KDoubleType allows you to use custom fields with double types (HR, Power, etc.)
- Karoo (tested on latest firmware) with version 1.527 or later
- Tested with Karoo 2 and Karoo 3 in both metric and imperial configurations
- Download the APK from the releases page.
- Prepare your Karoo for sideloading by following the step-by-step guide by DC Rainmaker.
- Install the app using the command
adb install app-release.apk.
- Copy the APK link:
https://github.com/lockevod/Karoo-KDoubleType/releases/latest/download/kdouble.apk - Share it with the Hammerhead companion app.
- Install the app using the Hammerhead companion app.
It's mandatory to reboot the Karoo after installation (shutdown and start again).
| Field | Slots | Description |
|---|---|---|
| KDouble (×3) | 1 slot | Two metrics side by side — horizontal or vertical split |
| KRolling (×3) | 1 slot | Cycles automatically between up to 3 metrics |
| KSextuple (×3) | 1 slot (large) | Six metrics in a 2×3 grid — ideal for a single full-width slot |
| Smart Climb (×1) | 1 slot | Adaptive climb field: 4 standard metrics + 1 smart center that switches between start-of-climb / on-climb metrics |
| Bell (×1) | action | Tap-to-buzz action field |
- Add custom fields to your profiles (HR, Power, Speed, etc.).
- Double fields: show two metrics horizontally (left/right) or vertically (top/bottom).
- Rolling fields: show one metric at a time and cycle between up to three — configurable interval (5 / 10 / 20 / 30 s). If you pick only one metric it behaves as a static field.
- Sextuple fields: show six metrics simultaneously in a compact 2×3 grid. Best used in a full-width or large slot. Up to 3 independent sextuple fields available.
⚠️ Avoid using more than one sextuple field simultaneously in the same profile on low-resource devices. - Smart Climb field: designed for the Karoo map page (1×2 large space). Displays 4 configurable metrics plus a smart center panel that shows a start-of-climb metric by default and automatically switches to an on-climb metric (e.g. distance-to-top) when a climb is detected. The field respects the reduced slot size inside the Karoo climber screen.
- Bell field: emulates a bell sound using the Karoo buzzer. Sound must be enabled on the device.
- W′ Balance field: tracks your anaerobic energy reserve in real-time based on power output above Critical Power (CP).
- For Double fields, configure left/top and right/bottom metric in the custom configuration tab.
- Horizontal fields round to integers (e.g. speed 12.6 → 13), except the IF field.
- Vertical fields show up to 5 characters (including decimal point for speed and slope).
- Colour zones are based on your Karoo zones. Slope zones use Hammerhead climber zones, or you can switch to Zwift colours.
- Alignment can be set to left, centre, or right, or you can follow the default Karoo profile alignment.
- Rolling fields — Extra Time option: when enabled the first metric gets 3× the display time of the others.
- Headwind field: reads data from the timklge Headwind extension. You must install and configure that app separately, and also add its headwind field to the same profile.
- Show KPower / Show KGhost fields (General tab): toggles whether the KPower (
KPW…) and KGhost (Ghost…) metrics appear in the field pickers. Both default ON; turn one OFF to declutter the pickers if you don't use that extension. Existing configured fields are left untouched. - Sextuple fields have 6 independently configurable metric slots. Each of the 3 sextuple field instances (One / Two / Three) stores its own configuration.
Configure your W′ Balance parameters in the W′BAL tab:
- Critical Power (CP): use your Karoo FTP as CP or set a custom value. CP represents the highest power output you can sustain indefinitely.
- W′ (W Prime): your anaerobic capacity in joules (typically 15,000–25,000 J for trained cyclists).
- Visual Zones: enable colour-coded zones (green = high reserve, yellow = moderate, red = low/depleted).
- Temporal constants: optimised defaults (τ+ = 546 s recovery, τ− = 316 s depletion) based on scientific research.
Online calculators:
Manual testing:
- Perform 3-minute and 12-minute all-out efforts on separate days and use the calculators above.
- A 20-minute FTP test result can be used as an approximation for CP.
If you also have KSafe, KGhost or KPower installed, their live data shows up as extra
metrics you can pick in any KDouble field (Double, Rolling, Sextuple, Smart Climb). Nothing
to configure here — just select them like any other metric. If the source extension isn't
installed (or its data isn't available yet) the metric simply stays blank (---).
