techie question....

[trickytiger]

So, I went out for a BEEE-YOU-TI-FULLLL outing tonight, more of a "getting to know each other" easy hour-long training ride with my new Cannondale- you know, the learning-how-to-use-the-drops-and-hand-signaling-and-water-bottle-drinking-and-feet-unstrapping-and-sharing-road-with-car-and-cruising-and-how-fast-can-I-go-anyhow-and-maybe-public-spandex-wearing-is-okay-and-did-a-bug-just-get-stuck-in-my-teeth?-ride.

It was fantastic. I'm primarily a runner, and I've found this marathon training program that has me running 3 days a week (all hard workouts/distance) and cross-training for 2 to 3 other days.

Well hello! Perfect! You mean I HAVE to ride my bike for my marathon training? Happy happy!

Thing is, I KNOW my fav running loops inside out, and my new Topeak bike computer is claiming it took me 45 minutes to ride 5 miles! I don't even RUN that slow! It's actually about twice the distance. I think the setup is okay on the wheel- the magnet is on the spoke within the sensor limits on the pickup, and I measured out the wheel (23X700c) circumference at 2100mm (and I confess, I'm such a nerd that I calculated it too, at 2110mm), so that's okay.

WTF? Any ideas? It's not the biggest deal, but my ego really really wants to see my speed at the correct number...... that's half the fun!

-Tricky

[DeniseGoldberg]

That wheel size sounds about right - checked one of the Topeak computer user guides online...

Are you talking about your average speed?

If you're talking about elapsed time, that usually is really elapsed time and not active time.

On the average speed front - many of the cycling computers out there have the ability to compute average speed based on either active time or elapsed time. That setting is usually something that is in the set up of the computer - not something that you can look at either way. If your computer is set to active time, your average speed will be based on the time that you were actually moving. If it is set to elapsed time, the average speed is based on the time between when you clicked start on the computer to the time you clicked stop - which can include both active time and time that you are stopped.

Of course it is entirely possible there is something wrong with the computer. Is it new? If not, try changing the batteries. If it is... I have had problems with new cycling computers in the past, and the only remedy I know for that is to take it back to the shop where you bought it!
--- Denise

[sarahfixit]

One important thing to have is a mile you can count on. Take something that is usually right(such as your car) and clock out a nice mile route on a quiet area that you know won't change landmarks on you.
Now ride the loop. If it reads over a mile then the programmed wheel size is too large. Too short means the size is too small. It will take some fine tuning usually, but once you have it you have it.

[Irulan]

I set my computer manually as something like what tire you have on your bike and what air pressure you run it at will affect the circumference. The manual should have instructions on how to do this.

irulan

[SadieKate]

Computers frequently have an "auto on/off" function that you may have to set. If this function is turned on (I use an Avocet), the computer will probably only need to be cleared between rides and then it will calculate avg sped based on ride time not total elapsed time. Just remember that the computer will avg in the speed your bike is travelling even when walking it from the door to the street.

I'm unfamiliar with Topeak computers so don't know how they function but my old Cateyes worked the same way.

[trickytiger]

Perhaps I should be more clear- the total ridden distance at the end of 45 minutes was reading 4.98 miles according to the odometer. Top speed was apparently 12.3 mph, average speed was much lower, about 6mph. However, the loop I rode was very familar to me because it's my running loop and I measured it with my car and years of running- at 10 miles. The computer is set correctly for my wheel circumference- which I both measured using a measuring tape in mm that was taped to the floor and calculated. Now, something's not right here! I find it really hard to believe top speed was that low, because it was downhill and I was keeping pace with traffic, and I KNOW that loop is twice as long as the odometer claimed it was! Plus my average biking speed on a road bike should not be LESS than my average running speed, yes?

Ah well, this just means I need to go test it out again. Aw shucks.....

[Grog]

Is it wireless? Maybe at times it is not transmitting your wheel rotations?

[Adventure Girl]

the total ridden distance at the end of 45 minutes was reading 4.98 miles according to the odometer... I KNOW that loop is twice as long as the odometer claimed it was!

4.98 miles in 45 minutes would be an average of 6.64mph. 10 miles in 45 minutes would be an average of 13.33mph. Did it actually take you 45 minutes of riding time? Does 13.33 sound more realistic?

If you are sure it is calibrated correctly, it sounds like your computer is not picking up all the miles. Maybe it is stopping and starting. If it is wireless, maybe there is some kind of radio interference (other electronic devices). Are you sure you have everything in miles and not kilometers?

If all else fails, I would recommend that you start all over. Remove the battery and zero out the whole thing. Reinstall the battery and reprogram the computer and see if that helps. My friend's computer (a cateye) was spazzing out on him. The mph would be erratic. It would jump from 13mph to 25mph for no reason at all. Resetting fixed it all.

[skibum]

I've occasionally had my bike computer give erratic readings while riding. If I know the sensors are lined up correctly, I've found that the next most common problem is the connection between the computer and the bracket that mounts to my handlebars. If the connection is flaky, it won't always count all the wheel revolutions. In that case, it helps to remove the computer from the bracket, wipe the contacts to make sure they are clean and put the computer back in the bracket, making sure it is fully seated. Just another thing you can check.

[DirtDiva]

Are you sure you have everything in miles and not kilometers?

Heh. If this were all in km instead of miles she'd be able to walk faster than the Cateye says she's riding!

[sarahfixit]

Heh. If this were all in km instead of miles she'd be able to walk faster than the Cateye says she's riding!

Its always fun to tell people you can ride 50 on flats.
Then you tell them kilometers

[trickytiger]

If you are sure it is calibrated correctly, it sounds like your computer is not picking up all the miles. Maybe it is stopping and starting. If it is wireless, maybe there is some kind of radio interference (other electronic devices). Are you sure you have everything in miles and not kilometers?

If all else fails, I would recommend that you start all over. Remove the battery and zero out the whole thing. Reinstall the battery and reprogram the computer and see if that helps. My friend's computer (a cateye) was spazzing out on him. The mph would be erratic. It would jump from 13mph to 25mph for no reason at all. Resetting fixed it all.[/QUOTE]


I think this is what it is- it's not reading every revolution. I think I'll try this and see if it works... thanks!

[CorsairMac]

Is it a 2 wheel option computer??....if yes- make sure you're computer isn't set for the second wheel. I had the same problem and checked the darn thing over Several times and yes the tire size was right and yes the time was right but the miles and speed were waaaaaaaaaaaay off. When I was checking it Again for the 100,00000,000000 time - I saw this 2 flashing at me and couldn't figure out what it was. After reading the instructions - I realized I had set my computer for a "2nd" wheel optiont that was who Knows what. Once I learned how to make sure the computer was registering wheel #1 (the Right wheel)....all my computer issues vanished!

[DeniseGoldberg]

Corsair -
That's a really good thought. I don't switch my computers between bikes, and I always make sure that both wheels (in the computer) are set to the same size - just in case I inadvertantly switch to the other wheel option.

--- Denise

[trickytiger]

Well, I'm sure you'll all breathe a little better knowing that my bike computer does, in fact, work! It just needed to be reset, remounted, and threatened with battery evisceration.

And, it worked so well it recorded my whole 27 mile ride last Saturday... the second longest ride I've ever done... but not for long!

Thanks for the input, y'all.

-Tricky