I totally stripped the adjuster bolt on my rear caliper, it had a hex head, now it's round and doesn't turn anymore. Do you know if it's possible to replace the pad adjuster bolt only without replacing the entire caliper?
I couldn't find that part online.
If you can extract that bolt and measure it, then identifying a replacement would be easier.
However when I tried to remove an adjuster from a different brand of caliper, it was locked in during manufacturing and couldn't be disassembled without unbending some retainer clips.
In the end I upgraded from a mechanical caliper to a low-end shimano hydraulic for relatively low cost.
Another temporary fix might be to use a hacksaw or dremel to cut a slot across the whole bolthead, and use a very large flathead screwdriver to adjust the bolt position. It's up to you whether this is acceptable.
Do consider this is part of your braking system, which is an area where function is critical and compromise can have consequences.
Consider an all-new replacement caliper if the bolt doesn't come out easily.
Update there's no chance you're going to find a replacement in a hardware store because its not a bolt; instead it is some kind of pancake head.
I expect it also has 2 or more spring-loaded ball bearings on the sides that push out into those recesses.
On the positive side, if you can grab the current one, it should come out without damage. Perhaps use an oversized torx bit and hammer into the hole as a sacrificial driver.
That looks like another BB5 copy (or almost, as it uses different pads). I've failed to find replacements for Promax's BB5 clone or Avid's original - but the thread is the same on both of those.
Stripping the head of this part seems like a common failure mode - they're aluminium and prone to binding and getting mucky. If you got a replacement (whether Tektro or one of the brands I mentioned) a little anti seize grease on the threads is a good idea. I clean and regrease mine when I change pads at home.
The fact that they're made of aluminium also means the trick of cutting a slot for a screwdriver is easy - but you're quite likely to tear it with the screwdriver. I suggest taking the pads out and applying penetrating oil (chain oil will do if you don't have anything lighter, but wait a few hours with the bike lying so gravity pulls it in).
Thanks to a reddit user I was able to find the part, I haven't purchased it since I replaced the caliper already but it is possible. This is the link https://tektro-usa.com/product/md-m280-pad-adjuster-spring-and-ball-bearing/
