I'm not sure if they're all like this, but my u-lock is a bit loose between the two pieces, the U and the bar. The provided mount snaps very very tightly onto the U, leaving the bar to fend for itself, so when I ride, any little bump makes the lock rattle. I believe the main source of the noise is the loose (non-locking) interface between U and bar; it's metal-on-metal there.

It's pretty obnoxious (and I feel like anyone I pass by must think my bike is broken), so if I have a bag I toss the lock in there instead. Sometimes that's not an option though, so I'd really love to stop the rattle while it's in the mount.

I believe it's one of these:

kryptonite series 2 u-lock

I expect that the little rubber rings are supposed to push up against the bar, and keep things held in place, but mine is loose enough that the right side wiggles around plenty.

  • What kind of lock is it? I hear some rattle more than others.
    – Hugo
    Commented Sep 6, 2011 at 15:10
  • 1
    Yes it's what the rubber rings are for. You just need to slip them down a bit so that they push against the other part of the U-lock when you re-assemble it. @kevin-reid's suggestion to use small cable ties behind the rubber rings is a good one so you don't haver to keep doing this. Commented Apr 2, 2014 at 9:36
  • Can you build a better lock holder on your bike? Are you handy? I've seen lock holders that clamp down on the bar and have a second clip to hold the U.
    – Criggie
    Commented Jul 28, 2017 at 21:53

10 Answers 10


Anything that will "bunch up" as Mathew suggests should work. You can slip a piece of tubing over the end of the U, or some O rings, or wrap with electrical tape. The object is not to have material actually go into the hole where the U fits, but to "bunch up" at the hole.

Otherwise, you could probably run a bungie from the loose piece to some frame member to keep it in tension.

  • +1. I tried a bungee this morning; it helped, but wasn't quite enough. I think the O-ring suggestion is probably good, but I don't have anything like that at the moment.
    – Cascabel
    Commented Sep 6, 2011 at 15:56
  • 1
    Okay, o-rings are definitely the right idea. The rings that are already on the lock are not actually fixed in place; when pushed down far enough they solve the problem, but they'll eventually migrate back up. Just need to effectively widen them and all will be well. Thanks!
    – Cascabel
    Commented Sep 7, 2011 at 7:18
  • 2
    Wrap a little masking tape behind the existing rings to keep them in place. Commented Sep 7, 2011 at 11:28

Heatshrink SOLVES this problem completely. Go to radioshack, buy the smallest about of heatshrink you can that'll fit, get a heat gun or a lighter or even a blowdrier in a pinch, and say goodbye to the rattling.

Photo of U-lock with heatshrink on shackle

If your shackle is difficult to slide into the crossbar after applying the heatshrink, smear PTFE lubricant on the heatshrink.

  • Agreed, very useful on bike accessories where you can get to the end of a tube or bar - but you might need to order online to get a large enough size without buying a huge pack.
    – Chris H
    Commented Mar 30, 2014 at 8:12
  • If the heat shrink is going around the end of the u-lock shackle, I don't think Radio Shack will sell heatshrink big enough to go over it.
    – Batman
    Commented Mar 30, 2014 at 14:01

I've just solved this with two washing machine hose washers (they're the rubber washers that make the seal between the screw part of the hose and the tap, and they cost a few pence). Take the existing sleeves off the ends of the U, put the washers on, put the sleeves back on. Problem solved. Lock silenced. It's like having a brand new bike.

  • Gidday and welcome to SE Bicycles. Thank you for your contribution, and I look forward to your future input.
    – Criggie
    Commented Nov 16, 2015 at 18:53
  • Do you have a photo with the washers on the u lock underneath the sleeves? My impression is that the sleeves will still rattle against the shackle. Don't the washers move? Commented Jan 24, 2023 at 9:03

I have a piece of normal inner tube surrounding the U part of my U-lock and that does the trick. It is a bit longer than the actual plastic coated part of the 'U' and bunches up when I close the lock.

I carry the lock on my bike rack or on my rucksack shoulder strap (it has a slot in it), depending on what bike I am on.

With your lock bracket clamping to the 'U' I am not sure if you will be able to get the inner tube approach to work, however, I thought I might share that idea with you to help you improvise a solution of your own.


I went the cheap route.

I cut small squares of rubber from a flat bike tube and then I cut a little slit in the center of each. I pushed each down the lock until it cleared the cut in the metal for the locking mechanism. I ended up using 3 squares per side of the lock.

  • Welcome to Bicycles @bikesquirrel. As with all new members we recommend taking the tour to make best use of the site. Check out the help center, and update your profile to tell us a bit about yourself.
    – andy256
    Commented Sep 6, 2016 at 0:46

On one of my locks none of the suggestions above would fit or work. Here's what did - hot glue:

I ran a bead of hot glue round the (degreased) body around the hole where the shackle goes in, then inserted the (previously greased) shackle briefly.

To make it easier I did one end at a time. I also had the shackle part way in while applying the glue, so I didn't push it into the lock body.

It's quite possible to peel the glue off and have another go if it doesn't work. A similar trick can be done with silicone sealant but then you have to leave the shackle in place while it sets. Both glues will cut with a knife if you manage to glue the lock shut.


I have a lock of the pictured design. The rubber rings at the ends of the U would be perfectly good for the job of pressing against the bar to keep it from rattling, except that they're not close enough to the bar to do that.

I used rubber O-rings from the hardware store (found in faucet repair parts) as shims between the original thick rubber rings and the black sleeve over the main body of the U.

The advantage of this approach over some of the other suggestions is that you are less likely to get stray material jammed in the interface between the U and the bar, because the supplied rubber rings are thick, close fitting, and otherwise suited for this job — just in need of a little spacer.

(I originally used plastic cable ties, but those are too wide, have a lump at one point, and eventually failed under sunlight.)


Simplest way I have found to do this is with a "Bag for life" from Sainsbury's or Tesco, cut a section about 2.5 inches square and push it inside with a pencil. Works perfectly for me. It tends to last about 10-12 months depending on how much you use the lock.


Another possible solution is to grease the mating points of the lock

Your bike lock lives on your bike, outside a lot and in the elements. Grease helps shed water, but it also fills voids which will cut down on the rattle.

Downsides, grease is messy and can get on your hands and clothes. But other parts of your bike are greasy/oily too.

Upside, your lock will rust less, and should close smoother.

  • Also grease attracts dirt, so potentially can make things worse :)
    – Sapphire64
    Commented Nov 5, 2018 at 19:49

I wrapped elastic/rubber bands round each end of the U. Enough to put force against the lock when seated.

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