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Losses in watts from worn drivetrain?

Old 07-09-19, 11:34 AM
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Losses in watts from worn drivetrain?

How much do I lose in watts when I let my chain and cassette get worn. I'm not sure how stretched mine are right now but when I'm going really hard I'm starting to hear more sound even when the chain is lubed. Yes, I could measure the stretch. But I'm wondering about how much are the losses as a system gets worn, as measured in watts. I'm not talking about the maximum of badness of a ruined system. Just as a drivetrain wears, what happens to its efficiency? Thanks.
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Old 07-09-19, 11:57 AM
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Old 07-09-19, 02:29 PM
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Originally Posted by JeffOYB View Post
How much do I lose in watts when I let my chain and cassette get worn. I'm not sure how stretched mine are right now but when I'm going really hard I'm starting to hear more sound even when the chain is lubed. Yes, I could measure the stretch. But I'm wondering about how much are the losses as a system gets worn, as measured in watts. I'm not talking about the maximum of badness of a ruined system. Just as a drivetrain wears, what happens to its efficiency? Thanks.
Nothing, then nothing, then bad, then really bad, then undeniably bad, crunch slip crunch slip, then replace whole drive train.

This isn't an experiment anyone does.
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Old 07-09-19, 05:18 PM
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I have read that a drive train perfectly maintained could be as much as 98% efficient (depending on the gear selection) and one poorly maintained could be as low as 88%. Poorly maintained may have broken gear teeth with a rusty chain and caked with mud for all I know, but there is the ballpark range that your drive train will fall somewhere inside.
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Old 07-09-19, 05:28 PM
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You'll lose more money than watts from a worn drivetrain.
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Old 07-09-19, 07:27 PM
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Old 07-09-19, 07:40 PM
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Originally Posted by Wileyrat View Post
You'll lose more money than watts from a worn drivetrain.
lol that's funny
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Old 07-09-19, 09:53 PM
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My guess is that the friction difference between a well lubed and a not well lubed chain

is much more than the difference between a new and worn drivetrain.

No one complains that the bike is harder to pedal because the chain & cassette are worn.
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Old 07-10-19, 02:52 AM
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Originally Posted by Wileyrat View Post
You'll lose more money than watts from a worn drivetrain.
This is'nt exactly true with cheap drivetrain components. For example, a chain and casette for $15 each will last for about 4000km before starting to skip, if the chain isn't replaced when recommended. If by timely replacement (say, after 2000km) of the chain you get 3 chains with one casette, you do 6000 km for 3x15+15=$60. That averages out $30/4000 = $0.0075/km in the former case, vs $60/6000 = $0.01/km in the latter.
Cheap crankset for $30 will outlive no less than 2 casettes, more likely 4.

Worrying about the drivetrain wear makes sense only if your cogs and chainwheels are significantly more expensive than the chain.
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Old 07-10-19, 03:07 AM
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I think I'd notice the poor shifting before I noticed the watts.
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Old 07-12-19, 05:27 AM
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With the cog ,chain rings , you loose watts based on weight , aero drag and chain line position .

With the chain you loose watts based on stiffness loss or flexibility , lube , weight and maybe slight aero drag , very slight though,

Bearings like hub and bb you get friction vs wear , so you can reduce friction by stripping grease but that increases wear time .

Over all change your chain often , even run 2 or 3 chains waxed with speed wax or home made Teflon powder , back it up with wet lube if it rains use some ceramic grease in your bearings , and use at the least a tt style crank and chain ring , but you can always use a 105 or Integra cassette or sram equal, if say anyway
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Old 07-12-19, 06:40 AM
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How many bicycle angels can fit on the head of a standard spoke? What about a DT Swiss spoke?

When I was a lad, I'd worry about getting the finest parts and frames and such. No doubt, good stuff is nice to ride on. And as an engineer, I do enjoy thinking about these questions. But as one matures, one realizes that life if fleeting. Its more important to ride, and to enjoy the ride, than to navel-gaze regarding hypothetical questions. Why worry about power loss (btw, it IS power loss, in Watts) due to unlubed chain friction when for pennies you can have a lubed chain?

So, lube your chain and you don't have to worry about that efficiency loss. And you should always ride with a lubed chain because once the lube wears off you are essentially doing a fine polishing/grinding operation using your bike as a machine tool.
If your chain is stretched, replace it.
If your lubed system with a good chain isn't skipping or having problems shifting, go for a ride.

Check your chain two ways. With the chain shifted to the large chainring, can you pull the chain off the chainring (pull the chain that is on the front facing edge of the chainring). If you can pull it off, check chain length with an accurate ruler. Twelve links should be exactly 12 inches. If they're between 12 and 12 1/16 inch, you're good. 12 1/16 to 12 1/8, you should replace the chain. Beyond 12 1/8, you may have to replace cogs or even chainrings.
See here.

