New Rims Have Any Effect On Speedometer?

white04alero · 01-12-2005, 11:53 PM

hey im thinkin of gettin new rims.. 18's to be exact.. and i was wondering, if the radius of your new tire/rim combo is larger than your stock tire/rim combo, will it affect the speedometer at all? im just wondering ive heard different stories.

Vtolds · 01-13-2005, 12:01 AM

Will be slightly off becuase you cant get a exact wheel tire oversize, but it is virtually unnoticeable.

01-13-2005, 12:08 AM

Umm you will notice 3 to 4mph difference, you will be going 3 or 4mph faster than your spedo says, and if you ask me, that's nowhere near virtualy unnoticeable. With my 17's and 225/45/17 tires, I got a 3mph difference

sound_xtreme · 01-13-2005, 12:16 AM

dude, no way. lol. 225/45/17 are .5% off.

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

01-13-2005, 12:19 AM

NO way, maybey my speedo is just retarded then... hmm that's weird. COuld it have just been off from the beginning? But the same thing happened to my friends corrola, he got 17's with 215/40/17 and it went 2 mph off....

01-13-2005, 12:20 AM

but I did have the 15's to begin with, what are they 205/60/16?

Vtolds · 01-13-2005, 12:26 AM

I new that 3 or 4 mph off had to be wrong but I didn't wanna call you on it and look like a fool, i'll let others do it. 1 sure way to find out if your speedo is off is drive bye a speed trap at the speed your speedo says and if you get pulled over find out how fast you where actaully going and the ticket will disapeer becuase your speedo is off and needs to be recalibrated.

01-13-2005, 12:38 AM

Quote:

Originally posted by |Rev|@Jan 12 2005, 11:20 PM
but I did have the 15's to begin with, what are they 205/60/16?

215/60/15.

01-13-2005, 10:16 AM

I know you have to reset like... the tire pressure light when you get new tires, or have them rotated or what not, I'm not sure if that would fix the problem or not, it probably won't, but you have to do it, or the stupid low pressure light will come on randomly and never turn off <_<

johny_boy32 · 01-13-2005, 06:31 PM

When i went from 15's to 17's my speedo was off 3 to 3.5 mph off my what i was really going to. And i proved it with a gps thing that we have on the shop and had a cop run his radar on me, TWICE(Friends with his son) So know what your talking about.

FormulaNERD · 01-13-2005, 06:35 PM

the radar things that tell you your speed... well i know they are never really "correct" but i have 18's and mine is dead on every single day... there's one posted in a school zone here, and i have to drive maybe a half mile doing 15... lol, it sucks, but i know my tires havent affected my speedo.

johny_boy32 · 01-13-2005, 06:39 PM

I'm not talking about the stupid radar shoots on the side of the road, I'm talking about an actual police radar. I know those arent wrong.

FormulaNERD · 01-13-2005, 06:41 PM

Quote:

Originally posted by johny_boy32@Jan 13 2005, 05:39 PM
I'm not talking about the stupid radar shoots on the side of the road, I'm talking about an actual police radar. I know those arent wrong.

i never even mentioned your police radar comment. i was telling my story, and didnt read your little post.

ImSoBored · 01-13-2005, 06:46 PM

mine was off 2-3 mph up to 80mph, and ive still got the stock rims.

johny_boy32 · 01-13-2005, 06:47 PM

Quote:

Originally posted by FormulaNERD+Jan 13 2005, 11:41 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (FormulaNERD @ Jan 13 2005, 11:41 PM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-johny_boy32@Jan 13 2005, 05:39 PM
I'm not talking about the stupid radar shoots on the side of the road, I'm talking about an actual police radar. I know those arent wrong.

i never even mentioned your police radar comment. i was telling my story, and didnt read your little post. [/b][/quote]
Alright, Sorry...no need to fight over the net.

white04alero · 01-13-2005, 09:30 PM

thanks for the help guys.. and for the site

01-13-2005, 11:25 PM

Hey guys, I am new checkout this site, I found it to be very helpful when I was considering getting a set of aftermarket wheels. You can compare any two sizes you want and it will do all the calculations for you. Here it is http://www.miata.net/garage/tirecalc.html

sound_xtreme · 01-14-2005, 01:33 AM

Quote:

When i went from 15's to 17's my speedo was off 3 to 3.5 mph off my what i was really going to. And i proved it with a gps thing that we have on the shop and had a cop run his radar on me, TWICE(Friends with his son) So know what your talking about.

either you got the wrong tire size or your speedo was already off. go use the calculator. there is just no way it can be that much. none, zip, zilch, no chance in hell .
considering if you go from stock 15" tires to the 225/45/17's you will be going SLOWER than what your stock did, .7% slow to be exact. so you'd be going 59.6mph with the speedo reading 60.

if you go from stock 16's to 225/45/17's you will be going .5% faster which is about .3 mph faster when your speedo reads 60.

stock tire sizes are:
15" wheels - 215/60/15
16" wheels - 225/50/16
correct tire size for 17" - 225/45/17

FormulaNERD · 01-14-2005, 02:48 AM

Quote:

Originally posted by firerat17@Jan 13 2005, 10:25 PM
Hey guys, I am new checkout this site, I found it to be very helpful when I was considering getting a set of aftermarket wheels. You can compare any two sizes you want and it will do all the calculations for you. Here it is http://www.miata.net/garage/tirecalc.html

haha, thanks... but it's already posted at the top of this thread :thumbsup:

johny_boy32 · 01-14-2005, 12:16 PM

Quote:

Originally posted by sound_xtreme@Jan 14 2005, 06:33 AM
correct tire size for 17" - 225/45/17

Thats why it was off was because I didn't have that tire size. And yes, my speedo said I was going faster than I really was, It would say 65 but I was only going 62.