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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 Sun, Nov-04-2018, 05:16:30 AM   #1
M3_Pilot
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Default 18" vs 19" Wheel & Tire Data Comparison

Update: Didn't realize I should have used the et22 offset for the 18" rear wheel and the results are very surprising. The 18" wheel setup is now actually heavier than the 19" setup! See attached photo below.

Made an excel file to compare the weights of a nearly identical wheel and tire setup. For my example, I compared 18" and 19" staggered ARC-8 wheels and staggered Michelin Pilot Sport 4S tires. Obviously, the 19" wheels are heavier but I was very surprised by how much more the 18" tires weigh. All the wheel and tire data were calculated using the respective manufacturer specifications.

The net difference of the whole wheel setup was only 2.42 pounds and the front 18" tires only have two fewer rotations per mile (rears being the same). Once I have time I'll calculate the moment of inertia of both setups but I already have a feeling it's going to be really close.

Btw feel free to modify the file and calculate your own wheel tire setup!

Sources:

Tires:
https://www.michelinman.com/upload/m...t-sport-4s.pdf

Wheels:
https://www.apexraceparts.com/wheels...wheel_model=45

Attached Files
File Type: xlsx 18%22 vs 19%22 Wheel & Tire Comparison.xlsx (9.7 KB, 6 views)
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Last edited by M3_Pilot; Mon, Nov-05-2018 at 07:19:35 PM.
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Old Sun, Nov-04-2018, 05:18:29 AM   #2
Drewster
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Default Re: 18" vs 19" Wheel & Tire Data Comparison

Did something similar for 18's vs 17's

Another thing to consider is drive ratio - I found that not only did 17's net a lighter/ cheaper overall wheel, but they give you a slight benefit in overall drive ratio
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Old Sun, Nov-04-2018, 05:19:56 AM   #3
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Default Re: 18" vs 19" Wheel & Tire Data Comparison

Where is the file?
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Old Sun, Nov-04-2018, 05:21:23 AM   #4
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Default Re: 18" vs 19" Wheel & Tire Data Comparison

Here's the data for users viewing on their mobile device.






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Old Sun, Nov-04-2018, 05:23:18 AM   #5
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Default Re: 18" vs 19" Wheel & Tire Data Comparison

Quote:
Originally Posted by Drewster View Post
Did something similar for 18's vs 17's

Another thing to consider is drive ratio - I found that not only did 17's net a lighter/ cheaper overall wheel, but they give you a slight benefit in overall drive ratio
Yeah, that's what I was hinting at with the revolutions per mile. Only the front 18" wheel had a shorter drive.
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Old Sun, Nov-04-2018, 05:24:40 AM   #6
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Default Re: 18" vs 19" Wheel & Tire Data Comparison

Quote:
Originally Posted by M3AZ View Post
Where is the file?
Updated.
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Old Mon, Nov-05-2018, 01:46:56 PM   #7
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Default Re: 18" vs 19" Wheel & Tire Data Comparison

Quote:
Originally Posted by M3_Pilot View Post
Here's the data for users viewing on their mobile device.






Excellent data. This is what I've been saying for years.

When you eliminate all variables except wheel diameter, the 'net' difference is inconsequential. Further, because the smaller tire weighs more and 100% of that extra weight is outside the wheel, the affect on rotational inertia is very likely greater than that due to an extra .5" wheel radius. In other words, the net (wheel/tire combo) rotational inertia might be actually higher with the 18" combo... or at least a wash.

The challenge with inertia of a 'wheel' is that we can only guesstimate since we don't know the actual weight distribution through the wheel. Yes, the barrel probably holds most of the weight but I bet it's 70/30 at most. A tire is MUCH easier since all of the weight is more/less at the outer limit.

People are so quick to proclaim that 19" wheels are bad but the truth is that diameter is meaningless - what matters is overall system weight. You want the lightest setup possible.

Someone run the inertia calcs.
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Old Mon, Nov-05-2018, 04:32:50 PM   #8
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Default Re: 18" vs 19" Wheel & Tire Data Comparison

You don't just want the lightest, but the lightest towards the edge of the rotating assembly.like for like 18s are inherently better
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Old Mon, Nov-05-2018, 07:26:49 PM   #9
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Default Re: 18" vs 19" Wheel & Tire Data Comparison

Quote:
Originally Posted by EricSMG View Post
People are so quick to proclaim that 19" wheels are bad but the truth is that diameter is meaningless - what matters is overall system weight. You want the lightest setup possible.
I just updated the data with the same offset rear wheels (which I see to be a very popular track wheel size) and the results are very interesting.


Quote:
Originally Posted by HassanEido View Post
You don't just want the lightest, but the lightest towards the edge of the rotating assembly.like for like 18s are inherently better
Yes. You know what I just thought about?! We can just get the two wheels we're trying to compare and roll them down a ramp to see which has more moment of inertia
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Old Mon, Nov-05-2018, 07:47:38 PM   #10
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Default Re: 18" vs 19" Wheel & Tire Data Comparison

Depends on tires too. Here are 18 and 19 rear wheels.

18x9 with 255/40 Bridgestone s-04 56.4lbs
And 19x9.5 Hankook v12 evo2 275/30 53.5lbs.

Bridgestone are known to be a few lbs heavier for the amount of thread they have (10/32) and that's at the outer-most circumference. Vs running a tire that is either worn down or comes with less thread depth. So keep driving, it'll get lighter!



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Discussing Comprehensive CSL Intake Thread 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)