Helicoil for brake caliper retaining bolt hole?

[GrahamB]

Beginning to wish I hadn't replaced my brake pads today.
 Has anyone ever repaired the M10 hole in a brake caliper using a helicoil thread insert? I'm scared!  I'm wondering if there's enough meat on the caliper to be drilling & tapping the bottom mount hole.

[AyJay]

I'm not a mechanic, and I'm sure there'll be someone along soon who is, but jeez - helicoiling a brake calliper? I know you can get great results and some say stronger, but this is your brakes. Get that wrong… gulp! I wouldn't even think about it. Plenty of R1/R6 FZS1000 callipers on eBay starting at 25 quid…. I'm sure they'd be a much better bet.

[b1k3rdude]

1. Which caliper? front or rear.
2. For the amount it would cost to get it heli-coiled and the saftey aspect you might as well pickup another caliper of ebay.
3. How the foc did you manage to snap one of the mounting bolts..?

[GrahamB]

Snap a bolt?  The thread in the caliper has stripped. Front.  General opinion is it's doable. Kit with 10 inserts is less than a tenner.  I'm in.

[mickvp]

A timesert might be a better option. I would probably just change the caliper though just for piece of mind.

[Dave48]

Very little metal around caliper bolt hole. Dont risk helicoiling-just replace caliper. Consider the forces acting under full braking!

[old son]

Very little metal around caliper bolt hole. Dont risk helicoiling-just replace caliper. Consider the forces acting under full braking!

Unless you ride like a wooosssi

[GrahamB]

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.

[b1k3rdude]

The time-cert option costs a lot more more than helicoil, a pair from front calipers only costs £75 on ebay.

[AyJay]

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.

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 did when they designed the calliper? There is no bullshit with engineering. It's pure science. Over the last 200 years every metal and every alloy of metals has been tested, examined under x-rays, improved and catalogued and if you look on the internet there are thousands of tables of precisely how strong each is for a given thickness, and how strong it is at every given temperature from -50 to its melting point. Yamaha engineers then design a part using finite element analysis and a back catalogue of tens of thousands of design tests.


And you want to put a helical in it and expect it to work on the basis of what? Have you even thought that brake callipers get very hot when they are working. How does that affect a helicoil insert?

And if you do it, how are you going to test it for strength afterwards?

I'm not saying it won't or can't work, what I'm saying is that it sounds like you are not in any way qualified to make that judgement, hell it might be fine, but ask a professional before you do it, I'm begging you. I'm in no position either, if it makes you feel any better, but I'd ask someone first.


You would be right to think I'm writing a very strongly worded post here, but braking from 100mph into a left handed hairpin bend on a 500lb bike is not when you want to find out you got it wrong!

[Simon.Pieman]

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.

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...

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.
 

[PaulSmith]

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).

[Dave48]

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).

Think you will find its the caliper that is threaded on the side nearest centre of wheel.

[AyJay]

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 some of the thread? Or am I wrong? It's been known to happen.

And are there not always sideways forces when you apply the brakes which will push and pull the calliper from side to side? The pistons push onto the disk in the same plane and unless you have perfectly equal pressure from both sides of the calliper, that is applying force in the same plane as the bolt.

As I said earlier, I have read that helicoils can be stronger, but first, how on earth were the threads stripped in the first place and secondly, if it was user error (no torque wrench perhaps), then jeezuz, what makes the user think that he can correctly fit a helicoil? That's why I said 'ask a pro'.

[GrahamB]

 

[Simon.Pieman]

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

The shear force isn't acting on the helicoil, it's acting on the bolt only where the caliper body is touching the bolt -ie not on the helicoiled bit.
The caliper doesn't move about and channel strange forces through the bolt and/or helicoil as you seem to imply, it's rigidly mounted.


 Really, this is 'O' Level Physics.

[AyJay]

You're right. It is 'O' Level physics. Did you get to the bit about pivots? Practical suggestion, get a pencil, hold it in your fist and wiggle it around. Then tell me where you feel it moving.

[richfzs]

Ayjay is on the money...