That surprises me. I've been fitting band-on front derailleurs for about half a century, and can't recall ever even damaging paintwork, let alone denting a seat tube. Mind you, 4Nm is quite a lot - I'm rather surprised that the marked setting would be that high. I've never used a torque wrench on an FD clamp when assembling a bike, but it doesn't need anything like that much force applied to the pinch bolt to hold the derailleur in place. After all, the handlebar clamp bolts on threadless stems are usually marked as 5Nm; that's sufficient to hold the handlebars in place, and the rotational force on a drop handlebar when you've got your weight out on the brake hoods is many times greater than that on an FD.
The other possible problem might be your torque wrench. If it's a torque wrench that goes up to 25Nm or 30Nm, then it's quite likely to have substantial error at low settings. Nick -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/rbw-owners-bunch/a89596aa-d20a-4f20-a64a-72ec0db5c4dbn%40googlegroups.com.
