What's the power loss to a squeaky chain?

Question

I've got an almost new chain, but forgot to oil it before today's ride. It would probably have been fine except for repeated dunkings in muddy water early on. Later in the ride it developed a noticeable squeak. Although I carry oil, I didn't particularly want to add oil on top of filth, and couldn't really be bothered (an ill-judged route led to a fair bit of walking/wading so time and cold were both sub-optimal).
But in hindsight, could stopping to oil the chain have actually got me home sooner? Was I wasting loads of power?
I ask in a general sense, but my setup is Sora 3x9, on a heavy tourer (and not very aero with extra bottles on the forks).

Weiwen Ng · Accepted Answer

The question of how much power was lost has been answered. I would just add this: if the chain is squeaking, it’s got insufficient lubricant. You are presumably having bare metal rub against bare metal. That will cause a lot of wear, in addition to drivetrain friction.
Even though the chain was dirty, I don’t see how adding lube on top of the chain could have worsened the situation. The lube should penetrate to the rollers and probably stop the metal on metal situation. That said, note the discussion in the comments; you could risk importing more dirt into the rollers, which would increase the abrasion rate. The question about which of the two situations is less bad might only be answerable if we experimented, and we'd probably need a microscope to measure the amount of contamination between the rollers and pins. In either case, the chain won't explode if you let this happen once or twice, and take this as a reminder to keep the chain lubricated.

thelawnet · Answer

This seems to answer your question:
https://cyclingtips.com/2020/05/how-many-watts-does-a-dirty-chain-steal/
It suggests a dry chain loses 7W out of 244W, which is 2.9%.
Your % speed loss will depend on your speed and aerodynamics - if you are producing, say, 80W, and cycling at 10mph on a flat road, then you could expect to lose almost that much time (so maybe another 100 seconds over an hour). At higher speeds, say 25mph on a flat road, then almost all of your losses are aerodynamic, so it comes increasingly true that your gains (or losses) are proportional to the square root of power losses, so you could expect to lose perhaps 1.5% of your time, so something like 54 seconds.
Of course stopping to lube isn't a bad thing as it helps avoid that little bit of premature wear to components meaning your chain lasts a few more miles, but  if it was raining or whatever, it is probably better to just keep going, as it would just wash off anyway.

Adam Rice · Answer

The amount of power you lose is proportional to the amount of power you're putting in, so there's not a one-size-fits-all answer to this question.
Although the question of which lube is best has been studied extensively, as far as I can tell, these studies don't include unlubed chains (which would be interesting as a control). What those lube tests show is that when riding at 250 W, a chain with a top-quality lubricant will cost you about 5 W, and a poor lube will cost you about 10 W.
I'm not sure if we can extrapolate from there to an unlubed chain, but perhaps that would cost 20 W, or 8% of your power input. That might have been a difference of 2–3 km/h.
For whatever it's worth, the factory lube on chains is usually very good. I always ride new chains without adding lube until they squeak, and then try to strip off all the lube before I add my own.

What's the power loss to a squeaky chain?

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