General Cycling Discussion - Bike Computer issues

Hi All,

I recently installed a new Trek Incite 9i bicycle computer on my road bike. I already have one of these devices installed on another bike and it works fine on my other machine. However, my newly installed computer is giving me incorrect readings. For example, I did a short ride this morning and it said that my max speed was something like 55 MPH and I'm pretty sure I was not going that fast! I don't know how fast I went but, it was probably between 30 and 40MPH. It also said that I road something like 17 miles when I probably road about 11 miles. I noticed that the instaneous speed seemed higher than what I was really going.

When I entered in the wheel size into the computer, I couldn't find my tire size (700x26c) so I selected 700x25 instead. Would this slight difference in tire dimension be responsible for such wildly inaccurate readings? Since I'm getting faster measured values, I'm assuming that the computer thinks that my wheels are much larger than they really are. Or could it be that the sensor is somehow incorrectly measuring the wheel revolutions?

Thanks in advance.

You'll need to do a "roll out" to get the best accuracy. This link has a lot of information:

http://sheldonbrown.com/cyclecomputer-calibration.html

Thanks Berg. I'll take a look at that link and figure out what tire setting would be best for my configuration.

I took the computer back to my LBS and they took the batteries out and let the system reset itself. Then they put it back in and reprogrammed the system (to 700x25) and it seems like it's working now. I haven't ridden it far yet, but I did some runs up and down the street with my mountain bike and then with my road bike and it looks like the two systems more or less agree. Now my max recorded speed seems more realistic (instead of 55 MPH!).

When I first installed the trip computer, I didn't reset it. It was on in the box so I simply stuck it onto its mounting base and rode with it. I think resetting it may have cured its problems.

Update - I did some more test runs and it appears that resetting the cycle computer has fixed the problem. I guess my cycle computer is sort of like my PC.

I have a Trek Incite (8i or 9i - wireless no cadence) and I have the exact same problem. I did a roll out calibration when I installed it. The trip distance is perfect, the average speed is right, but the Max Speed will read 64mph or 77 mph, always high.
The other day on my commute home I stopped on the top of the first hill and it showed a max speed of 38 MPH. I maybe broke 22mph on the flat on the before climbing the hill....

BTW - the othe day I moved the sensor and the magnet a few inches further away from the hub and it looked like it fixed it, but I still get the same crazy Max speed readings.

hunyak,

did you try removing the batteries and letting the system sit for a minute or two to reset? If you do this, make sure you write down your Odometer value before you take the batteries out. This seem to fix my woes. I took the bike for a ride this morning and it gave me consistent readings, including the max speed.

Do you have anything that might be interfering with the wireless transmission?

77mph looks familiar. I used to get this all the time with wireless computers and interference from power lines, lights and garage door openers.

Now I have a wired computer and don't see this anymore, guess now I'm riding slower than 77mph. ;)

The first thing I do when I get a new cyclometer is toss the battery that comes with it and install a new one. You never know how long those have been sitting around.

Thanks for the info - I'll pull the battery tomorrow.
As for interference, don't the wireless cyclometers use similar frequency (2.4ghz) as wireless routers?

hunyak - if you pull the batteries out, make sure the system completely resets (wait a few minutes before you put the batteries back in). The way you can tell is if the computer prompts you for the tire size, kilometers vs. miles, and degrees vs. fahrenheit.

I'm not sure what frequency the wireless cyclometers use, but I know that my wireless heart monitor can get screwed up if other wireless devices are present.

good luck!

Thanks for the info - I'll pull the battery tomorrow.
As for interference, don't the wireless cyclometers use similar frequency (2.4ghz) as wireless routers?

Actually, I had an interference issue with a wireless speedometer a few years ago...
http://www.bikeforums.net/showthread.php?t=136397

My PlanetBike speedometer served me well until it took on a bunch of water, last month. Now I'm using a Trek Incite 11i. I really like having cadence.:)