Gear

Technical FAQ: Balancing wheels, mismatched brakes, and more

Lennard Zinn addresses reader questions about fixing an unbalanced wheel, mixing parts, and even an unusual rim/disc brake setup.

Fixing an unbalanced wheel

Dear Lennard,
I recently purchased a deep-dish aero road bike wheel and noticed that its weight is slightly out of balance. Can you tell me how to weight balance a bicycle wheel?
— David

Dear David,
An unbalanced wheel can throw off the smoothness of the bike. You can demonstrate this on a rear wheel by cranking the pedal around as fast as you can in high gear while the bike is in a bike stand. Let go. The entire bike and bike stand will jump up and down due to the imbalance in the spinning rear wheel. This is what’s happening while you’re riding, but unless it is extreme, you don’t usually notice it because you are so heavy relative to the rim weight.

The wheel can be unbalanced due to asymmetries in material density and concentration in the rim, the tire, and the tube. To locate the imbalance, install the wheels on the bike while it is clamped in a bike stand. Install the rear wheel with the chain off so that the freewheel doesn’t slow the rotation of the wheel (you don’t have to remove the chain; just bypass it and leave it to hang below the cogs). Spin the wheel and let it spin down to a stop. Repeat. If it repeatedly stops with the same part of the rim at the bottom, that is the heavy spot, and the light spot is the one that is always on top when it stops. This obviously depends on having smooth hub bearings that are properly adjusted; they should be smooth enough that, once the wheel spins down to a stop, it rotates back the other direction at least once before reversing direction again and coming to a complete stop. If the hub is stopping the wheel abruptly, overhaul or replace the bearings and adjust them, and then try spinning the wheel again.

Aluminum rims have either a splint or a weld where the rim is joined opposite the valve, and this extra-dense area is heavy enough that, even though the valve is the heaviest part of the inner tube, the light spot of the entire wheel is generally at the valve. If the spin-down test indicates that the valve is at the light spot, balancing the wheel is easy; you can thread extra collars onto the (threaded) valve stem, and/or put on a metal valve cap. If that fixes it, you’re done. Check that the imbalance is gone by once again letting the wheel spin down, and if it doesn’t favor any particular spot at which to stop, the wheel is balanced sufficiently well.

If the light spot is not at the valve, then you need to add weight to the rim somewhere else. As I mentioned last week, one solution for balancing a wheel is the Effetto Mariposa Shelter Wheel Kit. The little stickers in the kit weigh one gram each and can be stuck onto the rim wherever the wheel’s light spot is. Snip the sticker down to the center hole to slip it around a spoke where it meets the rim.
― Lennard

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Upgrading Campy Record

Dear Lennard,
I currently use a Campagnolo V1 Record EPS set up and would like to upgrade to V3. I’ve been told this isn’t possible because the connectors are different. I noticed in this article you wrote that you had personal experience with upgrade. Were there any issues with the upgrade from V1 to V3, or was it as simple as upgrading the battery unit? No issues with connectors? Does anything else need to be upgraded to make this switch happen by chance?
— BK

Dear BK,
Perhaps you have Chorus EPS or Athena EPS? The Chorus/Athena connectors are different. Record and Super Record share the same connectors, no matter what the generation of EPS it is. In that case, there is no issue with the connectors, and you can upgrade from EPS V1 (external battery) to V3 (seatpost battery) simply by changing out the battery and the EPS interface.
― Lennard

Mixing Campy parts

Dear Lennard,
Will I be able to use a Campy-Ultra Torque BB on a Campy Power-Torque crankset?
— Victor

Dear Victor,
No. It’s a completely different system. The drive side bottom bracket cup is the same on both, but the non-drive cup on Power Torque has a bearing in it, while the non-drive Ultra Torque cup does not (the bearing stays with the left crank, press-fitted onto the spindle stub and secured with a circlip).
― Lennard

Mixing rim and disc brakes

Dear Lennard,
I have a question about adding disc brakes to an older road frame. I primarily ride an older (1999) Trek Carbon frame road bike. If I were to replace the standard fork on my bike with a disc-compatible fork, could I then run disc brakes in the front and a rim brake in the rear? Would there be any advantages to this or any disadvantages?
— Seth

Dear Seth,
There is no reason that you cannot do that. You of course would need to use a cable-actuated disc brake on the front; you couldn’t hook up a hydraulic brake without replacing your brifter.

An issue with your 17-year-old bike is that your steering tube will be 1-1/8” in diameter at the fork crown as well as at the top, whereas most carbon disc-brake-compatible forks have a tapered steerer that is 1-1/4” or 1-1/2” in diameter at the fork crown; these will not fit on your bike. WoundUp is the only disc-brake-compatible carbon fork I know of that will fit in your bike, as it does not have a tapered steering tube.

Advantages and disadvantages? An advantage is that more braking power can be applied in front than the rear, due to reduced traction in the rear when braking and descending, so having a more powerful brake up front makes sense. That’s why Campagnolo uses differential rim brakes front and rear on its groups. A disadvantage may be that the mismatched brakes may provoke questions and perhaps even ridicule from riding companions.
― Lennard

Shimano derailleur installation

Dear Lennard,
I have just installed a new Shimano M8000 Shadow Plus 11-speed rear derailleur. It’s working fine and there’s no installation problems; I love this new clutch system. My question is this. On the attached file you will see where I have annotated the port cover and questionable part. What is this port for, and does it require any maintenance, grease/oil?
— Steve

Dear Steve,
That’s the adjustment for the clutch (or whatever Shimano calls it). There is a band around a cylinder; the band has two ears and a bolt pulling them together that adjusts the friction between the cylinder and the band. You can access the bolt under the cap. The bolt has a carrier that is the weak point; Shimano sells rebuild kits for it.
― Lennard