Sorry for this beginner question, but I got a Rockhopper MTB, it's a hardtail. I also got a chunky bike lock, one of the foldable higher tier ones.

The problem is, with the mounting mechanism the lock comes with, it can't be mounted on the seat tube because there won't be enough vertical space to easily take it out.

I've seen two solutions to this:

1. There are alternate mounting mechanisms where the lock can be taken out toward the front. However, I keep finding comments about those that during a rougher ride, the lock may just fall out on its own.

2. And some people mount the lock on the front tube. At first, I thought that would be a great solution.

   However, I can't find much info about what the bike manufacturers say about this, since the top tube doesn't seem naturally designed to carry extra weight, especially in lighter bikes like MTBs or racing bikes.

Does anybody know if having a lock up there, fixed in position via velcro and without drilling any holes, can cause strucural issues for the bike frame? Or would it likely worsen accident outcomes significantly? Especially when driving on rougher terrain where the bike may get tossed around a little.

As far as I know the frame is aluminium, not carbon. But it's not steel either, of course.

Update 2026-07-06: I realized sidecage bottle mounts are a thing, I will try to get one of those now and see if perhaps I can fit the bottle on the seat tube after all. If that works, then I could have the lock sitting on the bottom tube after all!

It most likely isn't an issue for the frame, but it's going to be in the way getting on the bike, it'll suck in a crash, and it'll likely always be flopping to one side or another.

Personally, I just toss my lock in my pack - more comfortable, less annoying.

It is surprisingly fixed in place with just the velcro, there's been no flopping so far. If you think it doesn't bother the frame, what do you think would be the bad effect during a crash? It flying about or making a frame crack more likely?

(I do wonder a bit if somebody here has a top tube mounted lock and has any experience with if it had any noticeable effect during crashes!)

For what it's worth, here's a photo of the seat tube mount that I've seen with review comments claiming the lock fell out during the ride (it's an Abus mount, I got one of those Abus Bordos but not with this mount so far):

I wonder if anybody here has tried those mounts out?

This the type of velcro mount that I'm currently using on the top tube:

I have a Topeak Road Morph G pump mounted on my seat post, and it removes "forwards" but is velcroed in, and I've never had a problem with it on bumpy rides. I wonder if there are any general-purpose accessories like that, maybe with a padded bottom and backing and two straps for a heavier lock.

A bit of offtopic, but if you're a beginner, it might be helpful: don't trust any those locks much. It obviously depends on the area, but in a big city, I wouldn't leave my bike for more than like half an hour or so unattended. Even with a good lock. And definitely don't leave it overnight or so.

Like, some generic velcro strap mount that doesn't use these weird plastic flaps that apparently tend to let go mid-drive? Yeah that would be nice. Haven't found anything so far...

I tend to only stop briefly at stores to get food and water, and I prefer stores where I can see the bike from the inside through the front windows!

Couple options maybe?

https://www.amazon.com/Blackburn-Outpost-Cargo-Bottle-Cage/dp/B00NT4KXBA

https://bikersforums.com/product/gorix-bike-multipurpose-cage-waterproof-bag-set-bottlecage-frontfork-large-cage-global-edition-goricage

Hm I don't like that the blackburn cage is screwed in, from what I've read that's apparently a bad idea for some 1.5kg lock. It seems like that's too heavy for most frames and may cause the screws to break off. I wonder if there's something similar but with pure velcro? It also seems like the metal might scratch the frame a tiny bit, the current mount I'm using is some sort of medium hard'ish plastic.

The other option looks better in terms of no screws, but an entire bag for a lock seems a tad weird!

Ahh I wasn't aware that could be an issue with screws on bike mounts, but makes sense!

I don't think you need to use the bag, if the lock would sit snugly in there with the straps directly on it.

There is one of those uncuttable lock that will eat grinder wheel like breakfast, but then the second weakest part is the thing you lock it on. Lock is really just anti-oppotunist.

Another thing to consider, I've seen people with bottles on the underside of the down tube, but not sure off the top of my head how they mount them.

If you can do that then you can put everything on that tube. MTBs have a lot of vertical clearance, but it is for missing rocks and roots etc. But I've seen stuff mounted there anyway

Just since you mentioned it, you should NOT consider drilling extra mounting points. Definitely work with what you have!

I have the secound lock, but honestly i would recomment it bolting to the seat tube(light blue). I have mine with straps on yellow but i have tabed the frame because of paint damage. There is also the option to put it on the downtube(darker blue). Maybe this helps:)

I ended up going with a side cage for the bottle! So the bottle is now against the seat tube (light blue/turquoise) and the lock is now where the bottle used to be on the down tube.