M6 OEM vs. ELLIPSOID wheel weight difference

I found this rather interesting. Looking for a quick way to gain some performance? Change to OEM M6 wheels!

So I weighed my OEM "Ellipsoid" rear wheel (no tire). It came in at a whopping 37 lbs and 10 ounces!

I then weighed my OEM M6 rear wheel (forged) again with no tire. 24 lbs and 5 ounces!

Not sure if any of you follow unsprung mass weights and such, but this 13 lbs PER WHEEL is a HUGE difference in performance. Ultimately, that's upwards to about 52-54 lbs of unsprung weight reduction, which is roughly the same as removing 520 lbs from the inside if your car.

This is why wheel weights are important.

just sold some m6 wheels for super cheap with tpms sensors in immaculate condition you missed out?

Thanks for clearing that up.

From bmwfans.info:

BMW LA wheel, ellipsoid styling 121
81/2JX19 ET:14 13.266 kg / 29.247 lb
9JX19 ET:18 13.266 kg / 29.247 lb

I thought it was strange that the rear wheel weigh the same as the front.

BMW alloy wheel, M double spoke 167
81/2JX19 ET:12 12.000 kg / 26.455 lb
91/2JX19 ET:17 13.226 kg / 29.158 lb

Originally Posted by SehrSchnell

I found this rather interesting. Looking for a quick way to gain some performance? Change to OEM M6 wheels!

So I weighed my OEM "Ellipsoid" rear wheel (no tire). It came in at a whopping 37 lbs and 10 ounces!

I then weighed my OEM M6 rear wheel (forged) again with no tire. 24 lbs and 5 ounces!

Not sure if any of you follow unsprung mass weights and such, but this 13 lbs PER WHEEL is a HUGE difference in performance. Ultimately, that's upwards to about 52-54 lbs of unsprung weight reduction, which is roughly the same as removing 520 lbs from the inside if your car.

This is why wheel weights are important.

Strange that your weight came in at 24lbs while the chart below shows 29 lbs ?

Anyone know if Miro M6 Reps weigh around the same as the OEM M6 wheels ?

they were probably fake!

Originally Posted by joepipe

Strange that your weight came in at 24lbs while the chart below shows 29 lbs ?

Anyone know if Miro M6 Reps weigh around the same as the OEM M6 wheels ?

I have a certified shipping scale, which is what I used. I guess I shoulda taken a photo of the digital read out, eh? lol

I can guarantee that the Miro reps DO NOT weigh the same as the OEMS. The OEM's are forged, and the reps are a cast model. Not to mention the offsets are not the same.

Originally Posted by bmwlover1985

just sold some m6 wheels for super cheap with tpms sensors in immaculate condition you missed out?

Originally Posted by bmwlover1985

they were probably fake!

I am not sure what you mean in both of your above posts. What I am sure of is this;

I do not appreciate your previous PM's to me when I was attempting to sell my M6 rims. Furthermore, I do not appreciate what you did to me on Ebay - creating an account and hitting the buy it now button on my auction with a fake buyer. You sir, were reported and it was not hard to figure out that it was you that did this. Of course, the mere fact that your PM's to me specifically asking me to hold off on listing mine because they were cheaper than yours was a dead giveaway. People should be aware of your tactics.

From here on out, I'd kindly ask you that you not reply to any of my threads or comments.

Respectfully,
Sehrschnell

Pwned!

Jeesuz...didn't know oem wheels made that much of a difference! I'm on sucky AC Type IVs in 21". I'm basically owned....

serhschnell,

can you weigh the tires as well (if you have the run flats sitting around)... I wonder how much it weighs more than a michellin non rft.

thanks

i have the oem's best upgrade i ever bought for my 645! i picked them up from a bf member w tyres for under 2 k,

Originally Posted by SehrSchnell

I have a certified shipping scale, which is what I used. I guess I shoulda taken a photo of the digital read out, eh? lol

I can guarantee that the Miro reps DO NOT weigh the same as the OEMS. The OEM's are forged, and the reps are a cast model. Not to mention the offsets are not the same.

Modbargains lists miro reps at 24 lbs...You're saying M6 OEM are lighter ? I'm curious myself as I'll be buying either in the spring but the price does matter!

http://www.modbargains.com/_e/Wheels...0_BMW_only.htm

Originally Posted by mike6auto

i have the oem's best upgrade i ever bought for my 645! i picked them up from a bf member w tyres for under 2 k,

say it ain't so...the M6 mirrors are the best upgrade for the 645

Originally Posted by docpaulo

serhschnell,

can you weigh the tires as well (if you have the run flats sitting around)... I wonder how much it weighs more than a michellin non rft.

thanks

Sorry Doc, I no longer have any of the old tires. I know that Run-Flats are bit more weight then the average tire.

Originally Posted by joepipe

Modbargains lists miro reps at 24 lbs...You're saying M6 OEM are lighter ? I'm curious myself as I'll be buying either in the spring but the price does matter!

http://www.modbargains.com/_e/Wheels...0_BMW_only.htm

This would really really surprise me if this was the case. I'd like to put one on a scale to see for sure. (a rear, with center cap, stem, and weights like I had on both of mine in the above comparison).

