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View Full Version : Question about speedometer and rims.

Alero_Mod
03-10-2007, 06:55 PM
I have a friend that has 16'' rims on his intruige and I have 15'' on my alero I was wondering going from 15'' to 16'' will that mess with the speedometer?? or no?
any info guys?
TwistedDreams
03-10-2007, 08:07 PM
upgrading any size will
Spilner521
03-10-2007, 08:28 PM
You need to use tires that are the same, or very close in overall diameter to your stock tires, then the speedometer will read accurately.
TwistedDreams
03-10-2007, 08:55 PM
You need to use tires that are the same, or very close in overall diameter to your stock tires, then the speedometer will read accurately.

no it wont, it wont be off by much but it will still be off, diameter has nothing to do with it, its the weight of the rim (because the rim is bigger) that is gonna cause it to become inaccurate
[ion] C2
03-10-2007, 09:53 PM
why would the weight of the rim alter the sensor's perception of rotation speed? the rim spins the same amount at the axis at any certain speed, it's just heavier.
troyertrain
03-10-2007, 10:06 PM
ummm, it all has to do w/ wheel diameter. the bigger the rims, the slower your gonna go (for example, your speedo will read 55 but you will actually be going 53).

search google for a wheel calculator, actually i think tires.com has one...
[ion] C2
03-10-2007, 10:15 PM
overall wheel/tire diameter, the surface that's contacting the road is what makes the difference, same reason why you don't want to get skinnier tires without having bigger rims. you compensate the difference, that's what the calculator's do, find the tire size that should match up with your rims to make the overall diameter the same as stock.

ex:
15 inch rim with 4 inch of rubber sidewall
16 inch rim with 3 inch rubber sidewall

both equal 19 overall, that's all that matters (sizes not real, just example)
BlackJack
03-10-2007, 11:16 PM
no it wont, it wont be off by much but it will still be off, diameter has nothing to do with it, its the weight of the rim (because the rim is bigger) that is gonna cause it to become inaccurate

alright, it's not often that you step on your own crank, but I'm sure you must have been thinking one thing and said another. It happens.

But as we all know, it's the outer diameter of the tire that will affect the speedo computation.

So, a 15" with stock size tires will read the same as a 16" with low profile tires, provided the outer diameter of the tread is the same dimension.
Redog
03-10-2007, 11:20 PM
Have fun ;)

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