New Rotor Power LT (Light) Crankset Saves Weight w/ Single Left Sided Sensor

rotor-power-lt-left-sided-lightweight-power-meter-crankset

Costa’s bike with the new Rotor Power LT. Photo: Rotor’s Facebook page.

Introduced in the heat of the Tour de France aboard Rui Costa’s Merida Reacto KOM, the new Rotor Power LT takes their crankset based power meter introduced at Eurobike 2012 and covered in great detail in this post.

That system used a separate power meter gauge on each crank arm, each with its own transmitter and four distinct strain gauges inside each arm, using their 3D drilled design to tuck them inside the alloy arms. For the new Power LT, they simply dropped the drive side meter, relying on a single group of strain gauges and transmitter to process the data. Like other one-sided systems, it likely just doubles the measurement to send a single power figure to ANT+ compatible cycling computers rather than separate left- and right leg measurements.

Like the original, it still measures deformation of the crank arm in three axes, which lets it determine torque effectiveness (how much your leg drags on the system on the upstroke) and pedal smoothness (max torque vs. average torque). And it still only requires a single zero calibration when changing batteries, self adjusting for temperature, altitude, etc.

Rotor Power powermeter crankset with dual measurement for true left right power balance capture

Battery replacement is quick and easy with no tools. The crankset uses a 30mm spindle that works with their Universal Bottom Bracket to fit it into any frame, even standard threaded bikes originally built for 24mm spindle cranksets.

rotor-power-lt-left-sided-lightweight-power-meter-crankset

They’re available with either oval or round rings, 10- and 11-speed compatible. The crankset has a claimed weight of just 535g to 545g for 170mm arms – 172.5 and 175 are also available. 110 and 130 BCD available.

The idea was to offer a lighter weight, less costly option for measuring power. They’re about 50g heavier than a bare 3D+ crankset. A direct comparison to the dual sided Rotor Power crankset isn’t applicable since it uses their MAS (micro adjust) spider rather than the regular five-pronged spider.

Retail is much less, though, coming in at $1,490 (€990) for Power LT versus $2,350 for the regular Power. That’s about double the lowest cost one-side PM from Stages, but you’re getting a full crankset rather than just an arm, and it’s in between the various options of Quarq’s sets since they dropped the prices (and chainrings).

RotorBike.com 

Comments

Joao - 07/09/14 - 7:57pm

I like new powermeters on the market, but we have to be honest here:
– Rotor did not invent anything new… they simply stripped the strain gauges from the right side crank, and copied Stages “magic” formula to find total power (x 2). It has the same limitations
– Are Torque Effectiviness and Pedal Smoothness useful on single-leg PM’s? I mean, it is hard to find the usefulness in L/R applications… what is the value of knowing how smooth is your LEFT LEG?
– Does the weight include the battery, which is quite heavy (and difficult to find, by the way)? The claimed weight on Rotor website for the L/R PM is less than that but… even removing the batteries and chairing bolts, actual weight has proven to be higher than claimed
– The “no direct comparison claim” is BS… just install a MAS spider on the LT and you have an apples to apples comparison… which brings me to another point… why oh my didn’t Rotor used a removable spider on the L/R version… it would be a beautiful solution
– I understand the reasoning behind their price strategy, but I think they are making a mistake… if they are marketing this as a lower-cost alternative (or a Stages competitor), they should have used the 3D24 version, and make it cheaper. They are already having a hard time competing on the premium market… now they decide to enter at “low-cost” PM market with a higher price
– Pictures of the LT version being used with P2M as “reference” in the Lampre team bikes was bad marketing. Specially if you consider that P2M sells a Rotor version for the same price (but heavier), does not have the limitations of single-leg system and, it is considered rock solid and stable… which is not exactly the reputation of the L/R system so far

Frankly, I think Rotor has a good product from a mechanical and electronic perspective. But they have to understand the market a bit better (and fix their firmware).

greg - 07/10/14 - 1:34am

…aaannd… it’s back again. or did it ever disappear?

Reynard - 07/10/14 - 12:19pm

I find single leg power meters to be inaccurate. I had an opportunity to do a comparison recently during a time-trial. A friend beat my time be about 15 seconds. He uses Stages and I use a Quarq. He weighs about 10 lbs more than I do, also. The result? His power meter said he averaged almost 20 watts less than I did.

Aero - 07/10/14 - 1:36pm

Comparing your power to your friends power is not a comparison ride. Putting two power meters on your bike is a comparison ride. His average being less than yours does not mean his power was inaccurate either. It just means either 1) his position/gear is more aero and more efficient, b) he has a right leg dominance, or c) one of your power meters is inaccurate. Any 3 combinations of those could be in effect. Only c would mean either of the power meters were wrong.

Reynard - 07/10/14 - 2:05pm

No, it was a good comparison. The TT was Eddy Merckx style and I guarantee that I was far more aero than him (he’s an old guy who can’t get low, my stem is slammed and can ride low all day long). He admitted right leg dominance because he has a left hip replacement. I’ll qualify that one leg power meters are accurate at measuring one leg.

david - 07/10/14 - 2:54pm

Reynard, it really isn’t a scientific comparison. It’s anecdotal, that’s all.

Also, if you’re getting beat by an old guy, with a fake hip, riding Merckx style, I’m not sure you even need a power meter.

Frank - 07/10/14 - 11:38pm

So why not make it a spider-based system and pick up both legs contributions? Is there (still) a patent covering that method?

Edge - 07/11/14 - 9:14am

+1 for David.

saddlesniffer - 07/11/14 - 4:40pm

I don’t need a power meter. I KNOW I go HAM!

Post a comment:

Comment sections can be a beautiful source of knowledge, conversation and comedy. They can also get pretty ugly, which is why we've updated our Comments Policy. If your comment isn't showing up or suddenly disappears, you might want to check it out.