Frame locks are really useful and convenient for cargo bikes, where you want the bike secured enough out of sight for short periods, like childcare dropoffs. Where you are reasonably confident that the bike isn't going to end up in the back of a van, but you don't want someone to just wheel it down the street.

They also support a plugin chain so you can lock the back wheel and secure the bike to something solid.

The Cube Cargo has mounting points to fit a frame lock. However, due to the massive 2.6" tyres and large rear mudguard, it is a little tricky to get on there. Here's how I did it.

Lock Selection

You need a lock with a large opening. I went with the Abus 5755L, which has a 78mm opening, wide enough for the mudguards. There is also the Abus 5750L, which looks physically identical but with the Plus key, where as the newer 5755 has the XPlus key. Axa also make locks with massive openings, like the Axa Imenso X Large.

Do some measurements and check the product dimensions to find a lock that will work. If you're in Australia like me, you're going to be a bit limited by what you can find. I got the Abus lock from Amazon, and went with the key retaining version.

Fitting The Lock

The 5755L will not fit straight over the mudguard and wheel. The inside is large enough to fit them, but the actual opening is not. To get the lock in place:

1. Put the bike on its centre stand
2. Undo the rear wheel quick release and pull the rear wheel down out of the way
3. You can now slide the lock sideways over the mudguard and then rotate it into position
4. Push the rear wheel back into place. You might find it easier to deflate the rear wheel so it isn't a giant baloon.
5. Verify whether the lock will clear the rear wheel and lock

Dropout Adjustments

Following the steps above I got the lock in place, but it would not close. The shackle hit the rear wheel, as shown below:

I knew from forum posts that others had fitted locks like this onto this bike. So what gives?

Well, the position of the rear wheel can be adjusted back and forward. The dropout adapter is adjustable, so that the belt driven models can have the belt tensioned. We want to shorten the wheelbase slightly, bringing the rear wheel closer to the front of the mudguard, allowing the lock to clear the rear wheel.

If you've ever dealt with chain tensioning on a motorbike, it's essentially the same process.

Loosen the Dropout Adapter Bolts

There are 2 bolts on each side of the bike. These need to be loosened to allow the dropout adapter to slide. On my bike this was still quite tight to move, even with the bolts loosened.

Loosen the adjustment bolts

There is a small captive bolt on either side of the bike. You need to loosen these bolts, turning anticlockwise, until they are as far out as they can go. This gives you a bit of space to move the wheel forward.

Push the wheel forward

You can now push the wheel forward a little bit. I had to encourage my bike with a soft mallet to the rear wheel.

Check & Repeat

With the wheel forward slightly, check to see whether the lock clears the wheel. If it doesn't repeat the process to bring the rear wheel a little closer.

Verify the wheel is straight

Hopefully you've made the same amount of adjustment on each side of the bike! You want the rear wheel to be straight or you're run into issues with braking, wear on drivetrain, etc. On each side of the bike there is a visual indicator letting you know the position of the dropout adapter. All you need to do is make sure both sides of the bike are at the same marking.

Attach The Lock

With the lock clearing the wheel, you can now go ahead and attach the lock to the bike. My lock didn't come with any mounting hardware, so I went to Bunnings and bought some stainless steel bolts and washers. You could use security bolts for this, but it's not really necessary. With the lock closed, it doesn't matter if the lock was removed from the frame, it would still be locking the wheel.

Enjoy the convenience!

With the lock good to go, you can now feel more at ease if you need to leave the bike out of sight for short periods, and for longer periods a plugin chain works great.