Reviewed: Kryptonite Keeper 755 Lock

Locks that are secure enough to leave a kid’s bike on the streets of New York for a school day yet light and small enough for that kid to carry are hard to find.

The old-school U-lock is big, bulky, and nowadays allegedly somewhat easy to defeat. Modern folding locks are small and light but not super secure. And locks marketed as the ultimate in security are crazy heavy, like almost 15lbs for Kryponite’s New York Faghettaboudit Chain 1415, or the simpler, slightly less secure New York Lock Standard is over four pounds.

When we asked representatives at Kryptonite what they recommend, they suggested their Keeper 755 Mini Integrated Chain. It’s heavy-duty seeming and flexible and small. It uses their latest key technology. The chain links are covered with a nylon casing to protect paint and make threading the lock easy.

There’s an independent non-profit lock-rating institution called Sold Secure. Based in the United Kingdom, they’ve been testing and rating locks since 1992. They rate locks Gold, Silver, and Bronze. This Kryptonite rates Silver, meaning a “a compromise between security and cost.”  Supposedly, the lock should be able to withstand a thief who has three minutes or less of time and a moderately sophisticated set of tools.

In terms of size, it measures 21.5-inches long. It’s roughly the same circumference as the Pinhead lock we tested out, but can go around more stuff, thanks to the flexible chain links. This also means it can get pretty small in a bag and can be worked around the largest of posts; the links are 7mm thick. It can get down to into a cylinder about six inches tall and eight inches in diameter. Its one liability is weight. The mass comes out to 2.08lbs on our scale.

As mentioned, The 755 can get pretty small in a backpack. Because of its weight, it’s best to put it in at the bottom, probably first of the stuff for school. This isn’t great for rainy days, when you’d have to open up your bag and rifle around outside to pull out the lock, but it makes it much easier to carry. It can be wrapped around a frame, but the problem is there aren’t many spots where it can wrap, not slide around, and not get in the way of pedaling. A handlebar basket or rack bag are about the only places you could easily put it on a bike, but neither are terribly common for city commuters, particularly kid commuters.

Use is incredibly easy. The locking mechanism stays open so long as the key is in, which makes un/locking both secure and straightforward. The hardest thing about using the lock is pushing the key all the way in before turning. It takes adults some practice, like a few tries; kids took longer to get it right, like several.  This could be because of their pick and drill-resistant design bits.

The chain links make it easy to wrap the lock around even scaffolding supports, a wheel, and the frame at once. The more stuff you can thread the lock through, the harder it is to steal said stuff.

Kryptonite rates this as only five out of ten on their security rating scale, aka moderate security. According to their chart, that means a quick stop in a metropolitan area, a couple of hours in the suburbs, or all day and all night in a rural area. It’s hard to know how to regard their scale—on the one hand, they have far more experience than most anyone else when it comes to security, on the other, they’re probably more cautious than most as they do offer a money-backed warranty of $500, provided conditions are met.

Those conditions, which you can find here, are several, and including $9.99-$29.99 for the service, depending on how long you want to cover the bike. The low price is for a year, the high for four. Hard to know how to evaluate such an offer. On the one hand, the price seems reasonable, on the other, there are several steps one needs to take to claim the warranty.  At the very least, register your keys.

Over the course of several months using the lock a few times a week, the bikes this lock was used with were never stolen, nor did it seem that anyone attempted to steal it. The bike was locked for several hours only once, but left for a few hours many times. As we’ve noted less secure-looking locks on bikes locked outside of schools for the same time, it’s possible that this lock is more than enough for commuting-to-school kid bikes.

The frustration with this lock is the weight. As light as it is, it’s still heavy for a human weighing less than 100lbs, often less than 60. And kids are already burdened with too much stuff in backpacks. The thought of leaving the lock at school is appealing, but the lock is often needed to secure the bike at the home end of the trip as well.

The Kryptonite Keeper 755 lock ticks off most of the boxes necessary for an urban kids lock. The last box, low weight, is one we don’t see getting hit unless metals technology changes dramatically. For now, this seems like the right compromise.


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