Got a question or four about tires.

1. If I increase the overall diameter of my tires, I know it will mess up my speedo and odometer readings. Is there an easy way to recalibrate them to account for the size change?

2. I believe I've read in these forums that a 3% increase is the maximum increase that should be attempted. What would need to be done to safely exceed that limit?

3. Would it be better (in terms of a smooth ride) to increase the tire profile rather than the wheel diameter?

4. Will increasing the diameter, all other things being the same, result in a meaningful improvement in gas mileage?

Thanks in advance,

Dave

 

1: Yes. The dealer can do it by plugging into your truck's computer. It can also be done if you have the Max Tuner Superchip.

2: I don't know where you got 3% from. The largest tire size I am aware of that fits on stock rims and won't rub on things with a little trimming is over 34" in diameter, which is almost 9% larger than 265/70R17. If you have OEM 16" tires, the % increase is even more. Anything more than that, and you'll need to raise the truck up, most commonly with a body lift.

3: Yes, in theory. But most larger tires are constructed with stiffer rubber and could decrease the ride quality. Going from a P-rated tire (probably on your truck) to an LT Load C or D rated tire will feel stiffer, regardless of tire size chosen.

4: I doubt it. More likely that it goes down, but it depends on driving style. Again, credit larger tires with being heavier due to more rubber (size) and the construction. More rotational mass means it requires more power to turn the wheels which means more fuel useage.

Take a look at Tirerack's Tire Tech for some good general information.

 

Just to add

1) depending on the year your truck might just have a small gear that needs to be replaced.

 

97 and 98 had the VSS gear on the tailshaft of the transmission or transfer case (4x2 and 4x4 respectivly). 99+ use a computer controlled speedo so you'd need the tuner or a dealer to reprogram it.

 

Thanks guys...

I'll probably leave things alone...