Oval chainrings

[Mr Moofo]

Anyone using them - I am a bit stuffed on the Cotic as running some 12 year old cranks that know nothing of boost spacing. So there is not enough clearance for a 34 oval.
Major break through and a must have - or snake oil?

[weeksy]

I'm sure Crust will be along sometime later, but he ran Ovals on his for a while and really liked it... I've never tried one myself though

[bevvo]

So gearing is down to the relative number of teeth on each cog, right? How can the shape of the sprocket do anything but vary the chain slack?
Sounds like snake oil to me...

[weeksy]

it's to do with your pedal stroke that means you can make 'better' power on the different parts of each stroke.

[formula400]

ive seen these, look quite interesting, looking forward to seeing if there decent

[Mr Moofo]

Back in the olden days , Shimano introduced BioPace oval rings - they were meant to help with the power stoke. They were totally bollocks.
Ovals were reintroduced as a marketing tool several years ago - but with the ovalised bit moved 90 degrees ( to help smooth out the power stroke). So it still seems like a load of bullock to me ...
I am not sure that my legs, when grinding up a hill, are that perceptive ...

[Beancounter]

I've got an unused, orange anodised, Superstar Components oval chain ring, 32 tooth that you can have. Fairly sure it's a 104BCD and requires four bolts to mount to the crank arm.

[MingtheMerciless]

I run oval rings on the SS and it does make a difference grinding over TDC.

[Mr Moofo]

I've got an unused, orange anodised, Superstar Components oval chain ring, 32 tooth that you can have. Fairly sure it's a 104BCD and requires four bolts to mount to the crank arm.

How much?
It would be good to try
Thanks

[crust]

I run one on my Whyte, excellent piece of kit in some circumstances.

Forget the Shimano version, the Absolute Black rings are different.

For me I only really notice the difference if I'm struggling to get up a steep part of a climb at a low cadence (run out of gears) and I'm putting in max effort just to turn the pedals. It feels like you get through the dead part of the pedalling stroke quicker (which you do as the gearing is lower).

[cheb]

No bicycles but some examples of oddly shaped gearwheels and what they do:

http://www.douglas-self.com/MUSEUM/POWER/gear/gear.htm

[Mr Moofo]

No bicycles but some examples of oddly shaped gearwheels and what they do:

http://www.douglas-self.com/MUSEUM/POWER/gear/gear.htm

But you don’t see them now, right?

[Mr. Dazzle]

So gearing is down to the relative number of teeth on each cog, right? How can the shape of the sprocket do anything but vary the chain slack?
Sounds like snake oil to me...

Not quite.

Gearing is actually down to the relative radii of the two cogs. >99% of gears are made with constant pitch teeth and a circular shape, which means the number of teeth and the radius are directly proportional.

If you have an oval gear that relationship doesn't hold. Its the radius which matters. The idea is you change the radius of the the gear and hence the gear ratio as you turn the crank. Makes you have effectively a slightly higher gear at some points in the stroke and a slightly lower one at others.

[lostboy]

So gearing is down to the relative number of teeth on each cog, right? How can the shape of the sprocket do anything but vary the chain slack?
Sounds like snake oil to me...

Not quite.

Gearing is actually down to the relative radii of the two cogs. >99% of gears are made with constant pitch teeth and a circular shape, which means the number of teeth and the radius are directly proportional.

If you have an oval gear that relationship doesn't hold. Its the radius which matters. The idea is you change the radius of the the gear and hence the gear ratio as you turn the crank. Makes you have effectively a slightly higher gear at some points in the stroke and a slightly lower one at others.

It's why Rotor and Osymetric (two of the biggest proponents of the oval chainring) recommend going a size smaller if you want to keep a similar cadence/power output.

[Mr Moofo]

Went out on the PP HT with a 34 Absolute Black oval ...
Didn’t even notice it !
Not sure it makes any difference - but did notice the extra 2 teeth on the ring.

Climbing may have been easier - but hard to be objective ....