So the other day this olelongrooffan stopped at my local Stop-N-Rob to get me some cokes and smokes and I saw something I had not seen before. See the front axle on that tanker trailer? It is raised up off the ground about 10 inches or so. Of course, I had to ask the driver of this rig what was up?
He mentioned this was done so as not to scuff the tires while turning, improve the turning radius, and to increase fuel mileage while going on down the road with a light load. I can only wonder what the increase in cost for this set up versus the perceived savings in fuel and tire costs would be. Although the ease of turning would make it worthwhile to me.
In my 40+ years of driving, this olelongrooffan has never seen this set up previously. What about my fellow Hoons? Seen something like this or similar?
Image Copyright Hooniverse 2016/longrooffan
Quick Shifts: Save A Buck Where You Can Edition
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It makes perfect sense to me. I see it on concrete mixer trucks all the time. What’s the math on savings? Who knows, but they wouldn’t do it if it didn’t make sense.
It can also be handy for toll roads and bridges, many of which charge trucks based upon the number of tires (or axles) that actually touch the road.-
…or prohibit trucks with more than a certain number of axles. Rerouting can cost more than the toll, if it is a significant detour.
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Lots of motorcoaches have this feature, and I’ve often seen it on dump trucks. No reason to waste tires when empty or carrying light loads. It also helps mpgs by reducing drag, which seems pretty obvious.
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Interstate buses (a.k.a. motorcoaches) also only have dual wheels on one of the two rear axles. I don’t know for how long they were doing that, but I didn’t notice until the mid 2000s.
Also, evidently only one rear axle is a drive axle.
https://www.quora.com/Has-anyone-noticed-that-in-multi-axle-bus-one-chassis-of-rear-tyre-is-facing-outward-and-another-is-facing-inward-Is-there-any-specific-reason-behind-it
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With trailers of all kinds even a slight increase in efficiency can mean huge savings over hundreds of thousands of miles. Combined with less consumables( 1 less set of tires and brakes). The other benefit being a smoother ride due to a longer wheelbase. Most Van trailers have tandems that slide. In cities the drivers slide them forward for a shorter wheelbase and better turning radius.
Over the road guys generally try to stretch them as far as they can legally for a smoother ride. The main reason for sliding tandems however is to adjust the weight distribution so that the trailer is legal and rides smoothly. -
I don’t recall seeing it on tankers, but I see it regularly on others. I was told the main objective was to avoid wear on the tires when unloaded
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I’ve seen it a lot on gravel trailers and dump trucks.
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Just guessing here, but if it’s already an air suspension, cost in parts and controls should be limited to valving that deflates and isolates that axle and a spring or lead screw to pull it up when deflated.
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I also see it on flatbed trailers used for hauling oversized/overweight loads. If two axles on a trailer chew up tires and eat into turning radius, four axles must be a lot more severe.
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In theory it increases the tire life at least 25%, assuming that they are rotated regularly, not including the increase in tire life due to the lowered scrub on the dead head portion.
Since many heavy trucks are already equipped with air suspensions it is a matter of an extra set of bags to lift the axle and the control valve to switch the air supply between the sets of bags. So a couple hundred bucks to lift an axle. With a set of tires being an easy $2000 the system should pay for itself during the first set of tires. -
We took delivery of some sculptures here at the science museum. The trailer had to back right up and over the curb to get to the right place. I was amazed to see the driver basically step the rear truck up onto the curb using this feature. Didn’t have to gun the motor to get up the curb, or mash the brakes to stop after he popped over. Smoove.
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Very common in Europe, too. But seeing trailers like that has a bad reputation: It shows to everybody around that you’re not efficiently hauling stuff both ways…Bergen, Norway, has build a new garbage incinerator, but it is so expensive to run, that there’s money in hauling garbage to Sweden instead – a 10 hour drive one way. Most of these trucks return empty-handed to pick up more garbage. Shake your head in contempt for modern economics in 3…2…1.
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They usually use chains to hold the axle up. Only done while running empty.
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When I drove motor coaches for a living this feature was a godsend for improving maneuverability in urban areas. You did need to remember to lower it back down once you got back on the highway as the extra contact would improve your stability.
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Very common for decades. More on straight trucks than on trailers.
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My dad’s drop-deck flatbed has a dump valve for its rear axle, for low-speed maneuvering. There it’s needed because it has a 10′ spread between the axles so they’re considered under the bridge formula as 2x 20,000 lb axles instead of as a tandem (34,000 lb typical for a standard ~4′ spacing.)
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I’ve seen this quite a bit on dump trucks, not so much on trailers…
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Pretty common in Australia
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