Not that I really plan on replacing my rims and tires immediately, but researching stuff about my soon-to-be-mine car has been a good way to pass the time

I already searched the forums for the weight of a stock rim, and found it to be ~19 lbs. A stock ponteza is 23 lbs according to tirerack. I found a nice set of 17" rims on there that weigh 16 lbs each, and depending on the tire, I could lose another 2 or 3 lbs per tire there. (and they'd have better grip, but that's not a variable I'm trying to include here.)

So, it would be easy to shed 5-6 lbs per wheel. What I'm wondering is, would this give a noticable increase in performance (launching, acceleration, throttle response) due to less rotational mass? I've seen the statement "get lighter wheels" thrown around a lot on here, but no real results or claims of any increases. I'm especially interested in hearing from someone who may have done something similar already with their current, or past car. Thanks!

 

Not sure on the tc but my xb mag wheels, or whatever you call the aftermarkets these days, are noticably lighter than the stock steel wheels. I definitely felt an improvement in ride quality and tried to convince myself that the car is peppier. Wh knows without testing at a track??

Walt

 

FYI, you might find the following information interesting!

A vehicle's total weight is the sum of all of its parts and affects its ability to accelerate, brake and corner. Reducing the total weight will enhance the vehicle's performance because less weight needs to be controlled and therefore, less energy is required. Unsprung weight is the weight under the springs which moves up and down as the vehicle rides over uneven roads and leans in the corners. Reducing unsprung weight allows the springs and shock absorbers to be more effective in controlling the suspension's movement. Additionally, a vehicle's rotational weight includes all parts that spin including everything in the vehicle's driveline from the engine's crankshaft to its wheels and tires. This affects the energy required to change speed as the vehicle accelerates and brakes. As you would guess, reducing the weight of any of these rotating components will enhance the vehicle's performance because less energy will be required to increase or decrease their speed.

In order to get a better understanding of the effects of reductions or increases in wheel and tire weight on performance, comfort and feel, The Tire Rack Team conducted a Ride & Drive comparing a BMW 3-Series equipped with its Original Equipment (16") wheels and tires in order to establish a comfort and handling baseline, to a second BMW 3-Series equipped with Plus One (17") wheels & tires using lightweight aluminum alloy wheels, and a third BMW 3-Series equipped with the same size Plus One application, but this time using heavyweight aluminum alloy wheels.

Original Equipment (OE) BMW 3-Series Alloy Wheels and Tires

16" x 7" sized OE BMW wheels and 205/55R16 91H-sized Michelin Energy MXV4 Plus tires

The aluminum alloy wheels which came as Original Equipment on our 3-Series test car features cross-spoke styling and weigh an estimated 20.5 pounds each.

The Energy MXV4 Plus tires used as Original Equipment on our BMW 3-Series are Grand Touring tires which blend some of a performance tire's looks and handling with a standard passenger tire's longer life and more comfortable ride. The Energy MXV4 Plus incorporates an advanced version of Michelin's Radial XSE Technology (which consists of a Smart Tread Compound, Optimized Casing Shape and Optimized Mass Distribution). The OE Michelin Energy MXV4 Plus tires weigh 22.5 pounds each.

When combined, the weight of the Original Equipment Energy MXV4 Plus tires mounted on the BMW alloy wheels results in a 42.5 pound Tire & Wheel Package.

On the road, the OE BMW alloy wheels and Energy MXV4 Plus tires were praised for their good ride, low noise, real world handling and steering feel. The car felt balanced and generated a relatively light steering feel that felt appropriate for the car. This combination made it easy to understand the combination of real world ride, noise and handling qualities that BMW engineers wanted for their 3-Series sedan. On the track, this combination was rated as responsive and predictable while providing good braking, cornering traction and handling. However, as expected, this car turned in the slowest lap times of the three combinations tested.

Plus Size Wheels & Tires Using Lightweight Wheels

SSR Semi-Solid Forged 17" x 8" alloy wheels fitted with 245/45ZR17-sized Pirelli P Zero Asimmetrico tires

The SSR aluminum alloy wheels used in this test feature five-spoke styling and a unique manufacturing process called Semi-Solid Forging (SSF). Using a process originally developed for aircraft and automotive parts which require high strength, low porosity and lightweight, SSF produced wheels use a special aluminum alloy which is heated until it has about the consistency of warm butter, and then it is forced into the mold under high pressure. This results in a strong, lightweight wheel that offers many of the traits of wheels forged in the traditional ways, but costs less to manufacture and therefore is available at a more affordable price. The lightweight 17" x 8" SSR aluminum alloy wheels on our 3-Series test car weighs a scant 17 pounds each.

