g33k

Just got a cyclocross bike and I'm a total newb, so bear with me. Not wanting to spend more than I have to (I know, I know...), I picked up a cheap Bell wireless computer. Installed great, has all the functions I need, etc. Took the bike out for a spin along my normal jogging route. I have a Garmin Forerunner 101, which I love. Well, when I got to the spot where my GPS says is 1 mile, the bike computer only said like .84! I mapped the route on Google Maps and the GPS is dead-on accurate.

The bike computer had standard wheel sizes that you could put in. Is there another wheel size that I should try, or should I just junk this one and get a new one? FYI, here is the link to the manual for my computer.

If I need to get a new one, I'm kind of leaning towards just forgetting the whole magnet/tire size thing and going straight GPS with the Forerunner 205. That way, I can use the same thing jogging and biking. Any pros/cons for going this route?

dscheidt

It's got tire size wrong. Sheldon Brown has a page on calculating the number you need. it's reading low, so the number that you've entered is too small a wheel.

CraigVM62

I am not familiar with that specific Bell unit but have had 10+ wireless units from Vetta, Cateye, VDO, Sigma.... All have included a chart giving tire sizes and their general circumference in milimeters to which you enter when first programming the unit. They have also suggested for more accuracy, to actually measure the circumference of your tire at full pressure. You might see the same suggestion in your instructions.

This link to Cateye's website will give instructions:
https://knowledgebase.cateye.com/ques...tion+number%3F

g33k

Thanks for the link. He doesn't have my brand, but I think I can guess pretty close from the chart he gives. I'll try it out tonight and just make small adjustments as necessary. Thanks again!

Big M

I had that same computer. Bell Platinum Wireless Computer for $20 at KMart. It installed fine, I went through all the menus, set everything up, all was well.

Then I went for a ride and it read nothing but zeros. Bad magnet, bad sensor, bad battery in the sensor...whatever it was, it didn't work straight out of the package.

Yours is most likely just a wrong wheels size setting. But I don't have much faith in that computer.
For another $10 you can get something much more reliable. For $40 total, you can get a wireless, too. Personally, I took it back and told a couple people to get me a nicer one for Christmas.

HillRider

What wheel and tire size do you have and what was the recommended calibration number for the cyclometer? Being off by 16% is A LOT.

Mr. Underbridge

Sounds like he's got a 700C wheel and put in the code for a 26", that would account for about 12%. Add another couple of percent for using the wrong code and that would be close.

Still seems on the edge of reasonable, though.

deburn

In case you go the Forerunner route (to reply to one of your questions) I can't think of any cons. I recently bought a Forerunner 305 which has a heart rate monitor and a couple of other options that the 205 didnt have and REI had it at a really good price at the time. If you dont need a HRM (does the 205 upload your data to your computer? this was important for me; may not be for you) or cadence (I was going to buy the add-on but now I'm going to wait) then the 205 is a great option. HTH!

I needed (well, wanted is more accurate ) the upload capability and an integrated HRM means you can see what your heart rate was at any given point (after the fact; of course you can also see it while you're biking). Lastly it can be used for running which is also important for me. I have some minor issues with ease of use/intuitiveness but nothing I cant live it at this price-point)