Watts lost to powertrain & frame?

Triathlon Forum
1

I’m trying to figure out how much energy is lost in an improperly lubricated or aligned drivetrain. I’m looking for some hard numbers, like the kid you get when you put dynometers in the pedals to measure how many watts the rider is putting in, and a computrainer in the back to measure how many watts come out. (The difference should be watts lost in the drivetrain and in the frame flexing.)

I’ve seen so many people who spend hundreds of dollars on the latest carbon doodad but don’t bother to oil their chain for months, or grease their hubs & bottom bracket, or even take a screwdriver to their rear der. to make sure it’s set up correctly. A customer of ours who will remain nameless recently spent several hundred dollars to switch over to compact cranks but neglected to change his chain length, so in his small chainring the rear der is practically horizontal.

My crotchety contention is that a few dollars worth of maintenance will make them a lot faster than a few hundred dollars in new parts. But I need some numbers so I can sound like a geek, not just a grumbler.

Lee Silverman
JackRabbit Sports
Park Slope, Brooklyn

2

A chain and sprocket drive can/should be 96% efficient. It is pretty much the best method for conversion of rotary power there is.

Keeping a chain well lubed and clean will give you good savings.

Better bearings in the dearailleur jockeys is where you will see the most savings.

So your drivetrain is 96% efficient. I would say losses to friction could easily make this guys dirty one notably less efficient. I would say as much as a couple percent certainly. Probably more. When you calculate that ceramic bearings save like 0.5% in terms of wattage over other high-quality, properly lubricated bearings, you have to believe that a really dirty drivetrain is gonna slow you down.

Tell him 3%. That’s a safe, reasonable, educated guess…

3

3% is like 1:48 on an Olympic tri for a 60 min split. That is HUGE, but I think it is reasonable.

4

3% of power, not speed.

5

3% power loss equals roughly 1% loss in speed.