Home > Clothing-Gear-Tools

Curved Cranks Claim Greater Efficiency

Support us! Bikerumor may earn a small commission from affiliate links in this article. Learn More


Not sure where the text came from forwarded by our friends at Cycles de Oro, but since we’re in the rumor business, here’s you go:

E-Chein Crank is curved, it makes battery capabilities of British electric bike extended to 4~6km
– the normal travel range is around 32~34km.(Electric bike)
– The Revolution(s) Per Minute increases from 63 RPM to 85 RPM (Road bike)
– The average speed increase 20 km/h to 27 km/h (Road bike)
The weight is about 400 g heavier than the high-end crank’ (including gear ,bb), but the efficiency of driving force is more efficient . It is interesting.

Hit ‘more’ to see a closeup of the crankarm…


Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Newest Most Voted
Inline Feedbacks
View all comments
Rick Vosper
13 years ago

Editor, please do your homework! This is a blatant rip-off of the famous Italian PMP crank developed in 1981 and used successfully by Soviet Bloc teams in the ’84 and ’88 Olympic Games.

See http://www.classicrendezvous.com/Italy/PMP_crk_ad.htm

Unlike this cheap knock-off, the originals also incorporated Polchlopek (Rotor-style) eccentric ring technology (later copied and moved 90° out of phase by Shimano). The PMP Classic, with round rings, was also available in a doubled version to increase the power boost still further. See http://www.classicrendezvous.com/Rarest/pmp_extra.htm

Finally, please note the numerous technical studies indicating the curve on E-Chien crank is actually CURVED IN THE WRONG DIRECTION (i.e., 180° out of phase), effectively negating any biomechanical advantage whatever.

You should be ashamed of yourself for attempting to foist this technology off on an unsuspecting public.

13 years ago

Try the decaf, Rick.

Dale Brown
13 years ago

Rick is confused…
The PMP were proven to actually proved through years of research to have been curved in the wrong direction, and these new Asian cranks are a forward step..
Actually the most recent iteration (not yet released) have the ultimate development in that the cranks continue to curve in a way that the pedal holes end up about exactly where they would have been, had the cranks been straight!
Geez, you should have thought this all out before making such an outrageous posting!!!

13 years ago


There is a computation formula to calcualte the curved crank’s torque output on their website.


13 years ago

These curved cranks will have no benefits at all, anyone who understands basic physics will see this…
Don’t go buy this crap people, if you want better efficiency just get rotor cranks.
Or just buy a good lightweight crank, like middleburn and consorts.
Also, these cranks are one of the ugliest I’ve ever seen!

12 years ago

Very rude comment mister Vosper, similar ideas may come together to different people in the same decade, year or even a day….remember the radio invention… coincidences do exist…how can you possibly be sure its a rip-off? Can you read somebody else`s mind?

12 years ago

I love reading all the closed minded comments and after realizing the potential of these cranks I bought 2 sets, Road and MTB version and combined them for an increased effect, I have a Dual shock MTb weighing 18 kg and I am running 11-28t rear and 42-56t front, it cruises at 55-60kph and I have a spinal injury so you can beleive what you want but I have the true knowledge and put my money where my mouth is. You can see my bike at this site and I will be happy to re-educate you with fact. (http://forums.mtbr.com/showthread.php?t=501193)

11 years ago

Those have opposition or think lever theory about curved cranks, if their viewpoint is correct, why people so surprise curved crank’s efficiency after riding.
As I know the efficiency comes from the gravity of cranks forward , in other words, toe-out effect. The calculation formula is not using lever theory but using trigonometric function to calculate its effective force area
According to maker’ data, they did integral calculation by every 10 degree then total work got 33% efficiency that is compared with traditional straight crank.
On upper dead point , straight crank is vertical to axle ,so most of pedaling force are?lost on this angle. However sickle crank not only center gravity forward but also effectively pass through upper dead point and reduce loss, so output increases by 33% compared with straight crank..
My personal opinion
There are two kinds of scientist since long time ago- practice and laboratory scientists.
Science calculation is to explain nature phenomenon not simply to examine its possibility. The sickle crank’s efficiency is fact and proved. It is said that SGS was surprised, too when they got result
The follows comes from official website
1. calculation formula( by every 10 degree)
According to this data you can see torque output is bigger than straight crank before 160 degree and get more efficiency from 0 ~130 degree. Reduced force loss in the max pedaling force losing zone , so curved crank can get more torque output.
Straight crank is better than curved from 160~180 degree , however, it is in the low pedaling force losing zone ,besides on 180 degree position , the other crank already on the 0 degree(upper dead point) to start new circulation.
If using clipless pedal to pull from low dead point , the efficiency will be as same as 0~130 degree. One leg pedal and the other leg pull by clipless pedal , it will get multiple effect.
2.SGS Test report
3. USA Cyclist used computer trainer to test, AVE HR reduced 11 bpm?maximal oxygen consumption reduced 9%?MAX HR reduced 5 bpm?maximal oxygen consumption reduced 4%


I installed one set. When pedal harder , I could feel the explosive power form rear wheel .If I constant speed ride , the pedal seems be driven by certain force and automatically pass through upped dead point.
Some one had pedaled 53t gear and his rpm increased 20%. My experience is using front 56t and rear 11t , feel as same as 50 t gear. The speed is very fast and easy to reach 40km/h, well, because it is 56t. Some friends got good physical condition they could easy to reach 50~55km/h

One of my riding course is 20km and 9.75km is a slope. The slope is average 3.5% and last 2km is 7.5% slope. It took 90 minutes to run this course, but used this sickle crank , it only takes 70 minutes. 20% faster.

My good friend , a bicycle shop owner, he remodeled his MTB with sickle crank and 700C wheel to compared with his original road bike with straight crank. The former uses front 42t – rear 15t and the latter used 39-15, he said the former is much easier to pedal, pedaled 3 times rpm gone 60 , pedaled 5 times rpm gone 90,so it could save a half time to reach the latter’s rpm

From these riding experience , I know it really get efficiency

Sharing this information for you guy . If you want know more riding experience , you may check out official website.

Subscribe Now

Sign up to receive BikeRumor content direct to your inbox.

Subscribe Now

Sign up to receive BikeRumor content direct to your inbox.