Support road.cc

Like this site? Help us to make it better.

forum
road.cc bike forum

Hydraulic disk brakes - seized screw/pad axle

by DoctorFish
Mon, Jan 28, 2019 11:32
18

Hello,

I thought it was time I checked the pads on my disk brakes (they are Shimano BR785).  The front one is fine, but I cannot undo the retaining screw on the back one.  there is a small clip, and then a slot head screw, which I believe is called the pad axle.  It is completely seized and I am in danger (if not already done so) of damaging the head.

Any ideas on how to get it out?

It is like this, only with a slot head:

https://www.wiggle.co.uk/shimano-br-m785-pad-axle-snap-ring

 

 

If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

Add new comment

18 comments

Avatar
DoctorFish | 6 years ago
0 likes

Just an update.  The bike shop got the screw out by taking the caliper off and taking it apart.  They replaced the pads and fitted it with a split pin.  They also supplied me with a spare split pin when I commented that I would also replace the front one.

In the mean time I have also ordered some of the allen headed screws, so I have a choice, but probably stick with the split pin as it also seems a simple solution.

Avatar
CXR94Di2 replied to DoctorFish | 6 years ago
0 likes

DoctorFish wrote:

Just an update.  The bike shop got the screw out by taking the caliper off and taking it apart.  They replaced the pads and fitted it with a split pin.  They also supplied me with a spare split pin when I commented that I would also replace the front one.

In the mean time I have also ordered some of the allen headed screws, so I have a choice, but probably stick with the split pin as it also seems a simple solution.

 

I would replace the split pins because they could move under braking and mark the caliper body, aswell as ruin the threads where the pin goes.  A Better fit to use your new allen head pins with a dab of copper grease on the threads, spin in, unwind to check all threads are well covered, apply more if necessary.

Avatar
ibr17xvii | 6 years ago
0 likes

As I've gone into at length on another thread mine has done this too.

Not taken it to be the LBS yet but I won't be letting them put another screw in that's for sure.

Avatar
StraelGuy | 6 years ago
0 likes

Do you mean Shimano allen head bolts Peter or have you found a cool alternative?

Avatar
hawkinspeter replied to StraelGuy | 6 years ago
0 likes
StraelGuy wrote:

Do you mean Shimano allen head bolts Peter or have you found a cool alternative?

They're Shimano xt m785 pins. They're probably a couple of mm longer, but I can't see that ever being an issue.

Avatar
ibr17xvii replied to hawkinspeter | 6 years ago
0 likes

HawkinsPeter wrote:
StraelGuy wrote:

Do you mean Shimano allen head bolts Peter or have you found a cool alternative?

They're Shimano xt m785 pins. They're probably a couple of mm longer, but I can't see that ever being an issue.

I've got one of these in the front now & although it is a couple of mm longer it seems to be fine.

Avatar
hawkinspeter | 6 years ago
1 like

I had exactly this issue and mangled the screw in a very similar manner. My LBS used a dremel to get the screw out and I've replaced the screws (front and rear) with a hex bolt head screw instead.

Avatar
Pilot Pete | 6 years ago
0 likes

You are aware that the threaded bit is just behind the head, not on the other end like a ‘normal’ bolt? The slot head screws are made from cheese, but as others have said, a bit of coppaslip prevents seizure. 

PP

Avatar
DoctorFish replied to Pilot Pete | 6 years ago
0 likes

Pilot Pete wrote:

You are aware that the threaded bit is just behind the head, not on the other end like a ‘normal’ bolt? The slot head screws are made from cheese, but as others have said, a bit of coppaslip prevents seizure. 

PP

 

Hi Pete, yes, I worked that out about the thread thanks.  They are certainly made from cheese!

 

Avatar
CXR94Di2 | 6 years ago
4 likes

There is nothing wrong with the design that a dip of the thread in copper grease wouldn't sort out .  Ive been messing with motorcycle and cars for years, everytime i take a bolt or nut off, i reassemble with copper grease applied.  I even remove bolts and nuts on brand new vehicles that i intend to keep, on suspension and brake mounts apply copper grease

 

It saves so much hassle a few years later .  Prevention maintenance 

 

A neater solution would be to source a bolt with an allen/torq head

 

lWiggle do one for the BR M785

Avatar
DoctorFish replied to CXR94Di2 | 6 years ago
1 like

CXR94Di2 wrote:

There is nothing wrong with the design that a dip of the thread in copper grease wouldn't sort out .  Ive been messing with motorcycle and cars for years, everytime i take a bolt or nut off, i reassemble with copper grease applied.  I even remove bolts and nuts on brand new vehicles that i intend to keep, on suspension and brake mounts apply copper grease

 

It saves so much hassle a few years later .  Prevention maintenance 

 

A neater solution would be to source a bolt with an allen/torq head

 

lWiggle do one for the BR M785

Yes, if I had fitted them myself originally then it would have been greased.  This came fitted on the bike and this was my first attempt at removing it.  I note your point though, and will check on future bike purchases that grease has been applied (to be fair to evans, everything else I've taken off has been trouble free).

Avatar
DoctorFish | 6 years ago
0 likes

Thanks all for your suggestions.  I've actually just taken it to the LBS.  The option discussed was, if they can't get it out, to drill it out and then use a split pin in future rather than the screw.

Thank you so much for your time responding.  I was going to try and drill it myself but chickened out!

I have fairly small mole grips, but just couldn't get them to grip and then turn them.  I tried on the other end of the screw as well, but that just snapped straight off.  Seems a bit of a design flaw, a splt pin seems a far better solution.

 

Avatar
LastBoyScout | 6 years ago
1 like

I would make sure both pistons are fully pushed in and try and saw through it just outboard of the inner pad - the end of the axle will drop out. You should then, with a bit of wiggling, be able to remove that pad and then the spring and outer pad - you'll probably need an old flat knife to depress the spring to do this.

If you can get the pads out like this, try the mole grips on what's left of the inboard bit of the axle - I do have a really tiny pair of mole grips, though.

And clean the pads of the sawing dust before putting them back in.

Avatar
CXR94Di2 | 6 years ago
1 like

Two possible actions, involves power tools/Dremel.  

Cut away the spring and pad tabs and remove, then use a pair of mole grips on the shaft to turn.   The other is cut a bigger slot in the head and retry.  My option is first one, it offers better chance of removal with less damage to caliper.  

Apply copper grease to threads once replaced

Avatar
nikh | 6 years ago
1 like

Should be enough meat in it to use the smallest of these:

https://uk.farnell.com/duratool/d00163/screw-extractor-5pc/dp/1447442?gc...|pcrid|78108376509|&CAWELAID=120173390000027738&CAGPSPN=pla&CAAGID=14406255429&CMP=KNC-GUK-GEN-SHOPPING-1447442&CATCI=aud-310054926231:pla-61859544613#

Avatar
PRSboy | 6 years ago
1 like

Use proper penetrating oil... like plusgas, not normal WD40 (though they do a very good penetrating oil)

Cut a new slot in the head and try again.  Maybe apply a bit of heat beforehand.

Another option... have you enough space at the other end to grip with the molegrips without damaging the caliper?

Otherwise, it will need drilling out.

Avatar
DoctorFish | 6 years ago
0 likes

I tried with the mole grips, but they just smashed the head of the screw off!

Avatar
StraelGuy | 6 years ago
1 like

All you can really do is soak the pin with penetrating fluid and try a set of mole grips on the head. Careful with the penetrating fluid or you'll sacrifice the pads.

Latest Comments