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MERCMAN
03-03-2009, 07:10 AM
http://www.discounttire.com/dtcs/infoTireMath.do


This will compare tires oem VS replacement. VERY HELPFUL!!
Zack
03-03-2009, 07:40 AM
The value (in revs/mile) in the stock pcm is 723.
Tire Rack advertises a 245/55/18 tire as turning 704 revs/mile.

If you visit the BFG website, they too advertise 723 revs/mile
MERCMAN
03-03-2009, 07:59 AM
which means what relative to actual speed VS speedometer reading??
Zack
03-03-2009, 08:07 AM
which means what relative to actual speed VS speedometer reading??


Beats me, ive never done any testing.
ctrlraven
03-03-2009, 08:13 AM
I've always used http://www.miata.net/garage/tirecalc.html

It says the 245/55-18 is 705 revs per mile. So if that is incorrect I wonder what 255/55-18 and 255/50-16 are actually.
MERCMAN
03-03-2009, 08:22 AM
Its a conspiracy. The tire companies put out dis-information to keep the cunsumers confused. I know I am :rofl:
imorb1994
03-03-2009, 10:57 AM
http://www.1010tires.com/TireSizeCalculator.asp
This is the one I use and seems more accurate.
Paul T. Casey
03-03-2009, 11:04 AM
The value (in revs/mile) in the stock pcm is 723.
Tire Rack advertises a 245/55/18 tire as turning 704 revs/mile.

If you visit the BFG website, they too advertise 723 revs/mile

This probably explains the 2ish mph variable in the speedo.
red
03-04-2009, 10:04 PM
Unless tires become perfect circles, calculations that do not consider loading (among other factors) will have more deviation (e.g., from manufacturer revs/mile). One can apply a simple factor to account for loading, as detailed in the Tires article here (https://www.mymarauder.com/wiki/index.php?title=Tires#Revoluti ons_per_Mile), to get a value that will be closer to measurement.