Educate me on light wheels

OK, everyone talks up the importance of lightweight wheels, and I have a very rough understanding of why - helps the suspension work better, faster acceleration and better braking with less rotational mass - but how important are lightweight wheels really? I have more than a passing interest - I've picked up a set of stock 18 x 9.5 rear M3 wheels for my E46 M3 HPDE car to mount sticky tires to next year. They're heavy, at around 26-28# a wheel, but they were cheap at $260 for all 4. Learn me why I should sell these for scrap and spend $1.5-2k on lightweight 18 x 10 wheels for HPDE sessions.

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There was a wheel-weight comparison on the MX5 STR project car a few issues ago.

How much lighter does $1.5K get you? If its 10lbs saving, it may be worth it. If its 6 lbs, and its not an actual race, I wouldnt bother.

I had a set of pimpy panasports on my miata. they were 10lbs each in 13x8.5. I found a set of real racing wheels in the same size that were 11.5lbs for $300. I sold the panasports for $1100 and don't mind the extra 1.5lbs.

Everything I've read about the subject (magazine tests) only showed 100ths to 10ths of a second improvements on an auto-x course due to "lightweight" wheels. Personally I leave a lot more time on the clock due to mistakes and bad driving, so I can't possibly justify the extra costs.

I'd say put some good rubber on them meaty wheels and have some fun.

The stock M3 rear wheel are 18x9, not 9.5. With the offsets you'll have to run a decent amount of negative camber up front to tuck them into the fenders.

I ran SSR Comps 18x9.5 ET 35's on my old M3, I ran 10mm rear spacers with them.

The point of diminishing returns is in effect here. The $400/set 15Lb wheels will give you a measurable performance boost over the 25Lb stockers, but the $1200/set 10Lb ones aren't worth it (usually).

You'll see a bigger effect on rougher surfaces. Also, it's best to think of unsprung mass as a percentage - light cars are more affected by a few pounds on the wheels than heavy cars.

Javelin wrote: The point of diminishing returns is in effect here. The $400/set 15Lb wheels will give you a measurable performance boost over the 25Lb stockers, but the $1200/set 10Lb ones aren't worth it (usually).

^This.

It has a lot to do with intended use. Autox, where 0.1 could cost you the trophy? OK. Wheel to wheel where an effective 0.5hp gets you around a car on the straight? OK. HDPE where it does...??? Up to you.

docwyte wrote: The stock M3 rear wheel are 18x9, not 9.5. With the offsets you'll have to run a decent amount of negative camber up front to tuck them into the fenders. I ran SSR Comps 18x9.5 ET 35's on my old M3, I ran 10mm rear spacers with them.

My bad on the size, thanks. I know I'll have to run lots of camber; I hope to have decent coilover suspension and camber plates on it for next year. It should be fun trying to mount 275/35s on those 9" wheels, my tire guy will probably not be happy but he'll do it.

I love me some SSR Comps; the woman who owned the car before me and who I bought 3 of the 4 stock rear wheels from has 6 of them in that size, and I've told her that when she's ready to stop tracking her 1M and sell them to call me first.

PSSSHHHHH~

You aren't hardcore unless you buy Dymag Carbon Magnesium wheels. You know you wanna be hardcore. (At 10K+ a set, you would be REALLY hardcore)

In spite of the smaller sidewalls and wider rubber, my MS3 rides much, much better on my current setup (18x8 OZ Ultraleggera, 18lb apiece+Sumitomo HTR-Z III 235/40/18) than on the stock setup (18x7 stockers, 24lb apiece+Bridgestone Potenza RE050 215/45/18). The net loss per wheel is about 6lb when you factor in tire weight. There are lighter wheels out there for the MS3, but only a couple of pounds lighter and those get wayyyy expensive. I haven't raced the MS3 yet, but for DD work it is much less harsh over bumps while still being much grippier.

Don't forget that wheel construction plays a big role in their durability and price. Forged wheels are very light and durable but are much more expensive than cast wheels. Lightweight cast wheels like Koseis tend to get bent or break easily.. Buzzwords like Enkei's MAT Technology and TSW's Rotary Forging typically refer to spun-casting, which is exactly what it sounds like- the wheel is spun at high speed while it is being cast. Spun-cast wheels tend to be in the middle in terms of weight and durability.

The GRM article really opened my eyes. I'm probably not a good enough driver to notice a wheel that's a pound or two.

Where weight really matters is when you need to move them out to your barn and bring in the snow tires.

Wasn't the wheel weight test done on the Tire Rack test track? What's the surface like there? Pretty smooth, I expect.

I can tell you that going from 12" to 10" wheels on my Mini along with lighter calipers made an enormous difference in how the car felt. Some of that was the taller sidewall, but I think most of it was the wheel weight. That's on a 1350 lb car being driven on the street.

I think all the answers here are saying what I'm thinking. It depends on what you're doing. I've spent way more than the cost of light wheels to save a tenth on an autocross car. And I'll pony up for the Spinwerks wheels for Tom Celica to be sure. But if I wasn't trying to win something where a tenth is kinda a long time, I wouldn't bother.

RexSeven wrote: Don't forget that wheel construction plays a big role in their durability and price. Forged wheels are very light and durable but are much more expensive than cast wheels. Lightweight cast wheels like Koseis tend to get bent or break easily.. Buzzwords like Enkei's MAT Technology and TSW's Rotary Forging typically refer to spun-casting, which is exactly what it sounds like- the wheel is spun at high speed while it is being cast. Spun-cast wheels tend to be in the middle in terms of weight and durability.

I will put this out there. I have mangled two rims in my life. One was the stock aluminum rim that came on my Hyundai Tiburon.. and one was the Enkei RPO1 that replaced the stockers..

the stock rim broke in a NASTY pothole. Literally broke part of the rim off that required me to run with the spare.

The enkei, with it's MAT spun construction.. took a tall kerb, in the dark, during a rainstorm, and only bent where the tyre mounted to the rim.. and never ever lost air

I was also able to bang it mostly back into place with a deadblow hammer

hmm... Ive been thinking of picking up a set of e46 m3 rears for my 540i but I didnt realize they were so heavy.