Power Meters / Powermeters (SRM, Powertap, Quarq, Ergomo, Vector, Stages, power2max, P2M, 4iii, InPower, Cinch)

Vectors are much more of a pain than the P1's to swap between bikes - get the P1's.

If somebody has a source explaining or can explain succinctly how 5% variation in power meter reading can compromise your training that would be appreciated please.

It's not the 5%. But inconsistency.
If you only ever use one power meter, it doesn't matter what numbers it gives you, as long as it's consistent.

If it sometimes is 1% down and others 3% up, then that variation leads you to have no clue what your doing in training.

So in your training you have to ascertain that your effort over x amount of time can not be ~ 10 watts over or under lets say 200 Watts?

You do not want random variability. It's a scientific measurement and you need it to consistently give you consistent readings.

The key is consistent readings.

Say your threshold is 300 watts, that's 15 watts either way - quite a lot.

For e.g. you might see 285 average on your computer and push that much harder because you know you should be able to hold 300 for the whole climb, but due to the under-read that's enough to make you blow (if your FTP is accurate).

Also the L/R balance tends to move around depending on how hard you are working - so 300 watts might be 285 at one point in the ride, but 315 at another. That's a huge swing, and makes basing a pacing strategy on power quite challenging, and also setting training targets from a ride a bit hit and miss.

Power meter for cannondale cranks? What are the options, what's optimal?

P2M

SRM , P2M, Stages, possibly that chainring based one from Powertap, any of the pedal meters etc.

I'd look at p2m first - the SRM looks better but empties your wallet and is harder to live with.

Is Stages still frowned upon, even if I only want to hire one for a couple of months to pace myself on mountains?

Do you know if the rival crank arm has a different Q to an Omnium?

Rival1/Rival22 GXP Q=149.6
Rival1/Rival22 BB30 Q=147.4
Rival OCT 10-speed Q=147
Omnomnom Q=135

Ta, best leave my Omnomnom the way it is.

It's fine as long as it's the only PM you use- as a training tool. Mine is now surplus to requirements because I have a p2m on the other road bike and a powertap for track efforts so I've stopped using it.

I happen to have a Stages arm (and a choice of Red or Rival cranksets) for sale :)

what tester said. I tried compensating with cleat shifting for a while and it was rubbish. Best not to bother.

Ultimately, I'll probably get a p2m - I'm using Trainerroad a fair bit at the mo - but was wanting to be able to see what to aim for on a week in the Alps so I don't die on the first day.

Sadly, buying anything isn't an option at the mo, and I'd need DA!

I'd agree that some peoples L/R balance varies depending on where they are on their power curve but it does tend to be very consistent. If you are one leg bias at threshold you are always going to be bias towards that leg unless you do specific exercises to train it out of your self. But then you'd know you were altering your L/R balance. Long and short of it is they are still fine and it's still fine that you just don't like them. There is no need to constantly complain about them though because you prefer another option.

I'm not complaining about them, I have a single sided power meter myself (Vector-S), I think they are fine as long as you buy one with your eyes open/aware of the drawbacks.

I'm not complaining about them...

Phew! That's good to know.

But when you say "I", are you speaking on a personal basis (perhaps based upon how many miles you've flown (biz, natch), or the colour of the key you use to take a piss in a foreign city), or is that the "Royal we", as in "we (not withstanding my undisclosed and rather vague role) at Talbot"?

I appreciate you have your hands full, what with patronising Scoble [prick] and posting jokes of your hairglasses (and classifieds that put the "self-absorbed" into "tedious suit"), but no doubt I'm not the only reader who's reassured to feel your decisive arm around my uncertain shoulders.

Phew! That's good to know.

But when you say "I", are you speaking on a personal basis (perhaps based upon how many miles you've flown (biz, natch), or the colour of the key you use to take a piss in a foreign city), or is that the "Royal we", as in "we (not withstanding my undisclosed and rather vague role) at Talbot"?

I appreciate you have your hands full, what with patronising Scoble [prick] and posting jokes of your hairglasses (and classifieds that put the "self-absorbed" into "tedious suit"), but no doubt I'm not the only reader who's reassured to feel your decisive arm around my uncertain shoulders.

What are hairglasses?

What are hairglasses?

Yup, focus on that.

PS To clarify, when I wrote "I appreciate you have your hands full, what with patronising Scoble [prick]...", I should have written [you prick].

Apologies for any confusion.

No worries, you have my permission to buy a Stages if you feel it will help you.

What do people use for analysing their power balance, pedal efficiency and torque effectiveness? I have TP premium and it gives a balance figure for the laps or overall, but not anything else.

And do peoplr pay much attention to the effectiveness and torque measures?

What are you going to do with the information? BC don't bother with any of that any more...