Rears *Too* Heavy?

[webbmeister]

Well, I mowed the neighbors yard for him, and the same swaths of brown grass that I get on my property also appeared on his. I had assumed that the brown tire marks on my side were from the 4wd pulling the grass as the tractor held its own going down steep hills and being agressive going up the steep hills. Maybe I'm wrong! Can tires be too heavy?

Thanks,

Jim

 

[tc35dforme]

Meister... Yes and No !! The total weight of the tractor is the force that is applied to the contact patch at the tire/ground meeting point. The weight usually isn't too well balanced on a tractor and you'll see a bunch more weight on the rear. The tire weight and the fill are only part of the equation. What do you have for tires ?

Next question ... Is the grass dry ?? ...I mean in need of rain. If so, the grass 'leaves' may be crunching and breaking under the weight and not just folding and springing back. You can get the same effect from foot traffic believe it or not.

Two times grass isn't happy being crushed...very dry, and frozen ( frost ).

You may do better mowing in the morning before the sun has a chance to de-dew the grass fully. Your quality of cut may not be the best, but you won't harm the grass as much !!

 

[JackIL]

W,
Check the inflation pressure in your tires. For most compacts with a mid-mount deck, the pressures should be in the neighborhood of 12-14 psi front and 8-10 psi rear. The pressure (pounds per square inch) on the turf is just a little (1-2 psi) higher than the inflation pressure in the tires. It is this contact pressure that has the potential to damage the turf as well as generate soil compaction.

If you are mowing on flat ground, it is not necessary to use 4WD--on hills that is another matter. When turning with the front wheels engaged, you will need to make wide turns to prevent tearing the turf.

Jack

 

[Anonymous Poster]

Hi,

My rear tires are loaded and I cut the grass recently with a RFM and had no problem with browning tire tracks on the grass. It has been VERY dry here, by the way. The loader and the backhoe were not on the machine at that time.

Then I used the kubota B2910 with the loader and backhoe on to carry some cut tree away from behind the house, and I later noticed brown tire tracks...but narrow ones from the front wheels. I don't think I was using four wheel drive at the time...almost certainly not...but he marks are there...

So for what its worth...my rears are R4 running 12 psi. Have to check the fronts which are also R4s...seems like the weight of the loader plus wood made a big difference on the grass.

I don't see any marks from the rears though, even with the added weight of the backhoe on the machine...

Hope this adds something to the discussion!

Bill in Pgh, PA...almost...

 

[frank_f15]

has been very dry here in western ny, my 2400 leaves marks just runinng over grass, if in 4wd and turning it is worse, i am running r4:s don't really think it is a case of too heavy, even my 18 hp garden tractor lays the grass down. actually my walk behind trim mower leaves some marks in the grass. but all is ok the next day.

 

[Steelfan]

Hi Jim,
I get some of that too with my TC21D also. Mine goes away also the next day. Now a question, is your grass growing out there? I haven't mowed for 3 weeks, and there's no sign that I'm going to have to do it for a while. No rain to speak of around here in a month. My seat time is very very low. Catch you later, Kent

 

[MReeter]

Webb,In most cases when a compact is in 4WD the the front tires and the back tires are not turning in the exact same ratio.In other words, one axle is not turning the same as the other.

This is why is not recommended to drive on pavement or a hard surface in 4WD.This will, in time, bring damage to the drive train. The tires not being in perfect timing with one another is what is chewing up the turf.

This result is most noticable when the ground is either very dry or very wet.

 

[webbmeister]

Well, it is not in fwd unless it "senses" that it has to be, and then when slippage stops, it goes back to 2wd. It is the sensitrack that comes with NH supersteer. I can lock it into fwd, but there is no locking it into 2wd.

Jim

 

[webbmeister]

Yes, it is growing - "a little." It has been very dry and hot here too. The apples are not doing too well - I don't think I neede to spray them - the worms would have died of thirst!

When the guy next door cuts his lawn with his craftsman, he doesn't get tire marks. I did it for him, and got the brown tracks. it is 1 1/2 weeks later, and the tracks are still there.

I wonder if it is possible for the sensitrack to malfunction and get hung up in fwd?

Here's wishing water and cool temperatures for all of us hit by the dry heat.

