Speedometer adjustment
Thread Starter
Registered!!
Joined: Apr 2013
Posts: 43
Likes: 0
Rep Power: 0 
Speedometer adjustment
Hey guys,
So i have a 97 Civic Ex and I wanted to increase the wheel size from 14 inches to either 15 or 16 inches. And I know that in doing this i would need bigger tires as well. So my question is would the speedometer fix itself or would I have to do it myself? Ive read both but i wanted some clarification. Thanks in advance!
So i have a 97 Civic Ex and I wanted to increase the wheel size from 14 inches to either 15 or 16 inches. And I know that in doing this i would need bigger tires as well. So my question is would the speedometer fix itself or would I have to do it myself? Ive read both but i wanted some clarification. Thanks in advance!
Joined: Aug 2003
Posts: 21,620
Likes: 1,252
From: Las Vegas, NV
Rep Power: 511 
Re: Speedometer adjustment
First, go to tires.com and see what "plus sized" tire options they recommend for your car.
Second, go to http://www.miata.net/garage/tirecalc.html, input the OEM tire size into "stock size" and plug in one of the tire sizes they recommend for 16s. It'll give you a percentage of how off your new tires will make your speedometer. Repeat with the other sizes until you find one that is 0% or pretty darn close.
I upgraded my wheels from 185/65-15s to 215/45-17s, and my speedometer is only off by 0.2%. Using real numbers, is my speedometer indicated 60mph, I'd actually be traveling 60.4mph. Not enough of a difference to make me freak out. If I were to drop down to 16s rocking 205/50-16 tires, it results in 0% difference. The miata.net tire calculator will be about the closest you'll get to finding a matching tire combo. Realistically speaking, it's not gonna be perfect, but it's the best tool you'll have.
When you upsize your tires and you don't wanna screw with the speedometer, you wanna aim to have the same overall diameter. That said, the various tire sizes will essentially eat some of the sidewall height to compensate. You don't wanna be that guy that gets low-profile tires because that's what the cool kids are doing
Second, go to http://www.miata.net/garage/tirecalc.html, input the OEM tire size into "stock size" and plug in one of the tire sizes they recommend for 16s. It'll give you a percentage of how off your new tires will make your speedometer. Repeat with the other sizes until you find one that is 0% or pretty darn close.
I upgraded my wheels from 185/65-15s to 215/45-17s, and my speedometer is only off by 0.2%. Using real numbers, is my speedometer indicated 60mph, I'd actually be traveling 60.4mph. Not enough of a difference to make me freak out. If I were to drop down to 16s rocking 205/50-16 tires, it results in 0% difference. The miata.net tire calculator will be about the closest you'll get to finding a matching tire combo. Realistically speaking, it's not gonna be perfect, but it's the best tool you'll have.
When you upsize your tires and you don't wanna screw with the speedometer, you wanna aim to have the same overall diameter. That said, the various tire sizes will essentially eat some of the sidewall height to compensate. You don't wanna be that guy that gets low-profile tires because that's what the cool kids are doing
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
Rep Power: 518 Re: Speedometer adjustment
This is how I chose a tire size when I went from my stock 195-65-15 to 225-40-18.
I go through those radar "your speed is __" signs on the freeway and my speedo reads exactly what the signs flash at me.
I go through those radar "your speed is __" signs on the freeway and my speedo reads exactly what the signs flash at me.
Thread
Thread Starter
Honda Civic Forum
Replies
Last Post
Crazygrlinak
Mechanical Problems/Vehicle Issues and Fix-it Forum
3
Oct 8, 2015 05:06 PM
260000milesgoal
I.C.E. (Audio) & Electrical Upgrades
2
Sep 25, 2015 07:41 PM
