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  1. #1
    mtbr member
    Join Date
    Feb 2009

    Assistance on Trek 9i computer

    When I bought my bike I had a LBS install a Trek 9i on it. On my first ride with it I was on a marked rail to trails. My bike computer stated I had gone about 7 miles when I only went 5.

    When I arrived home I also noticed my max speed was 77 miles per hour! I checked the tire size and it was correct. This computer has the ability to do 2 wheel sizes so I set the other one to make sure. In my truck I found the road I live on is .3 miles long. On another bike with a Trek 6i wired computer it too read .3. When we rode the two bikes next to one another my 9i was going faster and also more distance.

    I took it back to the LBS and the guy pushes the reset on the back of the computer and then states that the wheel size is wrong. Funny since they set it. The kid who set it was there and stated it was correct. He then also states itís mounted on the wrong side. The kid mounted it to the same side as the disc brake. His final comment was if I still have problems to move it to the other fork and if that doesnít work they may need to replace it.

    I get home and nothing worked. Speed and distance is still off so I take everything off and then take it back. Well in working with the owner she pushes the reset button right away and says the wheel size is wrong. So now they have set it twice and they still state itís wrong. After much negotiating she breaks down and gives me a new one. She sets the wheel size and I come home and install it on the fork side that doesnít have the disc brake.

    The first ride is promising with the speed and distance being right. Tonight I go for a ride and it seems to be working fine until I hit some off road trails that are nothing really more then a woodchip walking path. By time I get back to the street my speed is at 0.

    I have moved the sensor thinking that is the problem but regardless of where I move it I either get no speed or my speed is 10 mph 1 second and then 4 mph the next. Look down a few moments later and Iím back at zero.

    Suggestions? I had an old wired Trek computer and that thing was rock solid and I went off road more then a wood chip trail.

    I plan to call Trek on Monday since I know the LBS wonít do anything. At this point I feel I have a $50 piece of junk. I may just ask Trek to swap it out with a wired 6i but Iím not sure if they will do that.

    I would like to go for a ride tomorrow though so Iím open to anything else I should try first.

  2. #2
    mtbr member
    Join Date
    Mar 2005
    So, what happened with your Trek computer? -gt2005

  3. #3
    mtbr member
    Reputation: Shaniac's Avatar
    Join Date
    Apr 2009
    I own the 9i as well. When mounting the sensor and magnet, you are supposed to put it on the fork opposite side of where your disk brake is (on the right as if you are sitting on the bike). When mounting the sensor, make sure that the magnet (the part that attaches to the spoke) is approximately 1Ė3 mm away from the sensor. If the magnet moves ever so slightly out of this range, the reading will be thrown off so position the magnet on the fork and tighten it down good.
    I have found that the best place to attach the magnet is on two spokes, right where they cross each other on the wheel. This ensures two things; one, is that you can guarantee that it won't slide up or down on the spokes and two, by using two spokes , you don't have to worry about the magnet twisting away from the sensor.

    If none of the above works, There is something wrong with the computer and I would get the bike shop you purchased it from to replace it.

    *BTW, you can select a tire size on the cyclo-computer when setting it up. This is not 100% accurate. You can also bypass the preset tire sizes and plug in the actual wheel diameter in mm. By doing that, you will be more accurate as the tire sizes are off by several mm's which adds up over a 12 mile ride...

    Alsoóof course you will have the wrong tire size plugged in when hitting the reset button on the back. By hitting the reset button, the computer defaults back to the smallest wheel size.

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