What is a GPS bike computer?
A normal bike computer needs a magnet, a sensor, a zip tie and a wheel size you have to get right. This needs none of that. Phone in a bar mount or a jersey pocket, press Start, and you get speed, distance, moving average, climbing and a split for every kilometre.
The dial is scaled for cycling, so 25 km/h sits in the middle of it instead of hiding down at the bottom of a car's. Speed shows one decimal, because a tenth matters at cycling speed and doesn't at 120.
Average or moving average?
Cyclists argue about this more than any other number, so you get both.
Moving average only counts the time you were actually pedalling. It describes how fast you ride. Average divides distance by the whole trip, red lights and café stops included. On a city commute the two can be 5 km/h apart, and that gap is a decent summary of how much of your ride was spent standing still.
Why is my climbing lower than Strava?
The Climb number adds up every metre you went up. GPS altitude is much less accurate than your position, often two or three times worse, and it wanders by several metres even when you're standing still. Adding up every wobble would report a mountain climbed in a car park.
So a change only counts once it clears three metres. That filter is deliberately cautious. It throws away real gain on gently rolling roads, and in exchange it never invents any. Expect a lower number than a barometric head unit, and a much lower one than apps that lay a terrain model over your route afterwards.
Splits
Every kilometre gets its own row, timed from moving time so a stop doesn't wreck it. Your fastest is highlighted. Switch to mph and they become miles automatically.
Where does GPS struggle?
- Trees. A wooded canal path or forest singletrack is the hardest thing a bike ride can throw at it. Accuracy climbs and the trace wanders.
- City centres. Signals bounce off buildings and arrive late, which reads as speed you didn't do.
- Track and turbo. A velodrome lap or a trainer gives no useful ground speed at all. Use a wheel sensor.
- Your pocket. It works, but a bar mount sees more sky and the reading is noticeably steadier.
Battery on a long ride
GPS with the screen on will empty a phone in a few hours. For a long day, turn off the graph and the route trace, drop the brightness and carry a battery pack. Turning off "Keep screen on" lets the display sleep, though some browsers suspend the page once the screen locks.
Typical cycling speeds
| Riding | Average | Per km |
|---|---|---|
| Easy, flat path | 15 km/h | 4:00 |
| Commuting in traffic | 18 km/h | 3:20 |
| Steady road ride | 25 km/h | 2:24 |
| Fast group ride | 32 km/h | 1:53 |
| Long climb | 9 km/h | 6:40 |
| Descending | 50 km/h+ | under 1:12 |
Frequently asked questions
Is GPS as good as a wheel sensor?
On open roads, yes, often better. A wheel sensor depends on a circumference you measured once and a tyre pressure that changes. Under trees or between buildings the wheel sensor wins easily, and on a velodrome or a turbo GPS is useless.
Why is my climbing lower than Strava says?
We only count what your phone actually measured, and we ignore anything under three metres so noise can't inflate it. Most apps replace your measured altitude with a terrain model of the route, which fills in the gentle gradients this filter drops.
Do I need a phone mount?
No, but it helps. In a pocket it still measures. On the bars it sees more sky, and you can read it.
Will it work on a mountain bike trail?
It measures, but tree cover hurts GPS badly and tight singletrack has more direction changes than one reading a second can follow. Distance on twisty trails comes out short.
Can I use it on an indoor trainer?
No. You're not moving over the ground, so there's nothing for satellites to measure.