“safe” u lock shackle diameter

ISTR that U (or D) locks with a certain shackle size are more secure as common bolt cutters are won’t go up to that size.

If so,what is that size? (and is this relevant given battery grinders?)

TIA

I think TJ usually quotes 16mm.

16mm is what Almax and Pragmasis maintain is the point where bolt cutters don’t cut it

I thought 16mm is for chains. Seems that d locks cannot be cut with bolt croppers if they are hardened regardless of the diameter within reason. My gold std d lock ones are less than 16mm thick.

Gold standard doesn’t mean cropper-proof. In fact it doesn’t mean much at all

TBH it seems fairly safe to assume that what applies for a chain will mostly apply for a u lock, it’s basically just a humunhous chain link. THe locks are different obviously but the shackle wcan’t be all that different

I watched a video and none of the hardened d locks were cut through with bolt croppers regardless of their diameter,but the chains were. I maybe wrong though.

If it can fit in the jaws of a bolt cropper it can be cut. D-locks are generally the same hardened steel as chains so the same rules apply. A lot of the tests I’m seeing online use 24″ croppers which could be hidden in a coat but the really brazen thieves will use 48″ croppers, the ground, and their body weight to munch their way through any lock that’ll fit in the jaws.

The reason 16mm is recommended is that it won’t fit in the jaws of most croppers, including the 48″ ones and so is immune to that attack. Angle grinders change this by being able to cut through any thickness of material eventually.

Yup. Basically, the industry tests don’t use the tools real thieves use. It’s like testing a bulletproof vest by firing nerf darts at it.

Sold Secure used to have a statement on their website that essentially said “It’s impossible to make a lock that will resist the really big boltcutters, so, we think it’s fine to give top grading to locks that don’t, and for that reason we don’t test with them.

Sure, lots of bikes are stolen with pocketable tools, but not the ones secured with half decent locks.

thanks for the info.

I spent ages agonising over what lock to get and in the end just got the standard krypronite d-lock.

Reasoning:
1) As above, you can’t defend against power tools, so why bother*.
2) I try and avoid leaving anything too nice locked outside anyway.
3) Still often the biggest lock on the bikes in the rack so there’s easier picking for a would be thief.

*also, insurance covers it as long as it’s locked. And “gold standard” locks are still fairly cheap, although oddly my version is sold secure gold rated, the new version is only silver, must have had a better tester!

I used to lock my bike up in a less secure area with two d locks and a chain. I now know I would have been better with a single 16mm diameter d lock as the extra 2 locks would have only stopped the thief for a few mins or seconds more. Interesting. I suppose having three locks would have meant that a thief would not be attracted, although they may be with a single lock and having three locks maybe better against angle grinder attacks for this reason. ( being overlooked )

Thanks all, seems there is a debate as to whether chains are heat treated/hardened to the same standards.

Given my bikes are half decent but not mega shiney/new/desirable, seems like 16mm would be nice but I’m put off by the added weight. They aren’t insured.

Any decent full size u lock bargains around? (my other is a kryptonite mini, a bit small at times).

Onguard Brute is always good value- sold secure gold if that matters to you, 17mm shackle, and usually around £25.

I have a kryptonite m18. it has prevented 3 thefts

When it comes to chains and locks there are two types of Sold Secure Gold, one for bicycles and one for motorbikes. Go for the motorbike it is a higher standard! Also looks like they’ve added Diamond whatever that means.

are bolt croppers the preferred type of tool for theifs over an angle grinder?

As well as the diameter you should also check how the U bar bit locks into the bit with the key.

If it locks in on both ends then the U bar bit will need cutting twice to remove it from the bike (presuming it’s not thin enough to be bent).

If only one end locks and the other end is just rotated to remove it then it only requires 1 cut to remove.

Checkout The LockPickingLawyer on YouTube.

Thanks again all, given it’s medium risk and the bikes are scruffy and old, I’m erring to something half-decent and light/flexible, like a medium U-lock or those extending ones like Abus Bordo

Any comments on the latter?

stick with a d lock. The onguard brute looks like a bargain for £25.

2kg and I don’t need that level of security

maybe a silly question but do you know how to use the d lock properly ( ie position locked up ) apologies if you are a forum regular. 2kg is alot.

YOu will be sorry if your bikes get stolen Al the average scally goes around with boltcroppers and will be off with your bike in seconds.

