Does upgrading RIM size affect speedometer?

Hi
for those of you who have upgraded your wheels to 17" rims. How did you fix the problem with your speedometer. I mean the stock rims are only 14", by upgrading the rims to 17" this must affect the accuracy of the speedometer... is getting thinner tires the only way to get your speedometer accurate?

Or do I have to re-calibrate the speedometer? (*Hopeefully not)

Please reply with your advice!
Thanks for all your help~
joe :confused:

As long as you keep the overall ratio of the tire the same as stock you should be fine.

So for a Civic:

185/65x14"
195/55x15"
205/45x16"
205/40x17"
215/35/18"

It's called plus sizing your tires. Basically you get a bigger wheel with thinner tire walls so the circumference of the tire is the same and therefore your speedometer remains accurate. If you want more info, just google search "Plus size tires" and there'll be links all over the place

we got a noob:biggrin:

Originally posted by mattyoung33
we got a noob:biggrin:
Hey - we all gotta start somewhere.

Originally posted by mattyoung33
we got a noob:biggrin:

calling people noobs is just a childish way of trying to be "cool" amongst the other users of the forum. so shut up .

yeah what he said............but anyways ummmmm my stock was 13" and i went to 205/40/16 what is the difference in the speed there.........im thinking like 5 miles an hour faster or slower but someone let me know

I know that my 92 dx speedo was off by like 5 mph or something when I bought it. and that was on stock 13's (I had the speedo checked). When I put on 205-40ZR-17's..it actaully corrected my speedo, which was nice...(I got it re-checked). Now its like 99.8% accurate (when it says 70mph, I am actually at 69 mph). But yea, for the most part, plus sizing won't do that, it will keep it all the same. My guess is the previous own put on 13's with less of a profile than the stock tires, but since I haven'ty actually bothered to do downstairs, dig up the old tires and look, I don't know, lol. But if you are worried about messing up the speedo, go to a speedometer shop and have it checked. Thats what I did, it only cost like 10 or 15 dollars, and in my opinion is worth the piece of mind.

Originally posted by candlaudio
yeah what he said............but anyways ummmmm my stock was 13" and i went to 205/40/16 what is the difference in the speed there.........im thinking like 5 miles an hour faster or slower but someone let me know

Well it's easy to figure out.

Take the overall diameter of your stock setup compared to your new setup and then multiply that percentage with your speedo and that should be your real speed.

heres a calculator you can use for this

http://www.c5-corvette.com/tirecalc.htm

Whalen Tire (www.whalentire.com)

shows all the info - example :
STOCK WHEEL WIDTH: 5.0"

STOCK TIRE SIZE: 185/60R14

DIAMETER: 22.7" SECTION WIDTH: 7.3" SIDEWALL HEIGHT: 4.4"
MINIMUM RIM WIDTH: 5.0" MAXIMUM RIM WIDTH: 6.5"
REVOLUTIONS PER MILE: 887


SELECTED TIRE SIZE:205/40R17

DIAMETER: 23.5" SECTION WIDTH: 8.1" SIDEWALL HEIGHT: 3.2"
MINIMUM RIM WIDTH: 7.0" MAXIMUM RIM WIDTH: 8.0"
REVOLUTIONS PER MILE: 860

IF YOU TRAVELED 60 MPH WITH THIS TIRE INSTALLED ON YOUR VEHICLE
YOUR SPEEDOMETER WOULD READ 58.2 MPH

Well all I know is that when I had my 15's, even that made a difference... I drove at lower RPM's... Now that Im back on my 13's... im using more gas... Im getting 17's in like a week... its MUCH bigger than my 13's. I have like a 6" gap right now and with the 17's theres like 0 gap... they barely fit... All I know is that in MY case it DOES make a big difference... The guy put the 17" rim with tire next to my car and is ALOT huge-er....

Originally posted by sageuvagony
Well all I know is that when I had my 15's, even that made a difference... I drove at lower RPM's... Now that Im back on my 13's... im using more gas... Im getting 17's in like a week... its MUCH bigger than my 13's. I have like a 6" gap right now and with the 17's theres like 0 gap... they barely fit... All I know is that in MY case it DOES make a big difference... The guy put the 17" rim with tire next to my car and is ALOT huge-er....


:bloated:

check this site for a visual calculator.
http://www.miata.net/garage/tirecalc.html