UKC

How secure are D-locks?

New Topic
This topic has been archived, and won't accept reply postings.
 The Potato 03 Jun 2016
On another forum someone was saying d locks are not that hard to get through, I thought they were the best form of lock.
I've got an Oxford motorbike chain and an abus granit plus chained to a ground bolt securing my bikes in the shed. Is this enough?
 Rob Parsons 03 Jun 2016
In reply to Pesda potato:

Depends on your expectations and what you're defending against. An angle grinder (and cordless ones are available) will make short work of a D-lock.
Post edited at 10:18
 nniff 03 Jun 2016
In reply to Pesda potato:

In the absolute sense, they are not invincible and all locks that I can think of are vulnerable to an angle grinder.

I work on the theory of two different types of lock, one cable and D shackle and one chain and lock, which present different challenges to the would be thief. My interest is in securing the bike in an open bike shed during the day though.

In a shed, I would be tempted by one of these - upsetting at least in a dark shed one night.

https://www.kickstarter.com/projects/673350631/bike-mine-the-ultimate-alarm...
OP The Potato 03 Jun 2016
In reply to nniff:

Scary as f! Looks good to me
 LastBoyScout 03 Jun 2016
In reply to Pesda potato:

I think it depends on the type of key it uses - the cylindrical keys are potentially very easy to get through - plenty on Google/YouTube about that. There are, of course, other methods of breaking a D-lock, which I won't list here.

I use MasterLock and Oxford motorbike chains secured to ground anchors to secure all our bikes. My best bike has 2 of them. I try and position them such that the lock is as awkward to get at as possible, to stop it getting drilled.

As mentioned by Rob, the invention of the cordless angle grinder has effectively made any security a bit redundant - all you can do is hope to slow them down enough to make your bikes a less attractive target than someone elses.

Some sort of alarm in the shed would be a good idea - I've been giving some thought to extending our house alarm to the garage.

The trick is not advertising if you've got decent bikes. It's apparently getting more common for people to be followed home either from trail centres or if you've got bikes on the back/roof of your car. I've even heard of thieves fitting tracking boxes to cars to save the bother of following you physically. Also, when you're home, don't leave bike racks on your car/van - which we're pretty sure is why a friend of mine was targetted - 5 bikes stolen.

If you've already been broken into and had bikes taken, there's a good chance you'll get broken into again in a few months time when the thieves figure you've bought the replacements. Happened to the friend mentioned above, but they heard them the second time - his garage is now like Fort Knox.
In reply to LastBoyScout:
> If you've already been broken into and had bikes taken, there's a good chance you'll get broken into again in a few months time when the thieves figure you've bought the replacements.

My LBS recently was telling me similar happened to one of his customers who lived just a few hundred down the road from his shop. The original bike, an expensive road bike, had been taken off the car by an opportunist when it had been left for a short time after the owner had forgotten something from his house and when back in. It was replaced within a month by another high end bike and three months after the first theft, since they knew where he stayed, the shed was broken into and the second bike was taken.

The LBS themselves had in a previous year lost £10k of stock to a break in.

 tjin 03 Jun 2016
In reply to Pesda potato:

Probably the most resistant to a angle grinder, but still cutable with the right disk.

The problem is the stiffness of a U-lock. If you lock the toptube of your frame, the thief can use the entire frame as a lever and twist the lock open.
 Oli 03 Jun 2016
In reply to Pesda potato:
Have a look on YouTube for Pragmasis or Almax. These are probably the best regarded motorcycle chains and they have a lot of videos showing other substantial chains being chopped with bolt croppers.

As someone else said, an angle grinder will get through pretty much anything. They key is to make your stuff less appealing to nick than someone else's by making sure it's more hassle to take yours
 Indy 03 Jun 2016
In reply to Pesda potato:

> On another forum someone was saying d locks are not that hard to get through

Does anyone think that ANY lock is secure?
 Timmd 06 Jul 2016
In reply to Indy:
I have a 'Sold Secure Gold' D lock, I don't think that somebody will never be able to get through it, but I think it'll stop somebody from having an easy time in stealing my bike if it's locked up out in public.

I gather it requires two angle grinder blades to get through it, and it has a square section 'D' to make it harder to torque and break - being made from hardened steel.

