Tires Exactly what is the "foam" in foam filled tires

[kwolfe]

Re: Exactly what is the "foam" in foam filled tires

I was at my local dealer the other day and they have a foam filled R4 that hhas a cross section cut out. They had also carved out little dscs of the stuff so that you could pick it up and playy with it. It would definitely yield a stiffer ride than air, however you could sqish it a little with your thumb. I seems to me that if you are gonig to be doing work where frequent tire punctures (nails, small stumps, etc.) are probable and you would like the ballast, this would be a great addition to your equipment.

 

[Harry c]

Re: Exactly what is the "foam" in foam filled tires

The foam in the tire is Polyurethane foam. It's a thermoset material produced by reacting two liquids, a Polyol and an Isocyanate. The polyurethane used in the foam application also contains a "blowing agent" similar to the baking powder in cakes or biscuits. The two liquids are mixed, react and solidify as the blowing agent produces bubbles. The bubbles are trapped in the solid material and foam has been produced. This type foam is very common. Almost all chair cushions, all foam mattresses and most importantly, the foam in the seat of your tractor are made of PU foam. The rigidity of Polyurethane foam can be adjusted chemically from very soft to extremely hard. The rigid foam insulation used in some building sheathing is PU (the tan stuff, not the white styrofoam, that's expanded polystyrene, different stuff altogether). In fact almost all bowling balls and the formed bumpers on cars are made of the same chemicals but without the blowing agent. It's really common stuff now.
The foam used in a tire has to support weight strictly by being very stiff. The air bubbles have to be very small or the tire would just squash flat when you picked up a load. The fewer and smaller the bubbles the more dense the foam. Also, in most of these applications , more weight is better. The urethane can be filled with powdered minerals to increase the weight and increase the stiffness at the same time. The powdered mineral fillers are cheaper too. One of the most common fillers is calcium carbonate, plain old ground up limestone...

Definitely loses some ride quality compared to air filled tires. No flats. No liquid fill needed for weight. DO NOT USE FOR CARS, TRUCKS OR ANY HIGH SPEED ROAD VEHICLE! Tires will self destruct violently at highway speeds.