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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 Mon, May-10-2010, 03:22:58 AM   #1
Obioban
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Exclamation e46 M3 Tire Sizing Thread

You can play with tire sizes to your heart's content here: http://www.miata.net/garage/tirecalc.html

Everything in this thread is aimed for optimal. There are lots of things you can do that are not listed here. I'm well aware that some people love the look of 11" wheels and have made it fit, and claim no decrease in handling, ride quality, etc. Congrats. This thread will focus on the best possible setups from a functional perspective, and you can vary it however you want from there.
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Last edited by Obioban; Mon, May-10-2010 at 02:45:02 PM.
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Old Mon, May-10-2010, 03:23:27 AM   #2
Obioban
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This first post is not about fitment. Just because I list a setup as matched DOES NOT MEAN IT WILL FIT ON YOUR WHEELS OR IN YOUR FENDERS.

I'm going to attempt to lay down some basics for tire sizing on this car. This thread is going to be geared mostly towards street use, where DSC interference matters.

Okay, ground rule: You want the front and rear tire to have, as close as possible, the same rolling diameter. DSC works by comparing the rotational speeds of the various tires. If your rear tires have a smaller rolling diameter than the car expects, and the fronts are the same, the DSC will think at all times that you are having slight wheel spin (as the rears are rotating faster than the fronts). If the system is predisposed to thinking that you have slight spin, then it's much more prone to intervening-- it'll take much less to set off the DSC. That makes for unfun driving dynamics.

Before going any further, I think we should make everyone has an understanding of what tires sizes actually mean, as it's not as intuitive as you might thing. I'm bolding the middle part on profile, as that's the key part to all of this and the most misunderstood:

Quote:
On the side of every tire is a host of numbers and ratings that describe the tire and its performance characteristics. A typical tire size numbering system will appear as a string of letters and numbers, such as this example: 215/70R16

215/70R16

The numbers before the slash (/) indicates the section width of the tire; the widest point from sidewall-to-sidewall. The larger this number, the wider the tire. This number is the wide of the tire in millimeters. In this example, the tire has a 215-millimeter section width.

215/70R16

The next number trailing the slash (/) indicates the height of the tire in a percentage of the section width. In our example, the number is 70, which means the tire height is 70% of the section width, which is 215 millimeters. The height of this tire would be 150.5 millimeters. The lower the number is, the lower the profile of the tire.

215/70R16

The next letter is reveals the construction of the tire. The most common is “R” such as found in our example. The “R” designation states the tire is of radial construction. Other construction types are rarer for modern passenger car use, and may include “D” for bias ply construction and “B” for belted tires.

215/70R16

The number following the construction code is the size of the wheel in inches. The example tire would be designed to fit a 16-inch wheel. Tire sizes on modern vehicles typically start at 13-inches and go up to 18-inches, but aftermarket and special package wheels can be 22-inches or even larger.
Take away: If you go with a wider tire, you need to run a smaller profile percentage to have the sidewall (and circumference with it) not become larger.

Okay, moving on:
The stock M3 tires sizes are
225/45/18, circumference: 81.6"
and
255/40/18, circumference: 81.8"

or

225/40/19, circumference: 82.0"
and
255/35/19, circumference: 81.8"

Notice how the circumference is nearly identical in stock spec. The closer you keep to that ratio, the less DSC interference you'll have. The numbers are close enough that for ease of use I just stick to 1:1.

Okay, so let's expand upon this. Most of us don't want to be running the stock setup as 225 is pretty small and understeery. So, what options does that leave us? Well, two categories: staggered (30mm) or square.


Staggered pairs that work well together:

18":

225/45/18, circumference: 81.6"
and
255/40/18, circumference: 81.8"

235/40/18, circumference: 79.8"
and
265/35/18, circumference: 79.5"

245/40/18, circumference: 80.8"
and
275/35/18, circumference: 80.4"

255/40/18, circumference: 81.8"
and
285/35/18, circumference: 81.2"

255/40/18, circumference: 81.8"
and
295/35/18, circumference: 82.1"


19":

225/40/19, circumference: 82.0"
and
255/35/19, circumference: 81.8"

235/35/19, circumference: 80.0"
and
265/30/19, circumference: 79.4"

245/35/19, circumference: 80.9"
and
275/30/19, circumference: 80.1"

245/35/19, circumference: 80.9"
and
285/30/19, circumference: 80.8"

255/35/19, circumference: 81.8"
and
285/30/19, circumference: 80.8"



Square setups that work:

225/45/18, circumference: 81.6"

235/40/18, circumference: 79.8"

245/40/18, circumference: 80.8"