All metrics in the pickers are listed in alphabetical order, so the extension fields group
together by their prefix (KPW… for KPower, Ghost… for KGhost). To keep the picker tidy if
you don't use these extensions, the General settings tab has Show KPower Fields and
Show KGhost Fields toggles (both ON by default). Turning one OFF just hides those entries
from the pickers — it does not change or remove fields you have already configured.
Requires the KSafe extension with fueling enabled. These update only while you are recording a ride:
| Metric | Shows |
|---|---|
| Carb g/h | Current carbohydrate burn rate (g/h) |
| Carb Avg g/h | Session-average carb burn rate (g/h) |
| Carbs Burned | Total carbohydrates burned so far (g) |
| Carb Deficit | Carb balance — positive = you need to eat, negative = surplus |
| Hydration | Fluid deficit — positive = you need to drink. Shown in millilitres, switching to litres from 1 L (e.g. 3.5L) |
| Kcal Rate | Energy expenditure (kcal/h) |
| Kcal Total | Total calories burned so far (kcal) |
Requires the KGhost extension with a ghost/target set.
| Metric | Shows |
|---|---|
| Ghost Gap Time | Time gap to the ghost, formatted M:SS (e.g. 1:30) |
| Ghost Gap Dist | Distance gap to the ghost — metres under 1 km (850m), km above (1.2k) |
The gap is signed: positive = you are ahead of the ghost, negative = behind (e.g. -1:30,
-850m). The M:SS / m·k formatting also makes it obvious at a glance whether a field is
the time or the distance gap.
When your position is briefly uncertain (a GPS dropout, or while you are off-route) KGhost
reports the gap as an estimate. Because the field can't recolour just the number, an
estimated value is prefixed with a tilde — e.g. ~-1:30 means about 1:30 behind, estimated.
Requires the KPower extension. The estimated fields work without any meter (KPower's physical model). The real meter fields only update while a power meter is enabled in KPower and you are recording a ride. Power fields are coloured by your Karoo power zones.
All KPower metrics are prefixed KPW. Fields marked Est come from KPower's estimated
model (no meter needed); everything else (KPW Pwr, KPW NP, …) comes from the real ANT+
meter.
| Metric | Shows |
|---|---|
| KPW Est Pwr | Estimated power, instant (W) |
| KPW Est Pwr 3s | Estimated power, 3 s smoothed (W) |
| KPW Est NP | Estimated normalized power (W) |
| KPW Pwr | Real meter power, instant (W) |
| KPW Pwr 3s | Real meter power, 3 s smoothed (W) |
| KPW NP | Real meter normalized power (W) |
Torque, balance, torque effectiveness and pedal smoothness are no longer listed. KPower no longer publishes streams for these — the Karoo shows them natively for a paired meter (torque, average/max torque, L/R pedal balance, torque effectiveness, pedal smoothness), and KPower still writes them to the FIT. Use the Karoo's own native fields for those metrics.
- The maximum number of digits in a horizontal field is 3 — avoid combining two metrics that both need 3 digits.
- Not all field combinations have been tested. Please report any display or rounding issues.
- Using many fields simultaneously (especially Rolling + Headwind on a Karoo 2) can cause performance issues. Use with care.
- The Hammerhead extension API occasionally causes fields to disappear randomly. If a field goes blank: switch your ride profile, force-stop the ride app, or reboot the Karoo. This is a known SDK issue being discussed with Hammerhead.
- Karoo 2 has limited resources. Be careful when combining multiple custom fields, rolling fields, and other extensions in the same profile.
- Made possible by the generous usage terms of timklge (Apache 2.0). Parts of his code are used in this extension.
- Thanks to valterc for the great ki2 app — colour definitions are based on his work.
- Thanks to kleinkm for the inspiration and contributions around the Sextuple field.
- Thanks to vinapp for sharing code and collaboration.
- Thanks to Hammerhead for the Karoo platform and SDK.
- Thanks to DC Rainmaker for the sideloading guide.
- Thanks to Boxicons and iconduck.com for icons.
- KDouble does not save or share any personal data.
