?

This is actually for my truck. What I want to know is how putting taller than stock tires (on my factory wheels) will affect things like mileage, acceleration, the speedo, etc etc....?

Thanks.

-Tim

 

Basically you have to look at it not so much as taller, but more circumference. The taller tire will throw your speedo off a little. You will be going faster than the speedo says. As for acceleration, it will slow it down a bit, unless you are pumping out major ***** or gears. The milage will be better on highway (each revolution of the taller tire is more distance than the stock) but you may see a drop in city if it is too drastic a change (bogging the engine on starts. But most changes will hardly be noticed, but watch your speed!

 

thanks

 

Taller tires = faster (top speed), not quicker (0-60, 1/4).

Shorter tires = quicker (0-60, 1/4 mile), but not faster (top speed).

You want to calculate your effective gear ratio. Search thru yahoo.com for more information on effective gear ratio. In fact, I think I posted a message here not too long ago about it.

For instance, I was running P255/70r15 tires a few years ago. With my 3.42 rear, those tires increased my effective gear ratio to a 3.18!! Not cool at all- except for speeding. My acceleration from a stop was noticably slower.

 

At highway speeds, putting a taller tire on would be like keeping the old tires and going from 3.73 gears to 3.42. The rpms will come down at highway speeds and low speed accelleration will be slower. Just like everyone who has 2.7x gears and want 3.73 gears to increase bottom end acceleration.

Mileage should increase on the highway because of the lower engine rpms.

If the speedo says you're going 60 mph you might actually be at 70 mph. This will also create problems trying to calculate mileage. Instead of going 200 miles on a fill, the odometer may say you've gone 240.

 

Check out this page I was shown... it will take your original tire/rim spec then when you enter the new tire/rim spec it will tell you ecatly how off your speedo will be:

http://www.miata.net/garage/tirecalc.html

 

That would depend on what rpm the engine was turning with the original tires and what it turns with the new tires. It's the same (but opposite) way that mileage doesn't change very much (for an engine with a decent amoung of power) when you step up to 3.73 gears--the engine is turning more rpms but it's not having to work as hard to do it. Assuming that the tire change makes a significan difference in rpm, he may see no change in mileage if the motor has to work harder to generate those (lower) rpms.