Wahoo Blue SC Mounted on Quest - Not Ideal

[kgantz]

I picked up a Wahoo Blue Speed & Cadence sensor from my local Apple store yesterday. Based on info from the Wahoo web site, it seemed like the Blue SC should work on the Quest. It does, but the mounting is not ideal and I can't tell if my unit is defective or if they all operate like this.

The cadence sensor was never a problem, it worked from the start and is easy to adjust. The speed/RPM sensor however is a bit of a mystery. It seems easy enough to get it the required distance away from the wheel magnet but doing so requires the sensor arm to be rotated toward the wheel, something that it is designed to do, but seems to present problems with my unit. The problem with my Blue SC is that it seems to stop sensing the magnet anytime the arm is swung more than about 50% of its total travel. Even if I remove the magnet from the wheel and pass it by the sensor by hand, it stops showing RPM when the arm is extended too far. The way the Blue SC fits the quest, to maintain that 1/8" gap between sensor and magnet requires that swing arm to be near the end of its travel.

So, unable to get an RPM signal at the specified gap, I noted the sensor arm swing angle where it stopped working and locked the arm down at that point. It picks up the wheel magnet at that point but the air gap between magnet and sensor is at least 1/2" if not larger! My concern with the setup I have now is that the air gap is so large I'm assuming I will lose connection to the spinning magnet as the batteries wear down in the Blue SC. I have a question into the Wahoo people about it but I don't know how familiar they are with Cruzbikes and thought that maybe someone here had experience with this installation. I did find mention of the Blue SC while searching the forum, but no one mentioned any particular problems getting it installed and set up. On my Blue SC unit, it seems like the angle of the sensor arm is more important than the gap between the magnet and the sensor. I can't believe it even "sees" the magnet with the large gap I have currently.

 

[Eric Winn]

I used my Wahoo Blue SC on my

I used my Wahoo Blue SC on my loaner Cruzbike Quest - 26 inch (559) wheels without any significant problem over 1,168 miles. I would occasionally lose my speed measure when I bumped the unit, knocking the speed sensor arm out of proper alignment with the wheel magnet. Sometimes it was the other way around - kept speed but lost cadence.

This didn't happen very often - typically the few times I threw the chain and once after repairing a flat. I would inadvertently bump the base mount during these recovery situations and forget to check it before riding again.

I typically had to have the speed arm sensor end pretty close to the wheel magnet for it to reliably work. I adjusted the base unit on the chain stay so the cadence sensor was close to the limit of reliable sensor reading to give myself a bit more adjustability for the speed sensor arm and wheel magnet.

Some of the ultracyclists and HPV crowd I know build up a custom mount point on their chainstays to prevent unintended bumping and misalignment of the base unit. One guy I know told me he uses some kind of tape which cures into a hard mount after it cures but I don't recall what it was.

I did have to loosen up the speed arm set screw and move the arm at close to the max deflection before tightening it back down to fit the Quest's chainstay+wheel geometry.

I've since switched to a Stages power meter with built in cadence on my Vendetta.

The Vendetta has "bladed" chain stays making the Wahoo Blue SC sensor base even easier to bump out of alignment so since I wasn't using the cadence part I quit using it and for the time being and relying on GPS for speed.

-Eric

 

[kgantz]

What About Battery Life

Thanks for the info Eric! I've only used my Blue SC on one actual bike ride so far and both cadence and speed worked fine throughout the 28 mile ride. I am amazed that speed continues to function since I can almost slide my pinky finger between the magnet and the sensor, the gap is that large.

I'm pretty sure I read somewhere that you use, or used to use, Cyclemeter too. Cyclemeter reports on my Blue SC battery strength, something that the Wahoo troubleshooting app doesn't do, and after just one ride it reports that the Blue SC battery is down to 36%. At that rate I will be replacing batteries quite frequently. Do (or did) you have frequent battery changes on the Blue SC? I'm hoping it's just the Cyclemeter software being inaccurate but Cyclemeter seems to be pretty solid software so I'm not optimistic.

 

[Eric Winn]

I bought my Wahoo Blue SC

I bought my Wahoo Blue SC around Aug or Sep 2012 and replaced the battery about 9 months later in June 2013 right before the N24HC but that was just to make sure the battery was fresh. It turned out a bust however because I ran into a problem with the external battery for my iPhone which resulted in the internal phone battery dying around the 80 mile mark.

So even though the SC battery was fresh my data collection battery went kaput and I only got data for that first 80 miles or so.

I also have the Wahoo Blue HR which I did have to replace the battery because it got too low to achieve the bluetooth connection with Cyclemeter. It lasted about 8 months or so which is why I went ahead and replaced the SC battery before the N24HC as I bought the HR monitor and put it into service AFTER the SC. Since I put the HR monitor on before my rides and take it off after my rides and sometimes forget to take it off for a while after riding, it probably was "running" a good bit more than the SC.

I just got my new RFLKT+ a few weeks ago but haven't tried it yet. Weather, work and my eldest son's wedding have been contributing to not riding hardly at all these last two months.

Love Cyclemeter - great little app. I try and help beta test it and helped them catch and squash at least one bug.

-Eric