i have the stock tyres which comes with the auto the 16 inches one. now i have 245 18 inch tyres and i like to know that will this effect the speedometer reading or not. as if the meter is showing 100 than will it be 100 or a little faster than than that. thankx

 

As long as your 245-18 has a profile of 40 then the speedo will be within a few percent of correct. What wheels did you get? (width and offset, post pics)
What's your location?

 

 

hello anyone?????

 

you're fine. so you got the 16s originally which means you have an automatic and you're learning to launch against a tibi. your threads get funnier and funnier.

 

16" stock? I didn't know there was such a thing. Anyway, you'd have to a much more dramatic alteration of the diameter of the wheel and the height of the tire to have any notable effect on the speedometer/odometer. As we know, the number after the slash in the tire size schema is the sidewall height; e.g. my stock 225/45ZR18 or potential 245/40ZR18. In my case going from 45 to 40 profile is negligible from a speedometer/odometer perspective.

Going from a 16" wheel to an 18" is of course more significant than altering your tire sidewall height.

With a larger than stock diameter wheel/tire height you will be going slightly faster than your speedomenter reading as you will be covering a slightly greater distance with each revolution (larger circumference). It's a Pi x Diameter thing.

All quite academic and nothing to worry about.

 

Try this online calculator...

http://www.1010tires.com/TireSizeCalculator.asp

 

the 5mt comes with a 16inch

 

not in the U.S. where are you located?

 

225/55-16 tire = 653.9mm dia.
225/45-18 tire = 659.7mm dia

< 1% diff in dia. thererfore no diff in speedo readout.

 

its 245/45-18 not 225/55-16

 

Huh, first productive topic posted by zainanwar. Good job!

https://www.rx8club.com/rx-8-discussion-3/rx8-vs-hyundai-coupe-help-133824/
https://www.rx8club.com/rx-8-discussion-3/quarter-mile-question-134054/
https://www.rx8club.com/rx-8-discussion-3/short-shifter-134168/
https://www.rx8club.com/rx-8-discussion-3/standard-power-vs-high-power-133878/
https://www.rx8club.com/series-i-aftermarket-performance-modifications-23/0-60mph-times-128629/

 

do your own math. oh all right.

245/45-18 = 677.7mm dia vs 653.9mm is approx. 3.5% diff.

go with a 245/40-18 to be closer to stock 225/45-18 tire.

 

tyre???

 

thankx guys. actually i love my car very much so i keep on asking stupid questions just to know every little thing abt my car. i am sorry if any of u find my questions stupid.

 

at least you're learning.

;D

 

You'll be ok. I have the same set up, 245/45/18 and I have a 04' AT that had 16" wheels.

 

It will be slower as the 18" are much heavier.