1M Conversion Complete

[dghits26]

Hey Guys,

I just finished my 1 M conversion and I went with the stock m3 18 setup, but I'm noticing some rubbing. I'm currently running 245/40/18 & 265/40/18. Should i drop down to a 245/40/18 in the front and a 265/35/18 in the rear?

This is how it looks now



The front is perfect, its only the rear right side that rubs.

[M3SQRD]

Have you had your alignment checked? Rubbing on only one side suggests the rear camber and toe settings are different. Also, if it’s slightly rubbing, you could try increasing the rear camber by an additional 0.25-“.5 deg of negative camber. As long as your negative camber is not more than 2.5 deg (2.25 deg or less would be better) you should be fine with putting the power to the ground.

[dghits26]

I had the car aligned twice, and it matches on both sides.

[dghits26]

Originally Posted by M3SQRD

Have you had your alignment checked? Rubbing on only one side suggests the rear camber and toe settings are different. Also, if it’s slightly rubbing, you could try increasing the rear camber by an additional 0.25-“.5 deg of negative camber. As long as your negative camber is not more than 2.5 deg (2.25 deg or less would be better) you should be fine with putting the power to the ground.

Do you think the 265/35/18 is not a good idea ?

[Kisenwether]

I have 265/35/18 front and 295/30/18 and lowered in HR springs. Front passenger has a slight rub but worked fender liner and it’s good now, rear has no rub unless I bottom out suspension going quick on a dip in road.

[M3SQRD]

Originally Posted by dghits26

Do you think the 265/35/18 is not a good idea ?

That’ll throw off your speedometer, affect ABS and DSC, and affect your gearing (equivalent to installing a diff with lower gearing, higher FD). The last one is not always a bad thing. Have you calculated the % diff in rolling diameters of the 265/40 and 265/35, and the 245/40 and 265/35? If it’s < +/-2% then you’re fine.

Car assembly tolerances and tolerance stackups can result in final assembled cars having fenders, etc. off by 1/8-1/4” or more. This could be the case with your car. What’s rubbing (e.g., fender liner, rear bumper, rolled metal lip, etc.) and where (e.g., 1 o’clock, 12 o’clock, etc. from the fender being 3 o’clock on the left side, 9 o’clock on the right side)?

% diff of 265/40 and 265/35 is 4%, 245/40 and 265/35 is 1.9%, and 245/40 and 265/35 is 2.0%. The 2% diff between the 245/40 and 265/35 is ok but the %diff of 265/40 and 265/35 is not. Your speedometer will be 4% off which is not insignificant as well as wheel speed sensors so SBS, traction control and DSC may all potentially be affected.

% diff of 265/35 and 295/30 is 1.6%.
The 265/35 and 295/30 at 2% diff is ok

[dghits26]

Originally Posted by Kisenwether

I have 265/35/18 front and 295/30/18 and lowered in HR springs. Front passenger has a slight rub but worked fender liner and it’s good now, rear has no rub unless I bottom out suspension going quick on a dip in road.

Did you do a rear hub conversion ?

[Redd]

Maybe the wheel offsets are wrong?

[Andy1M3]

I've got nothing to add but the car looks great! Post up some more pics. How did the swap go? Any unforseen troubles?

[Ajolives]

Thought I heard the left side of the M3’s suspension are ever so slightly higher to compensate for driver weight? Is it the same for 1M if true?

It’s odd that only ones side is rubbing. M3SQRD brought up a good point about tolerance stackup; what suspension parts were converted? If wheels are aligned I would think chassis/body asymmetry is a bit off.

[M3SQRD]

Originally Posted by Ajolives

Thought I heard the left side of the M3’s suspension are ever so slightly higher to compensate for driver weight? Is it the same for 1M if true?

It’s odd that only ones side is rubbing. M3SQRD brought up a good point about tolerance stackup; what suspension parts were converted? If wheels are aligned I would think chassis/body asymmetry is a bit off.

I have two e92 M3s and I’m unaware of their being a difference in springs. All four, actually eight, all had the same letter but no L or R labeling. I doubt there’s a difference.

I’ve had aftermarket suspensions (MCS and JRZ) and both have been corner balanced and lowered with wider more aggressive wheels and tires without rubbing.