New wheels/tires causing DSC w/iDrive

[DarthBeardy]

Hey ya’ll.

So I got some 513M wheels off an M4, and immediately switched to the typical e9x iDrive sizes of 235/40r18 and 265/35r18. Turns out, we have different tire sizes stock, and I didn’t bother to do the math.

So this is causing the dreaded iDrive out of sync DSC issues.


According to my math, 255/40r18 and 285/35r18 would be better matches for our stock staggered sizes (within the 1% iDrive requirements)

Stock 355m:

• 18x8J ET30 - 225/45r18
• 18x9J ET41 - 255/40r18

New 513m:

• 18x9 ET29 - 255/40r18
• 18x10 ET40 - 285/35r18

Thoughts? This is on my 15’ MSport 35i

[bucketfoot]

As far as diameter goes I agree those look like a good match.

I really think you are going to need spacers at least for the front tires, as you will be more than a 1/2" closer on the inside.

I went from stock 225/50/17 +34mm to 245/45/17 +30 (a move of 0.19") and was getting really close.
You have an extra 0.03" clearance to start with your OEM setup, but you are still going to end up at 0.48" closer versus my 0.19".

Once you add spacers in those 255s up front may be too wide. Personally I think I would go with 245/40r18 up front instead.
The 255s would probably be OK if you could do it without spacers, but I don't think they will work with the spacer you will need.

Of course I have the 28i, so I don't know if there are differences that would make this work better on a 35i.

Just food for thought.

[DarthBeardy]

The 255’s mount up juuuust barely on the front. I agree, spacers would be safer for SURE.

I’m shocked at how much room we have in the back. I could easily add more meat if the math lined up or if it was necessary.


Good to hear on the diameter though. I’m getting it all mounted up today and will report back.


Is a battery/ECU reset a good idea to get the DCS recalculating? Or is it just a certain amount of miles, anyone know?

[DarthBeardy]

Ok, for posterity.

This fitment works great. It’s VERY tight up front, so I’ll be adding a 3-5mm spacer. But the wobbles and DSC light on heavy turns are gone!