Disc brake caliper - advice/warning!

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Miguel Evans
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Joined: 15 Jul 2010, 6:15pm

Disc brake caliper - advice/warning!

Post by Miguel Evans »

I have a 2 year old bike with ultegra hydraulic discs. The disc pads are held in the caliper with a threaded bolt. My bolts are both seized, and despite soaking in releasing fluid (and all the other tricks I know), I destroyed the head of the bolt and am now faced with having to drill it out. Any advice on how else I might get them out? I will of course replace with split pins that the new pads come with (that's the advice bit to anyone else!)
Thanks.
Jdsk
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Joined: 5 Mar 2019, 5:42pm

Re: Disc brake caliper - advice/warning!

Post by Jdsk »

Can you add a photo of the head and position, please?

As an alternative to drilling it out you might be able to cut a slot and use a straight-tipped screwdriver.

Jonathan
rogerzilla
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Joined: 9 Jun 2008, 8:06pm

Re: Disc brake caliper - advice/warning!

Post by rogerzilla »

Drilling a prominent allen bolt is easy. You only need to get the head off, then you can remove the caliper and use mole grips on the rest.

Drilling a low-profile domed slotted screw with no washer under it, rusted to a Moulton mudguard, without ruining the mudguard - that's tricky!
Miguel Evans
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Joined: 15 Jul 2010, 6:15pm

Re: Disc brake caliper - advice/warning!

Post by Miguel Evans »

Forgot to say that I'll be off shopping for a better penetrant tomorrow before I commit to the perils of the drill (or at least ask the bike shop to).
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Redvee
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Joined: 8 Mar 2010, 8:58pm

Re: Disc brake caliper - advice/warning!

Post by Redvee »

You can buy replacement pins from SJSC but not cheaply but they do come with an allen head rather than a slotted screw head. Stable door/horse bolted situation but copper grease for the new bolt will stop this happening again.
Jupestar
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Joined: 29 Feb 2020, 3:03pm

Re: Disc brake caliper - advice/warning!

Post by Jupestar »

Heat has helped me in the past. Sticking the calliper in a mug of hot water.
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531colin
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Location: North Yorkshire

Re: Disc brake caliper - advice/warning!

Post by 531colin »

Bike shop is likely to just replace the caliper....thats a job that will take a "known" amount of time (unless the caliper bolts are stuck as well!), so they know how much it will cost for both parts and labour. Trying to get your existing caliper going is a complete unknown; they could spend a lot of time and still be unsuccessful, and the customer is reluctant to pay for "work" which hasn't resulted in a bike you can ride.

I have drilled out a similar bolt, after the owner "had a go" . It looked to me like the typical dissimilar metal corrosion you get with an ali saddle post in a steel frame, or a steel bottom bracket cup in an ali frame. Corrosion forms a white oxide, and you can be a lot more vigorous with bits stuck in frames than you can with a hydraulic caliper; I'm not sure the seals would appreciate penetrating oil, for example.

You may be able to cut an additional slot, as mentioned
If that doesn't work, I would try cutting the bolt (with Dremel) to release the head, then you only have to deal with the friction in the threaded bit, not the extra friction of the head end and the tension on the bolt. You might be able to turn the bolt with any pliers you can get in; failing that drill it from the threaded end, so any torque applied to the bolt by the drill will tend to undo the bolt.

(Not everybody knows you can get "left hand" drills to extract bolts from the head end.)

I would replace with a stainless bolt and either 2 locknuts or a nyloc nut.....I see some Shimano calipers use a pin with a spring retainer.

HANG ON A MINUTE!! just looked back at your photos, there is a spring clip on your bolt??

Have a look at the tech. docs. for the exact part number .............. if there is a spring clip on your bolt/pin then why would it be threaded into the caliper?
You might be able to remove the clip and push the pin out?

Pictures I found weren't clear,,,,the "head" end of the pin is thicker, and its not clear to me at the moment whether thats threaded or just thicker.....and they point to different ways of removing.
See why I doubt a shop would have a go?
Pin may be threaded at the head end, rather than the other end, which requires a completely different approach!
gxaustin
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Joined: 23 Sep 2015, 12:07pm

Re: Disc brake caliper - advice/warning!

