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AR15.COM
5/12/2005 7:19:43 AM EDT
let's say i have a tire that is 32" in diameter.
the spedo says 60MPH.  
what is the rpm of the tire?
how do you show your work?

thanks
5/12/2005 7:25:24 AM EDT
[#1]

Quoted:
let's say i have a tire that is 32" in diameter.
the spedo says 60MPH.  
what is the rpm of the tire?
how do you show your work?

thanks



You need to:
1.  Determine the circumference of the tire (this better be easy, if not you are really screwed).
2.  Convert the circumference and miles to a common measure (inches/feet, whatever)
3.  Determine how many times a tire must rotate to go 1 mile (this is easy division)

The reason for 1 mile is that at 60mph it takes 1 minute to cover a mile, thus this number is RPM's of the tire.

shooter
5/12/2005 7:26:13 AM EDT
[#2]
First find the circumference:  Pi*D

If you are going 60 MPH, you are going 63360 inches per minute (60 mph*12 in/mile*5280 ft/ mi/60 min/hr)...

divide by circumference...

I get about 630 RPM
5/12/2005 7:30:20 AM EDT
[#3]

Quoted:
First find the circumference:  Pi*D

If you are going 60 MPH, you are going 63360 inches per minute (60*12*5280/60)...

divide by circumference...

I get about 630 RPM



Me too:

630.25 (as if that quarter revolution matters)
5/12/2005 8:04:31 AM EDT
[#4]
thanks!
5/12/2005 8:49:40 AM EDT
[#5]

Quoted:
Me too:

630.25 (as if that quarter revolution matters)



It does every 4 minutes.