My bike computer doesn't have cadence, which I now need because recovering from a knee injury. I have read here that any computer can display cadence (instead of speed) just programming the number 1677 as wheel diameter. If this is true I do not understand why.

It isn't true, that won't display cadence.

However it does sound like it's an attempt to get the computer to display RPM of the wheel which is a different thing entirely.

Perhaps on a bicyle with one gear of the correct ratio you could put a figure in that would match wheel rpm to crank rpm and thereby display the equivalent of cadence, but even then it would tell you that you are pedalling when you aren't...

btw. I'd very highly recommend a wired Sigma with cadence

Mine is superb and even has a backlight.

Yes, that'll work but then you don't have speed or distance capabilities. You're better off getting an inexpensive computer with cadence.

oops..I didn't realise they were using a magnet on the crank.

If you want to go that route, I have a budget computer that actually displays wheel rpm, so if you used that for cadence you wouldn't haver to worry about getting the wheelsize exactly right.....

I bought a cheap 8 function computer for about $4.50 and unusually function No.7 is RPM of the wheel.



Might be ideal for what you want as if it was installed on the crank it would display the cadence very accurately (compared to entering a wheelsize).

or you could just count pedal strokes for 6 seconds....then multiply * 10.

I have a cheapie Blackburn computer on my bike. It doens't let you "input" anything. The tire sizes are all pre-set on the menu, so it'll only work accurately with common size tires.

That information on that link may be specific to that computer. The author probably hasn't even tried that with another brand.

At first I didn't realize myself that the magnet was on the crank... I still don't understand why 1667 though, should be easy to figure out.
The reason I am asking is that I bought a nice £20 computer just two weeks ago (with no cadence) and now I am pissed to buy another one. Plus I live remotely so it would be a mail order thing (10 days). I am also curious.

It doesn't work perfectly with the author's computer - not the easiest way to tell how fast you are pedalling.....

Well, you could try it, the problem is if you set your computer up for that one task, it won't be able to perform any of it's original functions, speed, trip averages etc.

With the magnet and pick up on the crank, you can just put in any number to adjust the computer read out to suit you. He chose to put in 1667 as that was the number that caused the computer to display 8 when his cadence was 80 and 9 when his cadence was 90.

In an attempt to fool the computer into dealing with decimals he doubled the number to 3334.
The result being that instead of displaying 8 at 80 rpm it displayed 16, making it possible to tell your cadence with more accuracy when not pedalling at exactly 80 or 90 rpm.

A better solution would have been to input 16670 (1667 x 10) instead of 3334 (1667 x 2) as this would have made the computer display a decimal with a more obvious relationship to the actual cadence, ie. a cadence of 80 rpm would be displayed as 80 mph or kmh.

My guess is that the most likely reason he didn't use 16670 is that it is a larger number than can be entered into that computer.

FWIW, you'd be much better off with the budget computer I mentioned earlier as it displays RPM as standard.

I hope the explanation helps.

My computer is a Sigma which allows to enter any number (if I recall correctly). I have been looking at the Sigma web site and the only models with cadence are wireless i.e. BC1606, which costs only $35 shipped. I really didn't want a wireless and all the extra (confusing) functions that come with more expensive computers, totally unneeded to me.

Some of the wired Sigmas support cadence.

I have a BC1606L WIRED and I added a cadence kit, it's quite neat too.

I'm sure some of the other wired Sigma computers support cadence.

What model is your's ?

I'm really bad at math so I just count for one minute and multiply by 1.

Do you do this in your head or do you use a calculator ?

Fingers and toes. Pull down my shorts if I have to count to 21.

Unknown Cyclist I have the Sigma 506, very basic but if it had cadence it would be perfect for me. However, I got confused with all the offers on eBay, indeed the Sigma 1606L wired w/cadence kit is apparently the most convenient. Either that or the Cateye Strada Cadence. Does the 1606L run only one wire to the sensors or two, it is not clear from the specs?

The cadence kit uses a fairly robust round cable, I don't think you can fit cadence on any of the lower models in the current range.

Cateye do some nice looking computers, but I haven't found them to be as robust or as reliable as Sigma.

One of my cycles still has a Sigma BC1100 with cadence which still works perfectly and I fitted that one about 13 years ago (at a guess).

I've found the 1606L does everything I could want and has a back light, it's perfect for me - I hope you find a computer that suits you.

I bought the wired version of Sigma BC 1606L at Campmor. To my surprise, the cadence kit was in the box, even though the Sigma's website says it's "an optional extra".

The Sigma's website says "The cadence sensor kit is available from your bicycle dealer." It's not clear to me -- does it mean "available free of charge"? Might be.

Ask the seller whether the computer ships with the cadence kit in the box. Or contact Sigma (toll-free number, email) and clarify it with them directly.

EDIT:
Interesting, the Sigma's website says here "Cadence included in delivery".

I'd stay away from wireless computers if you ride in a city or near high tension power lines as electrical interference will give wonky readings.

As far as setup goes, I've found that VDO computers have an extremely simple and easy to use setup interface.

The Sigma web site says "A cable-connected cadence sensor is available as an optional extra for the BC 1606L" but doesn't matter since on eBay it's $35 shipped, here, with cadence kit included.
My question was, since the Cateye costs pretty much the same, does the Sigma run a single wire, or two wires, from the computer to the two sensors...?

The computer mount supplied with the computer has a wire to a pick up on the fork.

The cadence kit has a wire that runs from the computer mount to the cadence pick up.

You add the cadence kit to the original supplied mount.

Too bad...I can get to 23 that way.