[AT] weighted tires or not???

[James Peck]

Intuitively, it is the sudden turn issue where the WFE tractors will have a higher tip over resistance.

From: AT <at-bounces at lists.antique-tractor.com> On Behalf Of deanvp at att.net
Sent: Tuesday, September 3, 2019 1:24 AM
To: 'Antique Tractor Email Discussion Group' <at at lists.antique-tractor.com>
Subject: Re: [AT] weighted tires or not???

If I could ever find that study it would answer a lot of our questions. It caught my attention primarily because it took into account the WFE pivoting on a center pin. I have not seen any other study that has. But to diverge a bit I would offer than I suspect dynamic forces are the largest contributor to roll overs not necessarily front end configuration. Here are some contributing factors that totally mess up static stability on a side hill:


  1.  A front mounted loader raised higher than normal
  2.  Making sharp turns at too high a speed
  3.  A sudden elevation change impacting either a front or rear wheel while moving.

Having 1 & 2 occur at the same time is enough to cause a roll over. Having 1,2 and 3 occur simultaneously guarantees a roll over.

But here may be why it is generally assumed that NFE is more dangerous than a WFE. In the 40, 50;s and early 60’s where row crop NFE were more popular than WFE’s.  One could make a much sharper turn with a NFE than one could with a WFE. That sharper turn probably is the source for many maybe even most roll overs.  WFE’s today can make sharper turns than those we had in the 40’s 50’s and 60’s.  I have a mix of front ends on my tractors here from a Single Tire to a Roll-o-Matic to WFE’s.  In my limited experience here on my 6 acres and 1000,s of hours of seat time as a teenager, I will take a Roll-O-Matic front end over the other two in a heartbeat. The WFE is too clumsy and the narrow Single tire Front End tends to plow into a corner rather than actually turn. Obviously, differential brakes I have on all of my JD’s can have a huge impact on turning performance. My 1958 JD 620 is a High Clearance version with narrow 42” rear tires on it so it sets a little higher off the ground. Also I have the wheel set a little closer in on that tractor. But it does have a WFE.  I feel less safe on it when I get on slopes than any of my other tractors and some are also high Clearance. I have tractors with 36”, 38” and 42” rear tires. And one might expect that the 42” drawbar height would be 3” higher than the 36” but due to significant difference in the tire profile is often less than half that.  I haven’t actually set them up on the same surface with the same tire pressure to do a scientific comparison. But I typically put around 12 psi in my rear tires sunless I’m going to pull competitively so my comparison probably is pretty close. The only real way to get accurate data would be to put all three sizes on the same tractor on the same surface and check how much the drawbar height changes. But, I bring this up because tire size and pressure can also have a significant influence in slope stability. How much lower is the COG on a Standard or Wheat Land tractor configuration vs a Row Crop. I would think it is fairly significant but the narrow rear tire center to center might play a big roll too.  Most row crop tractors have a pretty large adjustment on how far apart or close the wheels can be. Most of our tractors on the farm were set at a default of 80” due to our 40” rows that were standard then.  They could be set much narrower which made them an accident looking for a place to happen on slopes and/or rough ground.

There are so many factors that control the stability of a tractor that when we do our intuitive judgement about what is safer we kind of ignore a whole lot of important variables.  So our intuition may be our enemy. But…
I do know that these help prevent roll overs:


  1.  Be as close to the ground as possible.
  2.  Widest possible rear wheel setting
  3.  No sudden turns
  4.  Drive slowly
  5.  With loader keep the loaded bucket below the center line of the front axle.
  6.  Use Counter balance weight on the rear when using a front loader to move the COG further back.
  7.  Avoid obstructions or sudden elevation changes.

I’m sure there are more that can be added to this list.

PS: Normally I use a 50” Rotary Tiller on my JD 750 Compact three point hitch as a counter balance for the loader.  But when I rolled it I didn’t have it on for some reason.  That alone may have prevented the roll-over.

Dean VP
Snohomish, WA 98290

From: AT <at-bounces at lists.antique-tractor.com> On Behalf Of Jim Becker
Sent: Monday, September 2, 2019 8:37 PM
To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com>
Subject: Re: [AT] weighted tires or not???

The added 500# on the high side has more effect than the 500# on the low side.  It is farther away horizontally from the bottom of the low side rear tire (or the magic triangle/trapezoid) and thus has more leverage.  As far as it “having a greater effect than any change in CG”, it is the same thing.  Looking at the 500# by itself is just selecting one component of the CG to look at (a valid way to look at it).

Adding fluid to the tires definitely lowers the CG.  How much depends on a bunch of factors, including how tall the tires are, how high the CG is to begin with and the relative weight of the fluid vs. the weight of the tractor.  The taller the tractor, the more effect it has.  When we first started using mechanical grape pickers (1960s), many of them were built on a very high clearance tractor (6 feet+ under the axles).  The things were plenty heavy enough as delivered, but everyone loaded the tires to help the stability.

Jim Becker

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