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DRIVING THE TWIN Y

The construction truck market continues to be mired in a slump, but Mack Trucks hasn’t been sitting on the sidelines waiting for it to come back. They’ve been doing some interesting things in R&D, chief among them the...


I drove this Mack Pinnacle with Twin Y suspension on the interstate near Allentown.
I drove this Mack Pinnacle with Twin Y suspension on the interstate near Allentown.

The construction truck market continues to be mired in a slump, but Mack Trucks hasn’t been sitting on the sidelines waiting for it to come back. They’ve been doing some interesting things in R&D, chief among them the development of the Twin Y air suspension. I finally had the chance to drive a Pinnacle with the Twin Y when I was in Allentown earlier this month. I took it for a spin up the interstate pulling a trailer loaded to 74,000 lbs. I’ve always felt the Pinnacle is an underrated highway tractor and I’d say that’s true, even more so, when equipped with the Twin Y. The ride was smooth, as advertised, though it’s difficult to draw a direct comparison to other decent air suspensions when not driving both vehicles back-to-back. But forget about ride for a second. The real benefits of the Twin Y are the incredible weight and tire savings. Yes, I said tire savings.

The Twin Y is unique because its simple design consists only of the Y blade assembly, spring hanger bracket and upper and lower axle seats. Those axle seats never have to be retorqued. Also unique to the Twin Y is that the axle sits entirely upon the air bag, resulting in a smoother ride. The design is entirely lube- and maintenance-free. And at just 630 lbs, the Twin Y is 70-500 lbs lighter than other suspensions currently in the market, including 110 lbs less than Macks’ previous lightest-weight air suspension.

The weight savings are significant, but what’s really intriguing about this suspension is that fleets are claiming a 25% improvement in drive tire life, thanks to the smoother ride. And this is not a small sample size, it’s based on the experiences of 13 customers who’ve put three million miles on the suspension. So yes, it drove incredibly smooth, as many of today’s best trucks do. But the weight and tire savings bring some real value to customers’ bottom lines and that, I believe, will be what really drives this new suspension into the market. Incidentally, the Twin Y is now up for an award for being one of the greatest innovations made of steel. Well done, Mack, you’ve really got something here.

The Pinnacle I drove had some other great features as well, including the mDrive transmission, which is part of the Super Econodyne powertrain package, and an Econodyne+ MP8 engine. Mack has reconfigured its engine to give 15L-type power in a smaller, lighter-weight 13L package. One of the ways it does this is to provide an extra 200 lb.-ft. of torque, but only when it’s needed. The 1,660 lb.-ft. becomes 1,860 when pulling a grade or in other situations that need just a little more umph. This is possible thanks to improvements in engine design. Powertrain sales director David McKenna explained that traditionally, diesel engines could produce about 20-25 hp for every litre of displacement. That’s more like 38 hp per litre now, he said. That little Mack MP8 engine can produce 505 hp and 1,860 lb.-ft., while also providing all the efficiency benefits of running a 13L engine.


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