Undoing stripped allen key bolts.

So I’ve stripped the cheap aluminium seat bolt (not the seat post bolt, the one under the saddle). It’s an allen key bolt and I can’t get an allen key to sit in their firmly to undo it with out slipping. I need to move my seat forward a bit, and I’d like to replace the saddle one day soon as well.

Any tips? I don’t mind replacing the bolt if need be.

  • Use an imperial allen key that’s slightly larger
  • Get a sacrificial allen key and epoxy/jb weld it in place
  • Ride everywhere perched on the front of the saddle, don’t unweight for bumps, the bolt will eventually fail from fatigue.
  • Don’t tighten it so tight next time?

If it’s a normal microadjust post the bolt is likely to be an M8 or similar, easy replacement with an Unbrako from a hardware store.

Happened to me the other day.

I got a hack saw and cut across the face of the bolt.

Be very careful not to hit the frame - just go slow and put something between the blade and frame if you can.

Once I had cut in a bit I got a flat screw driver in the slot and got it out. I used one of those very fine files for a bit to open it up too.

Then I pegged the bolt into the distance for making me mad.

I seem to be a magnet for buying parts off ebay with stripped allen key bolts at the moment. A stem and some Dura Ace pedals are my most recent joys.

buy a new bike

I did! Then I bought a new seat post, put my seat on, put the seat post in, rode it, found I am too far back, went to undo the bolt, which I must have done up too tight originally… which takes us back to the beginning.

The hacksawing idea sounds the best though. Cause it’s under my seat, not against the frame I don’t think I have to worry about scratching the frame.

Is it a good quality seatpost, or cheap. ie is it worth saving?

that really sucks dude, i wish i had something constructive to say…

…i dont.

it’s not amazing, but it looks nice and it fits and I don’t want to drop $30 on another one.

You might be able to hack the bolt without damaging anything else. Depends on the clamp design.

cheap aluminium you say

If the hacksaw doesn’t work or you botch it or whatever then the drill is a good alternative. Choose a bit size bigger than the bolt shaft, stick it in the hole and drill till the head of the bolt pops off. Once the head is gone there won’t be any pressure on the threads and you can unscrew it with your fingers.

I stripped out the head of one of my cleats and it worked just dandy.

I’ve had success with the hacksaw method too so go to it.

Well after all of this, I swapped out the stem and and drop bars for a shorter stem and risers, which brought me further back on my bike, hence not needing to adjust the seat.

But thanks for all the tips.

there is always the option of geting a similar size torx key and jamming it in the hole and then hoping for the best, i have foiund this usually works the best for me