The Pirelli P Zero Asimmetrico Max Performance tires used in this test feature a lightweight construction and an asymmetric tread design developed to maximize the tire's ability to put the power down whether accelerating, braking or cornering. Additionally, the P Zero Asimmetrico tread compound combines traditional carbon black with a special blend of silica and synthetic polymers to enhance wet traction and reduce rolling resistance. The P Zero Asimmetrico is used as Original Equipment on many performance vehicles, and for that matter, the tires in this test have been used as Original Equipment on the BMW E36 M3. The 245/45ZR17-sized Pirelli P Zero Asimmetrico tires weigh a respectable 21.5 pounds each.

When combined, the weight of the Plus One-sized P Zero Asimmetrico tires mounted on the SSR Integral alloy wheel results in a 38.5 pound Tire & Wheel Package which is actually 3 pounds lighter than.

On the road, this combination was praised for its steering feel and responsiveness, while it generated a small increase in ride harshness on bumpy roads. On the track, this combination was praised for its feel, feedback and responsiveness. It felt light and nimble, ready to transform the driver's input into performance. The car equipped with the lightweight alloy wheels and Pirelli P Zero Asimmetrico tires turned in the fastest lap times of the three combinations tested!

 

my 'seat of pants' experience with lighter wheels on my old civic (8 lbs alloy vs. ~15lb stock steel) with similar tires is the car felt 'lighter on it's feet' which seems to be backed up by the previous post. braking FELT better, acceleration FELT unchanged (remember this car had 76 peak hp and little low end torque). I didn't ever run times/distance measurements, but I was happy with the results. A few pounds lost at the wheels makes a BIG improvement versus yanking out your backseat, the 'ratio' is like 10:1 (1 lb removed from wheel is like 10 lb removed from car interior).

http://www.thefabricator.com/Article...cle.cfm?ID=565

"Racing guys have a phrase about this-they say that taking 10 pounds off of a tire or wheel is like taking 100 pounds off of the chassis. This is because removing any weight from the tire or wheel makes it that much easier for all those parts-the engine, transmission, differential, axle shafts, wheels, and tires—to get up to speed," said Chandler, explaining his company's relentless efforts to reduce weight at the wheels and tires.

 

I think it makes a difference. My MagLites are 14 lbs each and when I was running a pair of my stockers in the front while i was waiting for tires, it definitely felt slower off the line and I lost almost 2 mpg. That could be due to diameter differences, I don't know but it felt better again with my wheels back on.

Hey Roger, what happened with the heavy wheels on car #3?

 

That's exactly the sort of info I was looking for- thanks everyone, and especially RogerTTR for pasting that article.

I never even thought that lighter wheels could also give a mpg boost- that's what it sounds like happened for TheScionicMan, anyways.

Hmm, adding lighter rims to my "eventual mods list"- heh.

 

I think the rule of thumb is for every 1 lb. of rotational mass lost is the equilalent of 5 lbs off the sprung weight of a car, from a performance standpoint. So if your wheel/tire combo is 10 lbs less it will feel as if you shed 200 lbs from your car (10 x 5 x 4 = 200...)

 

regardless of what the actual ratio is, lighter is definately better. just remember chaos, that to get rims the same size but lighter it will cost $$$ because of the process and/or material used to make them.

 

if yer looking tc. they weigh 25 pounds each not 19.

 

Also remember, a smaller diameter wheel/tire combo will help bring the weight down too. I'm getting 16s (eventually) to replace my 18s during autoXing...I ought to be able to lose 6-10lbs per corner.

And it does make a noticable difference in the performace of a car to put lighter wheels/tires on...better acceleration and handling are easy to detect.

 

the braking benefits are also easily felt.

 

No kidding, the rims that interest me are the Gram Lights 57C's- $255 each on tirerack.com. Suffice to say, dropping over $1k on new rims is not in my immediate future- lol. I will eventually want to do this though, the benefits sound very good.

 

You will notice a difference in your vehicle with lighter wheels. There was a definate improvement in overall response in cornering, and braking, and much smoother accelleration when I put my 15" Königs on my RS2 today.

 

one of the reasons i wished 16" alloys were available from the dealer as stock with the 17's optional. oh well least they look perty (subject to debate ;P)

 

I like the stock 17's, its nice not to have a car with teeny little hubcaps any more That alone is what would make me search for light 17's, even though 16's would be a bit lighter.