Technical FAQ: electronic shifting battery drain, disinfecting your bike

We answer reader questions about eTap battery drain, and what cleaners are safe for bike finishes and can also be used as disinfectants.

Have a question for Lennard? Please email us to be included in Technical FAQ.

Dear Lennard,
You replied to a reader that bumping a Di2 shift lever and then storing the bike can drain the battery. I have a related question about SRAM eTap. As I understand the eTap system, there are sensors in the derailleurs that detect motion and “wake up” the radios. So, when the bike is stationary, the derailleurs are in a low-power mode. And when the bike is in motion, whether it is in the back of your car, in an airplane cargo hold, or even leaning against a running washing machine, the system is on and burning power, as if you were riding and shifting. For this reason, I always remove the derailleur batteries when I travel with my bike. After hopping on my bike without the batteries a few times, I drilled small holes in the red battery covers and attached red ribbons, akin to “remove before flight” tags. I don’t remove the batteries from the shifters because… oh come on. Though I suppose leaving a shifter paddle depressed for an extended period would drain the little CR2032 battery. Does this square with your understanding of eTap?
— Mark

Dear Mark,
Your understanding of eTap squares with mine, and is correct. Since the eTap system is wireless, the shifters are not connected directly to the derailleurs and ready to send a signal at any time. In order to be ready to shift, the shifters must maintain a Bluetooth connection with the derailleurs. Since you want it to be awake any time you want to shift, the derailleurs stay active any time that the bike is in motion. To prevent losing battery charge in transit, remove the batteries when the bike is in motion, but not being ridden (or, cuddling up to a washing machine? That’s a new one.) eTap derailleurs are equipped with accelerometers that put the system to sleep after about 30 seconds of inactivity and lack of movement. You do not need to remove the shifter batteries, because the battery drain from them is only when buttons are activated during the shift, not just when a bike is in motion.
― Lennard

Dear Lennard,
In your recent column you gave advice on which cleaners were safe for bikes. You said, “Water-based cleaners are generally fine as long as you don’t leave parts soaking in them for longer than a couple of hours, in which case you could inspire some rusting in steel parts.”

Let’s not forget aluminum parts, either! I cleaned my shiny aluminum TA and Shimano chainrings in a citrus-based cleaner, leaving them to soak overnight.

They turned black! (The remaining bright spots were where parts were in contact with each other.)
— Peter

Dear Peter,
It’s funny that you mention this, as, when I was writing that column, I did ponder whether to mention aluminum oxidation as well as steel oxidation with regards to long-term contact with water-based cleaners. I decided against it and only mentioned steel rusting, as I was imagining people soaking chains and cogs in citrus cleaners, and I was not envisioning aluminum parts that people were likely to soak that way. Oops. Thanks for alerting me to this.
― Lennard

Dear Lennard,
In a recent Tech FAQ on the website, you stated that milder solvents like isopropyl alcohol would not damage bicycles. I had asked a similar question to a large bicycle manufacturer and they stated that isopropyl alcohol can damage the clear coat on frames causing the paint to go hazy over time. I did not get a sense of how many times you would have to clean your bike this way before things went sour, but it is good to note especially if you value your paint job. Also, isopropyl alcohol can damage (dry out) rubber components of bicycles such as tires, grips, and seals if used excessively over time; these are all normal wear items however.
— Vince

Dear Vince,
Point taken. Thanks. I can imagine how scrubbing or soaking an area of paint with rubbing alcohol could cloud it.

Given that we are constantly using isopropyl alcohol in my shop for wiping hydraulic brake fluid off of carbon forks and handlebars and frames after bleeding without noticeable damage to clear coats or to tires, I think that a quick wipe is pretty safe. For instance, mechanics for pro MTB teams probably do this dozens, if not hundreds of times on the powder coat on the rear swingarm and the suspension forks of team bikes following brake services, and those bikes generally look very shiny on the start line.
― Lennard

Dear Lennard,
Your Tech FAQ of April 14 says in the section on disinfecting: “mild solvents like isopropyl alcohol up to quite strong ones like acetone are not going to damage a bike.”

In my experience, acetone will certainly attack epoxy powder-coat, as I’ve found in the past that a cotton ball soaked in acetone and rubbed vigorously on a frame will remove the powdercoat. When I wanted to get some additional braze-ons added to a powder-coated frame, I used acetone to get the necessary parts of the frame back to bare metal before I took it to the frame builder.
— Nick

Dear Nick,
I’ve never tried that. Good to know. I have removed a lot of tubular glue from carbon rims with acetone — VM&P Naphtha, and Carogna Remover — and I have never noticed damage to the clear coat on the sidewalls of them.

We used to always wipe frames down with acetone before applying decals, whether painted, powder-coated, or raw titanium, and I don’t ever recall damaging the finish in the process. Again, this was a quick wipe, not a scrub. Now we generally do this wiper prior to decal application with rubbing alcohol just to minimize our exposure and that of the earth’s atmosphere to acetone.
― Lennard

Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is also a custom frame builder ( and purveyor of non-custom huge bikes (, a former U.S. national team rider, co-author of “The Haywire Heart,” and author of many bicycle books including “Zinn and the Art of Road Bike Maintenance,” “DVD, as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.” He holds a bachelor’s in physics from Colorado College.

Follow @lennardzinn