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Brakes Slider pin and bolt breaking when tightening

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BlueCan

New Member
Sep 9, 2021
14
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Australia
I’ve recently changed my front pads and rotors. The left side was fine, the right side is what gave me issues which is detailed below.

Changing over the pads and rotors itself went smoothly and I was able to do that like normal.

Now the issue I was running into is when tightening the bolt that goes with the slider pin for the caliper, the bolt has kept on breaking. It happen twice and I’ve had to wait for them to be ordered in as the car was not drivable with the caliper not being bolted on.

Note, I’ve been using a torque wrench with recommend spec of 21 N.m for tightening and this has still broken the bolt.

I finally got it fixed on the third try but don’t want to encounter a similar issue in future when I have to change over the pads again.

Any idea what may be causing this issue ? The bolts seems very soft that go into the slider pin.

I haven’t been able to find any aftermarket stuff that is stronger to use. And the oem part is like $20 a piece.

The part numbers are as follows:
581631G000 - caliper pin bolt
581611H000 - brake front guide

Let me know if anyone else has run into this issue.
 
Hi,
Very strange story.
I have often changed brakes on different cars and never had problems with the screws.
In general I don't use a torque wrench for these screws. They never came loose and you have double safety with loctite for used bolts or the OEM antiloosening stuff on them if they are new.
No problem with reusing them with middle loctite so far at other cars.

Didn't do the job on my i20n yet.
Before buying multiple times a new one for that crazy price I would have checked if a nother normal screw with correct thread would work.

In general: grease or other stuff on threads will increase the Stress in the screw while measuring the same torque with the wrench. So, more force more stress. Dangerous.
Either clean the threads thoroughly or decrease torque spec with the wrench little bit
 
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Breaking as in snapping or rounding off? I have changed pads myself twice now and noticed indeed that the bolt tends to round off if you don’t keep the wrench steady with your hand, they probably are not top notch quality... I torque down to 30Nm, which is on the high side of the suggested range (21-31), but I do not add loctite as there is still some glue from the factory which does not go away even by brushing it off…
 
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Hi All

@X-i20N, I might try not using a torque wrench in future, I have a 2-20nm torque wrench which I used initially. On my third go I just used an ordinary wrench which did the trick.
The figure of 20nm came from the service sheet for these parts, see figure attached. And thanks for those specs related to steel used on the bolt. Also, any idea what type of steel is used in those bolts?


@Jerome92, it snapped off, also had to get a new slider pin the first time as I couldn’t get the snapped off bit out of the pin hole.
 
Measure the bolt, maybe the sheet is wrong. Wouldn't be the first time.

An other explanation would be that the material is exhausted through excessive heat treatment of breaking.

I guess it is 8.8 material or 10.9 which is normally used and okay.

If this happened with a new bolt, check your torque wrench.

If it is 2-20 then normally it working area is 5-17 for example, the often won't work properly if go to lowest or highest setting. You may simply over torqued it. Or the wrench even clicked on your 20 / 21 setting and made 25 or 30Nm
 
Im confused. Maybe it's a M8 thread and therefore defined with 20-30 Nm?
What are the other numbers in the ( )

edit:
Okay foot pounds...
I checked that in most other cars on which I did brakes, these screws are M8.
Maybe also on I20N and the they should not snap.
I would try get the same screws from aftermarket brand.

Maybe you could do us a favour and make measurements.
Length, length of pitch, diameter, diameter head and have a look of there is an info for the strength grade on it.
Then we can learn and get new better screws for the future job
 
Last edited:
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With a slightly experience on working on Machines you get a feeling for torque.
20 Nm is quite strong with a little and nothing with a big wrench. I think that the torque wrench is defect.
You feel if it gets strange and too strong
 
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