Fifty Plus (50+) - Two bike computer questions

One: Can you replace a bike computer with another one (let's say same brand) and use the existing wires, etc.? Or do you have to install a new one from scratch? I'm thinking I want a cadence feature.

Two: My g/f's computer tracks miles slightly differently than mine. What I mean is, when we've gone ten miles by my computer, we've gone 9.85 or something on hers. Is it easy to adjust something to make 'em match?

1. Not sure, since I use wireless.

2. There should be an adjustment for tire diameter, and you can change the setting a bit on either yours or hers to make them come out reasonably close. Ride the same 10 miles exactly and if it comes up like you say (9.85 for her) then her wheel diameter reading is 1.5% larger than yours. Change her setting by 1.5% and they should be sorta close. Hubby and I went through this on our bikes and we thought we had it down to a science. Then they'd still be different at the end of a 20 mile ride. I started ignoring it, figuring I had a lot more important things to worry about, like whether or not he'd be taking me out to dinner later on. :lol:

1. I'll bet that if you buy a new computer it will come with the wires you need for it. Thus, if you need different wire's you'll have 'em. If you don't, the right ones will be on the bike.

2. Suzie is correct.

1. Some brands I have worked with will match up with the mounting of a different model, same brand. However, since you want to upgrade to a cadence feature, even if it matches mechanically, your old mount will not have the wiring for cadence.

2. Like Suzie says, don't worry about it, it's close enough.

But if you really want to get into it you can do a roll out on both bikes then measure in cm. You'll need the instructions from both computers to find out how to enter this number into the computer.

I think Sheldon Brown covers this on his website.

One: Can you replace a bike computer with another one (let's say same brand) and use the existing wires, etc.? Or do you have to install a new one from scratch? I'm thinking I want a cadence feature.

Two: My g/f's computer tracks miles slightly differently than mine. What I mean is, when we've gone ten miles by my computer, we've gone 9.85 or something on hers. Is it easy to adjust something to make 'em match?

Most mounts are different. If you want cadence then your mount needs to be cadence compatible. For what it is worth, I just ordered a cateye strada which is a cadence computer but only uses one wire to the back wheel and cranks so it will be as clean as a wireless computer with wired cadence and much less expensive than a wireless cadence and wireless speed computer.

As previous posters said, you need to get your wheel settings to be the same to measure the same distance since your cyclometer only goes off of revolutions and has to use a conversion factor, the wheels circumference, to get speed, distance, etc. A lot of computer manuals give you stock values for circumference, but if you want the most accurate value then you should inflate your tires to riding pressure and then sit on the bike in a normal riding position and then be pushed over so that the wheel that is picking up the speed goes through one revolution. Then measure this distance and put it in your computer.

With regard to adjustment of distance, check the manual of the computer. Usually, they have standard tire measurements built in to the computer. If their "standards" don't exactly match your existing tire size, you can measure your tire size using a "roll out". Inflate the tires to your normal pressure. Set the bike on a flat concrete surface and rotate the tire until the valve stem is down. Get on the bike and have DD mark the concrete at the valve stem. With you on the bike, roll the bike one complete revolution of the tire (until valve stem is down again) and have DD mark the concrete at the valve stem again. Measure the distance between the marks. You will probably have to convert inches to centimeters (2.54 centimeters per inch). Plug that number into the computer. I did this with 'Ol Fuj, and his computer matches the GPS number rather closely.

Now, aren't you sorry you asked?:D

If the wiring is for nothing other than a magnetic sensor, I would think the old wiring would work as long as the magnet and sensor are properly aligned.

Given DD's apparent progress in cycling, you may want to add an extra magnet to your bike!

Two: My g/f's computer tracks miles slightly differently than mine. What I mean is, when we've gone ten miles by my computer, we've gone 9.85 or something on hers. Is it easy to adjust something to make 'em match?
It's obvious that you've ridden farther than her: Are you trying to show off? Did you circle around her a couple of times?

2. There should be an adjustment for tire diameter, and you can change the setting a bit on either yours or hers to make them come out reasonably close. Ride the same 10 miles exactly and if it comes up like you say (9.85 for her) then her wheel diameter reading is 1.5% larger than yours. Change her setting by 1.5% and they should be sorta close.

Better answer: buy matching bikes. Then, matching bib shorts, matching helmets, matching gloves, matching shoes....

Oh, and matching cyclocomputers.

That would be hot.

Instead of doing a roll out , which means very little, considering the error introduced by trying to accurately measure one revolution, just use a string to measure tire circumference. Convert to MM and enter it into your computer.
You want cadence? Cheap?
http://www.instructables.com/id/Very-Easy-Cadence-Meter-For-Your-Bike-12/
I used 3 magnets & 5555 for a calibration number. Gotta save the weight of 2 magnets.

