E46 m3 Tyre Sizes

[m325i 709]

I came across some details on 'upsizing' your tyres and was wondering about this.

Stock is 225/40/19 is 255/35/19 but previous owner has installed 235 / 275.

Is there much advantage to moving away from the stock sizing?

Anyone have any experience / suggestions?

My understanding of 'upsized' options:

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

Cheers

Edited May 7, 2014 by Nick G

[Neal 545]

Changed from 225 / 255 combo to 235 / 265 combo. Dropped the profile by 5 on front and back to retain rolling radius.

Did this for no other reason than more tyre on the road and it's the standard widths for the CSL.

Only issue is the recommended rim sizes for the tyre is 8.5 & 9.5 inches respectively. I'm running 8&9 respectively .The reality is I'm not getting any abnormal tyre wear and no issues with tyre rubbing.

Handling wise the only noticeable difference has been grip. But I suspect this is down to tyre choice rather than width.

Mate was running 10 inch rears with a 275 / 19/ something on the rears. Filled the arches nicely but did have slight rubbing with rear passengers in car

[M3_Power 636]

Edit ... let me rephrase that actually ... The speedo reads closest to accurate (albeit still highly inaccurate) with 235 and 265 tyre sizing.

Edited May 8, 2014 by M3_Power

[m325i 709]

What about the whole Toyota GT 86 theory. (Weak tyres to encourage lower speed 'fun')

If I go for the stock set up will be 'benefiting' in that regard?

Seems a slightly odd set up I have now with 235 & 275 /30

Sounds like you guys reckon 235/265 or stock?

Cheers

[M3_Power 636]

What about the whole Toyota GT 86 theory. (Weak tyres to encourage lower speed 'fun')

If I go for the stock set up will be 'benefiting' in that regard?

Seems a slightly odd set up I have now with 235 & 275 /30

Sounds like you guys reckon 235/265 or stock?

Cheers

Tyre limiting doesn't equate to fun - it's just a fancy way for levelling the playing field and making sure those race cars run within a set laptime.

Fun = having the maximum grip out of all four corners and pushing to the limits of adhesion that the tyres and setup will give you.

Actually I should rephrase again .. .The cup tyres that came on the CSL albeit 265 - if you put it up against a standard road tyre the sizing is actually 275 as it's an oversized tyre.

So I'd stick with 235/ 275 if you are on road tyres and not semi slicks or similar.

If you want to kill understeer that's inherent in the E46 chassis ... go square setup - it'll completely transform the car and its turn in feedback.

[_ethrty-Andy_ 2133]

fatter the better. unless you are into skidding etc of course

[Neal 545]

Has anyone run a square setup on their M3 ?

Seems that running 265 s on all corners is a popular bmw cc USA auto cross setup,

I've got a spare set of rear factory 18s and was thinking about trying it.

Another consideration for width is grove percentage per tyre width, thats one thing I like about the current re11s is there is less total grove width that many other performance tyres . Basically more rubber on the road yet they still have good wet weather performance .

[M3_Power 636]

Bit of as myth going on here, the staggered set-up does not make the car under steer, the square setup actually makes it OVERSTEER .

- What happens at the grip limit with a STAGGERED is that the front generates a very soft break away.

- What happens with the rear on a SQUARE set up is that it squats and walks and can have quite unpredictable break away under moderate to aggressive driving.

The staggered set-up (much) is closer to neutral if the rest of the suspension is set up correctly.

If your car feels more stable with a square setup then something else is un balanced or your driving style doesn't match the chassis dynamics and is un balancing the chassis.

And I wouldn't bother copying what the Americans do they often have no idea about basic suspension and chassis dynamics- do some real research and work out what you want to achieve.

And you are basing the above on which E46 M3 you own????

[M3_Power 636]

I'm basing it on:

- the 9 (or more) E46 M3's I have driven,

- the 3 E90's and

- the E36, E39 and E53 I own all of which have had both staggered and square setups.

-- about 500 different cars and probably a gazillion kilometres across Europe , NZ and racetracks

-- plus 40 years experience in suspension setup from Alfas to Porsches and from utes to race cars

What are you basing yours on???

My encyclopedic knowledge on E46 M3 through my non interrupted "ownership" of them since 2001; plus my extensive network of owners from across the globe including those that race and drive the nurburgring and many European circuits on regular basis that I share setup knowledge with ... People that I know on first name basis that race in Britcars ... Personal setup feedback from BMW accredited driving instructors on what they think of the E46 chassis ... And race teams that run and set up WTCC E46 touring cars and their feedback both locally and abroad ... And finally my 10+ experience in front wheel drive Hondas so I actually know what understeer is and does and how to spot them.

So yes quite happy to agree to disagree with your take on things.

Edited May 17, 2014 by M3_Power

[M3_Power 636]

I am not one to get into a forum argument over setup ... as each driver is ultimately different and no one on these forum that I know of actually run a high end setup anyway so most of my throw away comments was (especially ones in this post) more or less in reference to the stock setup.

Ask anyone that knows the E46 chassis and they will tell you that there is one phase (through the three phases of cornering) that it understeers .... in stock form. That was what I was referring to. Seeing you are such an expert, perhaps you can tell everyone which phase of the cornering that happens.

Edited May 17, 2014 by M3_Power