I'm about to buy an Aether 7 frame and transfer over the kit from my hard tail. However, my Reverb would need a shim to fit the Bird. I asked Ben at Bird and he said they don't recommend it. Does STW think this is a bit too cautious (I'll be getting the longest shim I can find) or should I bite the bullet and buy a new post (I'm on a bit of a tight budget).
Sell your Reverb and buy a Brand-X? Probably wouldn’t lose money, wouldn’t lose functionality either (although upgrading the lever is widely recommended)
I'm running a USE shim on my Aeris145, 30.9 to 31.6. I've not had any issues
Wouldn’t have thought a decent fitting long shim would be an issue. That said if your reverb currently works then as suggested above you could probably sell it and mostly find a new brand x post. The Aether has a very short seat tube so you can run a long dropper. I’m on a medium at 5’9 and am running a Oneup 210mm post at 200mm drop. I couldn’t quite get it in far enough to run the full 210mm unfortunately!
I've been using shims for 20 years or so, never had a problem. Giant used to supply a lot of bikes with a 30.9 seattube shimmed down for a 27.2 seatpost. You want a shim that is at least 3" long, preferably 4", and you want it to extend below the seat tube-top tube junction so you aren't putting a lot of stress on the welds there.
Manufacturers will automatically say no to any question like that for legal reasons - they can then reject warranty claims if anything goes bad. It's not based on any engineering considerations, just the legally safest thing to do.
Thanks for the answers, I'm veering towards a shim for financial and 'I can't be bothered to sell the Reverb' reasons.
As long as the shim is a similar length to the minimum post insertion (usually around 10cm) or longer, then there really isn't a problem.