255/40/18, circumference: 81.8"

265/35/18, circumference: 79.5"

275/35/18, circumference: 80.4"

285/35/18, circumference: 81.2"


One final note: For the purposes of DSC, all that matters is that the front and rear have nearly the same circumference. That said, as you get further away from the stock 81.7", the speedo will read faster and faster at the same speed (and the speedo comes about 5% fast from the factory, so you're just making a bad situation worse).
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Past cars: 04 M3, 96 M3, S50B32 e36 M3 CM race car

Last edited by Obioban; Thu, May-13-2010 at 01:31:12 AM.
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Old Wed, May-12-2010, 05:59:17 PM   #3
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Quote:
Originally Posted by Obioban View Post
The stock M3 tires sizes are
225/45/18, circumference: 81.6"
and
255/40/18, circumference: 81.8"

what is the stock 19" size?
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Old Wed, May-12-2010, 07:36:01 PM   #4
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Quote:
Originally Posted by theBeachBoy View Post
what is the stock 19" size?
225/40/19, circumference: 82.0"
and
255/35/19, circumference: 81.8"
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Old Sun, Jan-12-2014, 05:04:24 PM   #5
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Default Re: e46 M3 Tire Sizing Thread

Quote:
Originally Posted by Cazz View Post
It is in post #2

Quote:
Originally Posted by Obioban View Post
If you go with a wider tire, you need to run a smaller profile percentage to have the sidewall (and circumference with it) not become larger.
The one you listed will be 8mm taller.
Since that is just 1 size up, if you aren't lowered you might get away with it.
But whats the problem with running a larger circumference? Only to due with the DSC traction control issues? Or also rubbing issues?
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Old Wed, Mar-05-2014, 06:27:06 AM   #6
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Default Re: e46 M3 Tire Sizing Thread

Is there a reason that the stagger should be 30mm? I am running 245/40/18F and 255/40/18R and it seems like the diameter numbers should be fine.

I'm guessing the advantages to a square setup include more grip in the front so less understeer etc. but is there anything wrong with being between the 30mm stagger and a square set up?
Quote:
Originally Posted by Obioban View Post
This first post is not about fitment. Just because I list a setup as matched DOES NOT MEAN IT WILL FIT ON YOUR WHEELS OR IN YOUR FENDERS.

I'm going to attempt to lay down some basics for tire sizing on this car. This thread is going to be geared mostly towards street use, where DSC interference matters.

Okay, ground rule: You want the front and rear tire to have, as close as possible, the same rolling diameter. DSC works by comparing the rotational speeds of the various tires. If your rear tires have a smaller rolling diameter than the car expects, and the fronts are the same, the DSC will think at all times that you are having slight wheel spin (as the rears are rotating faster than the fronts). If the system is predisposed to thinking that you have slight spin, then it's much more prone to intervening-- it'll take much less to set off the DSC. That makes for unfun driving dynamics.

Before going any further, I think we should make everyone has an understanding of what tires sizes actually mean, as it's not as intuitive as you might thing. I'm bolding the middle part on profile, as that's the key part to all of this and the most misunderstood:



Take away: If you go with a wider tire, you need to run a smaller profile percentage to have the sidewall (and circumference with it) not become larger.

Okay, moving on:
The stock M3 tires sizes are
225/45/18, circumference: 81.6"
and
255/40/18, circumference: 81.8"

or

225/40/19, circumference: 82.0"
and
255/35/19, circumference: 81.8"

Notice how the circumference is nearly identical in stock spec. The closer you keep to that ratio, the less DSC interference you'll have. The numbers are close enough that for ease of use I just stick to 1:1.

Okay, so let's expand upon this. Most of us don't want to be running the stock setup as 225 is pretty small and understeery. So, what options does that leave us? Well, two categories: staggered (30mm) or square.


Staggered pairs that work well together:

18":

225/45/18, circumference: 81.6"
and
255/40/18, circumference: 81.8"

235/40/18, circumference: 79.8"
and
265/35/18, circumference: 79.5"

245/40/18, circumference: 80.8"
and
275/35/18, circumference: 80.4"

255/40/18, circumference: 81.8"
and
285/35/18, circumference: 81.2"

255/40/18, circumference: 81.8"
and
295/35/18, circumference: 82.1"


19":

225/40/19, circumference: 82.0"
and
255/35/19, circumference: 81.8"

235/35/19, circumference: 80.0"
and
265/30/19, circumference: 79.4"

245/35/19, circumference: 80.9"
and
275/30/19, circumference: 80.1"

245/35/19, circumference: 80.9"
and
285/30/19, circumference: 80.8"

