A customer's weird trick for stuck seatposts actually worked

This guy came into my shop last month with a steel frame and an aluminum post that was totally frozen. He said, 'Try a mix of ammonia and automatic transmission fluid, let it sit for two days.' I thought it was nuts, but we were out of options. We poured it down the seat tube, left it over the weekend, and it broke free with just a hand wrench. Has anyone else used this mix, or is there a better way you've found for really bad cases?

3 comments

3 Comments

caseyflores2mo ago

Tried that exact mix on a crusty old Peugeot last year. Works like a charm but you gotta be smart about it. Wrap the top of the seat tube with a rag to stop it from splashing back on the frame's paint. That ammonia smell will knock you out, so do it outside. For anything less than totally frozen, a good penetrating oil and some heat from a hair dryer usually gets it moving. What's the worst stuck post you've ever dealt with?

colesanchez13d ago

Ngl, I saw this breakdown on a bike forum a while back where a guy tested that mix on a 80s Raleigh with a seatpost that looked like it had been welded in. He used the ammonia and ATF combo and said it took three days of reapplying but finally broke free without damaging the paint. What caught me was his warning about the frame, he wrapped the tube in a plastic bag first to catch any drips. You really gotta think about the paint like @caseyflores mentioned, that ammonia is no joke if it sits on the finish too long. Tbh, the worst stuck post I ever saw was on a Schwinn where the previous owner used epoxy. That thing was done for. No chemistry trick is pulling that out.

webb.derek2mo ago

Honestly, the chemistry angle is wild but it makes sense. Ammonia attacks aluminum oxide, and the ATF creeps. What gets me is the safety side of it, like, you're making a pretty nasty soup there. Good ventilation is a must, and I'd be real careful with any paint. It's a last-resort trick for sure, but it's cool to see why it actually works.