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speed increace with 53's or 395's

SCRAP

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on an m813 cargo, what kind of speed increases will you get with 395s or 53 inch michelins, truck has nh250 cummins , I want to run 6 super singles on the truck. thanks
 

M813A1

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I got a 8 mph gain is what I got on my M813 when I had 1400X R20's super singles on !! But I did loose pulling power because of the lack of Torque lost because of the taller tires !!
 

Hammer

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Whoops, when I put the 16.00's on it...
Kind of an important fact to leave out.

It cruises well at 60 to 65 mph. But really lacks the power when I want/need it.
 

gringeltaube

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on an m813 cargo, what kind of speed increases will you get with 395s or 53 inch michelins,.........................
Assuming you are running the 11.00-20 NDTs?

Looking at the Michelin XZL specs chart below... and also assuming that 11.00-20s and 11.00R20s are very close considering loaded radius and revolutions per mile...


then, at constant rpm, 52 mph would be increased to:
  • 56mph with 395/85R20
  • 60mph with 14.00R20
  • 63mph with 16.00R20
G.
 

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Hammer

Well-known member
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Well, my gps was reading 71 mph, but the tach was around 2300 ish. Didn't pay THAT close attention, just know that was where it topped out at.
Still, 63 mph sounds too low for 2150 rpm. But maybe my tach isn't so accurate....
 

Westech

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cow farts, Wisconsin
If your worried about MPG's in a 855 Cummins 5 ton.. maybe its time to buy a Honda.

I got 7-8 in my 5 ton with 11:00 tires... I would guess about the same plus or minus 1 MPG with my 14:00's
 

spicergear

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Another thing to consider is crawl speed. When I went from 1100x20 (measured 42") Goodyears on my Rockwelled M715 (Velvet) to 395/85 XML's my crawling speed increased a LOT. May not matter to a strictly road guy but if you're slow go or on trails...expect a speed increase. A low idle didn't have the power to pull you over objects like it had with the 42's. I adjusted my choke cable so that it would tip the throttle butterflies a bit ahead of the choke blade so I could use it to increase my idle so I wouldn't be struggling trying to drive all two feet on three pedals. It still got a bit bumpy as you'd carry more speed up a rock and drop hard on the other side...
 
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