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Thread: Original tiredimensions 1997 NH7840SLE?

  1. #1
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    Original tiredimensions 1997 NH7840SLE?

    Hope You gentlemen can help me out on this one:

    I am about to put new tires on the mentioned tractor.

    It now wears 480/65-28 and 600/65-38. They wear very uneven, and the front is approaching slick while the front is 70%? It had way to much forespin.

    What was the most common original tires on the tractor to begin with? This is an import from England. I have checked and have no idea What tires were original.
    This tractor had the Fiat-type front axle if that makes a difference?

    Did NH use different transferboxes?

    Possible to measure in some way to find out What tires would be the best?

    i was hoping 540/65-28 and 650/65-38 would be the ticket, maybe doing 60 profile on the front wheels?

  2. #2
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    Re: Original tiredimensions 1997 NH7840SLE?

    Look on the front axle for the makers plate which should have the gear ratio between the front and rear axles. With this info you can work out what tyre combinations will work ok. I expect there wasn't a standard size ex factory, but there would of been a range of preferred combinations that could be ordered as part of a new build but there would also be other options possible- in these cases it wasn't unusual for the tractors to be shipped on "slave" wheels- ones often used at the factory for export orders where shipping was often less wheels.

    We had a combine from NH come on rear slaves and our dealer had what we wanted made up and fitted here in the UK- the slaves then were shipped back to the factory.


    Usually the front tyres should lead by 2% any more and it will create inter axle wind up of the transmission and scrub tyres out quickly.


    Found this calculator tool on an American tire manufactures site- you should be able to work out what your existing ones are once you have the rolling circumference of them - that will give you the lead ratio your on now. I expect they are leading too fast- ie 4% or more?

    https://www.titan-intl.com/resources...Lag-Calculator
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    Re: Original tiredimensions 1997 NH7840SLE?

    Thank you for excellent advice!

    If I mark the front and back tires, and run one of the wheels one revolution in 4wd, I can also find the difference? Or...?

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    Re: Original tiredimensions 1997 NH7840SLE?

    Quote Originally Posted by Hill-farmer View Post
    Thank you for excellent advice!

    If I mark the front and back tires, and run one of the wheels one revolution in 4wd, I can also find the difference? Or...?

    Being pally with the brilliant Michelin Rep we had, I'd give him the details of tyres and ratio off the plate and he would work it out as part of the estimate for new tyres unless we were 100% sure they were correct.

    I'm pretty sure that you measuring the distance one revolution by each tyre/wheel will give you the exact rolling circumfernece- different pressures and loads will affect the figure so to get it as near to perfect it needs to be loaded and the pressures set to give correct results, then you can calculate it with the web tool mentioned above.
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