It's not thief proof, but I think it's 'thief annoying', I'd not leave my pride and joy (once it's restored) locked up outside anyway, and it's going to be hidden in my home where nobody will find it when I'm out.
Post edited at 11:07
 summo 06 Jul 2016
In reply to Timmd:

> I gather it requires two angle grinder blades to get through it, and it has a square section 'D' to make it harder to torque and break - being made from hardened steel.

apparently the preferred method of some is pipe freeze spray, then one hit with a hammer. Not willing to risk wrecking a lock to test the theory.
 Timmd 06 Jul 2016
In reply to summo:

That's very interesting. B*stards.
cb294 06 Jul 2016
In reply to summo:

This, or a slightly modified hydraulic car jack to push the crossbar off the U shaped section

CB
1
 doz generale 06 Jul 2016
In reply to Pesda potato:

Bike thieves will usually only have the tool required to break one type of lock so having a d lock and a chain is the best way.

Tool of choice for d locks is a car jack. Tool of choice for chain type lock are bolt cutters. Your average bike theive will not carry an angle grinder!
 EddInaBox 06 Jul 2016
In reply to summo:

Pipe freezing spray achieves a temperature of around -50°C, nowhere near cold enough to compromise a D-lock. Liquid nitrogen on the other hand would certainly do the job.
 summo 06 Jul 2016
In reply to EddInaBox:

> Pipe freezing spray achieves a temperature of around -50°C, nowhere near cold enough to compromise a D-lock. Liquid nitrogen on the other hand would certainly do the job.

maybe more urban myth than truth, which is a little reassuring.
 deepsoup 06 Jul 2016
In reply to Timmd:
> I gather it requires two angle grinder blades to get through it

Sorry to be the bearer of bad news, but this seems highly unlikely.

Cutting hardened steel (as opposed to any old common-or-garden steel) with an angle grinder is like a hot knife through butter when the butter has come straight out of the fridge.
KevinD 06 Jul 2016
In reply to doz generale:

> Tool of choice for d locks is a car jack. Tool of choice for chain type lock are bolt cutters.

Long handled bolt croppers or some scaffolding pole to extend smaller ones can chew through most things.

Ultimately a lock is just about getting your trainers on before the person next to you as the tiger emerges.
 Fraser 06 Jul 2016
In reply to Timmd:

> I gather it requires two angle grinder blades to get through it, and it has a square section 'D' to make it harder to torque and break - being made from hardened steel.

I might be wrong but I thought that generally speaking, circular sections are stronger than square ones.Can any engineering types confirm?
 gethin_allen 06 Jul 2016
In reply to deepsoup:

> Sorry to be the bearer of bad news, but this seems highly unlikely.

> Cutting hardened steel (as opposed to any old common-or-garden steel) with an angle grinder is like a hot knife through butter when the butter has come straight out of the fridge.

Depends on how good your blades are really. I've had cheap old blades that struggled to cut through re-bar so a D-lock would be more than safe.

As Kevin D says it's not about keeping your bike 100% safe it's more just deterring the majority and slowing down those that persevere.


 d_b 06 Jul 2016
In reply to Pesda potato:

I cut a D lock in about 30 seconds with a petrol powered angle grinder once. The little electric ones are mostly crap and would take a lot longer.

Funny thing was I removed the lock from railings on a busy street in broad daylight and threw it into the back of a car and everyone completely ignored me.

To clarify, it was my bike. Someone kindly locked it up for me while I was being loaded into an ambulance a few days earlier, but the keys had got lost somewhere in the hospital.
 Dax H 06 Jul 2016
In reply to Pesda potato:

If you go down the chain and lock route make sure it'sa good one.
A lot of people buy heavy looking chain from the car boot, auto jjumble or eBay and they look the part but generally are not hardened properl.
I used to use a high spec lifting chain, iIwas given it by a ccompanyiIused to work for and it was genuinely un cropable.
My motorbike used to live in the garden and Ifound broken bolt croppers a couple of times.
UUnfortunately it was buried in the concrete back garden so I had to leave it behind when i moved.
In reply to cb294:

have a dislike for telling how to do it yes this is the way and its fool proof ----it works
1
 summo 06 Jul 2016
In reply to Dax H:
> I used to use a high spec lifting chain, iIwas given it by a ccompanyiIused to work for and it was genuinely un cropable.
> My motorbike used to live in the garden and Ifound broken bolt croppers a couple of times.
> UUnfortunately it was buried in the concrete back garden so I had to leave it behind when i moved.

I have something similar in the ground under my quad bike, 13mm links on the it I think. I fasten the lock onto the chassis underneath, so it would be a pain to even access with cutting gear. I've tested driving away to pull the block out the ground too. Plus I have a few other noisy alarms in and around, which should stir the best alarm of all. The dog. Whilst nothing is totally secure, I feel I have done enough to justify an insurance claim should it go.
Post edited at 15:42
 Timmd 06 Jul 2016
In reply to Fraser:
> I might be wrong but I thought that generally speaking, circular sections are stronger than square ones.Can any engineering types confirm?

