Thetic elliptical chainwheel

Thetic chainwheel (yes I know it's not
oriented correctly!)

 

Here's one of those old fart, there's nothing new under the sun, it's all been done before posts...

The Thetic chainwheel is from the late thirties, Belgian made and is an eliptical chainwheel designed to flatten out dead spots in the pedalling stroke. I picked this one up a while back on fleabay. I've mated it to a Stronglight chainset and it'll find a home some time in the future on an appropriate cycle.

Vaguely popularised by Shimano with their 'Biopace' rings in the eighties and early nineties and now once again undergoing a resurgence. Elliptical chainrings have been around since the 1890s and they are an idea that gets trundled out with regularity to shift a few more units every two or three decades...

Do they work? Well, I used to ride with Biopace back in the day, like many others. Now I don't. Do I notice a difference not using them? No. The best I can find in favour of elliptical chainwheels is that they might work and they certainly won't hinder you.

Thetic chainwheel ad from the late thirties.