Padlock Chain

Almaxs chains are very well regarded. They do sell just the chains on their website.
To withstand bolt croppers I thing the chain needs to be about 16mm

 

Sadly the thieving moped scumbags are now using cordless angle grinders. Get the biggest chain you can.

 

You might want to watch this video. There are two guys on YouTube (Bosnian Bill and the Lock Picking Lawyer) that show how to defeat anything. They also push the manufacturers to make better products. In the process, they provide some really good information for users. One point is the hardness of the chain (Brinell Scale) and not necessarily the thickness.

 

another factor to consider is to ensure the lock is protected with a hard 'shoulder'
as an example:

 

At the end of a very long day, your chain, lock, alarm & mother in law resident in your garage you are only slowing down the inevitable .. All security adds time to scum trying to get at your bike. I use Almax chains, they are very heavy & are the best around for the money
Battery angle grinders will eventually beat them but chains of this magnatude will stop casual thief's & if they get through them then sadly your bike was gonna be taken any how.
I'd use a D lock across the forks & an Almax chain & Abloy lock through the frame if possible but do secure it to something & keep the lock off of the ground & the chain tight. Make sure that whatever lock you buy/have that it will take the chain link thickness too

 

Not sure what you ride, but I found on a speed triple. Putting a disc look on the rear disk is good, as it's difficult to get to with anything like disk cutters. Also I would suggest a bike cover, just make them go for a softer target.

 

Get a u lock as well the more locks there is the less likely they will go for yours

 

I used this small Oxford lock on my street triple r... It went between the radial caliper & the fork = zero movement but would cause serious damage if you tried to ride off with it still on... Doah

 

https://www.abus.com/uk/Mobile-Security/Motorbike-Scooter/U-Locks/GRANIT-Extreme-59
I have one of these which goes through the front forks nicely, followed by a disc lock placed in a less accessible spot.
Then I’ve also got a nice chain and padlock as well the links of which are 16mm.
Yet the bike could still be nicked despite those 3 and an alarm if the buggers want it.
Hopefully that lot will make them go for some one else’s first as there may be less security locks on it.
Not that I wish anyone’s bike to be stolen

 

One word.

Pragmasis.

https://securityforbikes.com/products.php?cat=High+Security+Chain+and+Lock+deals

I have two of these. The one I have as a 'permanent' anchor is 19mm boron steel. It's one link shorter than it used to be after someone tried cutting it with an angle grinder. The grinder ran out of battery before they got through it.

I have a lighter 16mm 'travel' chain. It wouldn't stop the angle grinder but they won't crop it, and keeping it off the ground stops them freezing and sledgehammering it.

They're not cheap, but they are good and their 22mm chain will likely exceed anything you'll likely get elsewhere.

Edit (for comedy value only): for the ultimate insurance against having your bike stolen.... Park it next to a much more expensive bike.

 

Personally I think physical & seeable security is best but always try & go one step further. If its hard for you to fit it'll be time consuming for thieves to attack.... Time & time again you see bikes on streets & in car parks with good security but it's just lying in the road inviting scum to have a go. Keep chain slack to a minimum & always if possible secure through the frame & to an immovable object like Halfton's wallet for instance

 

Yarp! For the big chain I use their 'pinch pin. It's a steel bar which slots through the rear axle, and the ends of the chain fit over the pin, and the padlock then anchors over a neck section of their pin holding it all together. When I don't have the pinch pin the links slide through each other and the lock fits over the end of the link. There is no weak spots really for them to attack.

The 16mm chain I have is longer and I route it through both the frame (awkward fit) and rear wheel as well as around the anchor and it has a roundlock which again minimises the scope for finding a weak spot for them to attack.

LOL reading up through the thread, StrippleMont has found the Pragmasis site already!

 

The locksmiths are selling you a product. However, all physical security is about imposing a time delay and thereby increasing the risk of observation/detection. You should plan from there. Concealment, lighting etc., are all part of the mix. Viewed from the perspective of a would be thief, what will make him pick a softer target or even overlook your bike completely?