How to know if you have a faulty Kryptonite New York Diamond?

Since I discovered the fault in my first Kryptonite New York Diamond lock, many people have contacted me to ask how they can tell if their lock is defective or not.

I’ve read comments suggesting that the extent to which the thin layer of textured, sparkly (anti grinder) material extends beyond the rubber cover of the shackle is a good indication of whether the lock is defective, or not.

Or that a big gap between the shackle and the crossbar indicates a faulty lock.

And a lot of people seem to be returning their locks based on these assessments.

So, I thought I would create a post where we can share our findings and hopefully dispel some of the misinformation (because I’m pretty sure many people are returning locks that are completely fine).

Below, I have provided better photos of the defective lock. Plus some photos of other locks that I have tested since (and were fine). And also photos of a load of new locks I have bought, to see if we identify another defective lock based on certain characteristics.

Spoiler: I am publishing this post before I have tested the newest locks (just so people can see some of the photos), but I suspect that they will all pass the tests and that Kryptonite has indeed fixed the problem.

First, a timeline recap:

• April 2025 I bought a lock from a European website which was very easily cut at the base of the shackle
• May 2025 Kryptonite contacted me and I sent the faulty lock back to them
• May 2025 Kryptonite sent me 2 replacement locks. I tested one and the fault was fixed
• September 2025 I bought another lock from a European website. I tested it, and again the fault was fixed
• September 2025 a French video was published, which showed the same fault
• January 2026 I bought 3 locks from Amazon and 1 lock from an independent shop to test again.

Here are the photos so far (you can click on the photos to see higher resolution versions)...

Locks I have Tested

1. The Faulty Lock

The faulty New York Diamond looked great when locked up. The shackle had a very tight fit into the crossbar with no gap at all:

However, you can see in the image below that there doesn't seem to be any textured, sparkly material (which is the anti grinder layer), extending beyond the shackle cover:

There does seem to be a third layer of material, but it seems like it's just the covering, with no texture, indicating that the actual anti grinder material which should be underneath, is absent.

Below is the crossbar of the faulty lock after the shackle was cut. Note the cut is straight across. I wasn't able to cut downwards into the shackle.

In the next photo of the shackle, you can see that the cut is after the anti angle grinder material (which is textured and sparkly) ends. Note also how high up the shackle I had to cut: it's nowhere near the tip.

I was able to cut the faulty lock at the base of the shackle with just 1 disc in just 13 seconds, with the disc completely unaffected at the end.

Kryptonite contacted me to say that the faulty lock was part of a bad batch and sent me two new locks to test.

2. The first lock that Kryptonite sent me

The first lock from Kryptonite performed really well. I needed 25 discs and over 6 minutes of active cutting to get through the base of the shackle.

In the photo below, you can see the edges of the sparkly layer of anti grinder material in the crossbar. This stops you cutting too far diagonally down into the shackle at the crossbar.

Look how high I was forced to cut the shackle. Again, I was nowhere near the tip. So there was plenty of anti grinder material to spare.

This lock was obviously protected just as well at the base as it was further up the shackle (where I needed 13 discs and 3 minutes 11 seconds of cutting to cut it).

3. The second lock I bought

I was aware that Kryptonite should have hand-picked the best locks for me to test, so I bought another lock to test again.

Again you can see how the anti grinder material extended the whole length of the shackle (that I was able to attack).

Once I had established that it was well protected at the base, I stopped cutting: it was clear that I would need to waste a load of discs to get through either side.

4. The second lock Kryptonite sent me

Once I'd finished testing the first lock that Kryptonite sent me, I didn't bother with the second one, as I presumed it would perform equally well.

However, bizarrely, the second lock, looks the most defective out of all the locks I have seen so far!

There is massive gap between the shackle and the crossbar:

And there appears to be very little anti grinder material at the ends of the shackle. However, I think I can see some on the left-hand side. And I suspect there is plenty underneath the cover.

It seems very unlikely that Kryptonite would make the mistake of sending me a faulty one, but I tested it to make sure.

And by attacking the gap between the shackle and the crossbar, I was able to cut it faster than the previous two locks.

I took me 3 discs and over 5 minutes to cut through the side with the big gap. I cut the other side with a diamond disc as part of another test.

So yes, it seems like a big gap can indicate a slightly less secure lock. But this is clearly not the same issue as with the original faulty lock. Two of my angle grinder discs were destroyed as I cut through this lock.

And most of the angle grinder resistant bike locks were (to varying degrees) easier to cut at the base of the shackle.

Most importantly: you still need to cut the other side to defeat the lock and in my experience, there is only ever a big gap on one side of the shackle. 

Locks I have not tested yet

1. Lock from an independent shop

I then bought one from an independent bike shop. This one looks pretty good. Not much of a gap between the shackle and the crossbar.

And it looks like thee is a fair bit of anti grinder material on both ends of the shackle.

2. First Lock from Amazon

I also bought three locks from Amazon. The first one has a pretty gap between the shackle and the crossbar.

But there's plenty of anti grinder material on both sides of the shackle. And it extends very close to the shackle grip.

3. Second Lock from Amazon

The second Amazon lock has a huge gap between the shackle and the crossbar. But you can see some anti grinder material glittering away through the gap. 

And a closer inspection of the ends of the shackle reveals plenty of the anti grinder material extending very close to the shackle grip.

4. Third Lock from Amazon

The third Amazon lock has a smaller gap between the shackle and the crossbar.

But while there is some material on the left part of the shackle, the right side looks less covered in this photo.

Conclusions so far

I don't think the gap between the shackle and the crossbar is an issue.

Even if you can get a disc into the gap and the shackle is unprotected at that point, you're going to hit the edge of the crossbar before you can cut through the shackle. And the crossbar is also protected with anti grinder material.

I also don't think that a smaller amount of anti grinder material at the end of the shackle means you've got a faulty lock.

In fact, I think it's the opposite: any amount of textured or shiny material extending beyond the shackle cover indicates it's protected.

The faulty lock had nothing: it was completely smooth at the end of the shackle and that's why it wasn't protected.

But don't forget: the angle grinder disc won't reach that far anyway. And there could be anti grinder material further up, hidden under the shackle cover.

So the only way to really know is by scraping off the cover further up the shackle (where an angle grinder can access), to see if the anti grinder material is underneath!

Next Steps

As soon as the rain stops here, I will have a go at two of the locks I haven't yet tested. If you have a lock that looks like it might be faulty, get in touch through the contact me page.