How much does the weight of a rim affect performance, ride, and handling? I'm looking at a cheap shady set of rims on craigslist. I imagine they're fairly heavy. I will probably be weighing them before I consider buying. Is there a certain weight range that is okay? Any numbers anyone can throw at me?

LOL I just got banned on B.I. for a couple of days for saying somone who said heavier rims would improve ride was ignorant of suspension design and shouldn't post threads about anything other than his specific experiences...

HEre goes:

Heavier rimtire combos negatively impact ride quality adn handling...
Here is why, they change the ratio of sprung to unsprung weight that the suspension designers set up the shock/spring combo for.

This leads to increased impact transfer over non smooth pavement...

If you are going to change to a heavier wheel and tire combo the shock and spring combo needs to be stiffer in compression to control that additional mass, which in and of itself also increases transfer.

UNOFRTUNATELY there is no such thing as a larger diameter wheel and correspondingly lower profile tire larger diameter tire that weighs the same as original e34 15" basketweaves and tires, so it is a relatively moot point.
You cna howerver help yourself in this area (as well as in acceleration: the heavier rim also has most of it's mass in the barrel of the rim which is now farther away increasing rotational inertia and decreasing accelleration and braking performance too)
By avoiding OVERLY heavy rims.

Most of alloy OEM wheels are going to be heavier than aftermarket forged rims, but are generally lighter than aftermarket no name cast wheels...

When within your budget, choose an OEM or forged wheel for best performance, and stick to 17's for the absolute best overall performance as they (and the tires too!) are generally lighter weight and also have taller and slightly more compliant sidewalls.

IF you can live with the ride harshness penalty ( and this depends on whether your are a Sports car guy or a sport sedan guy, and whether the roads you travel are smooth or relaitively choppy) nothing looks better than 18's in the e34s large wheel wells, and in comparison to it's broad sides.

Here in the Deep South and Southwest where we don't have freezing weather, our roads stay in pretty good shape, but from what I hear those folks farther north especially in High traffic density Urban MEGAplex areas deal with much harsher roadways than I do. They would probably find my car to be unacceptably harsh on their roadways.

DO not forget tht tires play a major role as well... Most compliant sidewalls I have ever experienced are the Toyo Proxes 4, a little bit too squishy in performance driving for me, but very very comfortable... IIRC they are also one of the lighter tires per size available.
In contrast my RE730 bridgestones were very stiff with very good turn in.
MY RE750 Bridgestones are a little bit more compliant and you can feel it a little in hard driving or in transitions on uneven or rutted pavement where you can feel a hint of initial 'squish' , but the remaining 90% of the time they are a far superior tire TO ME...
The Continentals were a bit more squishy than the 750s, a bit too soft for me but probably fine for most guys, as I'm an old firm riding Brit sports car nut and like a really tight turn in and minimal tire flex no matter what I do with the throttle in a turn.

YMMV, but that is the best I can come up with...

I'm guessing my wheel and tire combo is probably about 50 lbs based on lifting them compared to my 35lb son. I have never weighed them, but published specs are 24 lbs per rim and 27lbs per tire... RE750s have a HUGE rim protector (almost gives them the stretched tire look) which adds weight but also stiffer sidewalls means more weight...

I would bet the stock 15s don't weigh more than 40 -41 lbs... with oem non performance tires. I have no weights to back up my non calibrated arm scale guess from picking up my spare to put it back into the car.

Thank you for being informative. :)

Now the question is one of extent, preferably a quantifiable one. Say, difference in acceleration with basketweaves vs. 22" rhinestone-encrusted spinners? Increase in braking distance? Or more subjectively - 18's are said to be noticably harsher, but are 17's more than ignorably firmer than stock rims?

I'm curious about the same thing for bigger brake rotors, too.

bigger rotors do not have as an appreciable effect, for one thing the increased mass is a benefit in braking as it increases the heatsink, and for another the mass is not located as far from the center of rotation, nor is it as great a difference in mass. the increased mechanical advantage is a plus in braking.

http://www.tirerack.com/wheels-techpage-1/108.shtml

interesting read and where brandon J got his info... the reduction in percieved impact on expansion joits IMO has more to do with the natural frequency reduction in the higher mass wheels and the transmitting of more lowspeed ocillation and less highspeed. Not a good "ride" to me. UNfortunately there is no DATA accompanying the article, only perception, and this is the ONLY article which states this opinion. Surprisingly (or not) the process was never repeated on a car with a different suspesnion tune or ratio of sprung to unsprung weight.
Asingle example does not support a theory.

Thanks for the information! Very interesting. It's crazy how the heavyweight wheels seemed to decrease gas mileage by 1mpg. It is somewhat unfortunate that the article only really had opinions to back everything up.

Well, I'm going to have to say the $175 price tag one these will be worth it. I think the performance issues will probably be negligible and unnoticed on my rather small trips to class and work. And they don't look that bad. Somewhat similar to contours, but not quite. If I don't like them, I will refinish them and sell them for more! They will be temporary while I work on other aspects of the car.


http://img86.imageshack.us/img86/4901/attid015b1978bse3.jpg
http://img86.imageshack.us/img86/5661/attid015b15ef6bc9.jpg

great response AE. here are a few more data points.

Grassroots Motorsports just did an article on handling improvements, and a slightly larger wheel increased lap consistency, but times stayed about the same.

others here have said that they felt acceleration improved with a lighter wheel/tire combo.

honestly if you're not racing the car, you probably won't notice an acceleration difference, but might notice an improvement in steering response due to the stiffer/shorter tire sidewalls.

as far as OEM wheel weights go, i have a set of 17x7.5 BMW BBS OEM wheels (for an e36) with forged centers, and they weigh 19.6 lbs. i'll weigh a stock 15" wheel/tire when i put on snows in a few months.

anyone know what a 17x8 style 5, 19, 32 or 42 wheel weighs?

haha... I was going to post up the thread that was on B.I...

Here is it in a nut shell.. do you think you can push/move a bicycle wheel better than a car wheel? How about visa versa?

The heavier wheel will take more energy to move around. Do you want the power to go towards the wheel or the ground?

here's a data point for those looking to upgrade from stock to larger wheels.

i weighed my stock wheel/tire combo as well as new 17x8 style 19's this weekend and wanted to share the results.


15x7 style 5 basketweaves with 225/60R15 tire = 42.4 lbs
17x8 style 19 (7 spoke) with 235/45R17 tire = 44.2 lbs

so the 17" wheel is only 4% heavier, which is much closer than i thought it would be. we'll see if i feel a difference in acceleration and ride, i fully expect to feel an improvement in steering feel.

ian "once a geek always a geek" lomax