NACFE report lays out 6x2 axle advantages and drawbacks

[kscarbel2]

Fleet Owner / January 21, 2013

An exhaustive review of 10 different data sets in a new report issued by the North American Council for Freight Efficiency (NACFE) this week finds that a 6x2 axle configuration can on average improve Class 8 sleeper tractor fuel economy by 2.5% versus a traditional 6x4 setup, with a 20 month payback period required to offset the higher initial cost of the 6x2 package.

“We have medium to high confidence in these findings due to all the testing,” Mike Roeth, NACFE’s executive director, explained to Fleet Owner in an interview. “That’s in part because none of the 10 sets of data we examined have been published to our knowledge.”

Roeth noted that “data sets” included: two 6x2 axle truck tests conducted by axle builders; two conducted by truck OEMs; five fleets test; and three by NACFE using Society of Automotive Engineer (SAE) fuel economy test parameters.

“It’s very hard to test trucks because so many different variables are involved: weather, geography, temperature, load weight, etc.,” he pointed out. “That’s one reason why we believe the more data sets we can obtain about a particular technology, the better the analysis we can conduct. A lot of fleets test products but keep the results to themselves. We want to try and get more of them to share that in a non-competitive environment.”

For example, Roeth noted that NACFE’s research indicated that 6x2 axle packages cost on average $1,000 to $2,000 more than the 6x4 variant largely due to their small production volumes as only 2.3% of all new Class 8 sleeper trucks built in 2013 came equipped in 6x2 configuration.

“So if the confidence in the technology can be increased and more 6x2 configurations sold, that will drive down the price and improve resale values,” he explained. “That in turn helps those fleets already investing in 6x2 packages; thus they benefit from sharing their test data.”

NACFE’s goal is also to provide a “warts-and-all” view of potential fuel saving technologies, so fleets get a more straightforward look at potential trade-offs.

“In the case of 6x2s, there are several,” Roeth said. “Weight is lowered by 400 lbs. on average compared to a 6x4 but purchase price on the 6x2 is as noted before $1,000 to $2,000 higher. There is less mechanical maintenance needed on 6x2s compared to 6x4s but higher electronics service is need. That is because electronic load shifting technology helps mitigate traction losses in 6x2 configurations and we recommend that be spec'd for the 6x2 package.”

Indeed, the potential loss of traction is the number one issue turning fleets off from 6x2 axle packages despite the fuel savings potential, he pointed out.

“But we’ve found in our study that electronic load shifting systems, and even manual air-dump valves, can mitigate much of that traction issue,” Roeth said. "The science says you cannot equal 6x4 traction with a 6x2 package but you can get pretty close with load-shifting systems.”

Finally, NACFE found that tire wear is much higher in 6x2 configurations versus 6x4 setups, on average resulting in $466 more in tire wear costs per year.

“We will always address challenges and drawbacks of particular fuel-saving technologies in our reports,” Roeth stressed. “We need to provide fleets with a complete picture. But the more test data we can get about particular products, the more confidence we can provide to the industry in temrs of the fuel saving results.

Video: http://fleetowner.com/equipment/nacfe-report-lays-out-6x2-axle-advantages-and-drawbacks

[kscarbel2]

Roeth noted that .......6x2 axle packages cost on average $1,000 to $2,000 more than the 6x4 variant largely due to their small production volumes as only 2.3% of all new Class 8 sleeper trucks built in 2013 came equipped in 6x2 configuration.

It's unbelievable that the 6x2 is priced higher than a 6x4 in America. In Europe and elsewhere around the globe, the 6x2 is of course cheaper to purchase (and operate).

To blame it on low volume is ridiculous. To ultimately achieve volume sales, you have to launch with the appropriate price for a 6x2 (with savings over the 6x4), accepting reduced profits in the beginning.

[rsb502]

interesting, Ive been wondering when a report would come out on the 6x2 idea, seems odd to me there is more tire wear since you are not powering the front rear axle spo there is no torque scuff. however I could see more steer tire scuff if there is mopre weight on the front rear and more drive tire wear due to it being the only axle used to provide tractive effort. Still it seems like a 2+ percent fuel savings over a 5-10 year truck life would more than pay for the added initial cost of $1000-$2000 and the added tire wear. If your trucks travel 100,000miles a year at 5 mpg thats 20,000 gals, @$4/gal thats $80,000 a year for fuel, if it made a .5mpg difference that same truck would use 18181gal of fuel @$4 thats $72727 a year for fuel, then add the additional 400-600# of freight or added mpg benefit from a lighter combination and I see some money to be saved, at least $7000/year per truck with the added tire cost.

[rsb502]

Roeth noted that .......6x2 axle packages cost on average $1,000 to $2,000 more than the 6x4 variant largely due to their small production volumes as only 2.3% of all new Class 8 sleeper trucks built in 2013 came equipped in 6x2 configuration.

