Speedometer Question.
07-18-06, 09:07 AM
#5
Banned - could not follow forum rules
Join Date: Oct 2005
Location: CA
Posts: 1,020
Likes: 0
Received 0 Likes
on
0 Posts
If you shrink the diameter tire size (height) of the tire compared to the stock tires the speedo will read just a hair to fast...If you increase the size over stock the speedo will read a hair slow.....Because the if the tire is shorter you will get more revolutions (turnover) then as compared with a larger stock tire which the speedo is exactly calibrated too... Comprende Amigo? Any trie change with 18 inch rims should not make a noticeable difference....Unless you get crazy low profile tires on the 18's.. I have 18's with 275/35/zr18 tirs which are low profile and I didn't notice any change with the speedo....that shrunk down my wheel height...
07-18-06, 10:13 AM
#6
Those tire and wheel combinations will increase the total diameter of your tire/wheel by about 1.5 inches. Like the guy above said, that will cause your speedo to read just a hair slow. Because of the increase in circumference, the car will travel farther per tire revolution than on stock wheels/tires.
07-18-06, 11:04 AM
#7
Lead Lap
Join Date: Oct 2004
Location: Alabama
Posts: 448
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by KidPandJ
Those tire and wheel combinations will increase the total diameter of your tire/wheel by about 1.5 inches. Like the guy above said, that will cause your speedo to read just a hair slow. Because of the increase in circumference, the car will travel farther per tire revolution than on stock wheels/tires.
http://www.miata.net/garage/tirecalc.html
A) The front tires dont matter as far as speed goes. B) 265/35/18s will be .2" too small making your speedo 1.7% off (reading 60mph when you are actually traveling 59mph).....or so says my very well trusted miata tire size calculator.
Trending Topics
07-18-06, 12:33 PM
#8
I don't know about the miata tire size caluclator but...265/35/18's are (265 * .35 ) to get the side wall thickness. That number times two(you have two sidewalls in the diameter)...then converted to inches. Add that to 18 to get the new diameter. I used 225/45/16 for stock tires. I believe that it gives you 1.5" greater in diameter. Could be wrong though?
Thread
Thread Starter
Forum
Replies
Last Post
EyesOnly
GS - 2nd Gen (1998-2005)
6
03-10-06 05:11 AM