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Picked up the other day for my son. Deore triple and Deore front mech which has chuff all clearance on chainstay. It is about 3mm over big ring so I guess it must just be geometry of the stay. Not very well thought out.....
SRAM and Shimano spec for the angle between the centreline between rear wheel axle and BB, and clamp centreline for front mech (in this case the seat tube) is 66-69 degrees.
This can require tube juggling to get that dimension with some BB heights but I've only ever had issues with clearance on very short chainstays. I've never noticed poor performance.
If you think about what happens with a full suspension bike and that angle changing at sag or in riding conditions there's clearly a lot more than 3deg tolerance really.
Thanks Brant, that explains it well. I guess I may move it up a little so its not scraping if a bit muddy !
.....moved it up to give about 3mm clearance on chainstay, shifts ok in the bikestand ! Ta.
just twiggest also that with a 22, 30, 40 chainset the big ring diameter is relatievly small, hence need for mech to sit a bit lower.