It's unbelievable that the 6x2 is priced higher than a 6x4 in America. In Europe and elsewhere around the globe, the 6x2 is of course cheaper to purchase (and operate).

To blame it on low volume is ridiculous. To ultimately achieve volume sales, you have to launch with the appropriate price for a 6x2 (with savings over the 6x4), accepting reduced profits in the beginning.

Remember most of those european trucks are actually single axles with tag axles so there is no added electronic traction control changing the pressure on the front rear axle and it can be raised when empty for added fuel savings. Im guessing the electronics are a big part of the price tag and most are probably speced out with a locking differential which ads cost, whereas the traditional 6x4 road tractor just has a power divider not both power divider and axle lock.

[kscarbel2]

Typical with a Scania, there is no excessive tire wear with a 6x2 configuration. You're running a steerable pusher axle (steering in unison with the steer axle via a draglink), or a liftable tag axle. It's a professionally engineered arrangement delivering superb results.

.

[57 bcr]

..........Everything old is NEW again! I have heard horror stories from the old timers and present day line haul drivers that have had to put up with this type of set-up. Although the full-locking single axle is an improvement,the snow belt seems to be no place for the tag/pusher tandem. My .02

[kscarbel2]

..........Everything old is NEW again! I have heard horror stories from the old timers and present day line haul drivers that have had to put up with this type of set-up. Although the full-locking single axle is an improvement,the snow belt seems to be no place for the tag/pusher tandem. My .02

The 6x2 isn't for everyone. But having said that, speaking of snow belt use, the 6x2 is profitably, effectively and safely used in northern climates throughout Western and Eastern Europe, and China.

The US market steerable pusher axle as you know it is a primitive beast compared to the modern designs offered by Scania and others.

[BC Mack]

Typical with a Scania, there is no excessive tire wear with a 6x2 configuration. You're running a steerable pusher axle (steering in unison with the steer axle via a draglink), or a liftable tag axle. It's a professionally engineered arrangement delivering superb results.

.

a 6x4 double drive is a rarity in EU.. only used for heavy haul. Since most US mainline freight usually bulks out I really don't understand why the US hasn't gone for the 6x2 with a lift axle.. heck, even US made coaches are fitted with a steerable tag that can also be used for weight transfer when you need traction. I assume it's a culture thing as 6x4 has always been there. With new technology such as electric brakes now under development and VLT trailers with steering axles there will soon be a better understanding of fuel economics by US fleets.

BC Mack

[mackdaddy]

With the Mustang H model which is a single drive with a tag, I always pull out of the wet grassy hills at truck shows while the tandems sit and spin. I just release the air in the tag, and add pressure into the bags on the driver. In fact the first time I met Joe was at the bottom of the Siskiyou mountains during a bad snow storm and he told me with confidence that he would have no problem getting over the pass..........and he did.

[bbigrig]

Sodrel a long time Mack customer in Ohio I believe, has been using 6x2 with liftable pushers for years hauling U.S. Mail. I have loads I could use that set up for and see the value in it. The set up has good and bad things about it operating in the snow up here. The biggest problem I have come across is the loss of axle rating on having to use smaller tires on the pusher lift. (smaller tires here means lower axle carrying capability on the lift)

[slpwlker]

Friend of mine works for Custom Commodities and his last truck before going into dispatch was a binder 6x2. He said at first he didn't know how it would do. but after a few months and a few ice storms he liked it. you spun hell I spin but when he mashed on the throttle just for the hell of it the truck didn't get sideways Like I would in a 6x4.

[57 bcr]

The key is being able to adjust the pressure on the axles, everyone agrees.Most fleets will not allow that for the fear drivers will be adjusting it for traction, and overlook they're axle weights (and here come the "over on the axle" fines). They are pretty much pre-set, and offer the driver nothing to work with. Most won't even raise. That is useless, unless on clean dry roads. Don't get me wrong, it's a good idea in some applications. I would lay money on it, the 6X2 used tractor would have to be a really good deal, and would be the last truck off the lot around these parts.

[rsb502]

The biggest reason a single axle with a steerable tag axle for on highway use hasn't caught on is different weight laws. You would have to have enough tire for your axle to haul a minimum of 18,000# which means at minimum a 315/80r22.5. The other catch 22 is that each states laws are different regarding tag axles, some are legal for 20,000# with a switch inside or out and others are only legal for 12,000# with a switch outside only so it can't be operated from the cab. There would have to be a federal interstate guideline set up with the states ratifying or at the least recognizing the rule for it to even work out nationwide. Just ask anybody that does heavy haul what they can put on their tag axle and theyll say "where?".

[RFCDrum]

A lot of the tag and pusher axles in Europe are computer controlled and go up and down depending on whether you are loaded or slipping etc.

[slpwlker]

I've always gotten 20 on mine. Steer was another issuse

[57 bcr]

Don't look for uniformity in laws any time soon. The states have been playing this game since 1935 and they quite frankly,like the revenue it brings in!