Fuel Economy Impact of New Tires

[jimepting]

Just replaced my old Bridgestone RE92 LRR tires with a new set of same tire. Doing a bit of extrapulating of my baseline data, it looks like I lost 2-4 MPG.

If these tires don't improve shortly, I'm gonna shave them down to 4-5/32" , like we do on race tires for the Miata

[some_other_dave]

It always takes a while for new tires to "wear in" and drop down to their proper rolling resistance. I think it took something like 1K miles for the Hankooks that I put on my old car?

-soD

[Ladogaboy]

Remember that you were most likely seeing inflated (forgive) mpg numbers with your old tires. More rubber was worn off of them making them smaller and lighter.

[Mustang Dave]

I lost about 1 MPG on my Mustang for one fill-up when I "re-tired" it in May.

[F8L]

Shaving your tires will reduce treadlife and force you to buy new tires prematurely. Is the increase in mpg going to offset the price of new tires? I suggest giving them a couple thousand miles of break in before you do anything drastic.

[villain.ind]

i agree with F8L. the benefit youd gain from shaving the tires would likely offset the value due to the cost of new tires sooner. if they dont yeild the results u want maybe they changed something in the manufacturing process since the purchase of the old tires that is having an impact on the new ones.

[Hubert Farnsworth]

Lower tread depth = fewer revs per mile = artificially increased mpg figure as the odometer turns slower, so the effect of the new tires is to increase the outer diameter by the increased tread depth, which means more revs per mile by a couple, and then until they are broken in they will not have reached their ideal rolling resistance until then.

However if you were to shave them back down to a lower tread depth it would only help in the dry, ruin wet and or snow traction, and cause you to need to replace tires even sooner.

[KamperBob]

Mathematically the contribution of tread depth to outer diameter is pretty small. Ball park maybe one percent over the life of the tire.

[3-Wheeler]

Originally Posted by jimepting

Just replaced my old Bridgestone RE92 LRR tires with a new set of same tire. Doing a bit of extrapulating of my baseline data, it looks like I lost 2-4 MPG.

If these tires don't improve shortly, I'm gonna shave them down to 4-5/32" , like we do on race tires for the Miata

Hi Jim,

Hold tight and wait a while.

The tire rubber will get harder after 20 or so hot/cold cycles from running the car, then letting it sit and tires cool.

Whenever I put a new front tire on the motorcycle, I can really feel the grip of the new tire on the road during the first few rides. The handle bars are noticeably harder to push for turns as well.

After those hot/cold cycles are done, the tire feels much less sticky when turning.

The same thing will happens with our Insights after the tires harden somewhat.

Jim.

[jimepting]

Originally Posted by 3-Wheeler

Hi Jim,

Hold tight and wait a while.

The tire rubber will get harder after 20 or so hot/cold cycles from running the car, then letting it sit and tires cool.

Whenever I put a new front tire on the motorcycle, I can really feel the grip of the new tire on the road during the first few rides. The handle bars are noticeably harder to push for turns as well.

After those hot/cold cycles are done, the tire feels much less sticky when turning.

The same thing will happens with our Insights after the tires harden somewhat.

Jim.

Yeah, I suspect as much myself. It is probably a breakin process which will take some little bit of time. The actual change in diameter between old and new is so negligible that won'g be likely to have any effect.