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Tire size

tknight

Veteran Expediter
Offline
My new truck has 10r22.5 tires and I have brand new 11r22.5 drive and steer off my old truck
What mph difference is my speedo going to show , the dealer wants 350.00 to recalibrate it which I think is typical dealer bull crap
I'm pretty sure I can adjust my brain to it!
 

Ragman

Veteran Expediter
Retired Expediter
Offline
My new truck has 10r22.5 tires and I have brand new 11r22.5 drive and steer off my old truck
What mph difference is my speedo going to show , the dealer wants 350.00 to recalibrate it which I think is typical dealer bull crap
I'm pretty sure I can adjust my brain to it!
Too much math needed for this one.
 
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LDB

Veteran Expediter
Retired Expediter
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Do a search for tire size calculator. There are several online. You can put in two tire sizes and it will tell you the difference.
 
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tknight

Veteran Expediter
Offline
I havnt found a calculator that does large size tires, maybe you know of a specific one
 

tknight

Veteran Expediter
Offline
Apparently I'm being challenged here 10r 22.5 and 11 r 22.5 don't seem to be the correct numbers although I have discovered there is a 20 rpm difference per mile lower number being the 11r tire
 

LDB

Veteran Expediter
Retired Expediter
Offline
I don't know of a specific one. I used to use one on a Miata website but it takes Flash or something I don't have so I can't check it. I thought it did all sizes but maybe not.
 

tknight

Veteran Expediter
Offline
Get a GPS and use the speedo on that instead.
I have one just wanted to keep the miles on the speedo accurate ! I don't think it's gonna be that much of a difference anyways it's only 120 less revolutions an hr driving 60 mph
 

greasytshirt

Moderator
Staff member
Mechanic
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I don't know of a specific one. I used to use one on a Miata website but it takes Flash or something I don't have so I can't check it. I thought it did all sizes but maybe not.
Yes, the miata.net tire size calculator. Ive used it many times.
 

greasytshirt

Moderator
Staff member
Mechanic
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Engine rpm at different speeds can be calculated mathematically. You need to know the actual tire diameter (a measuring tape is close enough), final drive ratio, and the ratio of your overdrive gear. You can calculate it in every gear if you want, but you'll need to know the gear ratio of each gear.
 
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