38 and 42 inch rears

Discussion in 'Machinery' started by nick..., Jan 13, 2019.

  1. nick...

    nick... Member

    south norfolk
    what are the benefits of bigger over smaller tyres.are the 42s a lower aspect ratio to remain the same circumference as the 38s.is traction better on either or is the weight carrying capacity and ride better on one over the other.seems several 150hp tractorsare available with either size.just wondering,thanks
  2. Tarw Coch

    Tarw Coch Member

    I would think rim size is a byproduct of tyre size choice, a larger circumference will give a longer footprint but air volume also affects ground pressure/tyre pressure so for example a 800/65r32 has a similar rolling radius to a 650/65r38 or a 20.8r38, the more air volume the lower pressure the tyre can be ran at .
    Don’t think I’m explaining this too well so will give up now.:(
    Gordy1 likes this.
  3. fred.950

    fred.950 Member

    42s generally look better (y)
    ColinV6 likes this.
  4. Clive

    Clive Staff Member

    38’s put more air volume under the tractor but generally don’t have the load / speed ratings at lower pressures that 42’s do
    Gordy1 and fudge like this.
  5. Boohoo

    Boohoo Member

    Bigger rims look better, bigger tyres are better for the soil and carry more weight at a given pressure. Given the choice between 650/65r42 and 650/75r38 take the 42s if you care about looks and the 38s if you care about your soil.
    Gordy1, C.J, Cloonpotatoes and 5 others like this.
  6. cvx175

    cvx175 Member

    42s are better if you're doing a lot of road work not just about the look of them
    fudge likes this.
  7. kill

    kill Member

    South West
    But the 42's will also be alot cheaper to replace.
    KB6930 likes this.
  8. ColinV6

    ColinV6 Member

    When we bought our T7, we looked at one with 28’s and 38’s and 540/650’s and it looked half the tractor of the one on 30’s and 42’s.

    Maybe a bit vain, and I’m sure there are other benefits, but even Dad agreed and was asking if the one on 28/38’s was a smaller model tractor :ROFLMAO:
  9. mo!

    mo! Member

    Consider 620/70r42 as an option as well. I wish we'd bought the T7 on 650/75R38 rather than the 65 profile.
    Chae1 and Boothy like this.
  10. Boohoo

    Boohoo Member

    True, but if cost to replace is the main consideration something on 16.9x34s might be more appropriate
    Cloonpotatoes and Nearly like this.
  11. Exfarmer

    Exfarmer Member

    Bury St Edmunds
    I never would have beleived, I would come across farmers discussing the benefits of looks above traction and compaction!
  12. HarryB97

    HarryB97 Member

    Only worth having a 42 inch rim if it has a big tyre on it like a 710/70 or 710/75 otherwise you dont have enough air volume in it to run it at low enough pressures. Amazes me the amount of new tractors that people spec on tyres like 650/65/42 or 710/60/42 bad ride, look terrible and generally run at a higher pressure
    cosmagedon likes this.
  13. 09AD2308-2F09-4385-BA2C-27C499F81E4C.jpeg Run 650/75/38 & 600/65/28 on a Puma CVX 165. Took advise from Redpath tires when purchasing the tractor and they sent the Michelin rep out to weigh the tractor with all bits of kit we use on it which provided me with all the info I need when doing thecsaid operation. Happy so far with the choice.
    Rob Graham, Gordy1, Gerbert and 7 others like this.
  14. Speedstar

    Speedstar Member

    Scottish Borders
    We have a set of 710-60-42 have done over 8000 hours now and never had more than 14psi in them , ride is great on the road even as low as 8psi in them. Only thing with tyres that size do not put them on a tractor bigger than 200 hp as they are not rated for that hp
  15. cvx175

    cvx175 Member

    Really? trelleborg rate them for up to 300hp
  16. Speedstar

    Speedstar Member

    Scottish Borders
    Not xeobibs from Michelin 200 hp tops
  17. dazza b

    dazza b Member

    You have to go onto axio bibs above 200hp I think they are the same as xeobibs but rated for higher hp if that makes sense
  18. Boysground

    Boysground Member

    I swapped my drill tractor this autumn. Gone from 650x42 to 650x38. Tractor is near enough the same weight as the old one and it is noticeable (light chalk soils) that there is less mark from the new tractor.
    A few years ago I went on a vaderstad drill training thing. I remember the guy there saying how often people forget to get the right front tyre and that they had data to suggest the front tyre often caused more compaction than the rear. I have gone from 540 to 600 on the front.

    Most importantly I like the look of a big tyre on a 38 inch rim:)

    Exfarmer, Gordy1, clem dog and 2 others like this.
  19. farmerbill

    farmerbill Member

    Was the OP meaning (for example) 650/65R42 VS 650/65R38 or tyres of the same circumference IE 650/65R42 VS 650/75R38?
    snipe likes this.
  20. General-Lee

    General-Lee Member


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