"There's nothing's new under the sun Horatio...!" (Or whatever it was the great Bard said). And to prove it here's a pretty good example. Another ad from Commercial Motor in 1966 extolling the virture of wide single tyres on a tractor's drive axle..i.e lower weight, improved brake cooling, no trapped stones between the tyres....yadda-yadda-yadda. And it was Goodyear who came up with the name 'Super Single' which like many things quickly became the accepted industry generic term for a wide single tyre. Yet it wasn't for at least another 35 years before operators began to take them seriously on a tractors--and then mainly on the Continent.....now click through here to see what I mean.
Still using the same argument (i.e. increases in payload) here's the recently launched Goodyear 495/45R22.5 Omnitrac MSD super-single tyre for use in mixed service applications.
And if you were to use 495/45R22.5 Omnitrac MSD super single truck tyres on alloy rims instead of eight 315/80R22.5 MSD tyres the total weight saving would be an impressive 260kg. Goodyear says: "Vehicle types that will typically benefit the most are concrete mixers, bulk transport trucks, and other models where every kilo saved on the empty vehicle is a kilo gained on the payload. Used for the shuttle service in a major building project, the additional 260kg payload offered by the new Goodyear super single drive tyres will reduce substantially the overall number of trips required, and thus the fleet's total cost. Fewer drive cycles will also reduce the overall fuel consumption, reduce CO2 emissions and the overall impact of the construction works too."
However, never mind tippers the market that still to be cracked over here on tractors and with a few notable exceptions (as per this Biglorryblog story from 2007 below) wide single drive tyres haven't floated anyoner's canoe in the UK.....
At the time I wrote: "Biglorryblog notes with more than a passing interest that Derby-based Lockwood Haulage has become the first operator in the UK to specify Michelin's X-One XDA2 Energy wide single drive axle tyres. Interested because although wide single drive tyres have been around for quite a while they've been met with an underwhelming response by British artic hauliers. Of course there's a couple of very good reasons for this, namely that Authorised Weight Regulations (that's C&U regs to us old-timers) currently restrict drive axle weights on UK 44-tonners to 10.5 tonnes and you also have to have twin-wheels on their drive axles...So if you want to fit wide drive tyres on anything bigger than a 40-tonner you're stuffed, and as we sell far more 6x2 tractors in the UK than 4x2s the wide-single tyre providers haven't exactly had it on a plate...."
"However, Lockwoods can clearly live with that as they've had the wide 495/ 44 R22.5 Michelins fitted as original equipment to its new MAN TGA 4x2 tractor which, like the majority of their fleet, will run at 40-tonnes.Moreover, they're looking forward to the promised 2% reduction in fuel consumption compared to a truck with traditional twinned 315/70 R22.5 wheels and tyres. And this is on top of the 6% reduction the company already enjoys by fitting Michelin A2 Energy tyres across its fleet of 45 tractor units and 90 trailers."
It would be interesting to know how Lockwoods have got on with their wide singles....How about it JG?
Another huge plus with super singles is their extra tread life generally obtained. The reason for this is they don't have any competition from a partner on the same hub.
Very few people seem able to understand the most basic factor relating to pneumatic tyres -- that is that when you load a tyre it compresses down, squeezes - call it what you will - and the amount it compresses is a function of load and pressure.
In effect the RADIUS of the wheel assembly is reduced with the application of load. The radius controls the effective circumference of the wheel and thus the number of revs per mile/km the tyre makes.
SO - if you fit two new identical tyres together, but do not inflate them exactly the same pressure they each try to deflect to the loaded radius dictated by their pressures - but with differing pressures they are incompatible. What happens is the tyre with greater pressure takes control by taking on a greater proportion of the load while at same time taking fewer revs/mile than the softer (effectively smaller radius) tyre would like to make. With the greater effective load due to greater pressure the hard tyre wins the struggle and maintains its grip on the road surface. The softer tyre is trying to rotate more often (due to smaller potential radius) but, bolted to its partner, is forced to comply with the harder tyre's revs. The result is slippage or scrub of the softer tyre. This equals high rolling resistance = excess fuel consumption, plus high tyre wear on the softie = unnecessary tyre cost.
The rate of differential wear is directly proportional to the pressure difference between the tyres.
If you don't believe it, give it a try - Start with two new identical tyres, but inflate one, say, 15 or 25% less than the other. You can increase the hard tyre's pressure to compensate for the effective extra load - it won't make any difference. After a week or so put a tapemeasure round their circumpherences.
Better still, only inflate the soft tyre sufficient to hold it on the rim and then see how far it lasts.
Even the slightest pressure difference will lead to some degree of extra wear on the softer tyre.
Scammell were using Super Singles in the 1930s on a wide range of their vehicles. Did you all know this?