b3d_sage

I was wondering about wheel weights. Looking at manu's and dealer's websites I can never find wheel weight listed.

Laws of phyics state that on order for an object to change state (move faster / slower / different direction) a force must act on that object. A circle is not a direction. So, to spin something you have to be constantly exerting a force on every atom in the object. And, everyone knows that it's easier to move something light than it is to move something heavy. So, saving a wheel mde a few pounds lighter requires significantly less force to spin. Thus, one would assume that for performance you would want the lightest wheel possible (well, almost, you have to take into consideration that the outside of the wheel is moving faster+further than the inside and so weight on the outside requires more force than on the inside making the design of the wheel also a factor in some cases).

My question is how much, in the real world, does it matter. And, I would assume that would mean knock-off wheels are made of inferior material and thus are heavier, thus the real thing has real-world benefits.

So, how do I choose wheels? I know that going from 18 to 19 on C-class degrades performance slightly so I know that I'm looking for 18's. But, beyond basing my descision on size and looks I'm not sure what I should be considering.

and yes I have STFF'd

W0n6_3d4n

If u race a lot it would matter, if u don't then who cares, i change wheels only for style alone. Forged will generally be lighter, also 19 + tyre will have bigger diameter compare to 18 + tyre. If u want to save some fuel, lighter wheel will work too. But yes mainly people change wheels base on style or performance.

b3d_sage

so how big of an impact is it going to make? Let's say I get some knock-off Lorinser replica's, is there going to be much of a difference? I don't care if i knock my 1/4 mile down by 0.1 second. But, if it means my 70-90 speed gets a good drop then I'm all for it.

W0n6_3d4n

I don't think it will be that much of a disadvantge in real road at least. One member here used to mount lorinser lm-6 replica to his C32, i don't think he notice big difference. Since lorinser is not forged i would say the weight difference is not that great either.

dchou

A light wheel will make a difference but not a very significant one. Maybe you should look into whether you want a smaller wheel (15", 16") or a larger wheel (18", 19"). Smaller would get you better acceleration, bigger, better top speed. This would make a much bigger difference then a wheel weight difference. 17" is in the middle, which I recommend if you're serious about your racing.

b3d_sage

oh ok... i thought that it was at 19 that you started losing performance. why is it that larger wheels decrease performance if not weight?

skahung

changing lighter wheels alone will not make a difference in performance unless you change a lighter body (entire car)..etc

tommy

That's not true at all; less unsprung weight (brakes, rims, tires) has a direct impact on performance.

And to add to your question about bigger rims, the further you push mass out from the center, the more negative impact on performance you have. So, 17" rims that weigh the same as 19" rims will take away less, for example.

b3d_sage

lol duh... i answered that in my original post about physics but somehow i just didnt make the connection!

exactly how big of an impact on performance will this be. going with one of the heavier rims available would that be a comparable impact (in the opposite direction, of course) to, say, putting in green air filters?

edit:
oh yes, and how does wheel size affect ride softness?

Moviela

May I suggest The Auto Math Handbook. It's a great book to answer these questions in an interesting manner.

http://www.amazon.com/exec/obidos/tg...02213?v=glance

b3d_sage

THANKS!

E55AMG99

Removing 1 pound of un-sprung weight is roughly equivilent to adding 3-5HP. In some extreme cases, I've heard of as much as 7HP per pound depending on where the weight came off.

Don't forget about the shorter stopping distances and improved handling that come from lowering un-sprung weight. It makes a huge difference here, too.

b3d_sage

oh wow, okay! So how am I supposed to find out how much these things weigh? I cant find anywhere that actually lists the weight... is there any resource somewhere that I could use?

dchou

Most wheel dealers online show that information. If you're interested in a rim, you can email/call a particular dealer and they'll tell you if it's not listed.

E.g., I'm thinking of getting these rims, tho they're not at all light weight.
Here they list the wheel weight.
http://www.spyeng.com/product_info.p...roducts_id=291

pookie

ok. i'm trying to find out what the OEM wheels weight to make a better informed decision when upgrading and/or sizing up to 17' wheels. i have the reg. 2002, c240 (not sport) with the 7 spoke wheels. i already know my tire weights, but just need OEM wheel weight. anyone know?

i do not want to end up with worse performance than what the c240 already has.

SeaCoupe

If you know the weight of the tire, take off the wheel, minuse out the weight of the tire, and approx rim weight is left.

I know that heaver rims make a reduction in horsepower. When I had an Acura Integra, i went from an alloy 14" rim to a 16" and I felt the car just bog down on the weight.

I upgraded to 17" AMG 203 wheels, and I know that I want something lighter next. If I go 18, and if I go 18, it has to be lighter.

Ed

pookie

ok. this is just for reference purposes in case someone searchs.

for 2002, c240.

style: 7-spoke, alloy wheels.
Part#: 2034010302
Price: ~$350
size: 16x7
WEIGHT: 19 lbs

OEM tire: continentalcontouring Tires, all-seasonal
205/55 HR 16 91H
~$81
UTQG: 360 A A
WEIGHT: 21 lbs

so OEM total weight of tire+wheel= 40 lbs


now, time to size up to some 17' that = or less than OEM weight.