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Thread: Tire diameter increase boosts mileage

  1. #1

    Default Tire diameter increase boosts mileage

    At 120K miles, the factory Michelins that came on the C4500 were shot. Ordered up new Michelins for the rear, and Bridgestones for the steers. Went up two sizes to a 245/70/19.5 on the factory Alcoas.

    Tire diameter is 6% larger, causing speedometer to read 60mph when actual speed is 63. (I plan to adjust this when my Predator programmer with the C4500 tune arrives.) The loaded acceleration from a dead stop is a bit more sluggish than usual, but nothing noticeable from there on up to cruising speed.

    Cruise RPMs are ~1900 at 58 mph, not a bad speed in the right lane when you are 12' wide towing 36' of boat!

    So far, it looks like mileage is getting a .5 -.7 mpg boost. Need more miles and boats to have a meaningful average, but its enough of an increase to be noticeable on this first trip out.
    2011 Chevrolet Tahoe 5.3L daily driver
    • Previous owner of two 1994 6.5L K3500s, '01, '02, and '05 6.6L K2500s, '04 C4500, '06 K3500 dually, '06 K3500 SRW, '09 K3500HD SRW, '05 Denali
    • Total GM diesel miles to date : ~950K

  2. #2

    Default tire size

    Did you have any fit/rubbing problems? I just bought an 05 c4500 and it needs some new shoes. What do you recommend?

  3. #3

    Default

    Quote Originally Posted by jelly77 View Post
    Did you have any fit/rubbing problems? I just bought an 05 c4500 and it needs some new shoes. What do you recommend?
    Over the years, I've run BFGoodrich... Cooper... Firestone... Bridgestone and Michelin.

    The best tire overall... in terms of traction, comfort and tire wear have been the Michelin LTX M&S. I get 80K to 100K on each set. I rotate them every oil change and keep them properly inflated.

    2009 GMC SLT 3500 Xtended Cab 6.6L
    Lubricated By Rotella T-6 and Amsoil EAO52 Filter

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