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Old 04-22-2012, 07:46 AM   #1
Join Date: Nov 2011
Posts: 38

I need advice/opinions on changing tire sizes.I have a 97 dutchstar dp,currently have 245 75r 22.5 on it,am thinking of going to 255 75 r 22.5.Its a more common size and les expensive. any ideas?

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Old 04-22-2012, 09:23 AM   #2
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Welcome to the forum.

Things to consider. Your rim width is important so make sure that your rim width is compatible with the tires you select. Mine are 7.5 inches

Changing tires may affect your speedometer. You can always check it with your GPS after you switch.

Old 245/75Tires
245x.75 = 183.75mm tread to rim height
Tire diameter =(183.75x2) /25.4 + 22.5 =36.965 inches

New 255/75
255x.75 = 191.25mm tread to rim height
Tire Diameter =(191.25x2)/25.4 +22.5 = 37.559

So your new tires have a larger diameter and your speedometer will read low about 1.6 percent compared to your old tires.

My rig used to have 235/80 22.5 on them and when one blew I could not find one on the road in the big town of Jackson Ms so after a lot of talk I
relunctantly switched to 255/70's because they are a very common tire with a much higher load rating. Also I ws stranded at the time. And less money since they are common. My ride is a little rougher because of the reduce tread to rim height but my air suspension makes it almost unnoticeable. My speedometer reads about 2 percent high but I just put correctlion into my VMSpc.

Good luck on your selection

98 Endeavor DP, ISB275
RX300, Falcon II hitch, BB Vantage Select
VMSpc, 2002 Grey Ford Powerstroke
TST 507 w/ 10 Sensors
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Old 04-22-2012, 03:56 PM   #3
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Some good site to look at what the difference will be:

Tire Size Calculator: Tire size calculator
(if you don't want to use java, click on the link for the "older version).

1010 Tires gives the best information, but you have to use "22" or "23", because it will not take "22.5". Again, very detailed results: Tire Size Calculator - tire & wheel plus sizing

EDIT: Your difference appears to be "1.6". So you will be 1.6 slower on the speedo (bad for radar traps) and 1.6 less on the odo (good for warranties).
Dewey & Sharon
Southern Maryland suburbs of DC
2015 Tiffin Allegro Bus 45LP
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