Can anybody point me to the threads on the differences seen between 17" and 18" wheels? Have heard many say that this difference is subtle with obvious better take off grip and handling for the 18" but wonder about ride comfort on bumpy roads, etc.. Hope to pick this out of the threads.

 

Not sure about any previous threads, but when i went from 17" bullitts to 18" fanblades I did notice a few changes.

subtle:
a.) ever so slightly harsher ride (nothing to complain about)
b.) slightly more precise feel in corners
c.) heavier steering feel

not-so-subtle:
a.) less power to the ground. I definitely noticed a pronounced seat-of-the-pants difference, especially at partial throttle. You have to give it more gas to get the same result.
b.) great looks! The car was CLEARLY designed to have at least 18 inch wheels on it.

Eventually I'm going to try to acquire some lightweight 18s and see about getting a little of that grunt back.

 

ps: the tires on both sets of wheels were brand new and OEM, not replacements. Also, I didn't go to the drag strip or do any "scientific" testing, so my impressions are just based on driving around town.

 

The 18" are a little harder to spin but they do grab on the corners/curves .

 

Do you mean you have to use more throttle with the 17" or 18"?

 

with the 18s. It's not the end of the world, but there is a definite difference.

 

I agree. My gas mileage seemed to decrease about 10% over the course of a 200 mile trip that I have done many times before (so I know what it *should* get). Most of that was probably due to winter mix gas and perhaps a head wind, but either way it did decrease some.

Makes sense, as the wheels are probably heavier, and there is more rolling resistance due to the wider tires.

 

I upgraded from to 18 X 9.5. The upgraded tires are better than the oem. The car tracks quite a bit more in rutty pavement, the ride quality is a tad more stiff than before. As far as any noticable loss in power or acceleration, none that I can tell. The upgraded tires, even though wider, seem to handle rain with less hydroplane. Handles with more stability in the corners.

The biggest problem I've found with the upgrade was tire noise. The BFG gforce tires with the neat looking tread pattern are LOUD. I cannot hear my SLP loudmouths over the tire roar on the freeway.

But performance wise, I think they have really added to the car. No idea if or how much more the larger rim/tire combo weighs over stock but having lifted both, I'd say they are pretty close in weight. I kept the overall diameter the same as stock.

 

To be able to feel the seat of the pants difference from the stock 17's to 18's is crazy. throttle wise.
I switch back and forth in the spring/fall and cannot tell a difference what so ever.

And to say 10% change in fuel economy is a bit harsh.
Id be willing to bet the rolling resistance is darn near the same. With the 18's theres less sidewall flex as the tire goes around = less resitance.
Sure theres a tad more rubber on the road, but not that much more. Kind of cancel eachother out.

 

"I upgraded from to 18 x 9.5"

Were those Bullits you upgraded to, and is it hard to find polished bullits in 9.5 width, or are they slightly different than the Ford Bullits? Anotherwords can I just buy one pair of 9.5 polished Bullits somewhere for the back and leave my standard 18 x 8 on the front?

 

My mpg on the 200 mile cruise, at a speed of 5 mph over the limit and the cruise on the entire way, was always 25 mpg. Now, going on the route twice since changing the tires, it was 22.5 mpg. That equals a 10% drop.

Think about it: I'm running 20mm more rubber x 4 tires, and upgraded from 17x8" wheels to 18x9.5" wheels. That means more rubber on the road, and more rotational weight.

Like I said, a lot of it may have had to do with winter mix gas. Also, a change in psi may have to do with it (although I was running stock GT factory recommend psi before, and now with the new rims I'm running GT500 recommended psi...therefore, they should be the same).

But, the numbers don't lie.

 

I agree, and Im just giving a somewhat educated opinion. Either way, its an opinion. But it takes just one good WOT to throw off that avg MPG.

Ive tried to get the best gas mileage in a tank, but I just cant lay off the pedal, lol. Its a sickness!

 

Over the 200 mile trip, a WOT one time wouldn't do too much. But, either way, I am very careful about how I drive the car on the trip, to see what kind of mileage I can get. I am very smooth with the throttle. Also, that's why I keep the cruise on the whole way, and always at 5 over, to allow consistent driving.

The same results occurred when I had a predator, which is opposite of what other people's results are. But, it is one of the reasons that I got rid of it.

BTW, I can't stand it, because I want to open it up. The open road and 70mph speed limit scream to me, but I refrain, as it's not worth it in the long run.

 

What about speedo calibration?

 

I went with 255/45/18 all around, which are stock for the GT500 fronts.

Either way, they have the same outside diamter as the stock 17's, more or less (maybe a 0.5-1% difference)

 

Its them draggin **** Michelins

 

There was a discussion on here a while ago and a member indicated that the 18" wheel equipped stangs have different struts than the 17" wheel equiped ones. See post # 15 in this link http://forums.bradbarnett.net/showth...=wheels+struts (Stoenr was in that discuss too)

I've always wondered if I was going to get aftermarket 18s, if it would be advantageous to get 18" wheels from the factory just to get those struts.

 

never a definate answer given tho?

If I remember tomorrow Im gonna call my local dealer and ask them to look up the part #'s

 

Actually, these Michelin's are AWESOME, and are very quiet.

But they better be, because they are probably one of the most expensive tires you can buy in this size (about $275 each retail).

 

Yeah, I was only messin
<-- Goodyear store manager

M17577 MI 255/45-18 PIL ALPIN PA2 99V $192.00 0 0 0 $230.40
M61094 MI 255/45-18 PILOT XGT Z4 DIR $216.00 0 0 0 $259.20
M63035 MI 255/45-18 PIL HX MXM4 99W $282.00 0 0 5 $338.40
M66279 MI 255/45-18 PILOT SPRT ZR 99Y $267.00 0 0 4 $320.40
M92199 MI 255/45-18 PIL HX MXM4 XL 103H $254.00 0 0 0 $304.80

Your right, **** expensive. Still never liked Michelins personally. Sidewalls always to flimsy, and always were the ones that caused bad rim corrosion around the bead area, where other tires held up better.
And the F1 GS D3 won the Car and driver tire test.