Chainrings...

[tesseract]

Now that's what I'm talking about, and it's carbon

[combatdwarf]

I have watch this thread but now I have to put in....I am a rubbish climber....genetics/rugby and beer have ensured that...however now I choose flatter courses (ie not Wimblebitch) I have found that going to a 54/40 have made big differences to my times...I now do a 70.3 bike in around 2:40 whereas on a compact I was struggling to come in before 3hrs...

So whilst I agree on paper a compact sounds fine at my lower cadence of 80 a bigger gear works...

[King Sad]

But then again physiology also comes into play, if you have knackered knees pulling a 54 is not an option, if you are able to maintain a 53/11 throughput a race great, if however you are using 53/12 or 54/12 for most of the race but could handle a 50/11 a 50/11 is a bigger gear.

[tesseract]

But then again physiology also comes into play, if you have knackered knees pulling a 54 is not an option, if you are able to maintain a 53/11 throughput a race great, if however you are using 53/12 or 54/12 for most of the race but could handle a 50/11 a 50/11 is a bigger gear.

But isn't the power output a factor as well, or is that what you're saying? ie between 53/12 and 50/11 is there a difference in required power to hit the same speed, assuming same cadence?

...and if you can handle 50/11, what's the difference with 53/11? again in terms of power required for the same speed.

I'm not clear how it all fits together between power, cadence and gearing, or I'll re-phrase that - I'm not clear if different gearing actually reduces the power required to hit a speed?

[Bopomofo]

Power is torque multiplied by revs.

Or... how hard you stamp on the pedals multiplied by how often you do it. Simples.

To travel at x kph will take the same power* regardless of gear. In a low gear you'll be spinning away and pressing softly on the pedals. In a big gear you'll be spinning slowly and mashing the pedals hard.


*At extremes, ie really high or really low gears this isn't true, for 'biology' reasons. Spinning at 120rpm will knacker most people almost regardless of how much force is required: your muscles are moving very quickly. Also, most of us have shit technique so even free spinning wastes energy. Similarly, mashing away at 40rpm would probably be asking too much of your muscles.