Review – Scosche RHYTHM Bluetooth Speed/Cadence Sensor (and Mini-Review of the Wahoo Fitness App)

This is a review of the Scosche Rhythm Bluetooth Speed/Cadence Sensor but you’ll find some useful info (and mini-review I suppose) on the Wahoo Fitness app here too.

Scosche Rhythm Bluetooth Speed/Cadence Sensor

Scosche Rhythm Bluetooth Speed/Cadence Sensor

After I decided to get myself a bike trainer (see my review of the Magnet Steel bike trainer here) I found that the biggest issue with it is that there’s no way to tell how far I’m riding, or how fast.  More expensive trainers (like this one for example) may have sensors that can tell you, via Bluetooth or ANT+, your speed, distance, cadence, and even power.  But mine is pretty basic – but it does it’s job.

I had decided to just get myself a cheapo speedometer for the time being but then noticed that the Scosche Rhythm Bluetooth Speed/Cadence Sensor was marked down, seemingly across the Internet, to a very low price.  Not only would I have speed and distance (and time of course) but cadence – something hard to find on real cheap bike computers.  At the time I bought it, November 2015, it was going for less than $20 and as of this time (December 2015) it still is.  That’s dirt cheap.  But is it any good?

I’ve been told that this is the same device is sold to multiple fitness logging sites (like Runtastic) and companies (like Scosche) to brand with their own names and sell, and it certainly looks identical.

Looking at the reviews for this and the other versions you might notice some mixed reviews.  On cheaper devices like this you’re going to find these mixed reviews, and indeed that’s what I found with this device.  But with the amazingly low price I decided to give it a try.

When I received it I was surprised at how small the box was.  The box, unlike with the packing on some other cheaper electronics, is very professionally and brightly printed in English and French, with lots of nicely colored graphics and screenshots from the Scosche app and website dashboard, the company logo in color; all in a quality-looking cardboard box.  On the bottom is the serial number, model number, tech support number, and so on.

But unfortunately neither the app nor the Scosche Rhythm web dashboard, which are shown prominently on the back of the box, are alive any more.  You can look around and maybe download the old version of the app for an earlier version of Android and IOS but it won’t work on modern versions of either OS, nor can you find it on the regular app stores.  The web dashboard address redirects to the main Scosche site.  The app and web dashboard sure looked nice in the pictures ;(

The box opens with a quick slice of the tape covering the front flap and you can slide out, via a typical transparent plastic packing, the unit and its accompanying accessories.  In the back of the box there is a separate slot containing the instructions (printed in a number of languages) and a warranty card.  You can also fill out the warranty online.

The instructions are basic but give what you (mostly) need to know, though they are sparse.  The sensor positioning instructions, especially having to do with lining up the slots on the sensor with the magnets, could use some more detail and explanation.

The hardware.

The hardware.

The sensor body itself is very similar to the design you will see by other manufacturers like Garmin and Wahoo.  The unit attaches to the top of the chainstay behind the crank, on the opposite side of the bike from the chain itself.  It can be attached in one of two ways – either semi-permanently with the included zip ties or with a rubbery band sort of attachment that slips over the chainstay and around attachment points on the sensor in place of the zip ties.  It can be a little tricky to get this rubber band sort of thing to stay in place over these attachment points, but after a little practice it seems to work fine.  I’m not sure I would 100% trust them outside though, especially where my foot or something else might accidentally touch it.  The zip ties are likely more secure, sliding through the bottom of the sensor body via slots and then around the chainstay.

There are two magnets, one attaches to a rear spoke by loosening the magnet part where it screws into a plastic part and sliding the spoke magnet onto a spoke, then tightening it.  The other sensor is inside a flexible plastic ring that slips over the crank arm.  You have to take off the pedal to do this, as it should go on the crank arm below the pedal.  Some people just slide it over the end of the crank arm above the pedal, but I think you should consider this for temporary testing indoors as centrifugal force is likely to throw it off at some point.

The spoke magnet seems to fit fine on flat spokes as well as round ones, at least on my wife’s Trek with flat spokes.

Close running.

Close running.

