What torque for caliper brakes onto carbon-alloy forks?

Question

I've recently got a new bike with a Kinesis DC07 carbon/alloy fork. This comes with deep-drop calliper brakes (Shimano R451 Dual Pivot). The first time out I bumped one of the brakes and it twisted around the single attachment bolt and rubbed on the rim.

I managed to easily twist it back by hand and carry on, however I thought the bolt probably needs tightening. The question is: How tight can it be?

As the fork is part carbon I've so far only dared to take it up to 4Nm, but it still seems possible to twist the whole calliper around with a bump of the hand. Maybe that's normal? Perhaps it's easier to bump around because of the longer deep-drop lever. Should I be aiming to get it really secure?

I'm not sure whether the brake mount in the fork is all carbon, or some of it is alloy underneath, but either way I'd like to know what a sensible torque is. As far as I can see from the manufacturer's website there is no such specification. How can I find this out?

Answer 1

The Park Tool BBB-2 lists the recommended torque for side/dual/center pull Shimano brakes as a range from 7.84-9.8 Nm. I see no specific mention for carbon frames/forks. Bicycle tutor has a similar table here: http://bicycletutor.com/torque-specifications/

Answer 2

The site you liked to says "The 3k carbon blades are deep section with eyeletted forged alloy dropouts." and this suggests to me that the crown is aluminium.

You might be able to tell if you look up from the bottom, mine are a cast aluminium crown with carbon blades and this is quite obvious from below.