Do skidder tires all have to be the same size?

[Horselog]

I have a C5D Treefarmer, and I'm in the process of getting some new tires for it.  I've heard that all the tires have to be the same size, or at least that if you do have different size tires they should be on the same axle so that the differential can take care of the size difference.  To say it another way, I've heard that there is no diffential between the front and rear so if you have two tires on the rear that are bigger than the two tires on the front you could potentially mess up the driveline.  Anybody have thoughts?

[Ed_K]

I know my taylor skidder has to have same size tires 18.4-34s as the lower drive line is direct to both axle baskets.Maybe they ment 25% front 100% or new on back wouldn't hurt the axles to much.

[PAFaller]

Yes if you get new tires you want to get 2 and put them on the same axle. You dont want a wore out tire on say the left rear, and a brand new one on the right rear, it will wreak havoc on the differential. I think it would be especially bad in a locked up axle, like what is in timberjacks and most likely your C5. A slight variation probably wouldn't do too much, I know I had one tire that seemed to wear faster than the other in the back, but not inches of difference either.

[coxy]

got a jd 440 that has one new tire and one window smooth on back for over a year no problems so far  ran my case 300 with one new one smooth on back no problems with pr 75 axles     jmop    its yours do what you think is right ;D

[thenorthman]

I guess to clarify you mean, putting on new tires of the same size, so they would be slightly larger correct?  If that's the case most everyone does that, who can afford to buy 4 tires anyway (if ya can, can I have a loan?) A little bit of difference isn't so bad as long as your not getting super good traction one axle will slip a bit,  same thing with going slightly different from one side to the other on the same axle, as long as the difference isn't huge it should be OK.  Its not real good for em but you can get away with it as long as everything is in good shape.

Now things get a little funny when you start changing tire sizes, say one side is a 18.4 x 26 and the other is 18.4 x 30... bad things will insue.

As far as the rears on a jd 440 unless its a power lisp or a funny syncro rage... then the rear is a straight axle anyway, and then you'll just have a tendency to turn towards the smaller tire... especially under load

[Okrafarmer]

The closer they are in size the better. I've read in a construction magazine that if the tires are more than 3% different diameter on the same axle, it can cause the differential to overwork. This assumes, I suppose, that the machine does a lot of straight-line travel. If you are constantly turning anyway, the diff will get a workout regardless.

Note that the difference of 3% between two tires can be the difference of two tires the same nominal size, but one has new tread and the other has been worn down bald.

As for differences front and rear, you definitely want them as close as possible front and rear, because if you don't, one axle will be trying to go faster than the other, creating a bind. That bind puts undue pressure on every part of the drive train, from the drive shafts, differentials, axles, wheels, on down to the tires. The tires will wear out much more quickly, and the metal drive components will be stressed, possibly resulting in premature breakage sometime, sooner or later.

The terrain you are working can be a factor. If you are skidding in the mud or deep snow constantly, it won't matter as much as it will if you are on hard ground.

[loggah]

When ever i got new tires i would put the new pair on the back axle and the used ones on the front. this way under a load or heavy pull you dont have much weight on the front axle allowing for more slippage of the tires to ground,this helps compensate for the uneven tire size and less strain on the driveline. In the perfect skidder world all tires should be the same size!!! ;D ;D Don

[bill m]

When ever i got new tires i would put the new pair on the back axle and the used ones on the front. this way under a load or heavy pull you dont have much weight on the front axle allowing for more slippage of the tires to ground,this helps compensate for the uneven tire size and less strain on the driveline. In the perfect skidder world all tires should be the same size!!! ;D ;D Don

I would have thought just the opposite to be true. With new tires on the rear and the weight of a full hitch I would think the back would get better traction and the front would spin. Not good for the drive train.

[Ed_K]

No the fronts aren't wearing at all,their off the ground  ;D :D .

[loggah]

Bill, what i ment was the front would spin,and yes sometime they were up in the air !! ;D ;D and when that happened it was time to winch or lower the grapple. Don

[northern2bodies]

just my point of view,if you have chains up front and no chains on back,does anyone worry about it?
i have run my skidders and fowarders with chains on all 4 and sometimes only up front with no problems at all(34 yrs of O/O)

[loggah]

I always ran chains on all 4 wheels, running chains on one axle and not the other is almost like running 2 different size tires, i usually ran double diamond front and rear. Don

[Horselog]

Thanks for all the input.  Yes I am talking about all the same nominal size, with different amounts of wear on each tire.  I have all 23.1x26 tires ranging from maybe 30% to 60% or maybe 70% on one.  When I bought the machine (recently), the rear axle had one at maybe 70% and the other at maybe 25-30%.  The bigger tire would slip on turns, and the machine would not want to turn sometimes.  I'm wondering if it had to do with the different sized tires. 

I recently replaced the smaller rear tire with one at about 60%, I will drive it for the first time in a day or two.  I'll be interested to see if it behaves differently.

[gwilson]

My machine has all the same size tires, but on four different rims. I have two timberjack rims, a clark, and a john deere (based on colors) all the rims have the same pattern and outer size but different dish depths. We joke and say im strategically running a dirt tract set up.  ;D

[cutter88]

i think they should be the same some guys even say u shouldnt put a new tire on the same axle as a bald one...

[Okrafarmer]

Definitely better not to. But If you need to in a pinch, like for a few days or weeks, it is probably better to get it on there and get back in the woods until you can make enough money to pay for the other new tire.  ;)