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Old 07-12-19, 07:03 AM
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i'm interested in the numbers. there are a lot of numbers in biking. does anyone have numbers for chain and cog wear? that's all.

"losing watts" of course is 100% relative. ...do you lose 2 watts or 4? when riding on the rivet w a fast bunch, it matters.

a few aren't so bad but i'd like to keep all the ones i can. no need for philosophizing about a numbers question...
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Old 07-12-19, 07:27 AM
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I thought I did give you numbers already, but here's a few more details. Keeping in mind that this is all "ballpark" range.

A fixed gear drive train in good condition is 98%-99% efficient.

Derailleur drive tops out between 97% and 98%, in the right gears at enough power (it does make a difference)

Cross-chaining, using lower gears drops and other issues drops efficiency to the low to mid-90's.

Running without chain oil costs up to 1% efficiency. Elongated chain costs up to 1% efficiency. Bad DR bearings and pulleys allegedly cost another 2% but I'm not sure I believe that, unless they're jammed up or something.
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Old 07-12-19, 07:53 AM
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"Claimed saving of 10 watts from specially treated Dura-Ace chains....
Muc-Off claims over 400 miles in the dry and 250 miles in wet and/or muddy conditions."


https://www.cyclingweekly.com/news/p...-chains-429229

There we have it, after 400 miles in the dry: Done.
Time for a new fully treated DA chain or Lost Watts!
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Old 07-12-19, 08:08 AM
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Isn't it summer? I feel like these threads are usually relegated to other, colder seasons.

The answer is: we will probably never know. You would have to put the drivetrain on some sort of Friction-Facts-esque measurement device, repeatedly testing while gradually wearing the entire setup down to the point where all of the parts were knackered... and honestly, I doubt there would be much difference. New cogs and rings shift better. But for simply applying power in one gear, stuff can be really worn and you might never notice. I had a chain wear well past 1% and absolutely could not tell. It was an expensive oversight, but the bike didn't feel any different at all.
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Old 07-12-19, 08:33 AM
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Originally Posted by wphamilton View Post
Bad DR bearings and pulleys allegedly cost another 2% but I'm not sure I believe that, unless they're jammed up or something.
That sounds plausible, as you can certainly feel the difference between bad and good pulley bearings when turning the cranks backwards. I replaced my RD after last winter, and was quite surprised by the difference.
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Old 07-12-19, 09:15 AM
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So when you're riding at 200 watts, say, 5% from worn drivetrain + 1% from badly lubed chain + 1% from stretched chain = 7% = 15 watts. Noticeable.

The old efficiency stats seem probably from WAY before the era of 10speed cassettes. I wonder what thinner chains and losses due to wear and bad lube?

Yeah, it's summer and as I struggle to keep up and hold the wheels I wonder about those stray watts here and there and if I should bother chasing them down and fixing them up.

The last time I rode easily w the fast bunch I had deep section carbon wheels. I now have bladed Ksyriums and suffer. But they seem like they'd be fast. Hmmm... Lots of screwy things to try to track down.

...Getting skinnier has always been my #1 go-to, though...

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Old 07-12-19, 09:27 AM
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OP:

You do shave your legs, of course?
Can't waste those near zero expense Watts:

"The tests showed that shaving the test subject’s legs reduced drag by about seven percent, saving 15 watts at the same speed."

https://www.velonews.com/2014/09/new...-faster_344854

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Old 07-12-19, 09:30 AM
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Whoa! I didn't know. I haven't shaved in decades. Free speed! Ha! ...Might do it! Hmmm....
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Old 07-12-19, 09:36 AM
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Originally Posted by JeffOYB View Post
Whoa! I didn't know. I haven't shaved in decades. Free speed! Ha! ...Might do it! Hmmm....
With the well-fitted skin-suit, aero helmet, shoe-covers and long socks that you always wear and that perfectly honed aerodynamic position the Tuesday Night World Championships are in sight.

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Old 07-12-19, 09:47 AM
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Originally Posted by Bandera View Post
With the well-fitted skin-suit, aero helmet, shoe-covers and long socks that you always wear and that perfectly honed aerodynamic position the Tuesday Night World Championships are in sight.

-Bandera
Does he have to lose the beard? How many watts is facial hair? Trim the eyebrows, and experience time dilation!
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Old 07-12-19, 09:49 AM
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i used to run latex tubes and noticed that they felt nicer -- are they known to be faster? ...i have a couple around. that wd only take a few minutes. darn. i hope i have 4 of them coz i want them in 2 bikes! i did really like 'em. ...if they help RR that wd be awesome!
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Old 07-12-19, 09:50 AM
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quick google says latex saves 5 watts -- nice! (i have decent tires already but cd boost them a notch to Turbo Cottons...)
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Old 07-12-19, 10:01 AM
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Whatcha gonna do with all them saved watts?
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