Post by gxaustin »

Have a look at the tech. docs. for the exact part number .............. if there is a spring clip on your bolt/pin then why would it be threaded into the caliper?
They do thread in. They should not be graunched up tightly so the spring clip offers a bit of protection against their coming loose and coming right out. I've never had a problem with these over several years - I'm guessing these were over tightened.
slowster
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Re: Disc brake caliper - advice/warning!

Post by slowster »

There are quite a few reports of these bolts seizing and the slotted heads disintegrating. The bolts and the retaining snap rings are like those below. For some reason Shimano used the bolts on many of its brake calipers as OEM, but the various Shimano brand replacement pads are supplied with a split ring as standard to replace the bolt and snap ring.

Brucey recommended applying a blob of MIG weld to the damaged head - https://yacf.co.uk/forum/index.php?topi ... msg2147677.

It appears that any damage to the female thread in the caliper caused by drilling out the bolt may not matter much, since split pins will not need the female thread. Another option might be to remove the pads and spring, e.g. by using a Dremel on the bolt shaft. Leave as much of the bolt shaft as possible so that it can be gripped by pliers/mole grips. Grip what is left of the damaged slot head with another pair of pliers/mole grips, and then use both pliers to apply a turning force on the bolt either side of the seized thread.


Image
AndyA
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Joined: 21 Mar 2009, 9:16pm
Location: Edinburgh

Re: Disc brake caliper - advice/warning!

Post by AndyA »

These really are a bit of a pain in the neck. I've ground a screwdriver that's a very good fit in the slot which definitely helps. In the bikeshop I'll try this screwdriver, followed by cutting the pin as far to the inside as possible (with a set of knipex mini bolt croppers) to remove the pads and getting a set of molegrips on the pin. Try turning the pin with the molegrips and the screwdriver simultaneously, both clockwise and anticlockwise. If that doesn't work it's bin time, new caliper and bleed. You're unlikely to drill out the screw without going squint and damaging the caliper (unless you remove the caliper, get it in a drill press or mill, but by that point it's uneconomical and the caliper is still corroded and worse for wear)
A more economic (and often more available) replacement than Ultegra is Shimano BR-U300
gregoryoftours
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Joined: 22 May 2011, 7:14pm

Re: Disc brake caliper - advice/warning!

Post by gregoryoftours »

Would it be possible to remove the caliper body bolts plus the pin clip and split the caliper into its two halves? The pin at least should allow this because it's threaded on the head side and therefore should be completely free in one half of the caliper. Then you could grip the pin fully in some locking pliers and hopefully unscrew it. Of course the system would need a full bleed once back together.

Or you could try cutting the spring out of the way and clipping the pin as far to the non threaded side as possible, remove the unattached stub of pin. This may then get you enough room to remove the pads one by one and leave you enough pin to grip firmly in some narrow jawed locking pliers, and together with a screwdriver or any additional purchase you can get on the original fitting unscrew it. Edit- ah just saw that this second approach had already been suggested.
iandusud
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Re: Disc brake caliper - advice/warning!

Post by iandusud »

gregoryoftours wrote: 24 Jan 2022, 10:25pm Would it be possible to remove the caliper body bolts plus the pin clip and split the caliper into its two halves? The pin at least should allow this because it's threaded on the head side and therefore should be completely free in one half of the caliper. Then you could grip the pin fully in some locking pliers and hopefully unscrew it. Of course the system would need a full bleed once back together.
My thinking too.
bgnukem
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Joined: 20 Dec 2010, 5:21pm

Re: Disc brake caliper - advice/warning!

Post by bgnukem »

Maybe try playing a small gas torch flame over the bolt heads, then allow to cool, the differential thermal expansion of the steel bolt and ali caliper might help crack off any corrosion products binding the head?
Stevek76
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Joined: 28 Jul 2015, 11:23am

Re: Disc brake caliper - advice/warning!

Post by Stevek76 »

I had this on the rear caliper for my utility/pub bike. Salt from roads no doubt unhelpful, since made sure the threads are greased to avoid seizing up.

The stuck one was absolutely stuck though so ultimately just drilled it out using a drill press.
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