Anyone have firsthand experience going from 22.5's to tall rubber tires?

Discussion in 'Ask An Owner Operator' started by Farmerbob1, Oct 16, 2019.

  1. Farmerbob1

    Farmerbob1 Road Train Member

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    Backstory:

    I have a 2016 Freightliner with a DD15 motor, an Eaton 10 speed manual transmission, and a Detroit rear end. Unsure of the ratio. The truck is governed at 67 MPH until I pay it off.

    After I pay it off I would like to bring up that governed speed to 72 on cruise, and no limit on pedal.

    The problem with that is that the engine runs @1450 RPM at 67 MPH. at 72 MPH rolling hills, she's close to 1600. That's too many RPM for continuous operation, I think.

    The transmission has enough pull that I almost never need first gear even with I have 45k in the box.

    I figure if I put tall rubber on the truck, it will require that I use first gear more, but it will also allow me to hit higher speeds without cranking the RPMs so high.

    I have already spoken to Crete about this, and they have indicated that they have no issues with tall rubber on o/o trucks, even though all their trailers run 22.5's.

    From the point of view of an o/o, is there any significant extra wear and tear on the truck hauling a trailer with low profile tires behind a truck with tall rubber? Does the rearmost drive axle take significantly more weight? It will take a little more. Physics says so, but I don't know if it is enough to make a real difference.
     
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  3. starmac

    starmac Road Train Member

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    I have replaced low pro 2.5's with tall 22.5's, no problem with wear and tear. It did seem to cost me a hair in mileage, not much, and a hair in power, but again it was negligible

    That was a 12.7, 13spd and 370 rears, and she ran 1500 at 65. The computer on the dash claimed optimum speed for mileage was 70 at 1630 rpm, I took that with a grain of salt.
     
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  4. 062

    062 Road Train Member

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    Switching to tall rubber will drop you roughly 75 rpm or gain 3 mph. Just depends how you look at it.
    You can enter your numbers into a road speed calculator and get a better idea.
    I bought a set of Chinese drives that should have been 42” but were actually 41.5”
     
  5. Long FLD

    Long FLD Road Train Member

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    The weight on your axles will be the same as it is now, your 5th wheel is in the same spot. The difference in height of an inch or so won’t hardly be noticeable to the naked eye.

    Edit to add: The guy I pull for runs tall 22’s on everything. I run lo 22’s on my truck and without looking at the sidewall the difference isn’t noticeable.
     
  6. 201

    201 Road Train Member

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    IDK, with rims and tires, looking at several grand, is it really worth it? If you ruin one on the road, good luck finding a used one. Not many folks run tall rubber anymore. I'd probably leave it alone.
     
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  7. Long FLD

    Long FLD Road Train Member

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    Wait, he’s wanting to go from low 22’s to tall 24’s?
     
  8. 201

    201 Road Train Member

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    If they go that route, be easier hooking onto wagons. I remember years ago, all company trucks had small rubber, and it was a pain hooking a wagon that was dropped by someone with tall rubber, especially loaded in 5 degree weather. Lot of "high hooks" back then.
     
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  9. 062

    062 Road Train Member

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    The way I read it was 22.5lp to 11r22.5. Going to 11r24.5 will make a difference. Roughly double what I posted earlier.
     
  10. Long FLD

    Long FLD Road Train Member

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    That’s the way I read it too but thought maybe I interpreted it wrong.
     
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  11. snowwy

    snowwy Road Train Member

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    Looks like he wants to go low to tall.

    Anytime the diameter of the tire is changed. You change the accuracy of the speedo also. Keep that in mind.
    Same falls inline with tire wear. New tire vs. worn out tire. As the tread wears down, the tires spin faster.

    Won't notice it much on trucks. But if you have a motorcycle with a tachometer. You'll defenitely see a change.

    It's also a good idea to keep all tires same size. It effects brakes. Drums won't spin quite as fast on a tall tire vs. low tire. Again. Probably won't notice much. Between low and hi.

    My truck has hi 22 on the drives and drop axle. The steer has hi 24. The trailer has low 24. Brakes work good. But could be better if all the tires were the same size.

    And for those that don't believe. Back in my wrenching days. I put small 15's on the front. Tall 15's on the back. Lower the front end. Raise the back end. Brakes ROYALLY sucked.

    My truck is governed at 72. GPS says 74 new tires. It's down to 73 now that the tires are getting close to replacement.
     
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  12. Farmerbob1

    Farmerbob1 Road Train Member

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    Not immediately. I have 110k miles on my drives right now. They still have plenty of tread, but I'm looking ahead for replacement on the same rims.

    When I get my next truck, I might consider 24s, maybe.
     
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