quick question on tire sizing
Posting Guru
Joined: Jun 2003
Posts: 1,823
Likes: 0
From: Houston, Texas
I think the conversion is like this:
33"/2=16.5" (give the radius in inches)
16.5"x2x3.14159=103.67" (gives the circumference in inches)
1"=2.54 centimeters
Therefore 103.76"=263.3 cm
I belive that metric dimensions of tires use the circumference in cm's.
I also thought that the other number (ie 70 & 75) gave the distance from the bead to the top of the tread.
33"/2=16.5" (give the radius in inches)
16.5"x2x3.14159=103.67" (gives the circumference in inches)
1"=2.54 centimeters
Therefore 103.76"=263.3 cm
I belive that metric dimensions of tires use the circumference in cm's.
I also thought that the other number (ie 70 & 75) gave the distance from the bead to the top of the tread.
Moderator
Joined: Dec 2001
Posts: 22,436
Likes: 17
From: Louisville,Ky.
Ok, here is how it works. 265/70R17
265= width of tire
70= % of width that the side wall height is
R = radial
17= 17" rim
According to Goodyear, the 265/70R17 is
31.8" tall
10.7" wide (sidewall bulge included) on a 8" wide rim
So you would probably need around a 285/70 or so to get 33"'s.
Jimmy
265= width of tire
70= % of width that the side wall height is
R = radial
17= 17" rim
According to Goodyear, the 265/70R17 is
31.8" tall
10.7" wide (sidewall bulge included) on a 8" wide rim
So you would probably need around a 285/70 or so to get 33"'s.
Jimmy
Senior User
Joined: Sep 2003
Posts: 213
Likes: 0
From: Northwest BC Canada
This formula has always worked for me.
2 x (width) X (aspect ratio) / 2540 + (rim diameter)= overall height in inches.
Width= first # in mm (millimeters) 265,285 etc.
aspect ratio = % of tire height from tread to rim based on width.
2540= conversion factor between mm's and inches
rim diameter= diameter in inches (15,16 16.5 etc.)
Therefore 315/75R 16=
((2 X 315 X 75) / 2540) + 16= 34.6" tall
This number is theoretical and may not be the same as the installed height on your truck as tire makers are allowed some variance of tolerances in manufacturing. Most tire makers will also tell you what rim width they used as this will affect your section width ( tire bulge) and thus overall height. Hope this helps.
2 x (width) X (aspect ratio) / 2540 + (rim diameter)= overall height in inches.
Width= first # in mm (millimeters) 265,285 etc.
aspect ratio = % of tire height from tread to rim based on width.
2540= conversion factor between mm's and inches
rim diameter= diameter in inches (15,16 16.5 etc.)
Therefore 315/75R 16=
((2 X 315 X 75) / 2540) + 16= 34.6" tall
This number is theoretical and may not be the same as the installed height on your truck as tire makers are allowed some variance of tolerances in manufacturing. Most tire makers will also tell you what rim width they used as this will affect your section width ( tire bulge) and thus overall height. Hope this helps.
