Very little metal around caliper bolt hole. Dont risk helicoiling-just replace caliper. Consider the forces acting under full braking!
I considered the forces. Caliper is behind fork leg getting forced against it when brakes applied. Still not entirely sure what I will go with. See how I feel when it's done.
Quote from: GrahamB on 16 July 2014, 07:17:48 amI considered the forces. Caliper is behind fork leg getting forced against it when brakes applied. Still not entirely sure what I will go with. See how I feel when it's done.When you considered it, did you work out exactly how much torque is being applied, how strong a helicoil is and how well the insert will be seated? Like the Yamaha engineers blah blah...
Correct me if I go wrong here, but I don't remember there being any thread in the caliper. If he needs a helicoil, it is in the mounting hole on the fork leg, or the carrier on the rear. A replacement carrier is easy enough to get and would probably work out cheaper then helicoiling your busted one. However, if it is the fork that is forked, then I really don't recommend trying it as a DIY job. Check breakers yards and ebay for the cost of a replacement and consider bringing it to a local engineer for their opinion on cost of repair (if its possible).
There is no torque being applied on the helicoil. When you put on the brake the caliper is putting a shear force on the mounting bolt at 90 degrees to the bolts long axis, there are no braking forces going through the helicoil at all. All the helicoil is doing is putting up with the twisting forces you put on the bolt when doing it up -and that's it. Braking doesn't come into - it if you are talking about the 'strength' of the helicoil. Helicoils are usually well up to the job in most situations if properly inserted. Having said that -I'd fit a new caliper because it's less messing about -not because helicoils are not up to it.
You're right about it being a shear force (my mistake, it was late), I understand the calliper is trying to rotate with the disk putting 90 degree forces on the mounting bolts as you say. What I don't understand is where you say there are no braking forces going through it. Er, then what is that 90 degree shear force then? How does that not put force through at least