out of round or oval chain rings

O

Odinn

Likes Bikes
Gday,

I was watching a youtube clip and saw while a guy was commentating a girl warming up on a dualie, when the film was panning around I noted the chainring looked like it was moving forwards and back. Initailly I thought dayum this girl has some grunt in her legs, but then I watched it again and again and I think the chainring was oval.

Questions, is it possible it was oval? And what would the advantages/disadvantages be?

I've never seen it before and was wondering if I was seeing things or not?

Robb
 
B

banana.logic

Likes Bikes
A mate and I found an old road bike that had been put out for council pick-up a while ago and it has elliptical front chainrings. I don't really notice it while riding the bike though. There is definitely a lot of info on the net about them.
 
mik_git

mik_git

Likes Bikes and Dirt
I know most peopel hated them, but I never noticed anything bad with biopace... nothing good either...:rolleyes:
 
cam-o

cam-o

Likes Bikes and Dirt
I rode with a guy recently who had oval chainrings. There is a new generation of them coming through.

If i remember the explanation correctly: Biopace was intended to smooth out the pedal stroke, but the larger part of the ring was acting on the chain when the cranks were in the 6 and 12 O'clock position. (i.e. during the weakest part of the pedal stroke).
The new elliptical rings do the opposite, the "fat" part of the ring is acting on the chain when the cranks are at 3 and 9, allowing you do deliver more torque during the downstroke of the pedal cycle and spin across the weak part.

I haven't ridden them myself but the guy who had them is a very good roadie (races at the national level) and reckons they are great.
 
{ScarFace}

{ScarFace}

Likes Dirt
I've got a biopace on my old roadie, good when you've got your head down and pushing the big ring but feels horrible when you start to spin it in a higher cadence. Would be nice on a timetrial style roadie, but not on a everyday ride or a mountain. I reckon anyway.
 
D

dh1

Likes Dirt
Pinner said:
I think Fabian Barel used to run them. now he jut runs different length cranks.
Click to expand...
If i remember correctly he had one at the champs at stromlo because he wanted to decrease the force that was applied to his injured knee during the pedal stroke.
 
Dozer

Dozer

Heavy machinery.
Staff member
dh1 said:
If i remember correctly he had one at the champs at stromlo because he wanted to decrease the force that was applied to his injured knee during the pedal stroke.
Click to expand...
That is exactly what it was for. If he was fully fit he would have owned that day.;)
 
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