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View Full Version : bigger rims innacurate gauges?


FASN8U
24-11-2008, 04:13 PM
i was talking to a qualified mechanic i no , and mentioned putting bigger rims on my car. he told me that puttin bigger rims on any car will throw your speedometer and odometer out . ive never herd of this before? sounds wack , can anyone else shed some light on this for me?
bennjamin
24-11-2008, 04:17 PM
IF the overall circumference is altered...then YES it WILL put your speedo out by x%.

Try this online tool to work out exactly how much it will alter your speedo readout.

http://www.miata.net/garage/tirecalc.html
FASN8U
24-11-2008, 04:19 PM
thanks for the quick response that answers my main question , what about the odometer, will that stay accurate?
bennjamin
24-11-2008, 04:22 PM
no it will not.
It will be relative to the readout of the VSS. So if its off a tiny bit then so will your odo.
4p1ay
24-11-2008, 04:23 PM
it will be measuring wrong due to ur speedo measuring wrong.. etc
mugenrr
25-11-2008, 12:37 PM
IF the overall circumference is altered...then YES it WILL put your speedo out by x%.

x2 keep the circumference the same
so if you get bigger rims, you need lower profile tyres
smaller rims, you need bigger tyres..
FASN8U
25-11-2008, 05:36 PM
righto i get ya , thanks for putting it in simple terms mugenrr and thanks everyone else for posting in the thread cleared alot up for me
mugenrr
25-11-2008, 07:34 PM
no wuckas
OMG.JAI xD
25-11-2008, 08:04 PM
your rpm would be the same though.
rpm sensors are on the engine block.
but your speed will differ.
bigger circumference = slower reading.
smaller circumference = faster reading.

not good for cars with abs.
Zdster
26-11-2008, 10:16 AM
it will be measuring wrong due to ur speedo measuring wrong.. etc

That is not technically correct is it? (Ben can you confirm?). Reading for both the speedo and odom. come from the VSS dont they? The speedo doesnt get its feed from the odometer?
VTECMACHINE
26-11-2008, 01:29 PM
Yes, most of the time this is true, and this is why big rims are ghey. LOL. Just kidding yO!

Try playing around with the Tyre calculator (http://www.miata.net/garage/tirecalc.html)
VTECMACHINE
27-11-2008, 09:03 AM
IF the overall circumference is altered...then YES it WILL put your speedo out by x%.

Try this online tool to work out exactly how much it will alter your speedo readout.

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

Whoopse... shows how much I actually read ey! hahaha. Great minds man, great minds! haha.
bennjamin
27-11-2008, 09:23 AM
Whoopse... shows how much I actually read ey! hahaha. Great minds man, great minds! haha.

rofl. Dw its probably the most quoted weblink on the entire internet.
ekdez
27-11-2008, 09:32 AM
bigger circumference = slower reading.
smaller circumference = faster reading.


isnt it the other way around?
Lukey
27-11-2008, 08:33 PM
isnt it the other way around?

thats what i thought
mugenrr
27-11-2008, 10:18 PM
^thats not the point! lolz
the point is increasing or decreasing circumference of the total wheel+tire
will affect the speedo.. LOL
saikou27
28-11-2008, 10:33 PM
isnt it the other way around?

larger circumference will result in a slower reading meaning the speedo will show a speed slower than u are actually going. eg 100km/h reading
actual speed 105km/h

smaller circumference results in a faster reading meaning the speedo will show a faster reading than u are actualli going. eg 100km/h reading
actual speed 95km/h

i think the wording is just a little confusing and depends how u look at it :)