Here are some tips for deterring thieves if you've forgotten your lock:

https://www.bicycling.com/beginners/c...busVc0.twitter

That first part about rigging the drivetrain doesn't sound like it would work very well. I don't think my RD would be able to move over 10 sprockets without the chain actually moving over with it.

I carry a foot or so of Velcro tape. Besides its other uses, I can wrap around my rear wheel and seat stay. Bike ain't going nowhere and hopefully no one is sticking around to cipher it out.

interesting concept.

I wonder if there would be liability concerns for booby-trapping your bike and injuring the would-be thief... "I just grabbed the wrong bike!"

I've got lock nuts on a SS/Fixie. No loose QRs for me. The Velcro maybe, but problem is if I can remember velcro or carry it, I can easily carry a small lock and some thin coated cable to lock my bike up in my jumbo seat bag.

on just buy a ring lock like most ppl

I leave a cheap cable with master lock fastened to the rod under the seat. Booby trapping my bike as listed above would be too much trouble for me. Once or twice I've just leaned the bike where I could see it when I knew I wouldn't be too distracted. But still seems like a bad idea.

I don't endorse what I'm about to type in the slightest bit, just wanted to get that out of the way first.

A friend of mine swears by wrapping his seatpost with barbed wire sectioned with regular wire, so it's basically 1/4's he turns the wrap when he gets somewhere so the barbed wire parts are pointing out towards the thighs, and turns it back when he hops on, seems dangerous and stupid to me but it's what came to mind.

my former employer always talked about putting a long cork screw up the seat tube of a bike geared to the pedals you could engage when you park....all I could think about was what if you ever forgot to disengage it .

I don't think any of these things would do you any good in a major metropolitan area and it seems like most might just end in you hobbling your own ride. In NYC i lock it up or bring it with me and I don't even like locking it up on the street for more than a few hours.

I use velcro. I keep a 1/2" wide foot long strip rolled up on my stem and when I get off the bike I wrap it around my brake handle. Keeps the bike from rolling when you lean it on stuff and it doubles and a thief slower downer.

Forget about booby-trapping.. Just ride a brakeless fixie everytime you go into a high risk area and anybody dumb enough to steal one will very quickly find out it was a big mistake.

Same limitation applies to the suggestion of loosening QR and other painful booby traps for the forgetful owner. If the cyclist is that careless/forgetful about bringing a lock along, or using a lock is only a sometime thing, what makes him have a sharp memory for safing his own booby trap(s)?

And if the thief is successful he will have done the original owner a favor!

Just kidding, Mr Wolfchild.

As someone that used to do this, back in the late '70s, I can tell you that there is no solution for the memory issue, but that loose QR and gear shift thrown off only tend to cause you issues like dropping your wheel or jamming your chain, both embarrassing yet recoverable problems that don't mean too much unless you are trying to make a fast getaway on a stolen bike.

A thief can recover from these too, but it takes a few minutes, and in the mean time, hopefully you'll notice someone on your ride messing with it. These techniques only slow a thief down, they don't really stop 'em.... and if a thief is just grabbing your bike and tossing into a truck... it's gone baby.

I have a fixed gear road bike I bought for $30 that I use just for this purpose. I never lock it, fixed gear bikes are so uncommon around my town that any would-be thief is going to get thrown over the bars metres from where he first got on it. Perfect bike to ride to the shop with.

+1 Traps are illegal and indiscriminate. Definitely would be careful doing that especially on an unlocked bike, which is almost inviting someone to ride it.

Dropping a wheel and crashing at speed may do more damage to the forgetful booby(trapper) than only cause some embarrassment.