BBSHD C965 Display erratic speed

[fixitalldanj]

Hello, I have a BBSHD with C965 Display. The speedometer seems to be all over the place. When in top gear (Smallest cog) and holding the rear wheel in the air, it will read 32.8 MPH. But when in 6th gear, it reads 48Mph!! The magnet is about a sheet of paper width distance from the sensor. Also when testing with rear wheel in the air, I hold the throttle till I get highest reading, then when I let off and the tire freewheels, the speedo jumps up to like 60 - 70 Mph when coasting!! There is for sure a problem somewhere, not sure if it is the sensor, the display, or the firmware. It is the C965 display with the three button controls. Anyone else notice this?

 

[tomjasz]

Do you ride with the wheel in the air? Check it out riding. Unloaded speed means nothing.

 

[amberwolf]

Someone else reported a speed sensor problem, and has a troubleshooting thread for it if you look around for speedo problems in the last few weeks. I'd bet yours has the same cause/fix.

 

[tomjasz]

Ride it, erratic on the stand means nada.

 

[fixitalldanj]

Yes, it is erratic while riding. When in top gear (I have a 8 speed) my top speed is less than in 6th gear. Its really weird.

 

[fixitalldanj]

I was referring to the speeds on my cassette. It shows a higher top speed when in a lower gear compared to a taller gear. And its obvious I am going faster when in a taller gear. I have my max speed set to 60kph in the display.

 

[tomjasz]

What happens if you max the speed setting?

 

[fixitalldanj]

60kph is as high as I can set it.

 

[tomjasz]

Hmmm manual says 99, 3 button or 5?

Edit just checked mine 99 limit.

 

[fixitalldanj]

Its the three button version, per my first post. And 60kph is the highest I can set it. I put on a cheap bike speedo and it says 66 mph when I top out and the bafang says 32..

 

[tomjasz]

sorry I glazed over the last line...

Have another display to try? Near any other BBSxx users? You don't list a location, good idea, sometimes there are users close by that can be helpful.

(I always keep a spare display and throttle.)

 

[fixitalldanj]

I am in SLC, Utah.

 

[Bruno (YouTube)]

I use C961 older display next to the accurate Cycle Analyst, I have never experienced issues while riding (loaded) at high speeds (very strange).
Unloaded wheel: as you increase the speed it will increase the speed on the display and then eventually drop (even knowing that the wheel is spinning faster, it is like the sensor is not registering the magnet very well) = the closest to the tire you set the sensor+magnet, the fastest the magnet will pass in front the sensor and the less precision you will get (remember this is not an expensive precision sensor) the best way to avoid "precision" issues is to place it near the hub where the magnet travels at lower speed. I am not sure if this is the problem you're having there but it will definetelly help in some way.
Here is a video I made showing my BBSHD https://youtu.be/xfmUHbDRmxc
I remember testing my BBS02, unloaded speed used to reach 68kmh then the display would start read it as 50kmh (or lower) but as soon as you release the throttle it "picks up" and reads the correct speed around 78kmh.