[HCB]

Your idea of using Physan-20 in beet juice may have greater function than the commercial product. But, it may not qualify as non toxic.
From what I see, the using of nitrites (not nitrates) appears NOT to be likely as a "strong oxidizer" and is considered non-toxic. But, from a DIY point of view the importance of non toxic may be over doing it and something that is just an irritant may be sufficient.
We do not know all the tinkering the company did to perfect their product.
For instance they may have boiled the beet juice to get greater concentration of sugar and to get rid of all the microbes before putting in preservatives.
Nor, do we know what other things are in the product.
I am surprised that when the company put non toxic on the label that the MSDS did not show the specific ingredients with only approximate concentrations. But, I guess they stayed within legal guidelines.
You can do tests on a small sample basis to see how your mixture holds up to the needs. I think you may have come to a point that enough thinking has been done and testing may prove the quality of your ideas.
Be Safe

Important note
If you share this with fellow tractor people let them know that your mixture does not technically comply with non toxic.
Be Safe and do no harm
http://www.physan.com/Resources/MSDS-Physan%2020.pdf
Bill

Bill, sorry for the long delay in getting back but I have a variety of projects I work on and kind of bounce around.  You make good points and the bit about the MSDS being vague bothered me, too.  Regardless, here's what I finally did:

I mixed five sample bottles with 6 oz each water.  I then added the equivalent of 0 Lbs per gallon, 1, 2, 3, and 4 Lbs per gallon of sugar.  The 0# was my "control sample", not to sound too fancy or pretend to be an expert.  I then added more or less an arbitrary amount of Sodium Nitrite to the mix based on what quantity I could easily buy the stuff in which was 20 pounds across 2 tires = 10 Lbs per tire with an estimated volume of 64 gallons per tire and blah blah blah and finally came up with 1.78 Tbsp per gallon of mixture (this winds up being a higher concentration than I think I need but I didn't think it would hurt).  Finally, I added the equivalent of 1 quart per 4 quarts of RV antifreeze (potable-water safe).  The amount of sugar I was set on from the beginning but the amounts of Sodium Nitrite and RV AF were settled on through experimentation.

Over a couple of months I tweaked the amounts of RV AF and Sodium Nitrite in each sample and froze them in three freezers: one which gets below -4 F (the limits of the digital thermometer I was using), one which got to 0 F, and one which got to 12 F.  When I finally settled on a formula (to follow) the results were:

All samples froze at < -4 F, with higher concentrations of sugar making the samples more friable, but still hard enough to be a consideration.
All samples had ice crystals and ranged from fairly solid to fairly easy to crush as the sugar concentrations increased.
Samples 0-3 had more to less ice crystals at 12 F and were fairly friable/easy to massage and crush.  The sample with the equivalent of 4 Lbs per gallon was pure runny liquid.

I settled on the 4 Lbs per gallon and decided to use the solution in the tires because here in north central Texas the temperatures rarely get below 10 F.  One morning after filling the tires, when the temps the day before had not gotten above freezing, the temperature was 9 F and I went and kicked the tires and they felt the same as they did when the temperatures were above freezing (and when fresh filled).  I feel the liquid had not frozen.

All samples were done at atmospheric pressure (non-pressurized) and the addition of 16 PSI of air in the tires should further reduce the freeze point (but by how much I am completely unaware).

The final formula I used was:
1 Gallon H2O
1 Quart RV Antifreeze (for potable water systems)
1.78 Oz (by volume) Sodium Nitrite

I did not add any Physan 20 to the mix partly due to concerns for the toxicity and partly because I don't think the solution will grow funky stuff (that's a technical industry term, thank you). 

To each of my sample bottles I added some fresh cuttings from my cold-cut saw (14" diameter blade, carbide tipped, no coolant (dry cut)); approximately 1 Tbsp.  Prior to adding this solution to my tires I let the shavings sit in the solution for a month.  After a month the bare metal (mild steel) shavings still were shiny and clean looking.  I dated the samples with the date of addition of the shavings (as well as which sample had which amount of sugar) and I am keeping them as a witness mechanism to determine if the solution in the tires is breaking down/failing and is allowing corrosion to happen.  Furthermore I can periodically draw a sample from the tires to see if the liquid has turned color and shows rustiness.

I don't know if I posted it in an earlier post but: If potassium nitrate is an oxidizer and if sodium nitrite is an oxidizer and if potassium nitrate and sugar together are combustible then sodium nitrite and sugar should be combustible.  I had a document 20+ years ago about how to make "sugar rockets" which is where I got the idea.  So, on a whim, I set a very small sample of the Sodium Nitrite and sugar out and lit it on fire.  It does burn which isn't really surprising; but that the combustion was pretty tame made me feel fairly confident that I wasn't turning my tractor into a bomb.

Anyway, that's what I did and it's in my tractors tires (rear only, of course) right now.  The added weight when I was done is calculated to be #1,600 and made the machine act much nicer when using the FEL.  I'll keep an eye on my samples and the liquid in the tires and if it seems to fail to prevent corrosion then I'll drain them and pull them off and use the professional product next time and lesson learned.  But so far, so good and the metal shavings have been in the solution for over 2 months now and still look clean and shiny.

Hope this helps somebody and thank you all for your time and input.

--HC

[HCB]

 Similar to the guy who invented the apple-something rain coats in England about 100 years or more ago;

Are you by chance refering to a "Macintosh" 

Apple-something is anachronistically awesome.

Yeah, that was it.  Saw that on Connections, I think I mentioned.  Anyway, a cool idea a great use of an unwanted product (coal tar, IIRC).

--HC