The sensor body has an arm that must be positioned near the spoke magnet while the sensor body itself must be mounted along the chainstay near where the crank sensor swings past it.  This is the tricky part – getting the crank magnet, sensor body, sensor arm, and spoke magnet all positioned correctly.  You have to loosen the sensor arm with an allen tool (not included – you can usually find this on your bike toolset), place the sensor body so that it is close to the crank sensor when it spins past and then swing the sensor arm out so it is close to the spoke sensor as it too swings past.  Then you need to tweak it all by tweaking the position of sensor body, arm, and the magnets so that the little indented slot on the sensor body lines up with the middle of the crank magnet (see photo to the left) and then moving the spoke magnet so that the indented slot on the sensor arm lines up with the middle of the spoke sensor when it swings past.  Basically the slots on the sensor and sensor arm have to line up with the middle of their respective magnets.

The magnets that come with this device are not the best (strongest), and you may want to consider replacing them with stronger ones so that the sensor and the sensor arm do not need to be SOOOOO close to the crank and spokes, respectively.  Because for accuracy they have to be very close.  Uncomfortably close.  That’s why you may need better magnets.  You don’t want the sensor arm to snag the spokes of your bike – at best it may break the sensor arm, at worse it may drag itself into your spokes while riding.

With better magnets the whole thing won’t need to be in quite such close tolerances, allowing for any accidental movement of the sensor/sensor arm.

The rubber band-like part that holds the sensor body to the chainstay bar is okay, and it makes taking the sensor body off and putting it on as well as positioning it easier, but sometimes getting the rubber band thing onto the receiving hook/slot on the sensor can be tricky.  And believe me; putting it on wrong can mean that it can fall off or not stay in place.  I had mine fall off while on the bike trainer, it caught the spokes and went directly into them.  But fortunately it was quickly expelled out the other side of the wheel, and across the floor instead of actually catching in the spokes or breaking – or both.  The zip ties are much more secure, but make sure everything is perfectly in place before pulling them tight.  Some people may find using a pair of pliers to pull them tight can help, but make sure to hold the sensor body in place while doing this so it doesn’t get moved when you tighten it.

Back view, battery compartment and sensor arm. Note the hook for rubber band attachment point as well as slots for zip ties.

Back view, battery compartment and sensor arm (the small allen bolt for loosening it is at the base of the arm – not shown). Note the hook for rubber band attachment point (at the top of the sensor body) as well as slots for zip ties (near the top of the sensor body).


Upside down view and rubber band attachment.

Upside down view and close-up of rubber band and attachment point.

Many of the reviews for the Scosche Rhythm Speed/Cadence Sensor mentioned the need to replace the included battery right away.  Mine seemed to have some juice in it, enough for it to show up in my Bluetooth settings on my phone, but the sensor worked intermittently so I did put in a new battery.  Even with a new battery I incorrectly thought that it seemed to still be working intermittently but it turned out that the first time you connect it to whatever app/device you are syncing it to you must pedal or move the pedals and tire for a bit for the sensors to sync, possibly as much as a few minutes.  So I believe that the included battery may have been fine or at least usable – I just needed to sync everything up for the first time.  A new battery is probably a good idea though, especially since these devices may have sat around for a bit (i.e. the blurb on the back of the package advertising a retired app and site).  It takes a standard 2032 battery, accessed via a pretty standard sort of screw-out disc in the back.

The sensor has no physical buttons or physical controls whatsoever, with the Scosche logo on the front of the sensor body and a Bluetooth logo on the sensor arm.  To wake it from sleep you just start pedaling and it picks up almost immediately.  But the first time that you connect it to your device and whatever app that you want to use you will need to do a bit of pedaling, possibly a few minutes before it syncs.  Be patient, give it time.  Some people have mentioned setting the bike upside down and pedaling it by hand while the sensor connects.  But in my case I am using it primarily with a bike trainer so it was easy to jump on the bike while the bike was on the trainer and start pedaling.

