bstone Posted July 19, 2010 Share Posted July 19, 2010 My OBW currently has 205/70R15 tires, but I want to put on the Michelin Energy Saver A/S tires, but they come only in 195/65R15. What would happen if I put these smaller tires on? Quote Link to comment Share on other sites More sharing options...
mdjdc Posted July 19, 2010 Share Posted July 19, 2010 You need to google tire size calculator as your speedo is going to be off. The calculator will tell you by how much. Quote Link to comment Share on other sites More sharing options...
bstone Posted July 19, 2010 Author Share Posted July 19, 2010 You need to google tire size calculator as your speedo is going to be off. The calculator will tell you by how much. Specification Sidewall Radius Diameter Circumference Revs/Mile Difference 205/70-15 5.6in 13.1in 26.3in 82.6in 767 0.0% 195/65-15 5.0in 12.5in 25.0in 78.5in 807 -5.0% Quote Link to comment Share on other sites More sharing options...
macattack Posted July 19, 2010 Share Posted July 19, 2010 Going with a larger or smaller tire diameter throws off the speedometer and the antilock brakes and stability system calibrations, if your car has them. Increasing tire diameter also can be unsafe because it makes your brakes work harder to stop the car. A few automakers have taken a piece of the upgrade pie by offering larger-diameter tire-and-wheel packages that have been run through all their safety and durability testing. A certified dealer installs them and recalibrates the speedometer, ABS, etc. at the same time. Quote Link to comment Share on other sites More sharing options...
Rooster2 Posted July 19, 2010 Share Posted July 19, 2010 Specification Sidewall Radius Diameter Circumference Revs/Mile Difference205/70-15 5.6in 13.1in 26.3in 82.6in 767 0.0% 195/65-15 5.0in 12.5in 25.0in 78.5in 807 -5.0% The smaller tire will make your car lower to the ground, so you will have reduced ground clearance. Maybe loose one half, or close to an inch of ground clearance. The tire store should be able to tell you exactly how much. Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted July 19, 2010 Share Posted July 19, 2010 (edited) Specification Sidewall Radius Diameter Circumference Revs/Mile Difference205/70-15 5.6in 13.1in 26.3in 82.6in 767 0.0% 195/65-15 5.0in 12.5in 25.0in 78.5in 807 -5.0% The smaller tire will make your car lower to the ground, so you will have reduced ground clearance. Maybe loose one half, or close to an inch of ground clearance. The tire store should be able to tell you exactly how much. according to the numbers above it will lower your car .66 inches, more than 5/8 inch. stock 90s legacy, 185/70/15, is ~24.20 in diameter, which would make it another .4 inches lower. google ''miata tire calculator''. the speedometer is driven by the speedo gears in the trans. there is no way i know of short of replacing them that they can be calibrated. they match the stock tire size that came on the car. speedos can be swapped, but from what i have seen they are all the same in the 90s, they just swap out the face plates to match the speedo gears. so the speedo will always be off. you can remove and reset the speedo needle so it will read correctly at ONE SPEED, but it is very tricky and not recommended. in order to get the speedo to read accurately all the time you would have to make a custom faceplate and install it. Edited July 19, 2010 by johnceggleston Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.