Cyclocomputers

I wrote some weeks back about tracking my rides — keeping stats on distance, time, speed, etc. One reader suggested it would be easier with a cyclocomputer. I agree, which is why I’ve had one since the beginning of the year.

As you might have discerned by now, if you’ve read more than a few posts on this blog, I’m a tightwad miser frugal sort of person. When I considered which computer to buy, I glanced at the Garmin GPS gizmos, but decided that several hundred dollars was a lot more than I wanted to spend. I must admit that they do cool things, though. One acquaintance used his to post a map of his ride, and you could trace the route in motion. Altitude profiles are nifty, too. But I decided that what I really needed in a cyclocomputer was something that would register my speed, distance and time of the ride. Anything else would be a bonus.

The Ascent Delta V. The ride this day lasted 55 minutes and one second. The scratches on the face are from flipping the bike over without taking the unit off.

I decided on the Delta V, by Ascent. Picked one up at the local Performance store just after Christmas for around $25. It’s a small little unit, about the size of a silver dollar (remember those?) and mounted on the bike with a pair of zip ties. I was attracted to the unit because it’s wireless, and while that raised some dependability questions in my mind, I figured for the price, what the heck. Performance has a liberal return policy if it didn’t work out.

When the computer is first turned on, it has to be set for the diameter of your front wheel and tire. Hold down both buttons, and four digits flash. Starting with the digit on the far right, you click the right button for each time you want the number to advance. Ascent’s instruction manual says for a 700C x 23 tire like mine, the numbers should be 2096.

Another way to determine the setting is to figure the circumference of the front tire. I turned it until the presta valve was at its lowest point, and drew a pencil line on the garage floor at that point. Then, I pushed the bike forward for one full turn of the tire, and drew another pencil line opposite the presta valve. I measured the distance between the two lines. Eighty-three-something inches. You then multiply that number by 25.4 to get the metric figure. I got 2095.5. I figured the one-half a thing off wouldn’t make too much difference.

Well, it apparently made some difference. My trip from home to the Veloway, three laps around, then back home again measures 14.9 miles, when mapped on Map My Ride or similar programs. On the Delta V, it’s more like 14.7. Still, two-tenths of a mile difference over about 15 miles isn’t too bad. I guess.

It’s supposed to have a clock, and does, but it defaults to 12:00 at the beginning of a ride. The instructions say I can set it to real time, but I haven’t figured out how to do that yet. That’s not all that important, since it does clock the time of the ride, which is what I’m most interested in anyway. That, and average speed, which it measures. During the ride, I can set it to “scan,” or read all the numbers in progression: first distance, then maximum speed, average speed, and time. I don’t deliberately try to push up maximum speed, but it’s fun to chart. The max speed reading has a glitch, tho. On my long ride last weekend, it reported my maximum at 63.7 mph. Now, I like to think that I’m getting faster, but even I know my top that day was no more than 30.

When the ride is over, I take the computer off the bike, and enter its numbers into a spreadsheet I keep. (Except for a ridiculously high max like today’s.) So far, I’m satisfied with the computer. I know you get what you pay for, and I got a very basic model. If I can figure out how to adjust it so its mileage matches my mapped GPS mileage, this will turn out to be all the computer I need.

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18 thoughts on “Cyclocomputers

  1. I had 2 of these exact computers. One on my Commuter and one on my mountain bike. The one on my commuter would “freak out” all the time…the max speed would be in the 70s, I would routinely average 45mph over my daily commute…I was fast :)

    The one on my mountain bike has always been pretty reliable.

    I have a Shimano Flight Deck on my road bike. It’s awesome…never misses a beat…it’s wireless and the controls integrate into my brifters so I never have to take my hands off of the bars…

    I’m contemplating getting a GPS now just for more data…

  2. Jared, Did you ever get accurate mileages on your Delta V’s? I did the 14.9 mile route again today, and this time it registered 14.61.

  3. Hi Ray,

    I read your blog regularly and I must say it is very interesting and insightful as well. Great work, keep writing and riding.

    I read your post today and I see that you are logging your data in Excel sheet. Although, it is adequate, I can recommend you a nice software that does a lot more than recording data and what more, it is absolutely free!

    You can download it from this site – http://www.zonefivesoftware.com/SportTracks/

    Presently it is available for Windows only, so if you are using a Mac, then you gotta search the Internet for something equivalent.

    By the way, I am from Singapore and ride my bike quite frequently as well, although I am more into cycle touring.

    Cheers,
    Adi

  4. Up until last year I was an fan of the $9.88 Bell cyclocomputers I could get at Wal-Mart. They were cheap and stood up to rain fairly well (and when they didn’t, they were cheap). The only problem I had with them was more of a bad habit I had–I didn’t want them recording when I was pushing the bike around so I would loosen them in the cradle. I lost several on the road when I forget to snug them back down.

