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5 tips from the bike mechanic: How to buy a GOOD used bike

Bike guide — If you are on a tight student budget, money can be saved by buying a used bike. But you should know what to look for. Here are five tips from one of the UCPH student-run bike repair shops.

The bike is a favourite means of transport in Copenhagen. In fact, there are more bikes than inhabitants in Copenhagen.

For a student, bike purchases and bike repair shop bills can be a strain on a student budget. But it doesn’t have to cost you a fortune to bike around the city if you have mastered the art of buying a proper second-hand bike.

“You can find a quality bike in a reasonable condition for around DKK 1,000,” says Gareth Callear, a volunteer coordinator at Jernhesten, a student-driven bike repair shop on Frederiksberg Campus.

But apart from the price, what is it exactly that you need to be aware of when you buy a second-hand bicycle – technically and mechanically speaking?

With the help of the Jernhesten people, here are five tips on how to buy a second-hand bicycle.


1. Check the bottom bracket

The bottom bracket is one of the most expensive things to replace on a bike at a bike shop. In order to diagnose the state of the bearings inside the bottom bracket, hold the frame tightly, grab the crank arm (the pedal arm) and move it back and forth (not round and round). Pedal arms should not move – if they do, then there is every likelihood that the bracket is dead. Find another bike. The same applies if, when you turn the cranks around, there is a crunchy or gritty sound. Then the bearings have gone in the bottom bracket.


2. Check wheels and tires

New wheels are also a relatively large expenditure at the bike repair shop. The wheels should not be missing (right?!) or have loose spokes. Turn the bike on its head and turn the wheels around to check that they are not broken. Just like the bottom bracket, you can check if the bearings have gone in the wheels by gripping the frame and wiggling the wheels from side to side. The wheel can give slightly, but if it moves freely back and forth, find another bike.

Also check that the tread pattern on the tyres are not worn down. New tyres are an expense that needs to be taken into account.


3. Check the gears and brakes

Do the gears shift OK? Do all the gears work? If not, then most gear problems can be solved by replacing the gear cables. This is not a big expense at the bike repair shop. The same applies to the brakes. New brake pads or brake cables are not expensive to replace.


4. Check the chain

The chain should be well-oiled and not rusty. It should also fit snugly into place, so that you can’t move it more than 2-3 cm, when you press it. While we are at the chain, then check the teeth on the front chainring and the rear cassette/gear wheel are not worn down. If they are worn down, you risk the chain jumping off.


5. Is the bike legal?

When you buy used bikes, check the frame number to see if the bike has been reported stolen. The police have a very handy website for this purpose ( The frame number is typically located under the bottom bracket, engraved into the actual frame.

And do you have all the legally-required equipment on your bike? A legal bike must have a bell, a front and rear brake, bike reflectors (front, back, on both wheels and on the pedals) as well as lights for the hours of darkness. It can cost you a DKK 700 fine if the police catch you without the mandatory equipment.

And now it’s time to set off on the Copenhagen bike paths! And if your bike – whether you bought it used or brand new – is causing you problems, remember that there are two student-run bike repair shops at UCPH, the Jernhesten (‘the iron horse’) and the Pedalarmen (‘the crank arm’), where the volunteer bike enthusiasts are ready to lend you a hand.

Read also: Used bikes in Copenhagen – how to get one