7840 tyres

[WPL]

Hi all. Recently bought a 7840 tractor and want to get a new set of tyres for it. Problem is that I’m not sure if it has the right sizes already as it gets very stiff I’m 4wd. It has 16.9 r 38 on the back and 12.4-28 on the front. It has the newer type fiat front axel. Any advice appreciated. Wouldn’t mind going up a size either..

 

[agrimax]

It shouldn't really have 28s on the front unless the driven gear in the drop box has been changed to allow it. With those rears I think it should have 13.6x24s on the front.Others will know more but I'd guess 18.4x38 and 16.9x24 or the metric equivalent will work but you would still need to know the number of teeth on that gear in the drop box. IIRC, one has 37 and the other has 38 teeth but I can't recall which is for what size!!

 

[forblue]

F/ 14.9x24, R/ as above, it will feel stiff if you try 4 w/d on hard surfaces,as the only time this automatically engages is when using on the road with locked headland brake pedals which will as cnh states give you 4 wheel braking, slight bending of being true.

 

[Boohoo]

If you go up to 18.4r38 or equivalent on the rear you'll need 14.9r28 or equivalent on the front. 7840s on 28s are rare but not unheard of, you could order them that way when they were new. Would be worth checking the drop box, I know of a TS115 that was on 24s but had the gear for 28s in it.

 

[WPL]

Thanks for your reply’s lads. Very helpful. Just another quick question. How do I check the ratio of the drop box. There doesn’t seem to be any plate or numbers on it anywhere. Thanks

 

[40 series]

Normally a plate with a number on the inside of the bonnet anytime i was trying to sort ratios out for tyre sizes on them