A proper 16mm thick double locking d lock big enough to go around street furniture is the only lock worth having. Mine weighs over 2 kg and has saved my bike 3 times!

TJ how do you know your bike has been saved.ie marks / damage to the locks?

IMHO a cheaper/dirtier bike with a lighter lock is the better overall package. Obviously sometimes you need to leave your nice bike outside the shops for a minute, but you’re not going to carry round a 2kg lock on a ride are you?

are bolt croppers the preferred type of tool for theifs over an angle grinder?

The kind of bolt croppers you need to get through a d-lock won’t fit in a bag, a battery angle grinder does easily. Noisy but so fast it doesn’t really matter.

Saw this on reddit today:

I have a fairly sturdy d-lock on a bracket on my sheddy town bike. Anything nice I just wouldn’t leave out of sight.

London perspective:
100% use a 2kg solid secure 16mm u lock even on your cheapest pub bike.
Anything actually nice, don’t even think about leaving it out of sight.

You see people riding around on super shitty, squeaky, rusty old bikes with £80 locks dangling from the handlebars!

trumpton

Member
TJ how do you know your bike has been saved.ie marks / damage to the locks?

Once outside work a ned with a set of boltcroppers walked up to the bike shed, cropped the crap lock on the crap bike next to mine and rode off. It was seen, not by me.

Second time a partly dismantled bike but nothing missing which was somewhat weird. Again a crap lock and the bike would have been gone would be my bet

Third time marks on the lock

thanks.

TJ how come I’ve been using supposedly inferior locks for 30+ years without one theft?

My lock quality varies based on which bike it is and how and when it’ll get locked. I live and work in London

Commuter has an abus granit d lock. It’s properly heavy but very strong

Cargo bike has an abus x lock, the London one with a cable extension. Plus a combination quite thin chain lock for popping into a shop quickly

Brompton has an abus bordo

MTB is locked in my alarmed garage and if I go out on it in use an abus cafe lock for peace of mind when I stop

I like abus locks. The Kryptonite NY fahgeddaboutit locks are supposed to be good too

cynic-al

TJ how come I’ve been using supposedly inferior locks for 30+ years without one theft?

Cochlearphobic bike thieves?

trumpton

Member

are bolt croppers the preferred type of tool for theifs over an angle grinder?

It’s a more complicated question than it seems, this. Most thieves will only carry very basic hand tools, because most bikes are really badly secured. You can cut almost any cable lock on the market in seconds with £5 cable cutters frinstance, faster than the owner can find the key in his pocket. That’s assuming they’re locked at all- there’s no shortage of expensive bikes left totally unsecure in garages and on roofracks etc. And many respectable looking locks, even with thatcham and sold secure over them, can be broken with easily concealed tools (when Zanx and Almax first really started showing how bad many expensive locks are, that immediately led to a trend for massively overhardened chains. Oxford released a 14mm one that couldn’t be boltcuttered, but could literally be smashed with a hatchet because the hardening had embrittled it. I mean, really? Kindling locks\

Sad to say that I was totally complacent, living in a nice area for so long without even a scratched car, so the first time we got done over there was a load of unsecured stuff and while the bikes were nailed down, he still walked away with 2 grand’s worth of stuff after just breaking into the building. Truth is you can’t nail everything down but there’s a balance.

A thief with higher sights, that wants to steal a secured bike, will come equipped for it. Like, we know the last guy that did us, made 2 visits, once to carry off loose stuff and scope it, then another with boltcutters- he was disturbed the second time (he still got a bike, because I’d left it in bits in a workstand, grr) but if they want to nick an adequately secured bike, they won’t muck about with anything except from big boltcutters, hydraulics, or a cordless grinder.

The first 2 are apparently still preferred by some way, because they’re totally silent, and because they’ll still break most locks faster than a grinder, even ones that seem to offer good protection… If you’ve cut a big lock with a grinder, you know it takes a little time, it’s not instant. And with good locks, it’ll take 2 cuts and that’s kind of bloody awkward especially if the lock is reasonably tight around the frame.

(the thing about not putting it on the ground is 100% myth incidentally, but just having it reasonably well wrapped does raise the embuggerment level)

So basically it’s a sort of hierarchy. If someone steals my bikes these days, at least I can rest assured that it was a skilled professional not some oik.