How much does wheel weight affect performance?

[Slammillionaire]

Hey guys, I'm going to be in the market for some new wheels in the somewhat near future and I'm wondering how much wheel weight really affects performance. I've been looking between 17's and 18's and I honestly much prefer how the 18's look. I won't be tracking the car at all, but do enjoy some spirited driving through the country side. Some of the sets I've been looking at that are aesthetically pleasing are around 26lbs. Will I be gaining THAT much from going with a set of RPF-1's or something similar instead?

[jvincent]

If you're not timing at a track, it doesn't really matter.

FWIW, I have 18x8.5 on mine, which I take to the track. It's still fun. Enkei PF01, which are still lighter than stock.

[StraightOuttaCanadaEh]

there was a very thorough thread on this if you google it. Basically yes, people are saying the car feels more eager, but actual track data didn't reveal much. For road use, I enjoy my 18s much more than I did the 17s, though I suspect tires had a lot to do with it. With 18s, the car looks more exotic and aesthetically pleasing, to me at least

[ILLSMOQ]

My experience has been that increased weight (rotating mass) affects acceleration...once your going probably not as critical.

[Sapphireho]

Go with 18s. They look much better.

[Stang70Fastback]

That kind of weight increase will absolutely be noticeable at higher speeds in the form of stiffer, less eager steering due to the higher rotational moment of inertia.

26 lb is heavy for an 18" wheel when there are much lighter options. Hunt around. I don't know exactly what size you're looking at, but my 18x9s only weigh 20 lb each, which is actually lighter than the stock 17x7s.

At the end of the day, it won't ruin the car, but I would still do what I could to keep the weight gain to a minimum. Don't forget tires for 18s will also be a few lb heavier. So 6 lb heavier wheels plus 4 lb heavier tires means 10 lb per corner. That's 40 lb total, and 10 lb will definitely be noticeable in the steering at speed.

[imnotsureaboutbrz]

my 2 cents... I recently went from running 225/45/17 MPSS on the factory (22lb) wheels to a set of 245/40/17 MPSS on RPF1 (~15lbs) and I noticed an immediate difference. The car accelerates and decelerate more eagerly. The car felt more powerful even though I know no power was added... but the butt dyno makes me feel otherwise...

While I agree 18's look nicer on the car, the additional weight from the increased wheel and tire size might cancel it out.

21 lb tire + 22 lb wheel= 43lb a corner
24 lb tire + 18 lb wheel= 43lb a corner ... not too noticable

[ILLSMOQ]

Makes total sense, I believe it. Can’t say I’ve noticed the difference in turning as much as I’ve noticed the difference in acceleration but it definitely makes sense. You should always go as light as possible. I was once told 1 pound of rotating mass is equal to 7 pounds of dead weight. Searching on the internet the numbers are all over the place. Inertia and momentum invisible forces that affect speed and control.

Also 26lbs is really heavy for a 17 or 18 that will fit these cars...with all the options out there, you gotta be able to find something in the low 20 pound range if not lighter that you like.

And yes tire weight varies as well so if weight is important to you be sure to check the weight of the tires you’re going to use as well.

Originally Posted by Stang70Fastback

That kind of weight increase will absolutely be noticeable at higher speeds in the form of stiffer, less eager steering due to the higher rotational moment of inertia.

26 lb is heavy for an 18" wheel when there are much lighter options. Hunt around. I don't know exactly what size you're looking at, but my 18x9s only weigh 20 lb each, which is actually lighter than the stock 17x7s.

At the end of the day, it won't ruin the car, but I would still do what I could to keep the weight gain to a minimum. Don't forget tires for 18s will also be a few lb heavier. So 6 lb heavier wheels plus 4 lb heavier tires means 10 lb per corner. That's 40 lb total, and 10 lb will definitely be noticeable in the steering at speed.

[Stang70Fastback]

Originally Posted by imnotsureaboutbrz

While I agree 18's look nicer on the car, the additional weight from the increased wheel and tire size might cancel it out.

21 lb tire + 22 lb wheel= 43lb a corner
24 lb tire + 18 lb wheel= 43lb a corner ... not too noticable

This part of your statement is a bit confusingly worded, so I just want to clarify for people: a lower profile tire for a larger wheel will NOT necessarily be lighter, despite what your common sense might initially tell you. Lower profile tires have thicker sidewalls and require tougher construction to maintain their shape, so they are heavier. It's a 3-4 lb weight gain if you go from, say, a 215/45R17 to a 255/35R18 (people generally go wider when they buy aftermarket wheels.)

[Gunman]

Unsprung, rotational mass is bad, mmkaaay?

[srt4evah]

http://www.roadandtrack.com/car-cult...ransformation/

18's, mind you $3200 Advan RGII's, were slower than the stock wheels with better rubber, but faster than stock wheels with stock rubber. Those Advan's however are 17lbs per rim, lighter than stock.

[gtengr]

Originally Posted by ILLSMOQ

I was once told 1 pound of rotating mass is equal to 7 pounds of dead weight. Searching on the internet the numbers are all over the place. Inertia and momentum invisible forces that affect speed and control.

Unfortunately the numbers are, in fact, all over the place. The effect of heavier wheels is different in each gear and at different levels of horsepower. The best way to investigate is to set up a spreadsheet to determine wheel angular velocity and angular acceleration, then reference that against published road test results, input your changes, extrapolate what new accel times would be using spreadsheet output, ???, profit.

A larger diameter wheel will concentrate more mass towards the extremity of the wheel, and this is the worst place for the mass to be (inertia is a function of m*r^2). A 25 lb 18" tire packs mass at a greater average radius than a similarly constructed 25 lb 17" tire. Same with every feature of an 18" wheel that moves mass further from the center.

Increasing/decreasing tire diameter due to non-OE tire sizes affects gearing.

[Slammillionaire]

Based on the info in this thread, I'm probably gonna pick up some 17x9 gramlights. Thanks guys! lots of gr8 info.

[jasonojordan]

Originally Posted by Slammillionaire

Based on the info in this thread, I'm probably gonna pick up some 17x9 gramlights. Thanks guys! lots of gr8 info.

FYI Gramlights in general are normally opposite their name. Most Gramlights are actually pretty heavy wheels.