Either way, the Miro's are probably not too far off and that would still be a HUGE savings in unsprung weight.

I found this article online about performance gains with unsprung weight savings. Of course, it's online, but it seems to make since. Essentially, what they are saying is that with the amount of weight saving I gained in wheels, this would decrease my 1/4 mile time by .5 second. Not really noticeable in the overall feeling, but number wise, a fairly decent increase.



Unsprung Weight - Part 2

By: Eric Albert

Introduction

In the first part of this series, we took a look at the effects of high unsprung weight on suspension and handeling. In this part, we will look at rotating mass. Be careful not to confuse unsprung mass with rotating mass. Reducing both is good, but they are not the same. Let's take a look.

Rotational Inertia (or Momentum)

Rotational inertia is a concept a bit more difficult to deal with than unsprung weight. Inertia can be thought of as why a car wants to keep rolling once moving, or remain in place once stopped (unless you forget to set the parking brake on that hill). I believe the terms momentum and inertia are interchangeable. The term "flywheel effect" also refers to these concepts. In a car, there are a number of rotating masses which require energy to accelerate. Up front, ignoring the internal engine components like the crankshaft, we have to worry about the flywheel, clutch assembly, gears, axles, brake rotors and wheel/tire. Out back its a little simpler (for FWD) with just the brakes and wheel/tire contributing most of the mass.

The more mass an object has, the more energy it takes to accelerate it. To accelerate a rolling object such as a wheel, you must both accelerate its mass plus overcome its rotational inertia. As for braking, you must overcome its rotational inertia plus decelerate its mass. By reducing the weight of the vehicle's rotational mass, lightweight wheels provide more responsive acceleration and braking.

Before continuing with our informal analysis here, I want to point out something very important about rotational inertia. We've all seen the ice skating move where the skater starts spinning. She pulls her arms in and speeds up, then extends them again and slows down. Why is this? Well, the further a mass is from the center of rotation, the faster it must travel for a given angular speed (how many degrees of an arc it traverses per time unit). The faster anything moves, the more energy it has, so when the arms are pulled in, conservation of energy says that the rotation rate must increase due to equal energy being applied to the same mass over a smaller diameter. Applying this to wheels and tires, which have most of their mass spread as far as possible from the rotation center, I think you'll agree that it naturally takes more energy to accelerate them. Example: Take a two identical masses, but one is a solid disk of diameter D, the other is a ring of diameter 2D. The ring will require more force to accelerate it (in a rotational manner). Therefore a heavier rim with a smaller diameter could have less rotational mass than a lighter rim of a larger size, and accelerate faster with the same force applied.

The effect of rotating mass can be calculated using Moment of Inertia (MOI). MoI is related to not only the mass of the rotating object, but the distribution of that mass around the rotational center. The further from the center, the higher the MoI. The higher the MoI, the more torque required to accelerate the object. The higher the acceleration, the higher the torque required.

Because of this, the weight of rotating mass such as wheels and tires on a car have a bigger effect on acceleration than static weight such as on the chassis on a car. When purchasing new wheels and tires for a performance car, it can be useful to compare the effects of different wheel and tire combinations. This is especially true when considering upgrading to larger wheels or tires on a car.

The use of light-weight alloys in wheels reduces rotational mass. This means that less energy will be required to accelerate the wheel. Given that each pound of rotational mass lost provides an equivalent performance gain as a 10 pound reduction in vehicle weight, the benefits of light alloy wheels on vehicle performance cannot be overlooked.
For example:
A reduction in the weight of the rim/tire assembly of 5lbs x 4 (all around the car) is equivalent to a 200lb weight reduction in vehicle weight (thats worth 0.200 in the 1/4 mile)

So What's the Point?

The point of this discussion is as follows: There is a great deal of rotational mass to deal with in a car and tires and wheels may only make up half of it. Estimates for weight (o.k. for comparison since they're all in the same gravity field, therefore the mass would be a similar ratio)
Front: Rear:
Wheel/tire: 30-35 lbs each 30-35 lbs each
Flywheel: 15-20 lbs
Clutch: 15 lbs
Halfshafts: 7-10 lbs each
Gears: 5-7 lbs
Rotors: 3-5 lbs 3-5 lbs
Misc: 3-5 lbs 3-5 lbs
------------------------------------------------------------------
Total: 115-148 lbs 76-90 lbs

So a couple pounds here and there on wheels and tires will make a difference, but that difference is magnified because that weight is placed further from the axis of rotation than any other mentioned (remember the ice skater). All these masses must be accelerated, so any reduction is a good thing. Now you know why we always say don't get those 18" rims for your civic. Not only are the heavier, they have a larger overall diameter. Even with lower profile tires, most plus sizing leaves us with a slightly larger wheel.

thx for the article....im hoping the 24lbs modbargains listed for the MIRO M6 reps is correct or at least very close....i would normally get M6 OEM's but the price between them is huge...I'd save some money for future mods to my car