It's our second year with Ampel 24 305 cm trampoline. First year, it started squeaking more or less immediately after assembly. I tired fixing that with spray lubrication, household lubrication oil and food-safe silicon grease. Nothing helped.
The solution that we have good results with this year is:
- Use industrial multi-purpose grease
- Apply with a brush to all metal-on-metal connections including frame and spring ends
- We made sure to apply it on both sides of the connection e.g. outside of the male and inside the female frame ends
- Also apply inside the bolt holesand under the washer - this will likely cause your bolts to get loose faster so check them regularly
There are downsides to this, of course. It about doubles the assembly time, especially if you'd like to wipe off the excess, and the nasty grease gets on some of the things you didn't want it on.
Result is a squeak-less trampoline. We had to come again to some of the springs and grease some more as there was a bit of noise initially. The only noise you hear now is from the fibers and the mat.
So, if you didn't put your trampoline together yet, this trick is for you. Otherwise you might want to wait until the next year :-)
UPDATE: a week later some springs started squeaking again. Oh, well.