Buyer's guide to bike locks

By Paul Smith & Warren Rossiter, Cycling Plus | Monday, February 16, 2009 9.51am

Over 1,200 bikes are stolen every day in the UK alone – about 444,000 a year – so it's essential to invest in a decent lock if you want to keep your prized ride safe. There are three things to bear in mind when buying bike locks. 

First, you get what you pay for. Cheap locks offer cheap security; most are little more than a visual deterrent. A cheap lock is still better than no lock, but if a dedicated bike thief takes an interest in your bike, say goodbye to it. 

Second, cable locks that are light enough to be portable are also light enough to be broken – easily. Only use them in conjunction with a good U-lock to secure extra bits of the bike or stuff like your helmet

Third, less is NOT more. Unlike most other bike accessories, the performance of a cycle security device increases in proportion to its weight. So when it comes to portable locks, it's a trade-off between how much peace of mind you want and how much metal you are prepared to lug around.

Given enough time and the right tools, thieves will find a way to force pretty much any lock open. But the harder you can make it for them, the more likely they are to give up and move on to an easier target. 

What to look for when buying a lock

D-lock vs chain and padlock

The D-shaped shackle lock (also known as a U-lock) is now a classic design. It was introduced by lock manufacturer Kryptonite in 1972 and widely copied soon after. In effect, it's a scaled up padlock: your bike and a railing, lamp-post, etc, all fit inside the hoop. Well-designed D-locks, with good lock mechanisms, armoured shackles and heat-treated U-sections, are tough enough that they will slow a thief down enough to make him think about picking an easier target.

However, their rigidity and bulk can make D-locks hard to carry and use. Some riders therefore prefer a loop of high-strength chain and a padlock. This combination is usually heavier than a D-lock and a little more vulnerable to attack as chain is generally easier to cut than solid bar.

Shackle

The U-shaped section of a D-lock that slots into the barrel. Examine a lock for weak points before you buy. If the machined slot the lock mechanisms slide into is square-cut it can be a potential weakness. Also check how much of the lock barrel swings into place when it’s locked – this should be more than 5mm. If not, this could potentially be prised open.

Lock barrel

The best designs have the lock mechanism in the barrel’s centre. End-mounted locks are easier to attack with a drill. A high weight is a sign that it’s armoured.

Protection

So you arrive, park your bike, get your lock out and drop around a kilo of weight onto the frame tubing – at worst you’ll dent or crack a thin tube wall, at best you’ll scratch it. So look for a thick rubberised coating on the shackle to protect against accidents.

Keys

In 2004, Kryptonite came under fire following reports that some of its locks could be opened with the top or barrel of a Bic ball-point pen. It turned out that the problem with some cylinder-key locks had been known since 1992, and affected far more companies than just Kryptonite. Since then, cylinder keys have all but vanished from bike locks, but the bike industry is famous for reusing bad ideas; they'll no doubt be back, and should be avoided.

A spare set of keys is essential, more than one spare ideal. Keep one at home, one on your keyring and one at work. The best brands offer a replacement service so keep the key code somewhere safe.

Maintenance

We get a lot of letters from readers whose locks have seized – the unluckiest with their bikes still attached. So check the mechanism regularly and use a good water repellent (GT85 or WD40).

Will it fit?

Don’t buy a lock if it’s going to be too small to fit your bike, but don’t go for a very long shackle that’s hard to fill – if there is a space between the shackle and the bike frame that space can be used by a thief to stick in a levering bar. And longer shackles are easier to twist.

Security ratings

Almost all manufacturers have their own ratings. These are a reasonable indicator of the lock’s strength and are usually linked with price. 

Better still is a Sold Secure rating. Sold Secure is an independent organisation administered by the Master Locksmiths Association. Locks submitted receive one of three ratings: Gold, Silver or Bronze. These reflect the length of time a lock will hold out against escalating levels of attack. Bronze is a minute with basic tools; Silver is three, with a wider array of tools; Gold is five minutes with a more sophisticated array of tools. 

The largest manufacturers also submit to the German and Dutch ART1 to 5+ standards. These are a very tough standard and worth looking out for. Gold or high ART-rated locks can be more expensive but they may help you get a discount on your insurance if you use one.

How much should you spend?

As much as you can. Don’t pay thousands for your bike and just a tenner for a lock. Look for high ratings and manufacturers’ guarantees. No lock is unbreakable if you have enough equipment, but it’s daft to buy something cheap that’ll pose no opposition to even the casual criminal.

Warranty

An extended warranty is always good. It's not going to cover you against theft but it should be a sign that the lock won't fall apart or seize up on you.

Anti-theft guarantee

This is basically a form of insurance. Anti-theft guarantees bump up the price but they add peace of mind into the package.

Carrying it

Many D-lock makers supply or offer a bracket to mount the lock on your bike. Definitely a nice-to-have if you're down to two candidates.

Security tips

  • Always lock your bike: no matter how quick your stop, a good lock in your bag is no good
  • Always fill the shackle or cable – any slack can be exploited
  • Make the lock mechanism hard to get to: if it’s a pain for you to unlock it, it’s a pain for a thief to get at, and being a lazy bunch they’ll move on
  • Never lock your bike to something easier to break than a lock – don’t use a tree or wooden fence as an anchor
  • Always leave your bike in plain sight – don’t lock it somewhere quiet where a thief can spend time undisturbed. However, don't believe that leaving your bike on a busy street will guarantee its safety. Anyone who has had to cut a bike lock for legitimate reasons will tell you that people just stroll on past
  • On the other hand, never lock your bike up somewhere quiet and out of the way where a thief can really take his time. The maximum most thieves will spend trying to nick a bike is five minutes, unless you make it easy for them. 
  • Don’t leave a commuting lock on railings or bike racks – thieves can practise on it when you’re not around and break it when your bike’s in it
  • A bad lock well used is better than no lock and the equivalent of a good lock badly used
  • Always make the thief work

For more advice about how to protect your bike, see our article on how to Beat The Thieves.

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