Cycle computer sensor with carbon forks
 

Thought maybe this is the appropriate section since it is about the cycle computer. I have just a cheap Bell wireless computer that I bought last year when I started riding my Walmart bike. It worked just fine. This year I buy a Giant Escape 1 with a carbon fork and I have all kinds of trouble with the sensor reading the magnet. Step one obviously is change the batteries. I did that.

The carbon fork is not round like my old junk bike. It is difficult to keep in position, especially since I now remove the front wheel to carry the bike in the car. I find that I have to push the sensor over on the corner of the fork radius and actually have the magnet hitting the sensor for it to work flawlessly.

I'll be riding along and see my speed jump down to say 11 from my actual cruising speed. I'll see it fluctuate all the time. Sometimes I'll look down and see the speed at 0. At this point, I'll stop and look and find the magnet twisted on the spoke slightly and is no longer contacting the sensor when it spins around.

Is there interference from the carbon fork? It seems to be between the magnet and sensor rather than the wireless signal to the computer. I know in the RC airplane hobby, we have interference of the transmitting signal from carbon reinforcement rods. I don't know why the computer was flawless and didn't need contact between the sensor and magnet on the round aluminum fork of my old bike.

Thanks for the thoughts on this. It was only bought the end of last summer. If I had the cash, I'd go out and buy a "good" computer, but I'm just stuck with this one for now as I still need other things.

Perhaps a stronger magnet, a rare earth type... If the pickup is moving around or slipping on the fork leg, add some double stick tape under it.

That is really weird. My full carbon Specialized Tarmac and my carbon-fork specialized Sequoia both have a carbon fork, and a cycling computer that works flawlessly.

The first thing I might suggest is that you might try changing where the sensor is mounted on the fork? So move it up or down (and move the magnet as well to match) to a point where it's easier to keep mounted.

Otherwise, I might just suspect that something has gone bad - the magnet, the sensor, or the wire from the sensor to the computer (if the wire was frayed but not broken it could cause a problem like this).

Is it a wired computer or a wireless computer?

I had to give up my magnet sensor computer when I upgraded my wheels to some with aero spokes. The sensor on the spokes kept tilting and then one day on a fast descent it slipped and started hitting the other sensor repeatedly. Never worked again after that. Picked up my Garmin Edge 200 that week and never looked back.

It needs to work with the magnet just missing the sensor. If you have it striking the sensor it will always bounce out of position eventually.

I've twisted the sensor to be more to the inside of the fork (and rearward), to get it closer to the magnet. The magnet is positioned to pass near the very end of the sensor. If it doesn't work when it passes within two or three mm then the sensor switch is toast.

Yeah, I've moved it all around. I've put them down towards the hub where the magnet would be closer to the fork/sensor, moved it up the fork so the sensor had to be twisted around to reach the magnet. Pretty much it only seems to sense when it is making contact.

It is a wireless. I had the same Bell from Walmart wired years ago when I bought the first bike from Walmart to ride with my daughter when she was 5 but have since lost it.

I'd love a Garmin for mapping without needing to use my phone. With my finances, that's just a pipe dream to spend that much on something not entirely needed. Perhaps 8 years from now when I'm not paying for the kids anymore.

Yeah, within a mm, I'm not getting a reading. Hmm, I do have a magnet on the fridge that might be a bit stronger. I put it on the fridge and tell my kids and my wife to remove it. They can't pull it off, LOL. Heck, even I can barely pull it off the fridge. I could probably just snap that sucker right to the spoke and it would never come off even at my so far top downhill speed of 35 mph. I love to scare the crap out of the kids when they are getting into the fridge and I toss it towards the fridge door. It's quite a loud crack when it snaps to the fridge.

I was thinking it was wired. Wireless adds some variables and I've had bad luck with them. The one I have (a cheapo) has a range of two feet, in reality less than that I think, and it had to be near the brakes to work reliably. The sending unit battery died quickly, and now since a couple of rainstorms it doesn't work at all. I wouldn't be completely surprised if the carbon fork did cause some interference after all. You might try holding the display unit close to the transmitter and spin the wheel.

Bad switch still seems more likely though. I like the idea of trying the strong magnet. Just manually pass it near the sensor a few times in rapid succession and see if it displays anything!

If the magnet is moving around on the spoke, then that is the source of your problem. I have had the same issue. I little superglue to hold it in place works wonders. I figured that was my problem because I was getting obvious speed errors- would drop to half and then come back up, drop to 0 then come back up. My wife has the same computer, but has bladed spokes- the magnet can't rotate. We compared stats after rides together, and the difference in avg speed and distance over one of our regular loops was pretty dramatic- I got 16.25 miles instead of the 22.28 that she got, and my avg speed was a little over 11 mph, while she was at 15 and change, and we were together for the entire ride.