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      02-13-2013, 02:53 AM   #29
insomnia8888
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Drives: 2007 BMW 335i E92
Join Date: Dec 2012
Location: Kansas City, MO

Posts: 21
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Quote:
Originally Posted by MooseCaboose View Post
those look fantastic. im surprised you actually got 285 with thicker wall tire like those to fit. the non stretch looks makes a big difference
My main goal was avoiding stretch look, and same side wall hight for front and back. After lots of calculations I knew that 285s were going to fit just fine, I just didn't know how much to rub going over dips???

Here is how I started:

Originally I had 265/35/18s with factory wheels at 37 offset and 12mm spacers, which gave me a pretty flush look at ET25. So the distance from the center of the wheel to the hub is 25mm. This means center of the tire to the hub is also 25mm. Width of the tire is 265mm, So from the center of the tire to the outer edge of the tire would be 265/2=~133mm. 133mm-et25=108mm is the distance from the hub to the outer edge of the tire. So 108MM is the key number here.

Lets do the same thing for the new wheels and tires I was working on getting:

285/30/19s with et38 wheels (No Spacers this time). 285mm is the width of the tire, so 285/2=~143mm is center to outer edge of the tire. 143-et38=105mm is hub to outer edge of the tire.

As a result I knew the new tires were going to sit (108mm-105mm=) 3mm further away from the fenders compared to the old tires.

Now I had to compare the hight of the tires:
265/35/18s 643mm tall, and 285/30/19s 656mm tall
So the new tires were going to be (656-643=)13mm taller than the old ones. Which means I would have 13/2=6.5mm more tire tacking under the fender.

Here we go: Outer top corner of the new tires would be placed 3mm inner, but 6.5mm higher under the fender compared to the old tires.

With these numbers I went to my car and measured the room I have in there.
YESSS! I knew that 285s were fitting!!! Rubbing was possible but that was my next project to work on.

Finally this past monday, I got the fenders rolled and gained maybe another 3 to 5mm room under the fenders. Now, NO RUBBING at all. I tried dips at 90mph and no rubbing! Thankfully I won't have to deal with adding neg camber.

So yes, it was quite a process for me to fit all this rubber; sometimes I even thought I was gambling with high priced tires! What if it didn't fit??...

Anyway, let me know if you have any questions about my calculation. It worked for me. If you haven't bought your tire and wheels yet, give me your current set up. I'll put some numbers together we'll see what would fit or not...
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