Help please i'm Tired.
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Cargo Master
Joined: Jan 2005
Posts: 2,413
Likes: 11
Help please i'm Tired.
Pune intended. me and my buddy disagree about a tire's hight. I say that a 285/75r16 has the same hight of a 265/75r16 but just wider. He says that the 265 is taller therfore changing my reargear ratio on final drive.
Post Fiend
Joined: Jun 2004
Posts: 9,293
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From: Parker, CO
You are both wrong. The 285/75r16 is the taller and wider tire. First metric number is the tread width, second number is the sidewall height in relation to the width. Third is of course rim size.
On Edit: Dang, vloney beat me to it.
On Edit: Dang, vloney beat me to it.
Postmaster
Joined: Feb 2006
Posts: 3,201
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From: waynesville, mo.
Originally Posted by exiled
vloney, dont you mean that its 285mms wide?
so i guess my buddy was right i forgot the part about the 75 being a percentage of the width in hight.
so i guess my buddy was right i forgot the part about the 75 being a percentage of the width in hight.
Post Fiend
Joined: Jun 2004
Posts: 9,293
Likes: 10
From: Parker, CO
Originally Posted by vloney
nope, measure from the wheel to the top of the tire.
Senior User
Joined: May 2003
Posts: 481
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From: St. Petersburg, FL
Everything you ever wanted to know about tire designations. 
http://www.tirerack.com/tires/tirete....jsp?techid=46
http://www.tirerack.com/tires/tirete....jsp?techid=46
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Junior User
Joined: Feb 2006
Posts: 55
Likes: 0
From: Anchorage, Alaska
Wow!! Now I'm really confused.
Walk me through this one step at a time please.
You guys are saying 285 mm wide, that converts to 11.22 inches.
then the sidewall height is 75% of 285 mm which is 213.75 mm or 8.415 inches.
So that means you add sidewall height to 16 inch rim height for a grand total of 24.415 overall tire height?
That can't be right. What am I missing here?
........... 
Walk me through this one step at a time please.You guys are saying 285 mm wide, that converts to 11.22 inches.
then the sidewall height is 75% of 285 mm which is 213.75 mm or 8.415 inches.
So that means you add sidewall height to 16 inch rim height for a grand total of 24.415 overall tire height?
That can't be right. What am I missing here?
...........
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Logistics Pro
Joined: Mar 2004
Posts: 4,221
Likes: 3
Sockeye, you have to add 8.415 twice as there are two sidewalls. So 16 inches for the rim, 8.415 for the sidewall on the top side of the rim, and 8.415 for the sidewall across the rim on bottom. So looks like 32.83 inches overall height. I think that's how you do it...
Cargo Master
Joined: Aug 2005
Posts: 2,051
Likes: 1
From: Alberta, Canada
Originally Posted by Pocket
Wait a sec vloney, I just reread your post. The first number is the width of the tread, not the height of the sidewall.
265/75-16
section width 265mm
sidewall 7.8"
radius 15.8"
diameter 31.6"
circumference 99.4"
revs/mile 637
285/75-16
section width 285
sidewall 8.4
radius 16.4
diameter 32.8
circumference 103.1
revs/mile 614
Logistics Pro
Joined: Mar 2004
Posts: 4,221
Likes: 3
Don't feel bad... I didn't even know how to interpret the 285/75r16 except for the 16 inch rims part until this thread. Just never looked into it. I just saw how you were calculating and saw where you went wrong. I actually wrote this down as a note for how to calculate it in the future. Had no idea that the 75 meant sidewall height as 75% of the first number ("section width"). 
I actually wrote this down as a note for how to calculate it in the future. Had no idea that the 75 meant sidewall height as 75% of the first number ("section width").
Make sure you use the same units (convert the tire circumfrence to feet before you divide).