I have just done the same thing about four weeks ago.As long as the settings are right, there should not be a problem-mine works fine.

One: Can you replace a bike computer with another one (let's say same brand) and use the existing wires, etc.? Or do you have to install a new one from scratch? I'm thinking I want a cadence feature.

Two: My g/f's computer tracks miles slightly differently than mine. What I mean is, when we've gone ten miles by my computer, we've gone 9.85 or something on hers. Is it easy to adjust something to make 'em match?

Here's my recent experience. I replaced my Sigma 506 computer with a Sigma 1606L with cadence. Yes, I can use the current 506 wiring and head mount for the new 1606L computer, unless I intend to use the cadence feature. To use the 1606L cadence feature I'll need to rewire and use the 1606L head mount because the 1606L head mount has two additional connectors to attach the cadence wiring. I mainly bought the 1606L for the backlight feature so the cadence is not an issue. However, I may use the cadence in the future and I'll rewire the computer to my bike at that time. As for the difference in computer mileage readings between your bike and your girlfriend's, perhaps there's a difference in wheel size between the two bikes. The instructions included with her computer should show you how it should be calibrated/set. If you don't have the instructions, you may be able to obtain a copy of them from the manufacturer.

Usually, the computer takes a 4 digit # for wheel size during the setup. This # represents the centemeters of distance that the tire will cover during 1 revolution. Different computers may appear to use different #s depending on how much math their tiny brains can do. (some don't do pi and are therefor unsuited for use on a 50+ers bicycle).

The # given to you in the startup manual for any given tire size is an approximate (SWAG) that does not take into account tire inflation pressure, rider weight or minor differences in mounted tire diameter from manufacturer to manufacturer. Some people go so far as to sit on their bike and roll forward 1 revolution while an assistant makes very precise measurements of the distance traveled. The resulting measurement along with some chicken bones and fly wings is thrown into a bowl shaken and the resultant is entered into the computer. The computer will then return a different result from that given using the manuals # but that result will still disagree with the computers of all those riding with you.

Other people will skip this process and go out and ride more.

If you would like a slightly used Cat Eye 300DW wireless cadence computer very cheap, send me a pm (caution, DD may have to program it for you)

Just buy two Garmins and forget about wheel size, wires, etc:D

Just buy two Garmins and forget about wheel size, wires, etc:D

:love:

Computers don't measure distance, they count wheel revolutions, and you program in a number (easily changed if you have the instructions for your computer) which allows the computer to convert from wheel revolutions to miles. The number that you program in is the circumference of your wheel, but that will change with tire pressure, and the load on the bike.

Therefore three ways that you can get the two measurements to match:
1) Let a bit of air out of which ever tire she has which has the sensor on it - that will reduce the diameter of the wheel, and in 10 miles her wheel will make more revolutions and her computer will register more miles.
2) You lose some weight, which will make your tire diameter larger, and in 10 miles your wheel will make fewer revolutions
3) Change the numbers programmed into the computers.

Of course the best solution is to explain to your wife that the reason for the discrepancy is because she must have lost some weight - hence the computer is complimenting her with it's low reading :) Then suggest that she take you out for some pie to celebrate.

Of course the best solution is to explain to your wife that the reason for the discrepancy is because she must have lost some weight - hence the computer is complimenting her with it's low reading :) Then suggest that she take you out for some pie to celebrate.



I am guessing you eat a lot of pie. :lol:

Just buy two Garmins and forget about wheel size, wires, etc:D

And don't forget to charge it after every ride.

Of course the best solution is to explain to your wife that the reason for the discrepancy is because she must have lost some weight - hence the computer is complimenting her with it's low reading :)

That could backfire: "You think I was fat?! You can just go on a solo bike ride tonite!"

Looks like one of the discrepancies stems from me changing to 28 mm tires. Didn't realize that would upset the computer so much. Must be running on Vista, no? :D

And don't forget to charge it after every ride.

Yes, that's important but I solved that problem by buying a Gomadic battery charger for those times I have a senior moment:)

Looks like one of the discrepancies stems from me changing to 28 mm tires. Didn't realize that would upset the computer so much. Must be running on Vista, no? :D

Not only do you have to reprogram.............but the chicken bones must be replaced with new ones.

I think I'll leave well enough alone. The way it is, I get higher mileage when we ride together, and I like that. Now at least I understand why! :lol:

Looks like one of the discrepancies stems from me changing to 28 mm tires. Didn't realize that would upset the computer so much. Must be running on Vista, no? :D

didn't you install SP1 on it? that'll take care of the problem. Guaranteed. take care of the problem. Guaranteed. take care of the problem. Guaranteed. take care of the problem. Guaranteed. take care of the problem. Guaranteed. take care of the problem. Guaranteed. take care of the problem. Guaranteed.