255/35/19, circumference: 81.8"
and
285/30/19, circumference: 80.8"



Square setups that work:

225/45/18, circumference: 81.6"

235/40/18, circumference: 79.8"

245/40/18, circumference: 80.8"

255/40/18, circumference: 81.8"

265/35/18, circumference: 79.5"

275/35/18, circumference: 80.4"

285/35/18, circumference: 81.2"


One final note: For the purposes of DSC, all that matters is that the front and rear have nearly the same circumference. That said, as you get further away from the stock 81.7", the speedo will read faster and faster at the same speed (and the speedo comes about 5% fast from the factory, so you're just making a bad situation worse).
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Old Wed, Mar-05-2014, 01:54:32 PM   #7
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Default Re: e46 M3 Tire Sizing Thread

Quote:
Originally Posted by Yootim View Post
Is there a reason that the stagger should be 30mm? I am running 245/40/18F and 255/40/18R and it seems like the diameter numbers should be fine.

I'm guessing the advantages to a square setup include more grip in the front so less understeer etc. but is there anything wrong with being between the 30mm stagger and a square set up?
Nothing wrong at all with something in between.

The 30mm difference for the stock setup relates, in part, to the relative diameters being the closest to each other (26" and 26"). The DSC software is coded around this expectation.
However, a 245/40/18 and 255/40/18 set is still pretty close (25.7" and 26").
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Old Wed, Mar-05-2014, 08:03:24 PM   #8
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Default Re: e46 M3 Tire Sizing Thread

Quote:
Originally Posted by normcaldwell View Post
Nothing wrong at all with something in between.

The 30mm difference for the stock setup relates, in part, to the relative diameters being the closest to each other (26" and 26"). The DSC software is coded around this expectation.
However, a 245/40/18 and 255/40/18 set is still pretty close (25.7" and 26").
That is, indeed, the problem. Not having a 30mm stagger or square makes the rolling diameter more different, and the more different it is, the more DSC kicks in.

On my (foolish) 235/245 setup, the DSC can never recover from intervening unless M track mode is on, unless I fully let off the gas and coast for 2-3 seconds. MTM is a lifesaver with that setup, was really dumb of me to get it.
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Past cars: 04 M3, 96 M3, S50B32 e36 M3 CM race car
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Old Wed, Mar-05-2014, 08:16:09 PM   #9
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Default Re: e46 M3 Tire Sizing Thread

I haven't pushed my car hard enough or experienced it on different tire sizes to be able to tell any difference yet.

But aren't some of the "suggested" stagger sets even more different in rolling diameter front and back? I thought the only issue with the dsc was the rolling diameter, and I was assuming that a .3 difference was under the threshold where the dsc will start acting weird.

Also, are square setups generally preferred for their handling on the track or the ability to rotate tires front/back?

Quote:
Originally Posted by Obioban View Post
That is, indeed, the problem. Not having a 30mm stagger or square makes the rolling diameter more different, and the more different it is, the more DSC kicks in.

On my (foolish) 235/245 setup, the DSC can never recover from intervening unless M track mode is on, unless I fully let off the gas and coast for 2-3 seconds. MTM is a lifesaver with that setup, was really dumb of me to get it.
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Old Wed, Apr-08-2015, 06:44:11 AM   #10
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Default Re: e46 M3 Tire Sizing Thread

Quote:
Originally Posted by Obioban View Post
The stock M3 tires sizes are
225/45/18, circumference: 81.6"
and
255/40/18, circumference: 81.8"

************

Staggered pairs that work well together:

18":

225/45/18, circumference: 81.6"
and
255/40/18, circumference: 81.8"

235/40/18, circumference: 79.8"
and
265/35/18, circumference: 79.5"

245/40/18, circumference: 80.8"
and
275/35/18, circumference: 80.4"


255/40/18, circumference: 81.8"
and
285/35/18, circumference: 81.2"

255/40/18, circumference: 81.8"
and
295/35/18, circumference: 82.1"

I have a question. I would like to run a setup that is A. not smaller than 81.6 in circumference (don't want a smaller diameter, its a looks thing), and B. not overly wide - 255/295 is probably far too wide for my non-tracked daily driven car.

I would also like to run as narrow of a wheel as I can - original 8 / 9 size would be great, but I see most wheels that are for sale are 9.5/10. Wouldn't running a 225/45 on a 9-9.5" rim make it look stretched? same with a 255/40 on a 10" rim?

I am a total noob to tire sizing, I've read plenty, but obviously do not know enough

Thanks
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Discussing e46 M3 Tire Sizing 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)