Taller tire ?

[TexasR.N.]

Howdy All,
Does a taller tire make the engine work harder? For some reason I had it in my head that a taller tire acted like an "over drive" if you will. Does this cause the engine to be under a heavier load? The reason I ask is because I was looking up information on our expedition and I ran across this on a gasser site:

Additionally, a taller tire acts like a lower gear ratio number (less engine revs/per/mile). This puts the engine under a slightly heavier load. The ECM will adjust timing/fuel/tranny up shifts to compensate.

Anyways, just looking for some clarification / education on this topic.
Thanks,
Craig

[Evil Eye]

Yes, a taller tire causes your engine to work harder exactly for the reason you mention-less revs/mile.

[Raul@Stealth Automotive]

and your trans too... not to mention that your speedo will be off and your shift points will also be off because of that

[welder24]

would going from 235/85r16to 285/75r16 effect the shifting and speedometer also

[Raul@Stealth Automotive]

Originally Posted by welder24

would going from 235/85r16to 285/75r16 effect the shifting and speedometer also

yes any change will effect it... but that is not that big of a change so your ok... its when you go from like 33's to 37's when things start to take its tole... even running 35's your speedo will be off a few miles

[silverF250]

I guess you can say it has to work harder. Less revs to make as much power, but I don't think it is such a big deal. If you go taller you get better fuel mileage with the lowered rpm's. To me the higher the rpms the worse it is on the engine because the rev's create heat and that heat breaks down the oil. I don't know maybe a tech will chime in and tell me I'm wrong, but 1 or 2 sizes larger would have little effect.

[silverF250]

I would think the heavier load would have to do with more rolling mass and not so much the rpm.

[TexasR.N.]

Cool, thanks for the explanations fellas.
Craig