up to 55psi. I personally think it's insane to go 5, 10, 20 psi over the sidewall. Chances are you'll be fine 99% of the time, but the 1% chance of an Interstate or worse, inflation-time blowout isn't worth the extra 1mpg for me.

All that being said, obviously countless here have exceeded sidewall with no ill effects... this is just my personal feeling on the subject. OM = 34psi; SW = 44psi; Mine=40psi

[jandree22]

Originally Posted by Jim Dunlop

Can anyone comment on whether it's better, on a front-wheel drive car for example, to run the front tires a couple PSI lower than the rears? For me, it's a cheap way (along with removing the spare/jack/carpet from the trunk) to give the car an aggressive stance. However, I wonder if making them all the same pressure, or running the fronts higher than the rears, would be best.

Run the same PSI in all 4. I can't imagine 5 or even 10 psi less in the front tires will ever be noticeable to the untrained eye of bystanders. The crap removed from the trunk is an interesting method to raise the tush, though. If nothing else it's overall weight reduction for the car, lol