Polar CS100 cycle computer

In a world of smartphones and ever-cheaper GPS units, Polar's CS100 is old technology: it determines your speed by a wheel magnet rather than satellites, and the only way it will transmit data is into your brain, one toggled screen at a time. These days, when you're spending £90, that feels weird. On the other hand, it's much cheaper than your iPhones and Garmins, especially if you shop around. And sometimes all you really want to know when you're racing or training is your speed, your heart rate, and the elapsed time. That much it will do – and more.

The initial set up is logical but not user-friendly. Remember what it was like setting up a VHS video player? It's like that. I've used plenty of heart rate monitors and bike computers over the years and still had RTFM trouble.

Conversely, it's easy to fit to the bike. The twist-lock bike mount zip-ties to any diameter of handlebar or stem, and the computer goes on and off the mount in a second. The speed sensor zip-ties firmly to the fork and the wheel magnet should fit most spokes. The distance between sensor and magnet is meant to be 4mm or less, though the test sample worked okay beyond that.

Since it's wireless, the fitting hardware is neat. If you want to swap the CS100 between bikes – it supports two bikes at a time, or rather two wheel diameters – that's only practical with extra hardware. An extra speed sensor and twist-lock bike mount will cost £34.20. So if you want to use this on more than one bike, you'll eat into the price differential between the CS100 and GPS computers like Garmins – which can be used on any number of different bikes, with any wheel size, at no extra cost.

The CS100 will display all the usual measurements, such as heart rate (current and average), speed (ditto), distance (trip and total), lap times, time of day, calories burned (a very rough estimate), as well as things like whether you're above or below your average speed, whether you're in your target heart rate zone, and so on. By default, the CS100 sets heart rate zones using 220 minus your age, so it's better to set these manually.

You get three lines of information at a time, one of which is always heart rate. The two main tiers of the display use big, easy-to-read numbers. The top line is much smaller and is difficult to decipher when you're riding on the rivet. While there are different screen options, you can't customise them. It's frustrating if you want an unsupported mix of data.

The CS100 records more data than you can display at once, of course. When you get home you, the only way to log this is to do it manually. You can't transmit it to a home computer or to the internet. The Polar UpLink Tool merely allows you to send settings to the bike computer from your home computer, once you've downloaded the relevant software. It's Windows PC only, so it's too bad if you've got a Mac.

On the bike, however, the CS100 works well. You can operate the buttons even with winter gloves. The computer is rainproof and mine never lost its signal. The chest strap doesn't seem to have any problems picking up your heart rate – with one caveat. Spit on the chest strap is seldom enough. To guarantee pickup, you need to remove the battery compartment and hold the relevant bits of the strap under running water. (The manual recommends this.) A soggy strap around your chest is okay if you're going on the turbo but it's a rude beginning to a winter's ride.

There's an optional cadence sensor for another £26.95. That would make the CS100 almost as expensive as the CS200cad, so if you want to monitor your pedalling revolutions, you're better off buying that. It's much the same as the CS100, except that it also links to Polar's online training diary (www.polarpersonaltrainer.com) via a Windows PC... and only a Windows PC.

As for the CS100, I'm in two minds about it. On one hand, it gives you all the data you really need for training or racing and it is less than half the price of a Garmin Edge 500 – or less than a third if you get a good deal. But to get the most from it, in terms of performance and value, you need to: be happy with the display options; plan to use it on one or at most two bikes; be prepared to log its data manually. All three rule it out for me. So while it is decent entry-level computer/HRM, I'd save up for a Garmin Edge 500 instead or else make do with a Polar FT1 heart rate monitor (about £30 online) and a cheap stopwatch. Your mileage may vary.

Verdict

Key racing or training information in one compact wireless package, but you can't upload its data or customise its screens