4WD tractor wheel sizes

Milton09

Looking for advice here, if you have a 4wd tractor with 24" front and 34" back wheels (from factory), can you change the wheel sizes to 28 front and 38 back? If you do the calculations the wheel circumference ratio will not be the same, so can it be done or should the front axle or gearbox be changed to do it properly?

pajero12

Yeah should be no problem..We put 38s on the back an 28s on the front to fit the twins for bucking up! Had no problems!

JohnBoy

I would say no, if the ratio's not the same you're asking for trouble.

you could get away with it on slippery surfaces but if you get too much traction going on you'll suffer from transmission wind up, and break something, probably something expensive.

you have to keep the ratios very close to original.

Milton09

JohnBoy wrote: »

I would say no, if the ratio's not the same you're asking for trouble.

you could get away with it on slippery surfaces but if you get too much traction going on you'll suffer from transmission wind up, and break something, probably something expensive.

you have to keep the ratios very close to original.

I would agree, i'm looking at a 2nd hand 100hp massey that would normally be fitted 24/34 but this one has 28/38, cannot tell if this was a factory fit or not at this stage.
When you do the calculations you get a 4.16% difference in the ratios!

JohnBoy

Hmm, 4% doesnt seem like that much, but I dunno.

You might get some better answers to machinery questions on here

http://farmingforum.co.uk/forums/forumdisplay.php?f=20

Casinoking

Milton09 wrote: »

Looking for advice here, if you have a 4wd tractor with 24" front and 34" back wheels (from factory), can you change the wheel sizes to 28 front and 38 back? If you do the calculations the wheel circumference ratio will not be the same, so can it be done or should the front axle or gearbox be changed to do it properly?

Absolutely not, if the ratios are different you'll have all sorts of transmission problems in no time at all. Get a copy of the operators manual for the tractor, it will have a list of the suitable tyre combinations. Don't stray from them.

Milton09

Made an inquiry with Massey, they sent me a very speedy and informative reply as follows :

You can fit the MF5455 with a 38 and 28 wheel combination and the most common size will be 420/85R38 with 340/85R28, this is offered as a factory fit option. There is no need to change the gearbox as the front axle turns faster than the back when 4 wheel drive is engaged, and this allows different tyre combinations to be used, and also means that the tractor pulls correctly when in conditions where 4 wheel drive is required. We refer to this as front lead. We recommend a minimum of 1% to a maximum of 5%

JohnBoy

nice one.