Sheared Head

[Richard A Thackeray]

Whilst checking the brake-pads (or trying to) yesterday evening on my CGR, I rounded off the head of the small screw locating the pads
RS785 calipers

I guess it's my fault, for
1. Over-tightening
2. Ought to have added the smallest amount of copper-grease behind the screw-head
there's been some galvanitic corrosion over winter?)

Thankfully, there's probably another 4 - 5 months wear & tear left in it (hopefully)

Now, the problem is removing it.....
1. My father-in-law has a Dremel, so grind off the head, & drill it out, if he has any bits that small?
2. After drilling out, replace the current screw type, with a plain shaft, that can be simply circlipped?
(or, accept that the replacement -standard- screw will be loose, but it only keeps the pads in place, not locate them!)
3. 'Bite the Bullet' & take it to one of the local shops, & accept that a new caliper may be needed?


Or, other suggestions, please

 

[classic33]

Drill and use a stud extractor.

 

[Richard A Thackeray]

Drill and use a stud extractor.

Yes, another option, but we're talking an M2????

Are they available that small??

 

[Smokin Joe]

Drill a hole and hammer a Torx bit into it.

 

[flake99please]

Use Dremel and cut notch into head. Use a flat blade screwdriver to remove.

 

[Minotier]

On small diameter threads such as this I have this I have carefully drilled through with a tapping size drill and then just used the correct size tap. But 3mm is the smallest I have done.
Though if it is a through hole I have also ground the head off and then when tried drilling with the drill it has spun the screw out of the back, even if enough to grab with snipe-nose pliers.
Good luck.

 

[Levo-Lon]

Few options..
As said, make a cut and use a blade screwdriver
Can you grip whats left with a mole grip?
Remove caliper and grip the pin from the inside with nose plier.
Or drill the head and separate the caliper halves, removing the pin will be easy then.
The look like 2 piece.
Ive done this loads of times when dealing with Tokico caliper motorbike pad bolts as the heads weld and they round out.

 

[I like Skol]

I believe you are not alone in this problem, @Kestevan suffered a similar predicament and then went on to totally bodge a solution that involved hoping the pads would stay in place by magic, Ritualistic sacrifice and luck, until I gave him some genuine shimano split pins that were made for the job.

It is probably a bit late to suggest pre-emptive greasing of the thread (something I did before I was even aware that this was an issue ) but before resorting to drilling and other butchery I would keep trying to get that screw out by natural means.

A spot of oil around the head and some judicious tapping on the screw head with a hammer might be enough to break the corrosion hold that is preventing removal. If the screw were a bit bigger I would suggest use of an old skool impact driver which is perfect for situations like this, but they are usually to big and cumbersome for delicate jobs like this.

If you do manage to get the screw out I suggest replacing with the Allen Key hex head variant as fitted to Shimano XT calipers. These are a bit longer but fit nicely. If you are not bothered about the retaining circlip (who has ever had one of these screws come lose?) you could cut off the excess length.

www.cyclechat.net/threads/shimano-m785-r785-brake-pad-security-pin-spring-clip-y8jz98010.224990

 

[Kestevan]

Yeah, had to drill mine out.

Discarded the threaded bolt and used a split pin as donated by @I like Skol.

No magic or voodoo was involved and the only reason the pad fell out was because I foolishly believed that a skolly "road bike ride" would involve road rather than cobbles, dirt roads, plowed fields and the broken moonscape that passes for tarmac in Manchester...

 

[CXRAndy]

The thread i believe is on the head side. Dremel to cut out pads and leave a stub for pliers or mole grips to turn from other side. Or drill and use extraction tool of the screw head. You can get allen bolt versions of the same bolt

 

[Richard A Thackeray]

The thread i believe is on the head side. Dremel to cut out pads and leave a stub for pliers or mole grips to turn from other side. Or drill and use extraction tool of the screw head. You can get allen bolt versions of the same bolt

Threaded section is, yes, on the head side

I might, when I replace the pads, 'destroy' them, with a small hacksaw/Dremel cutting disc & try to grip the pin with pliers
(maybe some emery paper in the jaws for extra grip)

 

[si_c]

I've got an extractor kit which has a smallest thread of 5/64" or about 2mm, so you might get something like that to work - you just need to get enough bite to get it moving then you might be able to finish it off with a screwdriver.

 

[Richard A Thackeray]

Tried to be clever with it, when I got home from work this afternoon
Grasped the inner-end, after removing the circlip, with a pair of pliers..... thinking that not much torque would be required to turn it

Snapped off the end, at the machined circlip groove...……….. Bugger!!!

 

[Richard A Thackeray]

Sorted!!

New pads appeared in this mornings post


Therefore, after a ride out (Tadcaster & Sherburn-in-Elmet, with tea at 'Squires'), I had a think about what to do
Once home & changed, it was on with the job
Got bike in the work-stand, & once the back wheel was out, the junior hacksaw came out



With the pistons pushed back, with a big screw-driver (they were protected by the pads), & the handle back on, a few minutes work (with intermittent checks) saw the pin cut
The plain end, slid out, so the pads & spring came out of the caliper
Thin pliers could grip the pin & unscrew it, till it was out enough to use 'radio'/snipe-nose pliers on the chewed-up head
Hurrah!!!



And no damage to the piston either (a wipe through with a wet cloth, to remove dust/detritus, before the new pads went in)

Whilst checking the brake-pads (or trying to) yesterday evening on my CGR, I rounded off the head of the small screw locating the pads
RS785 calipers

I guess it's my fault, for
1. Over-tightening
2. Ought to have added the smallest amount of copper-grease behind the screw-head
there's been some galvanitic corrosion over winter?)

Thankfully, there's probably another 4 - 5 months wear & tear left in it (hopefully)

I know I could have waited that 4 months or so, but I decided to do it, anyway

I retained the standard 'screw' bolt in the front, but it's got the smallest dab of copper-grease behind the head, & was backed-off 1/2turn after fitting
The, supplied, split pin went in the rear, as I couldn't find the standard bolts from the last set of pads

Thanks again, guys, for all the suggestions

 

[Richard A Thackeray]

Update

The (new) sintered pads seem slightly noisy

Whether that's simply bedding in, or indicative of their materials?
I am given to understand, that they're slightly better in the wet, than the (still great) resin pads