[motorcycle.com] - Which is it: Lb-ft or Ft-lbs?

[Ninjette Newsbot]

Ask MO Anything: Which unit of torque measurement is the right one?

Dear MOby,

When I was growing up as an early baby boomer (bless our initially materially rebellious, yet ultimately avaricious souls – which in my case I blame on motorcycles being so much fun), torque was righteously represented as foot-pounds: usually stated as “ft-lbs” in any self-respecting moto rag. Now, it’s represented as pound-feet of torque, “lb-ft”.

About when did it change, and why? And really, why should most people give a s%$t? As always, thanks in advance for the erudite answer that I’m sure you’ll provide.
Walter B.




Dear Walter,

I wondered the same thing, especially since I‘ve spent a fair amount of my lifetime plugging entries into spec charts. It’s easier than it used to be, when we’d actually measure the circumference of the rear tire to calculate speed in all six gears (or five) using primary, final and internal gear ratios using an abacus. But that was in the pre-internet days when there was plenty of time to putz around the office, smoke cigarettes, sexually harass coworkers, etc.

Bitter as a result of how much more “work” I’m now tasked with, I was happy to just use whatever formatthe bike manufacturer in question decided to use, though like you, I thought it was foot-pounds for years. Aprilia and Moto Guzzi and Harley express themselves in ft-lbs, BMW and Ducati use lb-ft… the Japanese usually don’t make horsepower or torque claims, but Yamaha says the new Star Venture makes 126 pound-feet.

As long as people know you’re describing torque, and more is better, what difference does it make? Either way, we’re describing the twisting force produced by applying one pound of pressure to a lever one foot long, no?

Have the people who make Tekton tools got it wrong too?


We used the terms interchangeably here at MO, depending on which editor was writing, because there was no mystery that we were referring to torque output no matter which way it was stated. But in the interest of consistency, we researched the topic to determine the most accurate term, determining that pound-feet, or lb-ft, is correct.

Since you asked, though, we decided to get a statement from an expert in the field, Dustin Schaller, Senior Product Manager at Dynojet Research, who tells us:

Torque is always measured in force at a radius. The correct measurement is lbf-ft or “pounds force foot”, which we shorten to lb-ft. The metric guys always have it right, when they express torque in terms of Nm, or Newton-meter. Never have I seen meter-Newtons, but somehow foot-pounds became common verbiage…

Okay, lb-ft it is then. All we have to do now is get our Dynojet operators to quit giving us readouts that look like the one below, or we’re doomed to a lifetime of using lb-ft and ft-lbs interchangeably. Next question please.





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