I bought a GRX400 groupset from Merlin to build up my Trig frame and I've just realised that the front mech. is braze on whilst I'll need a band-on (checking the original Merlin pages show that there is only a braze-on option).
Looking around online I can only set braze-on mechs, so I guess that there's some sort of band-on adapter available but I'm not exactly sure what I need.
The Trig page doesn't list a front mech. clamp size, but the seat collar is 29.8mm (so's my Swift which I think has a 28.6mm mech. clamp).
Would this work with a non-Dura-Ace mech?
Could anyone point me to what I need?
Yes
https://www.wiggle.com/p/shimano-sm-ad91-clamp-for-dura-ace-ultegra-105-braze-on-derailleur
or
https://www.ribblecycles.co.uk/csn-s-leggera-clamp-for-braze-on-front-mech-blk-34-9mm-1/
Need to check tube diameter, if clamp is over size will need shims. The Ribble is good if bottle cages get in the way of clamp position as allow some vertical adjustment, the Wiggle shimano one is neater
Thanks, I've just checked the online instructions for the GRX400 mech. and the SM-AD91 is actually listed as the adapter for band-on mechs. so I'll give that a go 👍
Well that's interesting, the SM-AD91 is slightly too large for the seat tube. According to Shimano it should fit 31.8mm tubes or 28.6mm with a band adapter (shims).
I bought the 31.8mm and was expecting shims, but what turned up is just the clamp and some instructions wrapped in bubble wrap. However, Ragley have confirmed that I need a 31.8mm adapter so I don't know why it's too big! Wiggle's page confirms that it's a 31.8mm clamp, it's the only size available but there's no size marked on the packaging or clamp.
Interestingly I have some very thin shims left over from various front mechs and if I fit a single one of these inside the adapter if grips perfectly and it looks like it's making proper contact all around the clamp (no sign of gaps).
Is this a workable bodge, should I try something with inner tube or buy another adapter.
Does sound a bit odd. I have a GRX400 mech & SM-AD91 adaptor to go on my Camino, which is 31.8. It fits perfectly. Sounds like the Trig seat tube is undersized. I would use the thin shim in your picture. Have done similar in past and its worked fine.
I got back to Ragley saying that it didn't fit and was told that, actually, the Trig's seat tube is undersized.; 31.8mm doesn't fit but it's the closest there is.
I've glued some small strips of inner tube to the inside of the adapter and I think that'll work.
The bodge will work, I'd use something less squishy than inner tube as it will mean the mech will move with the cable pull. You want crisp sharp movements for optimal shifting.
