M5 offset wheels on 530i > Safer aspect ratio than stock?

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03-11-2011, 09:58 PM

#11

ZGERMAN

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My Ride: 2007 M5

Quote:

Originally Posted by TheRacerBoss

Why are profile ratios in the front higher when compared to the Rear ?

Okay,
1. You agree that both your wheels are 19inches diameter (Correct)
2. So now considering the radius for all 4 wheels will be 9.5 inches (Correct)
3. Our main goal with the calculation on the tires here is to have all 4 tires add the same height to the car all over (Correct)
4. Okay, now look at your rear tire
It is 275/ 35/19
Forget the 19 since that is common on all 4 wheels
consider 275/35 = Lets actually do the math on these
What is 275 * 35%
275* 35/100 (275 multiplied with 35) then divide by 100
= 96.25 (Correct)
So your sidewall height is 96.25 mm on the Rear Tyre (Remember this)

Same way for the front
245*40/100
= 98 mm

So now we are Xtremely close, there is virtually no difference between 96.25 and 98mm (correct)
You will say -- Racer they are different and they are not the same.
Okay let me explain
Convert mm to inches (Google a mm to inches calculator)
Converting 96.25 mm to inches = 3.78 inches (Lets say 3.8 inches)
Converting 98mm to inches = 3.85 inches
Now let me ask you -- Can your eye tell me the difference between 3.8 and 3.85 inches on a tire mounted on a car
IT CANNOT (period)
Thats why they are virtually the same.

Now lets suppose you had gotten a 35 profile tire in the front
you would have to buy 245/35/19 -- Do the math again
245 * 35 / 100
85.75 mm
3.3 inches

Comparing 245/35/19 and 275/35/19 on your car
front in inches will be 3.30
Rear in inches will be 3.85
you will have a front tire that is half inch shorter than the rear tire (lol) A sharp eye can catch this very easily

You dont want that buddy!

Hey, Racer... you know what? -- YOU ROCK, Bro!!!

Thanks so much for taking the time to write this down (or copy & paste it... doesn't really matter)!
Helped me a great deal to understand this matter; thanks, man!

P.S.: I'm sure this will be of much help to other n00bs too ;-)

Thanks,
Armin

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03-11-2011, 10:24 PM

#12

ZGERMAN

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Join Date: May 2010

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My Ride: 2007 M5

By the way....

Put the new shoes on my Stallion today: 19" Alufelgen wrapped in F:245/40-19 (ET35) + R:275-35/19 (ET20)... on Conti ExtremeContact DW.... and it looks just A-W-E-S-O-M-E !!!

The car looks just sick; especially the the rears do a lot to improve the looks. My Beamer has an even nicer "ass" now... really, really wide (ha ha!)

Will post some pics tomorrow. Just dug out my trusty old Nikon SLR...

(since Mom got my Digital cam and I still have my EVO phone camera).

The wheels look great; they are soooo concave

(even the fronts) - it's a dream!!!

The only (little) grieves I have right now (...and that might change over time):

1.) "Hyperblack"... it's still too silver; I wished the color would be a bit darker. Oh well, still looks Killer and have no real regrets... (Thanks, again, Tyler/TR930!)

;

2.) I simply can't hit any bumps/potholes anymore as the front tires [seem to..?] hit the fenders from the inside whenever I fail to remember about the loss of "headroom" (I can hear the "squeak") after going from 18" to 19"... Quite honestly, that freaks me out a little bit.
However, I can't see any traces of rubbing (while steering/turning) yet, but I just made 40 Miles on the new setup. Will have to look some more in daylight tomorrow....

Couldn't be happier right now; great investment (....yes, even despite the rim's color being lighter that expected)!!!

Pics to come...

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