Gearing efficiency question

sheffsimon

neeb wrote:

Real men ride in the big ring - always.

End of.

While metrosexual types change down to the small ring to save wearing the titanium sprockets on their dura-ace & super record cassettes...

Real men dont use the larger titanium sprokets...even when in the big ring.

billysan

neeb wrote:

to quote steeve 100. thats not true. every time a 50 tooth chainring rotates once 50 teeth have past a given point.
so for each rpm 50 teeth have gone round, but at the same rpm(cadence) on the small ring only 34 teeth have gone round. each tooth is 0.5 inches so 50 teeth is 25 inches gone round versus 17 inches gone round at the cicumference of the small ring. so the chain has only travelled 34 teeth on the small ring instead of 50, so its moving slower.

Yes, this is SO counter-intuitive at first but it must be right. You can visualise it from the back too - when you are using the same gear ratio on the big ring, you are using both a larger chainwheel at the front and a larger sprocket at the back, so the chain is of course moving faster at the back too (the sprocket set is doing the same rpm at the same gear ratio, just as the cranks are). Basically, on the large ring and a large sprocket, the rpm of both the cranks and the sprockets are the same as on the small chainring and a small sprocket, but the chain itself is doing more rpm.

So it follows that the chain is under less tension on the big ring because it is moving faster... but it is claimed that the greater tension when on the small ring (or when using a compact setup vs. standard) leads to greater efficiency in power transfer. On the other hand (if I have understood the jist of the article I linked to above), this may be counteracted by the greater amount of bending of each link...

So in terms of power transfer efficiency (as opposed to wear) there are at least two variables that may or may not cancel each other out, depending...

And in practice it's still not doing to make a blind iota of difference!!

This is pretty much the point we got to in the original argument I had. Its interesting to see this thread develop too as a few people have now pointed out, there are factors involved that one might not expect.

Im my mind, with regards to the original question, there must be a difference. But Ive no idea which is better (more efficient / less friction).

So Im just going to stay in the big ring

Cheers fellas