From a metal fatigue point of view, cracks start in corners, so a circular hole isn't going to fatigue and crack like a square one would.

The same principle doesn't apply to round and square bars, though. If you try bending bars of different shapes but the same materials/thicknesses, the circular ones will bend more easily.
Post edited at 15:59
 Fraser 06 Jul 2016
In reply to Timmd:

I'd never really thought about it but I'd always subconsciously assumed D-locks were hollow sections rather than solid bars, but perhaps they aren't.
 Timmd 06 Jul 2016
In reply to Fraser:
I'm guessing (hoping) my D lock which cost £60-ish has a D made from solid bar. It feels quite heavy & like it might be.
Post edited at 18:14
 Fraser 06 Jul 2016
In reply to Timmd:
Err, I've just checked my own Abus D-lock and it's clearly solid, sorry!

Edit: I rarely use mine these days and I had it in my mind that the bar was a much larger diameter.
Post edited at 18:33
 wilkesley 06 Jul 2016
In reply to davidbeynon:



> Funny thing was I removed the lock from railings on a busy street in broad daylight and threw it into the back of a car and everyone completely ignored me.

A couple of years go my son broke the key in his flimsy bike lock. I couldn't find the bolt cutters, so drove the pickup with petrol generator and 9" grinder to the shop (Morrisons). I parked just in front of the the main entrance, fired up the generator and after a few seconds of showers of sparks the lock was off. Nobody batted an eyelid. I was fully expecting hordes of security guards from inside and a police helicopter.

 d_b 06 Jul 2016
In reply to wilkesley:

At the time I assumed that it was the bystander effect in acton - people are more likely to intervene if nobody else is around. In a crowd everyone assumes it is someone elses problem and decides against getting involved.
cb294 06 Jul 2016
In reply to Name Changed 34:

Wondered where the dislike was coming from, thought this was common knowledge. I am definitlely sure it is among bike thieves, , so I don't belieb I am spreading some great secret, but may help bike owners to consider the usefulness of their lock.

For what it is worth, I use a Abus bordo folding lock, but even this can be opened is seconds using a dummy key that is hammered in an transiently pushes the locking bolts out of the way, Bizarrely, you even can find tutorials on youtube.

CB
 d_b 06 Jul 2016
In reply to cb294:
Car jacks are the magic tool for getting through locked doors generally. Wooden frames will often warp enough for the door to simply swing open and for everything else there is brute force.

In other news water is still wet and there is minimal honour among thieves
Post edited at 23:06
 dread-i 06 Jul 2016
In reply to Pesda potato:

I don't want to state the obvious but, it would be easier to cut the frame and sell all those expensive, untraceable parts on ebay. A frame has a serial number and might be distinctive in other ways that could get them caught. If they are determined enough to bring an angle grinder, they probably know what the parts will fetch.
 Rob Parsons 07 Jul 2016
In reply to cb294:

> For what it is worth, I use a Abus bordo folding lock, but even this can be opened is seconds using a dummy key that is hammered in an transiently pushes the locking bolts out of the way ...

You mean a so-called 'bump key'? Some locks (I'm not thinking specifically of bike locks here) are designed to make that harder to do, but you're right to point out that it's an easy method of attack - much easier than conventional lock-picking.

And if anybody thinks I have divulged a secret here, think again: the bad guys know all about this already.
 Lurking Dave 07 Jul 2016
In reply to Rob Parsons:

Sadly, two weeks ago a low life nicked both our good mountain bikes, he carried bolt cutters and an portable angle grinder. The good news is that CCTV footage showed him clearly (and he left by Cotic!), bad news from polices was that if they really want it, they will take it. This was from a locked storage cage under our apartment.

LD
1
 sparkymark 07 Jul 2016
In reply to deepsoup:

Seconded - I once cut a mid-range Abus d-lock with a cheapo B&Q grinder running a masonry disc - basically melted through like boiling water on an ice cube.

Almax chains are the best I've had, but they ain't cheap, or portable...
 Wsdconst 07 Jul 2016
In reply to Rob Parsons:

> You mean a so-called 'bump key'?

I think I've got a bump key knocking about in the workshop somewhere. I used to work for a window and door company and one of my 'special' jobs was opening doors for people who had misplaced their keys. I'd totally forgot about it until you just reminded me. I had a set of picks too but never really mastered them.

New Topic
This topic has been archived, and won't accept reply postings.
Loading Notifications...