New rims/Tires=Slower?

[Haywire6000]

So I just put a set ( all four) of 225/75/16's on crown vic steels on my 1993. I had the stock doe foot aluminum 15's with 235/75/15 tires on it. I don't know if it's me but the truck feels slower in accelerating.I know the steels are quite a bit heavier than the stock aluminum wheels. Just wondering if any one else has done this and noticed the same with. Also it's a 2.3. 4x4 4.10's 5 speed.

 

[JimsExplodingRanger]

I bet the new shoes have a larger circumference and that will take the away acceleration. I went from 14" rims to 15" on my '93 / 2.3 and between that and the larger tire can't really use fifth gear on the interstate any more! It's also really slow. A gear change will solve that but since you're already at 4.10 so you might be stuck with it.

You can check the circumference on this site in the tech / calculators section. If your new tires are bigger around, you've confirmed the problem.

Cheers!

-JK

 

[straycat]

Correct!!! Taller tires, taller wheel/tirepackage=poor gas milage and a huge loss of power. Re-gear that puppy!!!!!

 

[Captain Ledd]

225/75R16 = 29.29" diameter
235/75R15 = 28.88" diameter

soooo, 0.41" difference in diameter. I'll bet there are some tires out there that have that much difference in tread height from a new tire to a worn out one. If the old tires were getting on the bald side then I could see a small noticeable difference, but it shouldn't be that much. Hardly worth all the money re-gearing it if you're roughly satisfied with it's performance. Though I'm running 4.56 gears and about that tire size, and I do enjoy it. Those little 4 bangers need to rev.

On the other hand, not all tires come out to their mathematically calculated diameters, so you could be a little bigger, coming from a little smaller tire. And that would make it more noticeable., this will vary from brand to brand.

Technically you're be going ever so slightly faster than before at a certain speed than what your speedometer is telling you, but I'd say not much more than 5mph (if that) @70...

So that's probably what's going on, you've got about the best gear combo from the factory you could ask for in this situation. If you knocked down the tire size to a 225/70R16 (28.40") or 215/75R16 (28.70", probably the more ideal size) the next time you bought tires it'd help a little, but not much. As for the weight issue, I'm sure it effects it and is measurable, but it's not as drastic as most people think.

 

[trail B2]

A lot of people believe that adding one pound on the tires and wheels is like adding 5 to the body.I've also seen back to back comparisons on a dyno of smooth verses aggressive tread patterns.There was a difference there also it affects the little motors more.

 

[RonD]

What you feel in less acceleration is real.
And yes it does have to do with the new wheels and tires, and their added weight.

What was referred to above about unsprung weight is true to a point, because it is usually about tires and wheels.
Moving added weight down the road does require more power, but not that much more for the weight difference in the new wheels and tires.
What you are feeling is extra power draw that is required to get the heavier wheels and tires to rotate.
Plain and simple, it takes alot more horsepower to get those heavier wheels to start rotating and then up to speed.
But on the plus side you will be able to coast farther because of the heavier rotational mass, lol, but that may wear out your brakes faster

 

[Andy D]

Correct!!! Taller tires, taller wheel/tirepackage=poor gas milage and a huge loss of power. Re-gear that puppy!!!!!

Or go back to the stock tires/wheels. All the highboy stuff on a daily driver is purely for looks. Ka-Ching To re-gear, even more so. It has little to do with performance. Yours truly, Seymour Buzzkill.

 

[Haywire6000]

It doesn't really bother me, the trucks not a performance machine yet...

 

[adsm08]

225/75R16 = 29.29" diameter
235/75R15 = 28.88" diameter

soooo, 0.41" difference in diameter. I'll bet there are some tires out there that have that much difference in tread height from a new tire to a worn out one.

Yup. Average new tire is 12/32 new, and minimum allowable tread is 2/32. That's 10/32 a side, 20 overall on the diameter which is .6 something.