Tire size/roll out
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Post Fiend
Joined: May 2006
Posts: 10,007
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From: Central Florida
Tire size/roll out
I have to write a new tune for my new tires. The new tires are pretty close, with in about an 1" of the one I had tuned around. Size doesn't appear to be important, because I had 35s but my tune was closest with 36.5" diameter.
Is there an easy way to calculate roll out or do I have to trial and error it?
Right now, 25 on speedo is 29 and 52 is 55, I am comparing it off my GPS. I am going to figure
52/36.5 = 55/x for about 38.5 to get my top end right.
Is there an easy way to calculate roll out or do I have to trial and error it?
Right now, 25 on speedo is 29 and 52 is 55, I am comparing it off my GPS. I am going to figure
52/36.5 = 55/x for about 38.5 to get my top end right.
Former ******
Joined: Feb 2008
Posts: 138
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From: Winder, GA
What software do you use and what does it give you as far as Tire Size adjustments? Is it inches, mm, revs per mile?
Normally, I'd say use the three-roll method to get your rolling circumference and use that for your setting.
One thing to remember, the speedometer nearly always read 2 MPH faster than what the ECM is actually sending. I don't know for sure why this is, but if you were to get your needle dead-on then the ECM would actually be 2 MPH slow and your odometer would be off a small percentage.
Let me know...
Bill
Normally, I'd say use the three-roll method to get your rolling circumference and use that for your setting.
One thing to remember, the speedometer nearly always read 2 MPH faster than what the ECM is actually sending. I don't know for sure why this is, but if you were to get your needle dead-on then the ECM would actually be 2 MPH slow and your odometer would be off a small percentage.
Let me know...
Bill
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Post Fiend
Joined: May 2006
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From: Central Florida
I am using Sniper Special Forces, I have adjustment from the mid-20s to 42" I think.
That's odd about the speedo, so how do LE agencies get the speedos certified/calibrated?
That's odd about the speedo, so how do LE agencies get the speedos certified/calibrated?
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