Of course before all of this you want to make sure the Bluetooth on your phone or tablet is turned on, though forget syncing it via the device’s regular Bluetooth sync – you will be syncing it with the app that you use.  And if you want to try more than one app you must sync it the first time with each app, but once it is done once for each app it will pick up quickly the next time around.

wahoo fitness app workout data

Wahoo Fitness: Workout Tracker App part of the Post-Workout Screen

There’s a bunch of apps that work with the Scosche Rhythm Bluetooth Speed/Cadence Sensor, like the Strava app, as well as a bunch that don’t seem to.  I use the Wahoo app (link for Android app, link for IOS app) which also connects to a host of other fitness sites (Garmin, MapMyFitness, MyFitnessPal, Nike+, Runkeeper, Strava, Training Peaks, etc), and allows you to sync your data to them (you can find out a little more on how to sync all of your fitness data across multiple sites with my blog posts A Review of Some Exercise/Fitness Logging Sites and A Review of Some Fitness Syncing Sites).  This is important if you want to keep your data as the Wahoo app itself only saves your workout data on the device it is installed one, so if you get a new device and install the app on the new device your data will still be stuck on the first device.  That’s why syncing to a more permanent fitness logging site is a good idea, and it works quite well.  When you finish you can click the little cloud icon to sync it to one or multiple sites, or you can use the calendar in the Wahoo app to go back and sync if you forgot to after finishing a ride.

The Wahoo app is really pretty good, though it would be nice if it had a few additional features.  But the ability to push all the data to other sites and apps makes up for this, as all the data and missing features might be available on whatever site you sync it to, depending on the site.  One of the nice things about the Wahoo app is how it breaks down the cardio, nice feature.  There are also a few options, and a profile set up.  The app will use your phone’s voice synthesis to inform you of distance, speed, etc and other stats (some of which are adjustable in the app’s options).

One little idiosyncrasy I have noticed – and I am not sure whether this is the Wahoo app or the Scosche sensor itself but I suspect it is the sensor (and it may affect other apps also)- if you are playing around with the settings on the app for the tire size  you may notice that app suddenly doesn’t seem to want to show the sensor at all.  You likely won’t run into this problem but if you do; pull the battery on the sensor and leave it out for a minute or so before you put it back in.

The Wahoo app also interfaces with any other Bluetooth and ANT+ sensors, for example – the Wahoo app, running on a Samsung Galaxy Alpha, connects to this Scosche bike sensor with Bluetooth and also, at the same time, connects to my Garmin heart rate strap with Ant+.  Not all phones and tablet have an ANT+ chip but anything newer will have Bluetooth (click this link if you want to find out if your device supports ANT+ – you can also possibly use an OTG cable [see a little overview of an OTG cable here] to connect a Garmin ANT+ dongle to your phone or other device if it doesn’t support ANT+ directly)

As mentioned above, there are a number of options for apps to use with the Scosche sensor, but it is too bad that the company didn’t continue developing their own as it did look interesting.

In the Wahoo app after it all syncs the first time you can see your cadence and speed in Wahoo app’s sensor set up screen and adjust the tire size, which is initially set at a default which works okay.  Any app you use with this sensor SHOULD allow you to adjust the tire size for accuracy though.

wheel circumferenceThis app accepts tire circumference (pi, or 3.14 times your tire diameter approximately, though it’s better to use a chart like this one from the immortalized Sheldon Brown or this one for taking into account all tire size factors).  Some apps may have different inputs size methods, like tire radius perhaps – like what you see on the side of your bike tire, etc so keep this in mind.  Don’t stick in 700 or something like that if the input in that particular app that you are using requires circumference instead of radius.

At first when I was tweaking the tire size in the app I had it quit on me as I went back and forth between starting and stopping the ride over and over and going to the app’s settings – I’m not sure if that was the sensor’s fault or the app’s – but now that I am not doing that during my ‘testing’ and set up phase it works perfectly.

So, the important question – how well does the speed/cadence sensor work accuracy-wise?

I wanted to be as accurate with the speed and distance as possible, and to use the bike trainer in a resistance level comparable to the real world – versus just spinning with it or something like that.  So I double-checked the numbers I got from the above chart by taking the bike outside for a ride and comparing it to the GPS speed from my Garmin Forerunner.  You should be able to do this even if you don’t have a fitness tracking watch with GPS by borrowing another smart phone and running a biking app, or using another GPS of some sort.

