I have one PM that is MegaExo compatible (P2M) and another that is GXP (Quarq Riken AL).
MegaExo and GXP are both based on a 24mm axel diameter. So...
1. If your gossamer crank is the same diameter...
- the P2M should easily be swapped in.
- the GXP has a slightly smaller diameter on the non-drive side and you likely will need a small shim like this
2. If your gossamer is larger in diameter (i.e. 30mm).
You'll need a new PressFit bottom bracket like this
...I like the press fit BB's that thread into themselves.
In either case, I would also assume that your PM's have larger chainring sizes than the gossamer cross. If that's the case, you'll also need to adjust the height of your front derailleur.
Thanks for the info. I've swapped several BBs and cranks but have never dealt with PressFit BBs that is new to me.
Regarding the Chainrings: you are correct. Truth is, really only my MegaExo PM is one I could effectively use on my gravel bike because it is 110 bcd while the Quarq is 130 bcd and I want to keep my 46/36 rings. I have some experience moving the FD around and readjusting since I do that some on my TT bike when I swap rings from 50, 53, 54.
Thanks for your help on this.