Speedometer

Ian Robertson

Ian Robertson

Well-Known Member
118
76
Austin, TX
My google-fu has failed me, at least for newer model civics.

So the stock LX comes with 15's, and I'm finally able to put the 17's I bought on. I don't want my speedo to be completely off. Is there a way to swap in a speedo from the Si to make sure it would be accurate? I'm not even really sure how speedometers work, I imagine theres a box somewhere with a sensor that takes how many rotations the axle does and divides it by something based on the stock wheel size? If so...would a box like that be able to change to a 17" setup or would a whole new unit be necessary?

Thanks
 
All you have to do it adjust the aspect ratio of the tire and your speedo won't be off by very much. I posted a link to the tire size calculator and a quick explanation... Ill find it for you and just cause im bored Ill do the calculation for you.

Do the 17" wheels you have already have tires mounted on them or are you still needing to buy rubber?
 
A larger rim with a same sized O.D. tire will also tend to have a stiffer side wall. You'll feel the road more, but should experience snappier handling/response.
 
Thread:
http://9thcivic.com/forum/threads/some-help-for-choosing-wheel-and-tire-sizes.3158/

Stock DX/LX wheel size is 15x6
Tire is a 195/65/15 - 195 is tire width, 65 is sidewall height (65% of 195), 15 is wheel size.

Stock tire:
Sidewall - 5"
Diameter - 25"
Revs/Mile - 807.0


So you want to go to a 000/00/17" ? Also what width wheel in the 17 do you have?


New tire size should be:

225/45/17.

A tire this size is a perfect fit, match, and will fit a 17" rim from 7" to 8" wide.


Sidewall: 4.0"
Diameter: 25"
Revs/mile: 808.0


Your speedo will be off by less than 1%. Meaning when it says 60mph, you are going 60. No need to fuss with anything. Just a correctly sized tire.

http://www.miata.net/garage/tirecalcold.html
 
^^ what they've shown. You do not need to swap speedometers or anything. You can go to a proper sized 17" rim/tire, and still keep your speedometer in check.

find out what the width of your 17" rim is, and report back. Then you can get an idea of what width 17" tire to go with. You'll be fine.
 
unless you wanna run Enkei RPF-1's in 17x9 and stretch a 205/40 hahahah fender work and rubbing!
 
Nix man, thanks for the help on this! Total newb when it comes to tires.

The part number for these rims is awfp-c 17x7j 45. I'm assuming that means 17" rims, 7" wide.
 
Ah, those are 8th si rims. Yes, they're 7" wide. They came with 215 width tires stock
 
215/45-17 = slightly under speed. So when your speedo says you're driving 60mph, you're actually driving 59mph.
 
Hey no problem Ian. Get yourself some 225/45/17 tires and you'll be all set. You could definitely run a 215/45 also. Your speed won't be off by very much.

There are tons of tires in both sizes on tirerack.com. Are you looking for all seasons or a set of dedicated summer/high performance tires? Lots of options right around $100-115 per tire.
 
You guys were super helpful! Since it was only 1 MPH off, I went with the factory 215/45s. After looking at Consumer Reports and a couple articles by Car and Driver, I settled on Cooper Zeon RS3-S, got them for about $115 a piece which was a good deal I think. I was super worried the car would look to be "riding high" but actually they don't look to bad. I'd like to drop them, but it looks okay for now I think! I would love some nice big calipers in front and rear, but thats a pipe dream. College budget and what not. These tires have depleted my funds for a whiiiilleeee hahaha

Thanks again for all the help.

Here's how it looks!

7KA49.jpg
 
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