Larger Rear Tire effect on Pulling Capacity

[jrkendall]

I am thinking of running a 7-14 rear ag tire on the back of my 129 and was wondering what the effects were on available pulling capacity. I know a lot of you run 26x12x12's on the back and they are within a 1/2" radially. The ratio works out to be roughly 85% theoretical tq output to the ground because of the change in tire size.

I know this doesn't affect torque to the rear end (at the axles) but it does affect the pulling capacity (ie torque applied to the ground). Think of this as how doggy your truck feels after putting on bigger tires and not regearing.

Did anyone notice a difference when changing from their 23x8.50's to 26x12's when plowing or hauling a heavy load. Obviously the increased contact patch helped with traction but that will not benefit me since these tires are only 7.5" wide. I just don't want to put these on and find out I'm lacking applied torque when plowing or pulling something heavy.

Thanks!

[CADplans]

85% of the torque

but,

50% of the traction.




The big factor is the clutch, put enough weight on the rear, the 118% load on the clutch will cause slippage there before the axle fails.

The Colt had 3/4" axles and were known to fail, but, many are still operating. The Cub has 1" axles. I have seen no requests for axles in the want ads, other than fine splines for pullers.

I have been thinking about 27" tall rears on a custom Cub. High gear would only be for transport, not pullin'.

[jbollis]

The 129's have a hydro tranny. Infinite gear ratio.

[Matt G.]

I have heard of a handful of people twisting off coarse-spline axles after switching to 26" rear tires, so it is possible if you're able to get the power to the ground. That's an odd size to switch to...what are you trying to accomplish?

[CADplans]

OOps, I missed 129, hydro, no axle issues IMHO, unless excess weight is added to the rear of the tractor.

[jrkendall]

I am mostly going for the looks. The rear pan was beat up on the 129 so I'm going to make some bolt on rear fenders from a Power King (round). However I did not want to give up the pulling power due to a larger tire. I do plan on adding liquid ballast to the tires and some wheel weights. I don't plan on being stupid with it but I don't want it to be a dog while plowing either.

I know it's a strange idea - the mechanical engineer in me loves to experiment and run hypotheticals before making a purchase

[jrkendall]

Would anyone who switched from 23's or 6-12's to 26's like to comment on how it made their tractor operate? IE did it make the tractor feel noticeably less powerful or have trouble pulling / pushing a plow?

[jlampe94]

I have 23x10.50-12 and they seem fine, i plow with a 10inch brinly and plow snow with it. Did have 8.50's on it and theres not much difference if any.

[jbollis]

As I mentioned before. You have a hydro trans, therefore you have a theoretical infinite gear ratio. The gearing difference between the GT's with 23 inch tires and the Supers with 26 inch tires is only 2 teeth.

I seriously doubt that going from a 23 to 26 inch tire will make that noticeable of a difference on a hydro. On a gear drive maybe.

There are plenty of guys running 26's on reg GT's that plow and everything else with them, with no problems.

[green 4 acres]

Originally Posted by jrkendall

Would anyone who switched from 23's or 6-12's to 26's like to comment on how it made their tractor operate? IE did it make the tractor feel noticeably less powerful or have trouble pulling / pushing a plow?

I just switched to 26x12's the circumfrence of the 23's was 68 in the 26 is 81 in I wanted a higher speed in 2nd the 128 (gear drive) seemed very low geared for my likeing and use ,barely different than 1st . your torque will be lower to the ground but there is the inertia factor the 23,s weigh 19 lbs the 26's = 74 lbs mine are loader tires
I found that plowing before worked better with a little more speed and pushing the weight around ,not using the drive train exclusively for power

128