In my case the Scosche sensor was about one mile per hour different from what my Garmin was registering.  One thing when comparing my Garmin Forerunner to the Scosche sensor is that the Scosche speed sensor will display your current speed stats much faster than the GPS speed display on the watch, which is as expected.  Likely this is the case with any sensor directly connected to your bike versus GPS.  So when comparing the GPS from a watch or phone app you might want to keep this in mind – pedal at an even speed and hold that speed as much as possible and wait for the on both to stabilize before comparing,if you decide to double-check using this method.

I tweaked it just a little to get it to conform as exactly as possible to the GPS speed from the Forerunner – keeping in mind that the GPS watch might be a mile an hour off for all I know.  One thing I have found with GPS tracking of my rides, runs, hikes, and walks is that getting exact precision from something so small with such a tiny built-in antenna is too much to ask sometimes.  They are amazing devices built into a tiny space and they will continue to improve all the time.

But the thing about bike trainers in general – no matter how well you calibrate any speed and cadence sensors attached to your bike while using it; it’s all pretty relative.  Depending on the resistance adjustment and what gear you are using on your bike you can pump out a really high speed and distance with little effort or a very low speed and distance while under a tremendous load and with a high amount of effort.  So the numbers you might get off any speed/cadence sensors should be considered as a guideline and not an actual real-world comparison.  Even though I have tried to adjust the resistance and gearing to what I think I feel as well as what my normal cadence and heart rate would show under normal outdoor riding conditions (not including wind and other factors),  its hard to say how close I am to really simulating speeds and effort compared to outdoor riding.  Unless you go with something much more expensive there’s no calibrating the resistance you choose, except by personal preference.

Once I had this done I could get to the business of riding on the trainer when I wanted to.

[pullquote]So after a number of rides I’d say my conclusion, at least so far, is that for such a relatively inexpensive piece of electronics the Scosche Speed/Cadence sensor seems to work quite well; once the first set up is done.[/pullquote] I stick the bike on the trainer, start the Bluetooth on my phone (I usually have it turned off), load the Wahoo and press the Start button and start pedaling and it displays and records my stats.  Task accomplished.

By the way – if you do a lot of hours on your bike trainer check out my post “Bored on the Treadmill, Indoor Bike Trainer, Exercise Bike, Elliptical, or Rowing Machine?  Get a Chromecast!

The only issue is the occasional and momentary dropping out of the cadence or speed – it lasts maybe less than a revolution of the pedals and then it’s back, and it doesn’t happen that often.  If you’re a stickler for exactness this might bug you – but I doubt it has a measurable effect on either in the long run and likely this is the result of the somewhat weak stock magnets that came with the device.  At some point I will replace these magnets with better ones and update this review, but for now they work adequately for my purposes, though as I mentioned above they do have to be fairly close for consistent sensing.

Transferring the sensor body and magnets to another bike is moderately easy and only takes a few minutes.  The rubber band attachment makes this easier of course.

Concerning the rubber band attachment – I’m not sure how well it will hold up under outdoor conditions; from the possibility of jostling it with your foot or leg (or from something external if mountain biking) as well as the durability of the rubber.  I would definitely consider zip ties for outdoor conditions, and they are cheap enough where you may even consider them for temporary use if you transfer it between bikes, there’s enough space around the zip tie slots to snip them with small wire snips without coming too close to your bike’s paint job.  For using it on a trainer the rubber band attachment seems to be fine (as long as it’s secured correctly).

I might mention some alternatives to the Scosche cadence/speed sensor here also.  Like the Garmin Speed and Cadence Sensor (which does not use magnets and instead uses motion sensors, but it does use a rubber band attachment for the sensors, ANT+ only), the Wahoo Blue SC (very similar to this Scosche speed/cadence sensor in design, with both ANT+ and Bluetooth), and the same sensor as this Scosche one but sold by a number of Fitness sites and other companies that put their own name on it.  There’s also a lot of similar and other speed/cadence sensors of various types.

But all in all I believe that the Scosche Rhythm Bluetooth Speed/Cadence Sensor does it’s job, though I’d recommend better magnets which slightly increases the overall price if you plan on going that route.  For the $16 price it can’t be beat, even for the original $50 to $60 price it’s a fair deal.

 scoschespeedcadencesensor (1b)