Deep dish performance

The Screwdriver · May 7, 2005

I've got a daily driven 99 GT coupe- stock gearing, pulleys, shifter, sub frame connectors. My stock rims are looking pretty beat up and the tires need replacing soon. I was thinking about the 10.5 deep dish bullitts in the rear. I know that going from 17" to 18" wheels will seem to hurt performance if you don't change the gears. But what about a wider wheel/tire? There's a lot more aluminum and rubber and I was wondering how bad that felt if I don't upgrade the engine/gears at the same time?

Thanks

wms004 · May 7, 2005

The Screwdriver said:
I've got a daily driven 99 GT coupe- stock gearing, pulleys, shifter, sub frame connectors. My stock rims are looking pretty beat up and the tires need replacing soon. I was thinking about the 10.5 deep dish bullitts in the rear. I know that going from 17" to 18" wheels will seem to hurt performance if you don't change the gears. But what about a wider wheel/tire? There's a lot more aluminum and rubber and I was wondering how bad that felt if I don't upgrade the engine/gears at the same time?

Thanks

How would going from 17" to 18" hurt performance? You would only notice an acceleration difference if the 18's were heavier. Otherwise you are using the same diameter tire so there's no difference. Going to 3.73's, 3.90's, or 4.10's would help the change, if you are going with a heavier wheel. My rotational mass may have increased 3-4 pounds going from 17-18's on each corner. I added an alum driveshaft which counteracts taht a little bit, by being 8-10 pounds lighter than stock.

wade

Blue70 · May 7, 2005

I noticed a difference when I put on my wheels.
I went from stock aluminum wheels and tires to 17x10.5 chrome wheels with 315/35/17 Nittos. (yes, the same diameter as stock tires.)
You are correct, you will be adding more mass with the wider wheels. It will require more effort to get them moving, and to get them stopped.
The little 4.6 needs a boost in low end grunt so I plan on some 4.10's to help get these things moving

Mustang5L5 · May 7, 2005

wms004 said:
How would going from 17" to 18" hurt performance? You would only notice an acceleration difference if the 18's were heavier. Otherwise you are using the same diameter tire so there's no difference.

Most of a rim's rotational mass is in the rim portion and not the spokes. When you go from a 17" to an 18" wheel, you move this mass outward. The further away the mass is from the center of rotation the more energy it takes to spin it. It's the same concept as the figure skater spinning slow with her arms out and faster when she draws them in.

So moving to an 18" wheel will require more energy to turn even if the wheel weighs the same. Also, keep in mind most guys run bigger heavier tires when they upgrade wheel sizes. An 18x10" wheel with a 295 series tire weighs a lot more than a 17" wheel with a 245 series tire on it...even if the actual wheels themselves weight the same. The mass is just moved to the outer edge of the wheel...where it hurts the most.

twogts4us · May 8, 2005

Rotational Resistance - yes, your performance will suffer. Traction may be better, but it will take more power in get it moving and keep it going - that is a fact.

Deep dish performance

The Screwdriver

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wms004

Blue70

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Mustang5L5

That is…until I whipped out my Bissell

twogts4us

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