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I still have stock 185 on steelies.

I've been looking to upgrade, but wont going so something like 215 make the speedometer inaccurate?

What do i need to look out for? I dont want a bad speed reading...


Noob to rims, sorry. Search brought up nothing.

 
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i got 17s with 205/45/R17s and they dont effect my speedo but ive heard over 18s will effect your speedometer with a 6th gen. not sure about the 7th gens. prolly 18s would be fine lots of people run them.

 
Rep Power: 313

I'm not 100% sure, but you adjust for larger wheel size by buying smaller tires.

Example : 185/65/14

The first number is just tire width, so it will not affect your speedo at all.

The second number is tire heigth, this one has an effect.

The third number is wheel size in inches.

That being said, if you move from 14 inch steelies to 17 inch rims you would adjust accordingly.

185/65/14 < 14 inch steelies
225/35/17 < 17 inch rims.

These would be your tire sizes, see how you adjusted for wheel size by reducing the height of your tires, for every 1 inch you reduce 10 mills off your tire height.

Now to the problem, you can't always find the right sized tires height wise to suit your rims, and you kinda have to deal with that by buying whatever fits that particular rim. This is when you can screw your speedo up!

If someone can confirm this as I'm not 100% sure.

 
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yeah that's pretty much correct. The second number (e.g. the 65 in 185/65/14) is actually a ratio of the height to the width, not just the height in millimeters so it's a little more algebra to calculate the actual height of the wheel/tire combination. However, if you don't want to sit down and work this out, there are plenty of calculators on the internet that will tell you the total height of a certain wheel size with a certain tire size. Like tbohar said, only height affects the speedo reading, just get shorter tires so the total height will be the same as stock.

 
Rep Power: 230

tbohar: not sure if you know, but the width does actually matter. the height (35,45,55 etc) are all a percentage of the width, so a 225/45 and a 205/45 will have a different height. the 225/45 will be higher (45% of 225 mm) than the 205/45 (45% of 205 mm).

anyway, if you want to go with 215, you should use 215/45/r17. the overall diameter of a 215/45/17 is within only a couple of mm of stock 185/65/r15. it will keep everything on your car (height, wheel well gaps) basically the same as stock.

 
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Thanks for correcting me guys. I just made an educated guess with no research for a change. Last time I'll do that! Go with what these guys say and maybe use a calculator to figure out the best tire for you!

 
Rep Power: 352

ur speedo is off. it is going a big slower than OEM spec.



also, the rim width + width of the tire needs to be taken into consideration.

for example, a 17x6 rim will fit a 205/40/17 with stock ratio..

however, put the same 205/40/17 tire on a rim that is 17x7 and you will have a smaller sidewall because the tire will be doing this

/-----\ (because the rim width streches it a bit more

vs

|-----| which is what stock looks like.

 
Rep Power: 352

use http://www.miata.net/garage/tirecalc.html

and calculate what tire size you can get that wont effect the speedo too much.

that tire size calculator doesnt take into account the rim width on tire. it assumes all the tires are |-----|


stock civic tire size are:
2001-2003 LX: 185/70R14
2001-2003 EX: 185/65R15
2004-2005 EX/LX: 195/60/15 (SE is the same i believe)





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even if you have OEM rims/tires your speedo will ALWAYS be 5% (+/- a few) due to the pressure of ur tires, cold or warm