Rear axle track width, M versus non M

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Rear axle track width, M versus non M

Post by Gav. » Fri Oct 19, 2012 2:52 pm

It's been asked a few times before, but a search doesn't really bring anything up. So let's get a discussion going in here.


To start off with, I've got an M3 3.0 rear axle that i want to fit to the rear of my 328i touring. One of the reasons i went for the 3.0 axle is because i already have a sport LSD to fit to it (that won't fit into the Evo carrier) but also because i've heard that the M3's rear axle has a narrower track width than the standard 328i, and because of the slightly bigger rear brakes.

It doesn't neccesarily make sense to me that the track width would be any different, as i would expect the M3's track width to be wider if anything for handling reasons, but at the same time, they also have wide tyres on the back.

So, my question to start the ball rolling on this thread is, does the M3 (3.0 or Evo) have a wider track (hub to hub) than a standard 328i, a narrower one, or are they the same?

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Re: Rear axle track width, M versus non M

Post by Mints » Fri Oct 19, 2012 2:56 pm

Can you not just bolt the 3.0 one up and line it up against my Evo one, Gav? Or not as simple as it sounds?
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Re: Rear axle track width, M versus non M

Post by Gav. » Fri Oct 19, 2012 2:59 pm

Not really, with them on the floor the trailing arms can move around and not give an accurate reading. Plus, when they're fitted to the car they don't sit flat, as they would on the floor, the arms and spring cradle etc are at an angle.

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Re: Rear axle track width, M versus non M

Post by Iain » Fri Oct 19, 2012 3:09 pm

there the same, just lower et wheels.
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Re: Rear axle track width, M versus non M

Post by Burns » Fri Oct 19, 2012 3:09 pm

After playing around with wheel offsets a lot I'm convinced that the M3 (evo at least) has a thinner track because they have more clearance for wide wheels. I've no idea why they do or any proof though.

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Re: Rear axle track width, M versus non M

Post by Gav. » Fri Oct 19, 2012 3:13 pm

a bit of googling has come up with this..

The 328i has an overall vehicle length of 178.2 inches, a width of 71.5 inches and a height of 55.9 inches. It has a wheelbase of 108.7 inches, a front track width of 59.1 inches and a rear track width of 60.2 inches. The interior seats five passengers, has a front headroom of 38.5 inches, a front legroom of 41.4 inches and front shoulder room of 55.4 inches. The rear has a headroom of 37.5 inches, legroom of 34.6 inches and shoulder room of 55.1 inches.
Though it's not a technical site, so i don't know how true it is.

I've also come accross this on 'Carfolio.com'

mm inches
Wheelbase 2700 106.3
Track (front) 1422 56
Track (rear) 1444 56.9
Length 4433 174.5
Width 1710 67.3
Height 1335 52.6
Ground clearance 110 4.3
A bit more of a technical site, but again, i don't know how reliable it is.

From the above information, it looks like there is nearly 4 inches less track width on an M3. What it doesn't say, is wether it's hub to hub though.

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Re: Rear axle track width, M versus non M

Post by Gav. » Fri Oct 19, 2012 3:15 pm

Iain wrote:there the same, just lower et wheels.

That was what i expected too to be honest, but after googling for a bit, it does seem that they are indeed narrower. Wouldn't a wider track make more sense for a performance orientated car?

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Re: Rear axle track width, M versus non M

Post by Gav. » Fri Oct 19, 2012 3:23 pm

Looking up the 328i on 'carfolio.com', here's what it says..

Wheelbase 2700 106.3
Track (front) 1407 55.4
Track (rear) 1420 55.9
Length 4433 174.5
Width 1698 66.9
Height 1393 54.8
Ground clearance 145 5.7
So, if this is to be believed, there is still a difference in the track width, but only around an inch, and it makes the M3's rear axle wider.

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Re: Rear axle track width, M versus non M

Post by Gav. » Fri Oct 19, 2012 3:39 pm

Evo rear track width..

mm inches
Wheelbase 2710 106.7
Track (front) 1422 56
Track (rear) 1438 56.6
Length 4433 174.5
Width 1698 66.9
Height 1365 53.7
Again from carfolio.com

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Re: Rear axle track width, M versus non M

Post by Iain » Fri Oct 19, 2012 3:55 pm

They are the same, its just a wider wheel and tyre.

the trailing arms are not canted outwards, the axle carriers are interchangable and the upper platform and lower support are the same accross all models.

You wont gain or loose track width by changing a rear beam
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Re: Rear axle track width, M versus non M

Post by Burns » Fri Oct 19, 2012 5:04 pm

The difference could be in the hub / disc. The issue came up when I was fitting 10j rear wheels to my old Evo.

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Re: Rear axle track width, M versus non M

Post by Iain » Fri Oct 19, 2012 5:13 pm

Burns wrote:The difference could be in the hub / disc. The issue came up when I was fitting 10j rear wheels to my old Evo.
Drive flange

http://www.realoem.com/bmw/partxref.do? ... showeur=on

The the disk width is not going to be non standard or you would need over length bolts to mount the wheel.
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