In my country, bikes are packed in a van and driven away. So disc locks are only good for bending discs when you forget to take them out before starting.
Alarms are good just for keeping teenagers from sitting and taking photos on your bike (getting burnt on hot exhaust, or dropping with the bike).
The only security is a garage (out of sight), or, if it can't be garaged, a good fat, hard chain tied to a solid anchor (post, metal fence etc).
I'd recommend the most expensive and fattest Abus chain and lock you can find. This will also be breakable, but it will take time. Thieves will look for the easiest bike to steal, so make sure your bike isn't the easiest target -that's what fat chain does. Also, Abus locks are quite difficult to pick.
In order to get to this info I have enquired experts from both sides of the law.
1) Good short read on metal, chains etc:
http://lockitt.com/chaininfo.htm 2) Tips:
Try to lock the frame to something immobile, not easily cut.
Make sure chain isn't close to the ground (ie doesn't lie on the ground) so thieves can not use the ground as leverage, or use hammer/chisel to break locks/chains.
Make sure both the chain, lock and key mechanism are good. Chain is as good as it's weakest link. If you can afford, Abus stuff that is above protection level 15 (on Abus scale) is good. Don't know about other makes, but any other chain that's over 60 rockwell and a decent lock will probably do.
If your bike is apealing enough and if there is enough time, any lock/chain can be broken.
3) Keys:
Most locks are brute forced. However, there are lockpicks. Rule of thumb:
Locks with ordinary, regular keys are most easily picked. These keys should be avoided.
Locks with "double" sided keys can be a bit more complicated.
(Double sided key)
Although all the above are not too hard to pick. This one is a bit more tricky, so look for something like that:
As well as this (not bad):
4) Chains:
Look at Abus website. They have a security ranking of their own for their locks-chains. Anything above rank 15 is decent. Anything above 20, 25 is very good (but very expensive).
Hexagonal chain, over 12mm thick that is core hardened is a decent level of protection to look for. Even 10mm thick chain with the same qualities (hexagonal, core hardened) is very hard to cut with bolt cutters that fit under a jacket, especially if there's no leverage against the ground (i.e. the chain is not lying on the concrete).
5) Padlock (lock):
Make sure the chain fits tightly in the lock. Too big is not good. It will make room for leverage with a bar, or cutters. So keep it tight, if buying seperately, first get the chain you can afford, then look for a matching padlock.
Here's a decent one, about 20 euros here:
6) Conclusion:
If secured properly, not left lying close to the ground and so that lock can be easily accessed, these locks can buy you quite a lot of time (if thief doesn't give up in the first place and start looking for another easier target). However, nothing is 100% safe. Make sure you don't leave an expensive (looking) bike in the same place reugularly, or for a long period of time anywhere.
