Old timer told me to use a torch on a seized bottom bracket last month

I had a 90s Trek that wouldn't budge after a week of soaking in PB Blaster. He said heat it up for 30 seconds with a propane torch and it would come right off. Tried it and the shell cracked - was that a bad idea or did I just get unlucky with an old frame?

3 comments

3 Comments

green.noah15d ago

Was that a steel frame or aluminum? Makes a big difference with heat. If it was steel and you used a torch, 30 seconds should be fine unless you kept the flame in one spot the whole time. Aluminum frames are trickier though, you really gotta keep the heat moving and check it with your hand every few seconds. On steel bikes I've had good luck with just warming it enough to make the penetrating oil bubble a little, then letting it cool and hitting it with a breaker bar.

gracethomas15d ago

Yeah that sucks but honestly you probably held the torch too long or hit it uneven. I've done it plenty of times on old steel frames with no issues. 30 seconds is way overkill just get it warm to the touch not hot. Did you try a breaker bar first or just go straight to fire?

grace_knight1915d ago

Honestly sounds like you held the torch too long. 30 seconds direct flame on an aluminum shell will cook it. I only heat steel frames and just until the penetrating oil starts smoking, maybe 10 seconds. On aluminum you're better off with ice and heat cycles instead. Sorry about the frame though, that stings.