# Speedo off with 18s?

**URL:** <https://forums.speedlife.net/t/speedo-off-with-18s/85962>\
**Category:** SON240sx Automotive\
**Created:** [May 27, 2005, 12:29pm UTC](https://forums.speedlife.net/t/speedo-off-with-18s/85962 "2005-05-27T12:29:51Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![KoukiS14](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/koukis14/32/5522_2.png) [@KoukiS14](https://forums.speedlife.net/u/KoukiS14)\
**Post date:** [May 27, 2005, 12:29pm UTC](https://forums.speedlife.net/t/speedo-off-with-18s/85962/1 "2005-05-27T12:29:51Z")

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With my new 18-inch wheels on my S14, I am pretty sure that my speedo is going to be off because of the much taller overall diameter compared to my stock wheels. I really dont want to get booked for doing 50 over when I thought I was only doing 30.

Does anyone know of a calculation that I can do to figure out my actual speed or a way to remedy this?

FYI:  
235/40/18 18x9  
265/35/18 18x10

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**Author:** ![DTS](https://avatars.discourse-cdn.com/v4/letter/d/8491ac/32.png) [@DTS](https://forums.speedlife.net/u/DTS)\
**Post date:** [May 27, 2005, 12:55pm UTC](https://forums.speedlife.net/t/speedo-off-with-18s/85962/2 "2005-05-27T12:55:17Z")

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[www.miata.net/garage/tirecalc.html](http://www.miata.net/garage/tirecalc.html)