Author Topic: tire diameter measurment  (Read 488 times)

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Offline Charlie/Susie

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tire diameter measurment
« on: July 14, 2017, 11:38:07 AM »
The tire manufacturer will give you the diameter of their tire not mounted, not inflated and not under load.  This changes as soon as you put it on your rig. My question is how do you now calculate revolutions per mile since your tire is no longer round, remember the contact patch?

Offline Brett Wolfe

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Re: tire diameter measurment
« Reply #1 on: July 14, 2017, 12:34:16 PM »
Charlie/Susie,

Welcome to the Diesel RV Club.

Actually, most RV tire manufacturers will give you Revolutions Per Mile as well as tire dimensions.

What size tire and wheel do you have now?  What other sizes are you considering?

Offline Charlie/Susie

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Re: tire diameter measurment
« Reply #2 on: July 14, 2017, 12:59:54 PM »
Hi Brett,
 The tires are 255/70R22.5. Do you take load and tire pressure into consideration? Do you measure the tire horizontally or vertically?

Offline Brett Wolfe

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Re: tire diameter measurment
« Reply #3 on: July 14, 2017, 02:22:12 PM »
Sorry, I have a really terrible internet connection the next two days, so can't access reference material (each page is taking several minutes to load-- one of the negatives of being on a cruise ship in the middle of the Gulf of Mexico).

But, load/inflation (assuming proper inflation for the load) should have little affect on tire dimensions.  Said another way, the inflation tables are designed to keep the "proper foot-print" for the full range of loads.

Try doing a search for your brand and that tire size.  Likely you will get loaded radius, width, revolutions per mile, etc.

Offline Charlie/Susie

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Re: tire diameter measurment
« Reply #4 on: July 14, 2017, 06:12:51 PM »
Happy sailing Brett,
   Did the search and got some great info. Thanks, this site is a life saver for a new comer like me.

Offline WILDEBILL308

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Re: tire diameter measurment
« Reply #5 on: July 20, 2017, 08:32:53 AM »
I have been doing the research on a couple new tires and found this handy tool.
https://tiresize.com/comparison/
You can get most of this off the different sites but this is easier.
Bill
2003 Bounder 38N,300 HP 5.9 Cummins
Allison 3000MH Trans.Towing 2014 Honda CRV. Home base Fort Worth, Texas
A man who carries a cat by the tail learns something he can learn in no other way.
-Mark Twain-

Offline trekker01

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Re: tire diameter measurment
« Reply #6 on: July 23, 2017, 05:28:51 AM »
Bill,
That is a good on-line comparison tool but doesn't cover any 22.5" tires that I can see.
Gary
1998 Safari Sahara 300 Cat

Offline WILDEBILL308

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Re: tire diameter measurment
« Reply #7 on: July 23, 2017, 07:32:57 PM »
Bill,
That is a good on-line comparison tool but doesn't cover any 22.5" tires that I can see.
Went and followed the link. It worked for me. Just try entering the tire size say 255/80 22.5 in 1 and 275/60 22.5 in 2 and see what it says.
https://tiresize.com/comparison/
Bill
2003 Bounder 38N,300 HP 5.9 Cummins
Allison 3000MH Trans.Towing 2014 Honda CRV. Home base Fort Worth, Texas
A man who carries a cat by the tail learns something he can learn in no other way.
-Mark Twain-