# Wahoo vs Garmin Sensors



## MTB-More (May 25, 2017)

Hi All

Scenario:
So about 4 months ago I took the plunge and bought myself a Wahoo Speed and Cadence sensor and have to add it has been working flawlessly since then with no issues. 

Last week the wife was nice enough to let me upgrade to the Fenix 3 HR (They on decent specials now) and with it came free gifts in the form of a Garmin Speed and Cadence sensors.

So for the past week I have read every review I could about Wahoo and Garmin. DC Rainmaker has a really good breakdown of the Garmin sensors but there is no equivalent on the Wahoo to be able to draw a conclusion on accuracy. DC Rainmaker did say in a blog post in 2015 I think that he would do a review on the Wahoo but I think he never got around to it. 

Sensors:
Wahoo - https://www.wahoofit...nce-bundle.html
Garmin - https://shop.garmin....nce-sensor.html

What I would like to know:
1. Which one is more accurate?
2. Which one is better in the long run with more consistent results?
3. Is there a considerable difference in the pickup from the one to the other? (Referring to the Lag to log during interval sessions)

FYI - I am thinking of selling the 1 set seeing as I don't need 2 sets. Want to keep the "better" one ofc

Thank you for your time in reading my long post. Hopefully you guys/gals can help me make a informed decision with your experience with these sensors.


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## Harold (Dec 23, 2003)

You have both sets of sensors. Why don't you do a test? I think it's going to be difficult for you to come across someone who has done the kinds of tests you want. But consider these questions:

How do you define more accurate? What is your baseline or control for measuring accuracy of sensors?

Frankly, I don't think for most people, the answers to your questions matter. The impressions I get from most sensors (I have only used a few different ones, and from your selection, only the Garmin wheel sensor) is that they're MUCH better than not having them, and while there may be differences between them, those differences are likely to be from calibration errors rather than any core differences in the accuracy of the sensors. DC Rainmaker did do a review of the new magnetless Garmin sensors vs. the old GSC-10 combined sensor. There are differences and those might be relevant to you. The difference is not large enough for me to care.

When you consider how the sensors work, this makes sense. All the wheel and cadence sensors do is count rotations. If your sensor can't even do that right, there's a problem and you need to fix it. Most differences lie with the third question you ask - the lag for the sensor to pick up the motion and transmit it to the head unit. There are some small differences there, but again, they're not big enough for me to care about. If you're working out at a really high level, I can see how you might care. But that's not me, not by a long shot.


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## MTB-More (May 25, 2017)

Hi Harold. Thanks for the post

I think the 3rd question was actually to me the most relevant. What I noticed with the Wahoo is that there is a avg of 5-7 seconds delay in the sensor to the Fenix 3's logging. On trails where you peddle and stop every other second I was wondering how this would translate differently with the Garmin hence the performance question. 

Do you recon the Garmin sensors would have less of a lag?


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## Harold (Dec 23, 2003)

I haven't ever paid much attention to any lag or not. I only have the Garmin magnetless wheel sensor. as far as I can tell, there's maybe a couple seconds between starting and seeing my speed on the head unit. Not as many as 5-7. My Garmin can tell I'm moving with less than 1 wheel rotation (and beeps that I'm moving if I haven't yet started the timer).

No idea about the cadence sensor. I have a Bryton cadence sensor with a magnet on my road bike, and it won't register anything until the crank arm with the magnet passes the sensor. But once it does, it registers pretty quickly on the head unit.


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## MTB-More (May 25, 2017)

So did some testing with the Cadence sensor last night and it would seem that the Garmin has a 1 sec on avg quicker pickup to log (Negligible tbh). I will do some sensor swapping this weekend and go on the same trail to see if there is any difference.


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## ghettocruiser (Jun 21, 2008)

Note that with a wheel magnet (or cadence magnet) sensor, the magnet has to pass the sensor twice to give data. 

So if you take off like a batoutofhell, the lag should be less because the head unit is waiting less time for the second ping compared to a gentle start.

I can confirm that you can put two magnets on a wheel (in line with the wheel centre, find the right spokes) and set the wheel diameter size to 50%, you get much more responsive data on Garmin units when starting and stopping. Especially on slow-moving bikes with big wheels, like fatbikes. The reason I tried this (a few years back) was when overlaying GPS data (i.e. speedometer) on my Gopro video, the lag was way more apparent then it would ever be riding, and the two-magnet setup cut this lag in half.

I'm not sure if the new Garmin magnet-less sensors transmit one ping per rotation or a bunch. If it's the latter I might buy one, since two magnets are twice as likely to get knocked out of alignment as one...


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## notso (Jan 22, 2015)

One comment on the Garmin accelerometer based cadence sensor. I recently installed one on my hard tail. I think the fairly harsh bouncing on single track and gravel can give erroneous readings. From riding on the trainer, I know that my max cadence is somewhere around 140, but on a recent gravel ride, I had several chunks of data that showed up to twice that. My thought is that the accelerometer reads the bouncing as rotations. I saw non of this behavior with it mounted on a road bike and riding pavement.


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## Harold (Dec 23, 2003)

notso said:


> One comment on the Garmin accelerometer based cadence sensor. I recently installed one on my hard tail. I think the fairly harsh bouncing on single track and gravel can give erroneous readings. From riding on the trainer, I know that my max cadence is somewhere around 140, but on a recent gravel ride, I had several chunks of data that showed up to twice that. My thought is that the accelerometer reads the bouncing as rotations. I saw non of this behavior with it mounted on a road bike and riding pavement.


I think it likely that pedal ratcheting done in mtb riding (often in chunky, tech sections) gives erroneous readings. But it'll do that with a magnet-based cadence sensor if your dominant/forward foot is your right, and the left pedal hovers over the sensor all the time. Part of the reason why a cadence sensor on the mtb isn't really useful.


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## lazarus2405 (Jul 16, 2011)

ghettocruiser said:


> ...since two magnets are twice as likely to get knocked out of alignment as one...


Having never used a speed/cadence sensor on an MTB, I have to ask - how frequently does a magnet get knocked out of alignment during trail riding? Is it sort of once in a blue moon, or frequently enough to make magnetless sensors generally preferred?


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## Harold (Dec 23, 2003)

lazarus2405 said:


> Having never used a speed/cadence sensor on an MTB, I have to ask - how frequently does a magnet get knocked out of alignment during trail riding? Is it sort of once in a blue moon, or frequently enough to make magnetless sensors generally preferred?


the magnets less frequently than the sensors themselves. Cadence sensors get bumped ALL. THE. TIME. on road bikes. No reason to suspect it would be any better on a mtb.


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