If you ever get a flat tire on the rear wheel, you'll need to to be able to remove the wheel. Hub drive motors are a little different than a conventional pedal bike, as you have large axle nuts, torque washers, and an electrical connection to contend with. The system is intended to be serviceable, and this guide outlines the steps needed to remove the wheel.
Setting up your workspace
You will either be servicing your bike on a workstand, or upside down on the ground. If you're working with the bike flipped over, you'll want to move the LCD out of the way to make sure it doesn't get damaged. Also check that your shifters and anything else on the handlebar isn't in a position where it may be damaged. You may find it preferable to place a piece of thick foam padding under the handlebar to prevent damage.
If you're using a workstand, you'll want to have a rolling shop stool you can sit on, as it'll make it much easier to maneuver the wheel with the weight of the hub motor.
Preparing the bike
- Make sure the power system is completely shut off.
- Shift the gears to the smallest cog. This will make it easier to get the chain in the right place later when you put everything together.
- You'll want to follow the power wire to the motor, and slide the rubber dust cap out of the way to reveal the axle nut. Remove the cap from the left side of the axle and set that aside too.
- Use an 18mm wrench and crack both axle nuts loose, while the bike is still upright. You're not removing them. You're maybe putting a 1/4 turn on them for now.
- Hang the bike on the workstand, or flip it upside down on the floor
- Remove the zip ties securing the motor power cable to the chainstay. Unplug the power connector to the motor.
- Continue loosening the drive side axle nut. It doesn't have to be removed. You can just back it off a couple millimeters.
- The wheel will begin to feel loose. If you're using a workstand, prop the wheel on your leg to stabilize it (you may want to adjust the tilt of the bike if the wheel is up too high).
- Loosen the left side axle nut.
- Check how loose the wheel is. You should be able to rock the wheel easily in the dropouts.
Parts orientation:
Before removing the wheel, you'll want to note the positioning of several parts. The power wire for the motor goes through the axle. The axle has a slot cut in it to prevent strain on the power cable. This slot should be pointed down.
Note that the axle itself has a pair of flat faces along its length. The flats of the axle must be parallel with the dropout opening.
In addition to the axle nuts, there are several washers on either side of the dropout openings. You don't want to mix these up. There should one washer directly under each each axle nut on the outside of the dropouts. On the inside of the dropouts are torque washers (AKA anti-spin washers). These washers have a tab that protrudes in the dropout opening underneath the axle and prevent the axle from spinning freely when power is applied. If the torque washers are not in the right place, it's very possible that motor torque will twist the axle and sever the power wires.
Removing the wheel (workstand):
Pull back the derailleur cage to get the chain to unwrap from the cogs, and lower your leg a bit to get the axle to slide out of the dropouts. Guide the wheel out, and make sure the power wire doesn't snag on the chain.
Removing the wheel with the (bike upside down):
Push up on the axle, while at the same time pulling back on the derailleur cage. You can also stand over the bike, pulling up on the wheel, while guiding the chain off the cogs. Make sure the power wire doesn't snag on the chain.
Patching the tire:
Park Tool has an excellent video on the full procedure for removing/repairing/replacing an inner tube:
Reinstalling the wheel (workstand):
- The wheel tends to come out easier than it goes back in. Prop the wheel on your leg. Drape the chain over the smallest cog, and feed the power cable through the chain loop. Lift your knee to position the wheel close to where it needs to go.
- Observe the brake rotor, and make sure it inserts cleanly past the brake pads.
- Pull back on the derailleur cage, and bring the axle closer to the dropouts.
- Make sure the axle slot for the power cable faces the bottom of the bike.
- Use a 10mm wrench on the flats of the axle to tweak its position so that the flats are parallel with the dropout faces.
- Make sure the tabs on the torque washer also face towards the bottom of the bike, and will be on the inside of the dropouts.
- Make sure the axle nut washers will be on the outside of the dropouts.
- Lift your knee and send the axle home.
- While maintaining pressure to keep the axle seated in the dropouts, tighten the left side axle nut. Make sure this is snug enough that the wheel won't fall out.
- Remove the bike from the workstand, and set the bike on the floor.
- Lean over the bike, putting weight on the seat, loose the left side axle nut, then tighten it again.
- Continue applying weight and tighten the drive side axle nut. Make sure both nuts are firmly torqued to about 40 ft lbs.
- Put the bike back on the workstand, spin the rear wheel and confirm that the brake rotor isn't rubbing on the brake pads. Reseat the axle in the dropouts if this is the case.
- Reconnect the power cable, and secure it with a new zip tie.
- Secure the dust caps over the axle nuts.
- Spin the pedals, and test gear shift function.
- Squeeze brakes and confirm brake function.
- Turn system power on, and confirm motor operation (keep clear of wheel).
Reinstalling the wheel (bike upside down):
- The wheel tends to come out easier than it goes back in. Lower the wheel over the bike. Pull up on the lower derailleur pulley, feeding the power cable through the chain opening. Wrap the chain over the smallest cog.
- Observe the brake rotor, and make sure it inserts cleanly past the brake pads.
- Pull back on the derailleur cage, and lower the axle closer to the dropouts.
- Make sure the axle slot for the power cable faces the bottom of the bike.
- Use a 10mm wrench on the flats of the axle to tweak its position so that the flats are parallel with the dropout faces.
- Make sure the tabs on the torque washer also face towards the bottom of the bike, and will be on the inside of the dropouts.
- Make sure the axle nut washers will be on the outside of the dropouts.
- Lower the wheel and send the axle home.
- While maintaining pressure to keep the axle seated in the dropouts, start snugging the left side axle nut.
- Lean over the tire, putting weight on and tighten the drive side axle nut. Make sure both nuts are firmly torqued to about 40 ft lbs.
- Spin the rear wheel and confirm that the brake rotor isn't rubbing on the brake pads. Reseat the axle in the dropouts if this is the case.
- Reconnect the power cable, and secure it with a new zip tie.
- Secure the dust caps over the axle nuts.
- Spin the pedals, and test gear shift function.
- Squeeze brakes and confirm brake function.
- Turn system power on, and confirm motor operation (keep clear of wheel).