Jim

 

[Steelfan]

Hi Jim,
I guess its possible for the tractor to hang up in FWD. I know the wider rear tires on my 21 will make more of a mark then my Craftsman, and Wheelhorse. Usually when the grass grows they go away, but we had no rain for a while. I checked today, and I can still see where I mowed about three weeks ago. I hope that helps some. I'm here in Pa hoping for rain. Talk to you later. Kent

 

[Kodiak]

Hi Jim:

I have a couple of suggestions. First try reducing your air pressure in your tires. I have a TC29, same size and weight as yours. Currently I am running 12 in the rears and 15 in the front. I run the fronts a little stiffer as I do a lot of loader work. By lowering them you are providing a larger, more flexible footprint, that produces less pounds per square inch over the same area. Second try to make your turns as wide you can. When your running at PTO RPM if you make a tight turn sometimes the inside rear tire gets a little light and has a tendency to just barely spin.

I don't have supersteer on my tractor so I am not familiar with all its functions. Can you you turn the steerable axle off, and just run the conventional steering? If so you might want to run like that while the grass is under this drought stress.

Also you mentioned this as happening on hills. It could be a matter of your soil is not as compacted on the hills. Some soils, especially those that contain a lot of sand never adhere to hills as well as it does on a flat area. And some soils don't develop a good turf root base on hills. Just somethings that might help you.

 

[webbmeister]

Thanks, Russ:

I'll check the pressure and drop it a little this weekend. As for the turns, it is not there (in particular) that the problem is. I have long straight-aways over which the brown tire marks stretch.

As for the SuperSteer, the best I can tell is that when the sensitrack in on, you're in 2wd except when the tractor senses that you need fwd. It then shifts back to 2wd when the slippage stops. The only other choice that I can see is locking it in fwd. So, there is no (that I can see) locking it into 2wd.

That is a good thought on the hills - although I am now hoping that by lowering the tire pressure I can lessen some of that damage.

Thanks for the great reply!

Jim

 

[webbmeister]

I learned a few things about the brown tire marks this weekend.

First, on level ground, as in the area in my neighbor's yard that I marked up with brown streaks several weeks ago, the brown streaks do not occur if the grass is not overly dry when the tires go over it. I mowed his side yard for him yesterday, and when I came back to work on my property today, there were no tracks - brown or otherwise. Lesson 1: Don't use Thor to mow when the grass is dry and stressed.

Second, when going down a steep hill, if the tractor is heavy and wants to go down the hill faster than the hydro wants to let the wheels spin, the tractor will slide down the hill with the tires scuffing the grass out at ground level. This essentially makes brown skid marks, and it is the soil - not stressed grass - that makes the stripes brown. Now this is also fairly scary! If the tractor is sliding down the hill, it is also not entirely under control until it stops its slide - even if it's sliding in a straight line! So, today I did some experimenting to see if I could do the hill without sliding. I came up with this:

1. Up the hill, 4WD, 1st Range. No sliding, no scuffing.
2. Down the hill, 4WD, 1st Range, BACKWARDS (w/FEL on and low), no sliding, no scuffing, stiff neck.

Anybody have a better idea? Am I safe enough? I didn't think the hill was that steep! I am forever grateful that I read about slope/pucker factor here before I got Thor and never tried to do that hill sideways!

Regards,

Jim

 

[Anonymous Poster]

Mowing is an activity that combines factors which tend to facilitate sliding on hills:
1. Tires that aren't aggressive enough to resist slides (R4's or turf type)
2. Heavy 3ph mowers.
3. Grassy ground that acts "greasy"

I follow certain rules to minimize sliding and damage to the turf:
a. stay in 4wd
b. mow the steepest parts by going uphill only
c. go downhill in the straightest line to the bottom; if you're descending at an angle, the mower will pull you sideways
d. if you lose traction and start sliding, do what's contrary to instinct -- accelerate the tire speed to equal the tractor's slide speed. ride out the "descent" by steering to a safe area and when the slope angle is less, slowly decelerate to pull out of the slide.
e. when going uphill or sidehill, use the differential lock on the rear wheels. however, avoid keeping them locked together when making turns, or the inside rear tire will do as much damage as any slide.
It takes time, trial-and-error, and repetition to figure out techniques to drive a tractor on hilly ground -- the trick is to minimize the penalties when you guess wrong.
jim

 

[Kodiak]

One more thing adjust your air pressure. A hard tire tends to act as an ice skate. so by lowering your air pressure you provide a larger foot thus more traction. However to little air pressure can make the sidewalls to flexible thus less stability. Its a trial and error thing, but it should help.