Flyon Speed Sensor

[arawa]

Back in February when out in the hills, the speed sensor failed on my Alltrail 6 with the message: "Warning Speed Sensor. Speed sensor problem. Power reduced".
My LBS said the disk had warped and fixed the problem although I subsequently realised something was still not right as the motor support ceased at 13mph in a very jerky fashion and it was impossible to pedal faster almost as if the brakes were on. Below 13mph everything was fine.
Well, out on the hill at the weekend, quite a long way from the car, the same message popped up again.
I had bought a replacement speed disk, just in case, and have fitted it but the bike really does not like it. The indicated speed flashes all over the place say 5-14-25-6 etc and the power cuts in and out. As far as I can see the speed disk, and the brake disk to which the speed disk is fitted, are absolutely flat.
I take great care with the bike and it has not had any falls or knocks.
My bike shop will try and sort things out for me but is closed for another 2 weeks.
I know AJR has experienced this, but has anyone else had similar problems?

 

[Jetpilot]

I dont think there seem to be many Flyon owners here to get that support. I dont wish to be negative but on your previous thread on the subject and mentions from your lbs that it only needs to be 1mm out is going to cause you problems. My only advise is to log these episodes because if its going to be reoccurring you have some recourse if you ever decide to reject it.

 

[arawa]

Thanks Jetpilot. I am hoping there are lots of Flyon owners on the board but that their bikes are operating perfectly (as did my first Haibike)! Because, this fault aside, the Flyon is ideal for my use.
Having examined my and my friend's identical bike and with the benefit of some advice from forum members, I think unless there is a fault in the frame sensor itself (beyond my ability to diagnose and I suspect less likely) the problem lies with a distorted speed sensor disc. The disc itself has some flex but is held rigid by being bolted to the rear brake disc. However, the Magura MT5 203 mm brake disc is fairly flexible and could be out of true sufficiently to affect the speed sensor tolerances. I was going to swap the front and rear brake disks to see if it made a difference but my LBS is going to sort things out next Monday so I will leave it in their capable hands. I am very glad I bought from a good bike shop.
As an aside, my friend is using his Alltrail Flyon a lot and since a software update in January he has had no problems at all. He is no lightweight but is getting a range of about 40 miles using a mix of modes (but only rarely extreme as that is just not needed) on fairly hilly minor roads and forest tracks.

 

[AJR]

In my experience the sensor only has to be slightly distorted to make a difference in performance. It is a very thin pressed piece of steel, I now keep spares so if it happens I can sort it quickly.

 

[arawa]

Sorted. The problem was not the speed sensor disk but a very slightly warped brake disk. The brake disk was replaced and both the original and the replacement speed sensor disks now work properly.

 

[Steve h]

Sorted. The problem was not the speed sensor disk but a very slightly warped brake disk. The brake disk was replaced and both the original and the replacement speed sensor disks now work properly.

Thanks for posting. At least I know what it is if it happens on mine. Especially after the grief it’s given you!! Glad it’s sorted for you now.