Is a speed sensor worth adding to bike computer (Wahoo)?
 

So I have a Wahoo ELEMNT Bolt and just added the cadence sensor. Is there any advantage to adding a speed sensor? Ie. does the speed sensor have any advantage over just the GPS built into the computer? Perhaps more reliable at times? More accurate? I don’t know. Interested in thoughts.

It might help smooth out things like your average speed at times when you have poor satellite connectivity, but I don't think that it's of great value.

How much will you be bummed out if poor satellite reception or some other interference messes up a ride? Otherwise your gps alone is probably accurate enough for distance. Time, it'll do nothing for.

However I do use both a cadence sensor and wheel sensor. Just so I have another piece of frequently useless data to marvel or quibble about.

Also lets you track your rides in the velodrome

I can't imagine having a bike computer without speed. Even the cheapest models have speed, distance and average speed. I want to know my cadence at all times, particularly when climbing 10% grades. I also want to watch my speed drop below 6 mph on the way up and hit as high as 54 going down. I also want heart rate. Without that, you've got no idea how hard you're working. I've had a power meter too, but now I'm too old to worry about it.

I really can't imagine a company selling a bike computer without a speed sensor.

...his Wahoo has GPS. Even under heavy tree cover, my Wahoo almost never loses signal, but the indicated speed may be a smidge jumpy.

I’ve read about potential glitches with the speed sensor. Has anyone had this issue? Seems like it can’t hurt to try one even though I haven’t had issues with the GPS on the computer. Needed the cadence anyways.

The answer is a lot of "it depends." I'll get GPS drops on my Garmin here and there on routes with underpasses, and the lapse is maybe 20 seconds. IIRC it records an assumed straight-line path for the drop, and I'd think it'd just do the math on figuring out speed if I didn't have a wheel speed sensor. I also have the wheel speed sensor installed because I use rollers.

If I had to pay for the sensor separately and didn't have a use for it indoors, I'd probably go without and live with the extremely minor GPS drops.

I never bother with the speed sensor. The extremely minor improvement it makes when there is a poor GPS signal or low speeds just doesn't justify having another thing on the bike.
When I do utilise a sensor it is off my power tap wheel set and the difference between having it and not is just insignificant.
Only use I can see is if you were doing specific equipment testing and were trying to get the best data you can.

So the real issue is that you have speed readout but question it's accuracy. That's much different than not having speed info. I ride in mountain canyons, so a speed sensor might be wise, rather than depend on GPS entirely.

I have the Wahoo speed sensor. My results are dead accurate, but I'm not sure how inaccurate the GPS results would be. The one nice thing you get with the sensor is faster updates on road speed.

Well, for one thing not having a speed/cadence sensor means you'll get less info from a trainer/roller ride and it won't be as interesting. GPS won't help at all. It also makes the gradient number more responsive and accurate. When reviewing a ride, if one zooms in on a graphical bit, the numbers one sees will be more meaningful. Plus riding on forested or mountain roads, one will still have data other than power and HR when the satellites go bye-bye.

When I ride, I normally watch 2 things: cadence and either HR or power. Also distance if I'm working off a cue sheet, though I mostly let the Garmin tell me what to do when I'm following a route. I try to put in a new battery about the same time every year. If I forget and the sensor stops working, I really, really miss it. I like my Garmin's automatic tire circumference feature which keeps the wheel sensor's output aligned with the GPS input, so when I change tires or tire pressures I don't have to fool with anything.

I have one on the bike I use occasionally on the trainer, I don’t have one on the other bike, just rely on the GPS. Riding outdoors I don’t perceive any difference in what I see for speed between the two. I actually have another speed sensor that came with the cadence sensor, just never got around to installing it.

If glitches bother you then you should probably give up the gps too. Eventually everything has glitches.

If you haven't had any reception issues with your current GPS that caused a difference in distance traveled, then you probably won't get any benefit from a wheel sensor.

GPS units generate speed data. There’s only a few times you need the added accuracy.

As others have stated, a speed sensor improves accuracy. Mt. bikers use them a lot when riding in heavily wooded areas where the already weak GPS signal causes dropouts. A speed sensor gives an accurate track of speed and distance. As well if using on group road rides, the data from the sensor is more recent and gives a more accurate speed. Useful for maintaining a steady pace. And of course it’s needed on an indoor trainer.

The bolt will auto calibrate wheel diameter for responsive and accurate speed.
The bolt will be quicker to Auto-Pause and the continue a ride.

Barry

I use both: GPS via phone app, and older style Wahoo magnet type speed/cadence sensors paired with the bike computer. There's hardly ever much difference between the two readouts on segments or overall rides.

I also have one of those no-magnet convertible earth induction speed/cadence sensors but haven't used it for awhile. Results were comparable to GPS and magnet sensors, but with more dropouts and glitches.

I don't worry much about speed. Mostly I use the computer to monitor my heart rate, distance and ride time.

The cadence info was useful last year when I switched my style from spinning 90-100 rpm to slower 60-75 rpm. But now that the slower cadence is in muscle memory I don't really need the reminder anymore.

My thoughts. Steep terrain can cause GPS reception issues. Part of the reason I bought my Bolt was that my Polar used GPS for elevation and steep mountain terrain made it worthless for recording elevation.

how does auto calibrating work? Is that better than just imputing the actual?

Auto calibrate varies from mfr to mfr and even between devices. However auto calibrate can be very accurate. Or if when the auto calibrate is being done you are in poor reception, then it can be way off.

I've read some devices auto calibrate several times during the ride and others only do it once near the beginning of the ride. You can, at least on my device see in the settings what the last autocalibrate came up with and if you believe it correct, then put that number in as circumference of your wheel.

An actual rollout can be very accurate or inaccurate depending on the person doing it. I put a drop of paint or something on my tire that will make a mark on clean concrete and ride my bike for a few wheel turns then measure as many marks as I can and compute the number for the wheels circumference.

That number depends on ride weight, tire pressure and other things for accuracy. But in the grand scheme.... much of the arguments between gps accuracy and wheel sensors for the average person with decent satellite reception are only arguing over a few percent. Who really cares to have that much accuracy. It's meaningless.

I prefer my bike's speed sensor than my computers. It's more accurate.

My bike came with an integrated speed & cadence sensor so I didn't have to buy any aditionnal device.

It's more accurate at any given instant. Over the course of a segment or ride, most won't see a difference.

If you look down at the computer and expect to see your actual speed, then a speed sensor is probably a good idea.

In the Wahoo Element (Bolt) App you set the Speed sensor to "Auto" and not pick a circumference yourself.
Looking in the Wahoo App it thinks my wheel has a circumference of 2.096 Metres
So it appears to have self calibrated to the Millimetre (MM)

I'd say that is pretty precise, but I can't judge it's accuracy.

It installed the speed sensor just for the Auto-Pause on a ride.
The Bolt will Auto-Pause on it's own, but apparently it is more responsive with a speed sensor added.
I use the same Bolt on my Fixed without a speed sensor and it Auto-Pauses well enough for me needs on that bike.

Barry

BTW I do like the Bolt handles multiple bikes. All of your Sensors are registered in the Bolt, and It just detects the ones on the bike you brought with you today.
This might cause a problem if you bring more than one bike.

Example
Bike 1 = Stages Power (Power and Cadence) and Wahoo Speed
Bike 2 = Wahoo Cadence
Both = Wahoo Tickr HRM