Cadence vs higher gears

[HovR]

Ah, well I failed to realise it because you failed to mention you were on an old clunker. Anyway, of course there will still be cross-over ratios - just not as many. Presume you have a 12 and something like a 15 or 16 do you not..?

How nice of you. If you're going to continue like this I can't be bothered to continue this "debate".

 

[black'n'yellow]

'clunker' - look it up. Anyway - you do have cross-over gears. I actually don't care if you use them or not. I'm just saying you would be daft not to use the big ring where you have the option.

 

[fossyant]

Give over for flip sake. Sheesh.

 

[MrJamie]

At 30mph, you will ride at the same cadence (give or take) on 42/12 as you will on 52/15 - ironically, if you bothered to change up to the big ring, you would get an easier time, not a harder one, as the bigger ring gives you a better mechanical advantage for the same cadence...

Sorry for the dumb question, but can you explain this? I get that the ratios are near enough the same, so the cadence would be the same, but what is this mechanical advantage? I always thought if the ratios were the same then the gears were essentially identical, from a user point of view.

 

[black'n'yellow]

Sorry for the dumb question, but can you explain this? I get that the ratios are near enough the same, so the cadence would be the same, but what is this mechanical advantage? I always thought if the ratios were the same then the gears were essentially identical, from a user point of view.

Not dumb at all - the differences aren't huge, that's for sure, but friction loss is reckoned to be less on the big ring as it is effectively hanging onto the chain for longer on each turn of the crank.

I'm no scientist though, so my explanation will be crap, and the only link I can find which attempts to explain it is here: http://www.velominati.com/technique/sur-la-plaque-physics-of-the-big-ringle/

 

[fossyant]

Right, assuming chain displacement is not factored, anyone would be hard pushed to tell the difference between gear overlaps in resistance. Impossible. The main resistance on a bike is the blob of a human on top.

Mechanically, it's better to keep a straighter chain, and in theory, bigger sprockets and chain rings spread load, but you would not notice it on a bike unless the chain was at a skewed angle. Running big to big and small small isn't good on the chain, and can be rough.

Running gears and chains at high angles of deflection promotes wear.

I can't tell the difference in resistance from switching a 39x16 to a 53x19, slight gear ratio change but no difference, even on an old bike, but rather well maintained one. That's my overlap gear.

 

[black'n'yellow]

I can't tell the difference in resistance from switching a 39x16 to a 53x19, slight gear ratio change but no difference, even on an old bike, but rather well maintained one. That's my overlap gear.

You should be able to tell the difference between 39/16 and 53/19, because you will be going almost 3mph faster for the same cadence. So it's not an 'overlap' gear.

 

[Garz]

So - in other words, stop 'debating' and agree to disagree that there's alot of talk wasted on gear ratio - virtually no difference here let's move on..

 

[Garz]

You should be able to tell the difference between 39/16 and 53/19, because you will be going almost 3mph faster for the same cadence. So it's not an 'overlap' gear.

Let's take this hypothetical example, and assume you were approaching a steady incline. It would be far easier to shift down one or two (back in the cassette) to maintain the same cadence in the lower ring than to either cross chain in the larger ring, or use the FD to drop into the lower ring and lose momentum.

 

[black'n'yellow]

Let's take this hypothetical example, and assume you were approaching a steady incline. It would be far easier to shift down one or two (back in the cassette) to maintain the same cadence in the lower ring than to either cross chain in the larger ring, or use the FD to drop into the lower ring and lose momentum.

what speed are you approaching the incline at, and how long/steep is the incline..?

 

[Garz]

what speed are you approaching the incline at, and how long/steep is the incline..?

The exact speed and incline to support my hypothetical argument of course!

 

[black'n'yellow]

ok - but I think you're missing the point a bit. My point is that whatever gear you happen to be riding in the small ring - if there is a big ring equivalent, you will be more efficient in that gear...

 

[Hacienda71]

ok - but I think you're missing the point a bit. My point is that whatever gear you happen to be riding in the small ring - if there is a big ring equivalent, you will be more efficient in that gear...

Even if it means you are riding with a carp chain line?

 

[black'n'yellow]

Even if it means you are riding with a carp chain line?

depends what you mean by a crap chainline - if the situation demands it, I will cross chain and ride on big/big. But if you are still running out of gears at that point (ie you lack the power to maintain your current gear/cadence), then you will have no option but to shift down anyway....

 

[Garz]

But if you are still running out of gears at that point (ie you lack the power to maintain your current gear/cadence), then you will have no option but to shift down anyway....

..which is when it becomes inefficient in that gear! Horses for courses.