Snapped chainring

Peanutt

Don't ask me how I managed it, maybe I need to loose a few pounds or I just have incredibly powerful thighs but I've managed to shear a chainring bolt and snap my lower chainring in two.

Does anyone know where I can get hold of a shimano biopace chainring, think it's a 36t

mitchgixer6

You don't need to get the sepcific Shimano chainring. As long as you get the same BCD (bolt circle diameter) measurement then you can use virtually any ring as long as it's Shimano compatible.

Have a look here http://www.spacycles.co.uk/products.php?plid=m2b0s149p0

Peanutt

Ooh I didn't know that, top tip!!!

Thanks

me-109

Although if you want a Biopace it will have to be Shimano ;-). Not sure they have so much effect in the lower ratios so probably nothing missing by just getting a standard ring.

mitchgixer6

Sorry, excuse my ignorance. Just done a quick search and realised that the Biopace is an elliptical ring?

If so then you will have to search for exactly the same kind as mentioned above. Although I'm sure the Rotor Q rings or O Symmetric rings would do the same job and I'm sure they'd be easier to get hold of (if at a premium).

Peanutt

I'm guessing it's not going to be that easy finding an exact replacement, toying with the idea of putting spacers in there and just running the top ring until I can get one. It's for my commuter bike, at least it would make winter training a bit tougher!!!

rolf_f

Biopace is far less pronounced than modern eliptical rings. I can't really tell the difference riding them though it maybe more obvious if you are on the flat (which I don't have access to up here!).

As mitchgixer6 said, Spa Cycles is always good for a look. Can't recall though if the inner rings of Biopace were elliptical anyway. Might only be the outer.

Monty Dog

Biopace is 20+ years old so your chainring has had a good life and likely needed replacing anyway. Whilst it was elliptical, unlike Rotor rings, the high spot is not aligned to the crank. Expect your chainring is 110mm BCD as it's a 36 and Stronglight make cheap, suitable replacements. You'll only likely find a Biopace ring on ebay.

rolf_f

Monty Dog wrote:

Biopace is 20+ years old so your chainring has had a good life and likely needed replacing anyway.

That assumes that time ages chainrings rather than useage. The lovely drilled chainrings on my 32 year old Raleigh show no signs of wear yet. You certainly can't assume it would have been due for replacement!

Peanutt

Thanx chaps, looks like stronglight is a good contender and in my price bracket too, doubt I'll notice much difference in the lower ring.