Downsizing my wheels from 18” to 17”. Where/how to recalibrate speedometer?

bugboy32337

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OP, like another poster mentioned, you can go down an inch in wheel size, but simply use a higher profile than stock tire to keep your speedo accurate. In this case you could use the 215/50-17 size like on my non-Si.

But, I have an even better solution for your Si:

Use the 17" stock European Civic tire size... 235/45-17. It's much meatier yet will still keep your speedo numbers virtually identical to stock. The great thing with this is you'll have the same width as the stock Si tire but will get a cushier ride due to the 45 profile.
Absolutely nothing wrong with the 215/50R17 ... but why decrease the tire footprint on an Si, unless it's for winter tires?
(did I miss that part of thread? is this for winter tires?)
Could also go with a 245/45R17 ... that would put you at 812 revolutions per mile (vs. 235/40R18 @ 820 revolutions per mile) and your speedo will be off by 1%.
At 50 (speedo) miles per hour, your car would actually be traveling 50.5 miles per hour ... I'm as anal retentive as anyone here, and I'd sleep easy with this discrepancy!
(245/45R17 on 17x8.5 or 17x9 is actually a wheel and tire option that I am currently entertaining ... so that I can get a slightly meatier footprint, slightly more rim protection. However, I do have some nagging concern that finding replacement tires, in the future, will be more difficult)
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bikejog

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Found this solution:


This may be the route i’d have to go with. Unless someone has a better solution. I can’t just “deal with it.” It’s going to bother the crap out of me knowing my speedometer is off...
Is that thing even legal? Seem to me you can use it to slow down your speedo so similar crime as turning back the odometer?
 


 


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