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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Tue, Feb-06-2018, 11:43:27 PM   #71
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Default Re: Value of OEM wheels

My car is lighter and faster on 22s than 18s..

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Old Wed, Feb-07-2018, 11:32:59 AM   #72
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Default Re: Value of OEM wheels

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Originally Posted by terraphantm View Post
All those factors do matter when considering what the car feels like from the butt dyno (and even the real dyno for that matter). Take everything past the crankshaft together, and we're probably talking an improvement of less than 1%. If you had magic physics 101 wheels that weighed nothing, it's not like the car would accelerate infinitely fast.
If you're expecting infinitely fast, you're setting yourself up for disappointment

Every component certainly matters, and I would never argue to the contrary. But, to get the system lighter, the only way to do it is to address components individually.

... and at a 10% rotational inertia difference, a 27 lbs 19" wheel will accelerate and brake like a 30 lb 18" wheel (ignoring that outside of the stock wheels, a like for like 18" wheel will also be lighter, as well).
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Old Wed, Feb-07-2018, 12:05:43 PM   #73
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Default Re: Value of OEM wheels

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Originally Posted by Obioban View Post
If you're expecting infinitely fast, you're setting yourself up for disappointment

Every component certainly matters, and I would never argue to the contrary. But, to get the system lighter, the only way to do it is to address components individually.

... and at a 10% rotational inertia difference, a 27 lbs 19" wheel will accelerate and brake like a 30 lb 18" wheel (ignoring that outside of the stock wheels, a like for like 18" wheel will also be lighter, as well).
You have to address each component individually, but for rotating mass there isn't a whole lot you can do. Lighter tires can certainly help, but for those of us who use high end michelins, we've already reached the best compromise there. Rotors aren't going to get dramatically lighter where they matter unless you go CCB. The components beyond that aren't particularly large diameter, but in the diff and transmission you're going to have huge frictional losses that you can't do much about (maybe polish the gears). Then as speed increases, angular velocity will play a larger role in "consuming" energy than the moment of inertia.

At the end of it all, I suspect the improvement would be on par with the ambient temperature going down 10
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Old Wed, Feb-07-2018, 12:50:22 PM   #74
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Default Re: Value of OEM wheels

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Originally Posted by terraphantm View Post
You have to address each component individually, but for rotating mass there isn't a whole lot you can do. Lighter tires can certainly help, but for those of us who use high end michelins, we've already reached the best compromise there. Rotors aren't going to get dramatically lighter where they matter unless you go CCB. The components beyond that aren't particularly large diameter, but in the diff and transmission you're going to have huge frictional losses that you can't do much about (maybe polish the gears). Then as speed increases, angular velocity will play a larger role in "consuming" energy than the moment of inertia.

At the end of it all, I suspect the improvement would be on par with the ambient temperature going down 10
Or, another way to look at it...
-Wheels are the highest diameter components in the system outside of tires, which (as you point out) are more or less fixed once you go to a quality set... making them one of the most significant components of rotational inertia.
-wheels are the easiest place in the system to lose the weight
-wheels are the cheapest place in the system to lose the weight
-wheels are also unsprung, so you can improve handling/ride quality with a lighter set
-smaller wheels inherently ride better and have less NHV, all else equal

I'm not really arguing for OE 18s over OE 19s, though all that minus the unsprung bit remains true (to a lesser degree). I'm arguing that I can't bring myself to run any OE wheel on the car because a light weight and 18" setup is significant an easily noticeable-- comparable to having a passenger in the car vs not.

It's also just all better, without tradeoff-- I can't think of any other place on the car where that's possible. Better acceleration, better braking, better handling, better ride quality, reduced NHV, cheaper tires, harder to damage wheels on potholes.

10 drop results in a ~2% change in air density, so I could agree to that being comparable (to the acceleration change).

... I hope CCBs become a viable mod, one day
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Old Wed, Feb-07-2018, 01:47:19 PM   #75
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Default Re: Value of OEM wheels

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All of those things matter in the greater context. You're argument is black and white: 19s are functionally worse.

That's a baseless argument without further qualifications, which you've provided in the quote above, since it is very obvious that a 19", given the right criteria, can be functionally superior.

Now you're making sense
All of that is a given, unless we want to start introducing random obvious clarifications into every single post.
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Old Wed, Feb-07-2018, 02:14:31 PM   #76
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Default Re: Value of OEM wheels

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Originally Posted by Obioban View Post
Or, another way to look at it...
-Wheels are the highest diameter components in the system outside of tires, which (as you point out) are more or less fixed once you go to a quality set... making them one of the most significant components of rotational inertia.
-wheels are the easiest place in the system to lose the weight
-wheels are the cheapest place in the system to lose the weight
-wheels are also unsprung, so you can improve handling/ride quality with a lighter set
-smaller wheels inherently ride better and have less NHV, all else equal

I'm not really arguing for OE 18s over OE 19s, though all that minus the unsprung bit remains true (to a lesser degree). I'm arguing that I can't bring myself to run any OE wheel on the car because a light weight and 18" setup is significant an easily noticeable-- comparable to having a passenger in the car vs not.

It's also just all better, without tradeoff-- I can't think of any other place on the car where that's possible. Better acceleration, better braking, better handling, better ride quality, reduced NHV, cheaper tires, harder to damage wheels on potholes.

10 drop results in a ~2% change in air density, so I could agree to that being comparable (to the acceleration change).

... I hope CCBs become a viable mod, one day
I run 18s myself (though I don't think my CHs are any lighter than stock if at all), mostly for the ride quality and damage reduction. I just don't find the rotational inertia difference between otherwise equivalent 18/19 inch wheels to be particularly compelling when taking the picture as a whole into account. Subjectively one reason to go with 19s is aesthetics, which are important to a lot of people. I'm happy with my setup for the most part, but I can't say I'm never tempted to go with CSL/ZCP wheels whenever I run into a clean M3 with those mounted.
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Old Mon, Feb-19-2018, 07:57:11 PM   #77
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Default Re: Value of OEM wheels

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Similarly: if I were looking for a nice used set of OEM 19s, what's the most I should spend?
Just picked up a set of OEM 19's for $600, not a mark on them. Couldn't find a set of clean OEM 18's. Though lacking the performance of 18in as others have mentioned, still better than beat Beyern's.
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Discussing Value of OEM wheels in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)