I did a lot of research on locks and how bikes get stolen on youtube after my bike got taken from the train station. A camera was pointed right at the bike so i thought that would make it super safe and it was 3 feet from the station entrance. I left it overnight. Big mistake but BT police caught the guy that stole my bike as it was on camera, went to court but he didn't pay back my bike cost so got an extra month in prison just for my bike.
On youtube i enjoyed seeing the bike thieves getting nicked by the cops with bait bikes and tracked down with GPS trackers. Shocking how easy it is to open locks. There is an independent UK security test called solid secure which has bronze, silver, gold, diamond levels.
The main ways they break your lock:
1) Cheapest Cable lock 10 UK pounds - cable sniper that fits in pocket. Only takes 2 seconds so never buy a cable lock.
2) Cheaper Silver level U-lock 30 UK pounds - Bolt cutters 3 to 5 seconds as its softer metal. Bolt cutter are big but thieves do carry them in a bag.
3) Expensive Gold level U-lock 70 UK pounds. Angle grinder which is battery operated. takes about 15 to 30 seconds and makes sparks like a construction worker.
So never leave you bike overnight at station or outside the cinema. Always park where your bike can be seen easily by the public. But even so people surprisingly ignore the thieves with angle grinders and mostly walk past. You can see this happen on youtube with thieves using angle grinders stealing bikes.
After all the research i settled on a folding lock with gold rating. Better than a U lock as its compact.
Shop ABUS Bordo Granit X-Plus Folding Lock - Black, 85 cm. Free delivery and returns on all eligible orders.
www.amazon.co.uk
It will stop bolt cutters and it fits well on the bike. Nothing will stop an angle grinder only slow it down.
I plan to get a GPS tracker. Dont get the cheap red tail light one thats on amazon, its too obvious and thieves just throw it away. You can get a smaller than a matchbox size one that fits under the seat or in the handlebar grip for about 45 UK pounds and works with a GSM sim card.