I dont know if this has been posted but if it has oh well this might help other people. Since i placed my orders for my rims and tires i have been worried about everything. Its a combination of the thoughts of rubbing, the tirerack phone conversation, and just thinking about it all day. So i have looked into the effects of changing tire size and overall diameter. I found this site that i think is pretty damn cool. Enter your stock size and the new size and it will tell you how many mph you will be off.

Tire Size Calculator

It says when my gauge reads 60 mph, it will really be 61.5. I will be 2.5% too slow. This was measured by my rear wheels. Does it matter that my fronts are also different from my rears? Should I be as worried as i am?

 

The calculator from 1010tires.com allow for comparison up to 4 different sizes,
which is good if you want to compare 2 sets of staggered wheels and tires. They
also offer an offset calculator, which is helpful when considering new wheels.

• Tire Size Calculator - http://www.1010tires.com/TireSizeCalculator.asp
• Wheel Offset Calculator - http://www.1010tires.com/WheelOffsetCalculator.asp

Nah... the difference is minimal. IMHO, I wouldn't worry about it. This is of course assuming that you went with 245/35/20 fronts and 275/30/20 (or 285/30/20) rears.

 

There are a ton of online tire size calculators out there and yes, links to a bunch of them have been posted here before...a quick search returned a ton of threads on the subject...

Hope everything turns out okay with your new wheel & tire combination!

 

i did go with those tire sizes in the general exclaim tire that everyone seems to love.

 

Not sure what your new sizes are, but assuming they are not over 20", I'd personally be more concerned with proper fitment (Rim ET, tire size/width, etc) then I would be with the effects on the speedometer. I believe that becomes more of a concern with very large wheel sizes, 21 or 22"

 

This is my exact setup.

miro m6 reps

fronts -> 245/35/20 rim ->20x9 et 20
rears -> 275/30/20 rim ->20x10 et 25

What what i saw on this forum this fitment should be good to go. BTW i have a stock non sport suspension

 

You will be fine. You won't rub at all. I think your gonna start posting a lot about lowering your car once you get the wheels on.

 

domino effect....im sure i will if i think its sitting to high. we'll see how it looks first. What im thinking i want to do next is m5 trunk finisher and a spoiler.

Doing the sub, but that really doesnt matter that much.

 

I think your speedo will actually be more accurate as a result. The typical BMW odometer runs around 2 mph too fast (all 3 of my E60's like this), so with your larger rolling diameter, you should be right on the money...or thereabouts.

 

With that larger rolling diameter you will be a lot less speedy to Its ok since you have that whopping 220 foot pounds of torque to work with, losing torque with your new set up is no big deal

Enjoy the huge tires and loss of torque! Plus who knows how heavy those things are which will worsen things even more!