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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Wheels and Tires Forum Sponsored by The Tire Rack > Tire sidewall question... Who has the facts?



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      06-01-2010, 03:25 PM   #1
Biimmer
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Tire sidewall question... Who has the facts?

So, I have been doing some tire research and I am seeing that a ton of people are going with a thinner sidewall for the rear tire setup ex: 235/35/19 front and 275/30/19 rear.

What is the reason for a thinner sidewall for the rear instead of maybe a thicker "rear" or perhaps a even sidewall setup?

Thanks for the help!
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      06-01-2010, 03:33 PM   #2
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peformance aspects? hardly
most ppl choose this route due to clearance/speedo/looks
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      06-01-2010, 03:50 PM   #3
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Still confused.. I have always thought that the "30" in a 275/30/19 tire would refer to the thickness of the sidewall. How does the width have any effect on the diameter/aspect ratio?

Thanks for the help I'm trying to learn
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      06-01-2010, 03:53 PM   #4
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275 is the width of the tire
30 is the aspect ratio - 30% of the width
19 is the diameter
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      06-01-2010, 03:56 PM   #5
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Quote:
Originally Posted by I335 View Post
275 is the width of the tire
30 is the aspect ratio - 30% of the width
19 is the diameter
3-2 =+1
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      06-01-2010, 04:02 PM   #6
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So based on the width with a 235/35 and 275/30 the aspect ratio would be the same?
I want the sidewall thickness in the front to be equal to the rear. I wouldn't be a fan of the look when running a lower profile tire in the rear. ** if people are even doing that**

Thanks!
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      06-01-2010, 04:07 PM   #7
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Quote:
Originally Posted by Tee212 View Post
3-2 =+1
Thanks, I didn't have a calculator handy.
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      06-01-2010, 04:20 PM   #8
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Quote:
Originally Posted by Biimmer View Post
Still confused.. I have always thought that the "30" in a 275/30/19 tire would refer to the thickness of the sidewall. How does the width have any effect on the diameter/aspect ratio?

Thanks for the help I'm trying to learn

If you are talking about the distance from the rim edge to the tread, you'll want to refer to it as "sidewall height."

Sidewall "thickness" denotes something else completely--(i.e. RFT sidewalls are thicker so they won't collapse when punctured)
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      06-01-2010, 04:55 PM   #9
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Quote:
Originally Posted by kramerica72 View Post
If you are talking about the distance from the rim edge to the tread, you'll want to refer to it as "sidewall height."

Sidewall "thickness" denotes something else completely--(i.e. RFT sidewalls are thicker so they won't collapse when punctured)
Thx, but you know what I'm refferimg to as my initial question was not about "Run Flats".
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      06-01-2010, 05:14 PM   #10
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BTW Thanks to everyone who helped :-)
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      06-01-2010, 09:47 PM   #11
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275/30/19

275 is the width
30 is the aspect ratio, ratio of sidewall height to width.

so the sidewall height is 275 *0.30=82.5mm
235/35/19
235*0.35= 82.25mm

sidewall height almost exactly the same
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      06-02-2010, 12:39 AM   #12
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Quote:
Originally Posted by Orient330iNYC View Post
275/30/19

275 is the width
30 is the aspect ratio, ratio of sidewall height to width.

so the sidewall height is 275 *0.30=82.5mm
235/35/19
235*0.35= 82.25mm

sidewall height almost exactly the same
Thanks, I completely understand now

Hey, I guess you learn something new everyday!
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      06-02-2010, 12:13 PM   #13
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Tech Rat's first reply had a link explaining it all.

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      06-02-2010, 09:33 PM   #14
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Quote:
Originally Posted by Gary@TireRack View Post
Tech Rat's first reply had a link explaining it all.

Thanks Mr. TireRack.
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