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Installing Wheeltop GeX

I've already had experience with the first of the new, value-priced electronic groupsets from China in LTWOO eGR. You can read about that experience here, but in summary it's pretty good but wasn't perfect for my application for two main reasons

  • It expects to stash the battery inside the frame and have a wire run out to the derailleur. Unfortunately, my V1 Cutthroat isn't set up that way and I had to strap it to a bottle cage in a less-than-pretty way
  • Officially it only supports up to a 46t cassette and I run a 50t. It does actually work, but it's a little cranky about it in setup and operations.

But along comes the Wheeltop GeX solution. Same idea from a company that has been making components for others for many years and MTB electronics for a couple of them. It promised to address my issues in that it uses a battery attached to the rear derailleur directly and officially supports 51t cassettes. Reports are they tested to 52t and it works on some bikes but not others so they spec'ed conservatively.

So, given the value pricing, I decided to give it a try.

First Impressions

It arrived, making a quality impression.



Brake calipers are in a separate, similar box

Note that this 'groupset' is another 'mini groupset' in that it contains:

  • Left brifter with single-control paddle
  • Right brifter with dual paddles
  • Front and rear calipers
  • Rear derailleur with permanently attached battery (Others have shown it to be replaceable with tools)
  • Charging cable (proprietary magnetic, USB-A)
You will need to provide the following for a 'full groupset':
  • Cranks and chainring
  • Chain
  • Cassette of your choice

Unfortunately, the instructions and the app don't make as good of an impression. The translations from Chinese are terrible. You will spend time interpreting what they mean. If you're familiar with installing similar parts, you'll figure it out, but I've got some tips below.

Fortunately, the mechanical installation is generally pretty simple as one would expect. Bolt on the rear derailleur, mount the brifters, and conventional mineral oil brake setup. Note: I decided to leave the Shimano RS-785 calipers installed as they were working fine and plumbed. I just hooked up the lines to the brifters with no hassles. I did end up using the calipers elsewhere and they work fine (note below about the pads)

So, let me give you the tips.

Installation Tips

System Pairing

Your kit might come pre-paired. Wake up the components and give it a try. If the buttons make the derailleur move in each direction, skip the pairing process. If nothing happens, continue.

  • Remove batteries from front shifter (one at a time)
    • To access the shifter batteries, you need to remove the caps. These caps are beveled/lopsided relative to the plane of the battery. It's easy enough to turn open. Look for the arrows for the open and closed positions. They are different on each side. Do NOT reinstall at this time.
    • Attach the charger cable, then disconnect it to get a flashing blue light
    • The RD has TWO LEDs. The one near the power connector indicates charge status. But there is another one in the arm, behind the translucent panel that goes blue/green for pairing.
  • Re-insert batteries in one shifter and replace caps
    • When replacing the caps, pay attention to the flat underside for alignment. The bevel top will confuse you. Put it in right and press down for a light snap. Then turn.
  • It might require you to push a shift paddle. The manual suggests yes, but I'm not sure if that was actually necessary. It certainly works if you do.
  • Look at RD to see it flash green, then back to blue flashing for the next pairing
  • Repeat for the other shifter

You may want to watch the Trace Velo video on pairing. 

Mechanical installation

  • The brifters, derailleur and calipers all install conventionally. 
    • Pay attention to torque specs.
    • Make sure the B-screw ends up in the right place on your derailleur hanger.
  • Some people have trouble manipulating the rubber hoods. They are quite stiff. But I didn't have any extreme issues accessing the bolts etc.
  • The hydraulics come ready to go. But if you need to cut them or use other parts due to routing issues, they are conventional BH90 parts

Mechanical setup and calibration

Please read and interpret the manual before doing the installation. But here are some cheat notes:

First set the B Screw to set vertical distance:

  • Click the shifters to align the jockey wheels to the largest cog
  • Screw the "Backward Tension Screw H" (B screw) to get a vertical clearance of 8-10mm between the jockey wheel and the largest cog. You may chose to refine this after using it. Use an 8 or 10mm hex wrench as a feeler gauge. With a big cassette, this setting is critical to establish before trying the cog by cog calibration

