I now have 215/70/15 if i increased my rear tire size to 255/70/15,with 3.55 Ring Pinion on my 1948 1/2 ton, at normal high way RPM i now go about 50 MPH.I do not have tac or working speedomiter. If increase my tire size to the 255/70/15 how much will my MPH. increase? And will the tires fit my wheelwell ? I saw that tire size on truck like mine, but i never talked to the ouner.Thanks
8.2% faster at the same RPM. So the RPM that gave you 50 MPH on the 215 tires would give 55 with the 25 tires.
Tires & MPG Actually that would reduce your fuel economy because the outer diameter of the tire would be slightly smaller and yes , less than 1/4" makes a big difference . What you are looking for is about a 30" diameter radial LT tire , each different brand will be different even with the same size rating so it pays to take a tape measure or ask the seller , tire dealers have the diameter info in the tire catalog . Be aware they'll always try to sell you what's in stock or has the largest profit margin . IIRC my best fuel economy came with LT215/85/16 radials , they were a bit tricky to find because most salesmen didn't want to order them in , America's Tire Store and one other I've posted but forgot the name of , actually stock them for the basic Gardener's / Tradesman trucks . I used and really like Daytons , after 40,000 miles of hard Commercial Service they still looked new . DO NOT buy by price ! you'll wind up with a cheapo tire that fails in a year or so , BT , DT , lo$t my @$$ by being cheap .
I don't understand Nate. OCG said that he had 215/70/15 (26.9" diameter) tires and asked about 255/70/15 (29.1" diameter) tires. That would make the 255 tires 2.2" (8.2%) larger in diameter. I agree with everything else you said about using the LT tires. Also, OCG really doesn't want those 255 tires on the front wheels of his truck. Really hard to turn, especially when standing still. I know, my old '57 had 255s on it when I bought it. If OCG wants to stick with his 15" wheels, maybe 215/85/15 would be the best bet. They are about 0.3" larger diameter than the 255s, so about another 1% increase in speed at any given RPM. I don't know if they are available in LT.
GPS, GPS, GPS. It has made the speedometer issue so easy to solve and is dead accurate no matter what gears or tires you have. Once you are satisfied with the performance with the tires and gearing you have use the GPS to show how much the speedo is off (percent wise) and get a set of drive/driven gears that will increase/decrease your speed by that percent and your home free. I'm so lazy I run around with the GPS stuck to the dash for months before I finally decide to get greasy swapping out speedo gears.
I agree with both of you guys about the GPS, but Old Chevy Guys question was "I now have 215/70/15 if i increased my rear tire size to 255/70/15 ....... how much will my MPH. increase? ". That is what I answered
Maybe you need to draw those guys a picture Just thought I'd mess with someone today. Haven't done that in a while. No offense..
http://www.powerblocktv.com/resources/ You would have around a 250RPM difference. Probably less than a 5 MPH difference.
