Looking for a slightly taller rear tire
#11
03-05-2013, 11:06 AM
Road Warrior
I have an 8th grade math "ejikashun"so my math may not be right.
The 160/70 is 112mm or about 4.41 inches tall and the 170/17 is 119mm or 4.69 inches tall.The difference would be .28 inches or .56 inches overall.
Last edited by popawcritter; 03-05-2013 at 11:15 AM.
#12
03-05-2013, 01:33 PM
#13
03-05-2013, 05:06 PM
spankdog! Remember your geometry...a tire is a geometric circle and the diameter of a circle is the distance across...or height...same-same.
The relationship with diameter, radius, and circumference is stated by the formulas C=2πr and C=πd. Therefore, if one tire is 0.64 in. taller, then the diameter of the tire from center outside tread to center outside tread is increased by 0.64 in. more than the other tire...the radius is half of the diameter, or 0.32 in this application because radius is one-half of the diameter.
Using a diameter of 10 inches and 3.14 for pi for demonstration purposes; the circumference is approximately 31.4 inches. Increasing the diameter, or height, by 0.64 inches yields an increase of approximately 2 inches circumference, or just over a 6% increase. A 10 inch circumference wheel will rotate just over 168 revolutions per mile and the 0.64 inch increase will decrease the rotation by approximately 10 revolutions per mile, again just over 6%.
The relationship with diameter, radius, and circumference is stated by the formulas C=2πr and C=πd. Therefore, if one tire is 0.64 in. taller, then the diameter of the tire from center outside tread to center outside tread is increased by 0.64 in. more than the other tire...the radius is half of the diameter, or 0.32 in this application because radius is one-half of the diameter.
Using a diameter of 10 inches and 3.14 for pi for demonstration purposes; the circumference is approximately 31.4 inches. Increasing the diameter, or height, by 0.64 inches yields an increase of approximately 2 inches circumference, or just over a 6% increase. A 10 inch circumference wheel will rotate just over 168 revolutions per mile and the 0.64 inch increase will decrease the rotation by approximately 10 revolutions per mile, again just over 6%.
#14
03-05-2013, 05:26 PM
Elite HDF Member
Join Date: Jul 2007
Location: sand mountain Alabama
Posts: 4,749
Likes: 0
Received 15 Likes
on
14 Posts
It will make the speedo slower by about 2.5%, not faster. larger overall diameter means less revolutions per mile and that makes the speedo slower. that doesn't really concern me and when I say "taller", I don't mean making the bike taller, I mean that when you stand up the tires side by side, one is .64" taller than the other and yes it will change my final drive ratio from 3.1625 :1 to about 3.085 :1 which is exactly why I am doing it. it will lower the RPMs by about 85rpm at 75 mph .
Thread
Thread Starter
Forum
Replies
Last Post
bowhuntenbob
Want To Buy Motorcycles/Parts/Accessories
0
07-10-2013 05:00 AM