Mountain Biking - Problems with Cyclometer

I'm a first time poster so first off, I'd like to say hello -- so, Hello!

Second, I had a question. I went biking this morning and my cyclometer was totally off. The tripometer, odometer and speedometer were all reading my speed too fast (i.e., I was going about 20 mph and it said 33mph). I checked it out and nothing seems out of the ordinary. Does anyone know what happened?? Is it time to get a new one or is there some fix to the problem?

Thanks!

You should recalibrate it .. check your manual for instructions and make sure you do a rollout measurement.. Some models have support for multiple bikes make sure you didn't select bike #2 or something.. also make sure it's not on Kmph.. check that you have proper distance between the magnet and sensor(this is usually a slower reading though instead of faster)

other than that you could try taking the 2nd magnet off the wheel ... j/k

edit:: 33 Kmph = 20.49 mph there's your problem

How do you know you were going 20mph??? Was that what a friends odometer said? Maybe he was wrong.

Yes, you should do a rollout test. Make sure it is one with you on the bicycle. Suggestions have been made for using toothpaste, shaving cream and chalk to make marks on the pavement at the pavement using your wheel. Then just measure.

How do you know you were going 20mph??? Was that what a friends odometer said? Maybe he was wrong.

There's quite a difference between 20 and 30 mph on a bike....

There's quite a difference between 20 and 30 mph on a bike....

yeah most riders with a little experience can ballpark it and be pretty close.

dirtpedaler has a point, if you think you were going about 20mph and happen to be right, you very well might be on kmph, my cyclometer has huge numbers but a tiny little icon that says kh or mh, i had it on the wrong one at first and took a while to notice it.

I bet your bike PC is a Cateye...

They come preset to kph. or at least my last two did...

There's quite a difference between 20 and 30 mph on a bike....

Yes, and there is also a difference between 17 and 20 mph. There is also a difference between 23 and 20 mph. If you're that far off, your cyclometer is WAY out of calibration.



yeah most riders with a little experience can ballpark it and be pretty close.


Why do you need a cyclometer then. Just "ballpark" everything and you'll be pretty close. Perhaps even closer than a cyclometer that has not been calibrated using a rollout test on a given set of rims and tires (the tires being inflated to the same amount they are when used while riding).