Graham Betts: Ash, when you purchased your Miller sprayer a few years ago, how long did your first lot of tyres last for?

Ashley Wakefield: Approximately 2 years, I reckon.

Graham Betts: And why did they only last 2 years?

Ashley Wakefield: The sidewalls kept bubbling up and they were just failing, cracking and eventually blowing.

Graham Betts: So what process did you go through to replace the tyres?

Ashley Wakefield: We started looking at the tyre ratings and the numbers on the side of the tyres. We found that the tyres that were on there were only barely specced to do what we needed, so we started looking in the industry to find tyres with a better load rating and better quality.

Graham Betts: With the tyres that you put on, what did you notice?

Ashley Wakefield: Firstly, because we went for a tyre that has more tread on the ground, we noticed less compaction and less cutting up of the soil. Also, since we opted for better quality and better-rated tyres, they were carrying the weight better.

Graham Betts: You had damage on one of the new tyres. What do you think caused that?

Ashley Wakefield: One of the new tyres developed a bubble on the sidewall. We don’t know what caused it, but we had to replace it to avoid the risk of it blowing out when driving down the road at 40 kilometres an hour.

Graham Betts: To select the correct tyre, we need to be able to weigh the sprayer. What have you done to accommodate that?

Ashley Wakefield: A few years ago, I bought a set of scales for weighing grain. We use those scales to weigh the sprayer, allowing us to measure the weight on the front axle, back axle, or individual tyres. This way, we know the exact weight of the machine front-to-rear and on each individual tyre.

Graham Betts: What did you notice physically about the new tyres?

Ashley Wakefield: One tyre had a significant bulge after we installed it. I got the tyre rep to check it, and while he said the pressure was fine, we still had one tyre with a major bulge, another with a minor one, and the other two weren’t too bad.

Graham Betts: Now that we’ve adjusted the pressure in the tyres with the boom folded and the tank full, what have you noticed about their shape?

Ashley Wakefield: Two of them look as though they’re pumped up normally, but the other two still seem flat even though they have the same pressure.

Graham Betts: You added the tyre dog system on your sprayer tyres, which monitors pressure via the valve stem and displays it on a screen in the cab. What have you noticed?

Ashley Wakefield: It shows the accurate pressure in the tyre. The only thing is that you do notice a slight increase in pressure as the tyres go from cold to running temperatures, usually by 2 or 3 psi.

Graham Betts: That’s not uncommon. How did you figure out the issue with the tyre shapes being uneven?

Ashley Wakefield: By chance, we weighed the front and back tyres on the dual pads, then weighed them individually. We found a significant discrepancy in weight between the side-by-side tyres, front and rear—up to 2-3 tonnes.

Graham Betts: That’s a lot. So what are you going to do about the pressure?

Ashley Wakefield: We’ve adjusted the pressures so the tyres look the same. There’s now a 30-psi difference between two of the tyres to balance the load properly.

Graham Betts: Does the shape of the tyres look better now?

Ashley Wakefield: Yes, all four tyres now look as though they’re evenly pumped, even though two of them have a 30-psi difference.

Graham Betts: Just a good little handy tip, a farmer tip. Run an imaginery line down your tyre there, if you've got a bit of dirt up here that means the tyre could be too low a pressure, and if you've got a black line and the dirty line finishes just there that would mean your tyre is too high. It's very important that when you're travelling down the road, or down a bit of bitumen or whatever that that contact point just across the leading edge there.

Graham Betts: Something we found recently is that tyre pressure gauges aren't reading exactly as they should do. I've had a situation where a farmers guage the other day was 8 PSI lower than this gauge that had been checked against a calibrator pressure gauge at the tyre reseller. It's very very very important to have your gauges on the farm checked with a calibrated gauge in town.

Graham Betts: The next part of this process is to understand all the information on the tyre and when you're buying or purchasing a tyre the information you need to look for. Obviously brand that's pretty common sense. This one's very important that's the model of the tyre. Obviously we're all familiar with this. The 540 is the width of the tread, 80 is 80 percent of the 540 is the depth of the tyre. R - it's a radial. 38 inch is the rim, and this one just happens to be an industrial tyre and this is the old imperial figures which now is the new metric 540, 80R 38, but that's only about twenty-five percent of a tyre. 75-percent of the tyre is this information - the load rating and speed. The 172 is the load rating and the A8 is the speed symbol. That equals a certain amount of kgs and that's at 40 kilometers an hour.

If you want to go faster it's a lower load capacity and a bit higher speed the d stands for 50 kilometers per hour. I've graffitied the tyre but this information should be on there also, it's very very important. RCI stands for rolling circumference index 48, and that 48 is a group number to tell you the rolling circumference of the tyre. Very important this 2.5, that's the beading pressure, has nothing to do with the operating pressure. So it's saying don't go over 2.5 bar when you're beading the tire. Very important to find out what the maximum inflation pressure is, a lot of tyres will have maximum pressure at maximum kilograms the tyre can carry. They're only maximums, you don't need to operate the tyre there and we don't like to operate tyres at that pressure, we like to operate down to about 75% of the maximum. It's not on this tyre, this industrial tyre, but has a tread pattern very similar to an R3. What that means, is we've got seventy percent contact and thirty percent void, where the other R1 tyres will have seventy percent void and thirty percent contact. Why we're going for this type of tyre is that it cuts up the paddock a lot less.

To summarize all of what we've learnt, we've learned about all the numbers on the tyres, we also need the weight information and these numbers when we go into our tyre dealer, including the rim number. When you have a look at the tyre manufacturers catalog to see what tyre is matched up to what rim, that's very important. The reason we're doing all this is that we've got a lot of weight about us, a big tank capacity and the big issue is we're damaging our paddocks because we aren't getting this right. We're having to put far too much pressure in these tyres. We need to get that tyre pressure down to about 20 to 25 psi, but also tyres and the tyre pressure has a very big impact on the stability of the boom, and obviously the comfort of the operator, and also your auto steer, if you don't get all this right your auto steer could not work properly.

Graham Betts: I know this is a header tyre, but it relates exactly the same to a sprayer tyre.

The tyre information is a VF 620/70 R26. The VF stands for ""very flexion."" What that means is you can carry forty percent greater load at the same tyre pressure, or at an increased tyre pressure, you can actually carry more load.

The 620, once again, is the width of the tread. The 70 is the aspect, meaning seventy percent of 620 is the depth of the tyre. The R stands for radial, and the 26 obviously refers to the rim size.

Another little tip: with our auto-steer now being as precise as 2-centimetre accuracy, it’s a good idea to line up the centre of the tyres rather than the outside. You might have, say, 800s on the front and 620s on the back. In the past, we lined up the outside, which worked fine, but with auto-steer being so accurate now, we really need to be lining up the centre.

Graham Betts: I know this is a header tyre, but it relates exactly the same to a sprayer tyre.

The tyre information is a VF 620/70 R26. The VF stands for ""very flexion."" What that means is you can carry forty percent greater load at the same tyre pressure, or at an increased tyre pressure, you can actually carry more load.

The 620, once again, is the width of the tread. The 70 is the aspect, meaning seventy percent of 620 is the depth of the tyre. The R stands for radial, and the 26 obviously refers to the rim size.

Another little tip: with our auto-steer now being as precise as 2-centimetre accuracy, it’s a good idea to line up the centre of the tyres rather than the outside. You might have, say, 800s on the front and 620s on the back. In the past, we lined up the outside, which worked fine, but with auto-steer being so accurate now, we really need to be lining up the centre.