Set the Limit Screws

Note that with electronic shifters these are safety limits not generally engaged. So they are not fussy.
  • Shift to the smallest cog
    • Screw "Maximum flywheel limit G" (Low) until it touches (stops turning) then back off a 1/4 turn
      Note: This screw is back by the charge port
    • Test shift back and forth. If it hangs or lags, back off another 1/4 turn
  • Shift to the biggest cog
    • Screw "Minimum flywheel limit K" (High) until the screw it touches (stops turning) then turn back off a 1/4 turn.
      Note: This screw is hidden under the cover for the clutch adjustment. You must remove the locking screw to remove this cover. Don't lose the parts. This is the same cover for access to the clutch adjustment. Mine was fine as shipped and I have not changed it.
    • Test shift back and forth. If it hangs or lags, back off another 1/4 turn
Annotated image from the manual

Set electronic derailleur calibration

One of the odd things about the Wheeltop system is that each individual cog must be calibrated. It does not come preset with an index point and the correct spacing from there. This is an unfortunate side-effect of them supporting basically any cassette from 3-14 cogs/speeds. Issues in this area are what seem to come up in online forums the most. 

My recommendation is to just try it at the default. If it works, great (not likely). If not, start from one end of the cassette and work your way across then repeat.

Make sure you index the smallest cog first. Get it right.

This adjustment can be done with the shift paddles, but I don't recommend that because it is all relative without any values to anchor your settings. I think that is confusing. Use the app.
  • Enter "Debugging" mode
    • Home screen
    • Settings 'gear' icon in the bottom row
    • Debug
    • >Device Debugging>Initial Calibration>Debug page
  • For gear trim
    • Raising values moves the derailleur IN
    • Lowering values move the derailleur OUT
  • Make sure you move the number (buttons or direct entry) to a trial value, then shift one way, then back. You will not see the effect until you've shifted back and forth. 
  • Don't be afraid of the numeric value, they are arbitrary. Just move them a few at a time. I took to moving in blocks of 5 'units' for consistency 
  • After the first pass, go up and down the cassette one step at a time
  • Go through the setup until you're basically happy. Then walk away. Seriously. Don't chase it. Come back again and run through the gears again one at a time to verify correctness. If you see a problem, more adjustments are in order.
  • When you're done, screenshot or write down your values. This way if you need to reset the system for some reason, or it gets messed up, you can put it back easily. 
    • There is no way to explicitly save a configuration for one cassette vs another.

Software configuration

One of the strengths of this system is good flexibility in how to configure the controls. The brifters are asymmetrical
  • Left has a single, large paddle
  • Right has a large and a small paddle
The default setting is to use the right only in a Di2-type configuration. Small paddle for easier gears, large paddle for harder gears. Rear derailleur only as this is 1x

However, since I run SRAM AXS on another bike, I actually prefer to use that pattern. Wheeltop allows this and I recommend setting up the paddles the way I do:
  • Left paddle goes to larger, easier cogs
  • Right large paddle goes to smaller, harder cogs
  • Right small paddle remains as an option for easier gears. Handy sometimes to be single handed or if you ride Di2-type as well.

One of the other settings is the "Usage Mode". This is an interesting feature that can bind the derailleur to your system. It might be useful if you're around other Wheeltop users or you fear it might be stolen and want to make it useless to them. But I've read of other users getting trouble after resetting etc. if the lock it. I left mine in 'shared' mode.

Note: The app has a usability oddity in my opinion. It will open showing what looks to be a connected derailleur. But it is not. You must click on the little Bluetooth icon in the upper right to go reconnect.

Living experience

So far (~400 miles as of this writing), I've been quite impressed. The system shifts notably well on an 11s 11-50t cassette. The GeX replaced two prior configurations that were extended beyond their specification and just weren't as clean. The GeX acts like it is doing what it was designed to do.

Battery life seems to be excellent. I check the battery status every few weeks or hundred miles-ish and it drains slowly and predictably. No 'whoopsie, there it went'.  I'm estimating that it's good for ~400 miles on a charge. I don't have precise info because it discharges slowly and I've recharged it before empty because I was going to events where I didn't want to worry.

The stock brake pads are deceptive. At first, they feel good. Quiet, modulate well, seem to stop well. However, if you either ride in big mountains or are a Clydesdale or both, change them immediately. I had one 3000ft descent where I was feeling them getting soft (melting) and had to manage heat. The next time coming down a 2000ft descent with a bunch of stop signs, (can't defer the braking), I had one where they did not stop me before I had to turn rather than run the intersection 😱. That was it. I put common Shimano L04C metallic disc brake pads in. You could use the resin equivalents if you prefer. No complaints about the brakes now.

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