What the ???

[Daddybus]

Saw this bizarre chainring on eBay ... what why ?

 

[pclay]

Have you not heard of oval chain rings. They are all the rage.
https://www.google.co.uk/search?q=o...&ie=UTF-8&hl=en-GB#hl=en-GB&q=oval+chainrings

 

[winjim]

It increases effective chainring diameter on the pedal downstroke, creating a higher gear at the point where the most power is produced. I think Froome might use them.

 

[midlife]

All the rage from years ago....

Shaun

 

[winjim]

Modern version.

 

[Daddybus]

Well I never ...

 

[Illaveago]

I think they fitted a similar crank on a Raleigh ATB in the late 80's early 90's, I think there is one on an old Raleigh that I have but the ovality is not so pronounced but it did feel odd.

 

[Sharky]

Stronglight 49d cranks were very popular when I started and had a similar bolt pattern

http://www.classiclightweights.co.uk/designs/hs-stronglight.html

 

[Drago]

It increases effective chainring diameter on the pedal downstroke, creating a higher gear at the point where the most power is produced. I think Froome might use them.

and there's the other sort espoused by the likes of Geoff Apps which have the maximum chain travel at the dead point in the pedal stroke, not to produce more power but to even out the power delivery when off road and reduce the chance of breaking traction in slimy surfaces. Supposedly.

 

[swee'pea99]

Shimano flirted with that back in the day with their Biopace chainsets. Far less extreme, but the same basic idea. I used to have one on a Raleigh Dyna-Tech. Don't remember it making a lot of difference TBH.

 

[MichaelW2]

Biopace was rigged so that max diameter was phased to the crank position. In other systems, max diameter is 90 degrees from crank or 180 degrees, reversing the hard/easy part of each pedal stroke. Who knows why?

 

[fossyant]

You have to laugh. They keep re-inventing the 'oval chain ring', but the good old round ones seem to work OK?