    Then last year I got the urge to track cadence because from all I have read, it is a better metric of fitness than speed alone. The first unit I bought had wired cadence and wireless speed. It was a cheap unit (around $30) and was highly susceptible to interference. Whenever I would ride along high tension power lines, the speed went berserk. Also, whenever I turned on my headlight (a L&M Arc–an HID lamp) it would cease recording at all no matter how much separation I put between the computer and headlamp. So then I tried the Topeak Comp 140–this unit has wired cadence and speed. Once I got the sensors mounted properly it has worked flawlessly (except in heavy rain where water got into the cradle and started shorting the contacts–dried the contacts and all was well).

    The biggest problem I have with ALL cyclocomputers is the tire size setting. The charts that come with the units seem to be universally inaccurate. That’s were the late, great Sheldon Brown comes in. http://sheldonbrown.com/cyclecomputer-calibration.html This chart contains fairly accurate starting points for a wide range of tires. I never seem to be running a common size so this has been a sanity saver. Now note, I said starting point, not tried and true gospel for any given tire. Rim sizes, manufacturers fudging the listed size (there are specious business reasons for that), etc, mean you may need to adjust the number a few millimeters either way. If for some reason your tire size is not listed there is still hope. Just about every tire has an ERTRO size printed on it in the form sw-dia where sw is the sidewall size and dia is the rim diameter (both in millimeters). To derive your tire circumference use this formula: (dia+sw+sw)*Pi-10. You use the sidewall twice because it add to the total diameter on both sides of the wheel and you subtract 10 millimeter from the total to allow for compression of the wheel when loaded (something you won’t see if you roll out the tire without being on the bike). The next step is to ride on a measured distance and adjust the size as appropriate until the computer agrees with measurements. Use at least one mile for calibrating (I use my homeward commute of 9.6 miles). Once you have the golden number, use a paint marker to record it on the back of the computer for when the battery dies.

  5. I used to use a CatEye Enduro. I really liked it, and for ~$30 it handled a lot of numbers, with a decently sized and configurable display. It wasn’t wireless though. They’re wireless cycloputers are a little bit more expensive.

    You may be surprised how much difference half a millimeter makes over distance and time. Another method is to take a string and wrap it around your tire, marking on the string where it meets up, and measuring that. Of course, that wouldn’t take into account tire compression while riding, which will affect circumference… but then we’re just getting silly, given the type of rides we go on, eh?

  6. Adi, Thanks for the kind comment. I’m going to start sticking pins into my wall map of the world to keep track of the international readers who check in. Anyway, I’m a Mac guy, through and through, and now I hope the company comes out with a Mac version. I could go crazy putting data into that program. Neat stuff.
    Dvicci, thanks for checking in again. I think I’ll just add single millimeters to the reading until it approximates the mileage I think it should get. You’re right — no need to go overboard, but I’d kinda like it to be sorta accurate.

  7. Michael, your looong comment wound up in the spam queue. Blame WordPress. I’m not sure if they have a word count limit on comments. I caught the problem and checked the “de-spam” box.

  8. 14.61/14.9 would be accurate enough for me. I never tested it with my GPS as GPS has about that same ammount of inaccuracy unless you’re going in a straight line. Plus the GPS was pretty close to the Sigma and it would really cause it to freak out!

    A while back I was on a ride with a guy that had an Edge 305 and I was on my road bike with the Flight Deck. The flight deck was accurate to within .25 miles after a 60 mile ride according to his GPS.

    A 3% margin of error isn’t too bad. I know you want to accurately track every mile (I’m the same way) but you won’t be able to get on the dot accuracy with any cyclocomputer…I honestly don’t know how “bad” mine where…I still have them. You’re welcome to try one of them out if you would like….the clock is set and everything :)

  9. Michael, It had occurred to me that the late, great Sheldon Brown would probably have the answer, but I hadn’t checked his site lately. I’ll have to spend more time there, because he doesn’t have any listings for Ascent. Thanks for the tip.

  10. One thing that is missing from that computer that I would miss very much is cadence. I regard average cadence as a more important guide to fitness and riding style than average speed. I use a Catseye computer ( I think it is the Astral 8) and usually have only the cadence and average speed on the display.

  11. On Sheldon’s chart, if your computer uses circumference in millimenters (most do that I have seen), use column F.

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  14. I just changed out the batteries in my Ascent V cyclometer and now I can’t get the thing to register anything when the wheel turns. Is there something I’m not doing after changing the battery? some calculations I’m not putting in? I can’t find anything helpful in the manual so any advice is appreciated. Thanks.

  15. When I had mine and that happened, it was usually a case of the sensor being knocked awry. Take a look at both the one on the fork and the magnet on the spoke to make sure they’re close enough to each other.

  16. Pingback: Bike computers « Bike Noob

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