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Shimano 105 Hydro Caliper Bolt Replacement

by 0-0
Sat, Nov 13, 2021 17:40
15

Has anyone replaced their hydraulic caliper bolts with regular M6 cap head bolts, instead of the overpriced/soft of sh1t official ones?

I've rounded off the hex key hole (with using ball head hex keys), and just wondered if I can replace the bolt with any cap head bolt, as long as it's the correct length.

Official Shimano product codes are Y8PU08010, Y8PU08020, Y8PU08030 (depending on length).

Thank you.

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.

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15 comments

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Cycologist | 3 years ago
0 likes

Replaced the rear caliper M5 bolts with stainless M5 hex bolts on a jump bike (SHIMANO SLX caliper and lever), torqued correctly and blue locked - no problems.

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Creakingcrank | 3 years ago
2 likes

I've just done a similar replacement on one of my bikes. The brake was a low end Shimano MTB hydraulic brake, and the bolts replaced were two low profile M6 cap head screws holding the post-mount adapter to my IS frame.

In my case, the orginal bolts fell out, resulting in a rather scary brake failure as the whole calliper lifted away from the frame and rotated with the disc (luckily low speed and back brake so no harm done).

(This sort of thing probably less likely to happen with modern flat mount brakes as braking action will push the caliper against the frame)

One of the original bolts was lost, but the second was still dangling from the hole. I suspect the failure had had been looming for some time.

Reason for this post: Looking at the remaining orginal Shimano bolt, it has a tiny hole drilled through the head. This is designed to take a wire, which you thread and wrap between the two bolts such that if one loosens, it tries to tighten the other. Shimano disc brake installation instructions explain this well.

This wire had not been installed on my bike (which was a factory build). I suspect it rarely is, although it is supplied with Shimano aftermarket brakes. 

Moral of story: Don't be like me. Inspect your bike every so often to ensure critical bolts are tight. There's clearly redundancy built in as I was probably riding around with a missing bolt for some time and didn't notice a thing, but I could have prevented the issue with proper vigilance.

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Cycologist replied to Creakingcrank | 3 years ago
0 likes

Yep, sensible advice, imo. Inspect your torque settings.

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0-0 | 3 years ago
0 likes

Thank you both for your replies, and the confirmation that "regular" bolts will do.

*** Edit ***
The bolts are M5, not M6.
30mm in length for the back brake. I also used the "thick" washer for the original bolt.
15 or 16mm in length for the front brake.
These lengths may differ if your frame is wider.

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zeeridesbikes replied to 0-0 | 3 years ago
1 like

Ultegra ones are the same, I replaced mine with a split pin. 

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0-0 replied to zeeridesbikes | 3 years ago
1 like
zeeridesbikes wrote:

Ultegra ones are the same, I replaced mine with a split pin. 

Thanks for the reply.
Sorry for the confusion. I was talking about the bolts that attach the brake caliper to the bike frame, not the bolt that goes through the brake pads.

But I've had to replace that bolt too, as it's made of cheese.

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Pilot Pete replied to 0-0 | 3 years ago
2 likes

There is a solution to your bolt issues, and I'm not being facetious.

Use coppaslip grease on the threads. Torque the caliper bolts to the correct setting so as not to over tighten. Use a well fitting hex key, not the ball end to undo and they shouldn't get damaged.

For the 'cheese' slotted head pad retainer bolt, again use a dab of coppaslip on the thread and don't do it up too tight - the circlip will prevent it coming out - so just nip it up. 

I've never had an issue with any of those bolts using that technique, they simply don't seize and require excessive force to undo.

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0-0 replied to Pilot Pete | 3 years ago
1 like
Pilot Pete wrote:

There is a solution to your bolt issues, and I'm not being facetious.

Use coppaslip grease on the threads. Torque the caliper bolts to the correct setting so as not to over tighten. Use a well fitting hex key, not the ball end to undo and they shouldn't get damaged.

For the 'cheese' slotted head pad retainer bolt, again use a dab of coppaslip on the thread and don't do it up too tight - the circlip will prevent it coming out - so just nip it up. 

I've never had an issue with any of those bolts using that technique, they simply don't seize and require excessive force to undo.

Thank you again for your words of wisdom 😀
Sometimes I need to learn the hard way, when I should be doing it the correct way.

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wycombewheeler replied to Pilot Pete | 3 years ago
0 likes

Pilot Pete wrote:

For the 'cheese' slotted head pad retainer bolt, again use a dab of coppaslip on the thread and don't do it up too tight - the circlip will prevent it coming out - so just nip it up. 

It shouldn't be necesarry to remove the bolts on a new bike to apply copperslip so that when the pads wear out the caliper isn't dead. But it seems it is.

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Pilot Pete replied to wycombewheeler | 3 years ago
0 likes

Indeed. But you could say that of every bolt, then ride it for 3 years dripping sweat and energy drink all over them, covering them in road salt, etc etc. It's hardly difficult to remove the pad retainer bolt, coppaslip it and replace it. 5 min job at most.

I do stem bolts, bottle cage bolts, hanger bolts and seat post clamp bolt(s). Once done they can be removed and refitted several times without issue or extra greasing.

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wycombewheeler replied to Pilot Pete | 3 years ago
0 likes

Pilot Pete wrote:

Indeed. But you could say that of every bolt, then ride it for 3 years dripping sweat and energy drink all over them, covering them in road salt, etc etc. It's hardly difficult to remove the pad retainer bolt, coppaslip it and replace it. 5 min job at most.

I do stem bolts, bottle cage bolts, hanger bolts and seat post clamp bolt(s). Once done they can be removed and refitted several times without issue or extra greasing.

More of a grumble about the manufacturer or bike shop assembling bikes in this manner. Such that the customer 2 years down the line when replacing pads, finds they can't

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zeeridesbikes replied to 0-0 | 3 years ago
1 like

Ah ok, I managed to round that one off too on the rear but I thought that was down to poor quality tools. Had to replace it but the OEM part was really hard to get. 

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wycombewheeler replied to 0-0 | 3 years ago
1 like

0-0 wrote:
zeeridesbikes wrote:

Ultegra ones are the same, I replaced mine with a split pin. 

Thanks for the reply. Sorry for the confusion. I was talking about the bolts that attach the brake caliper to the bike frame, not the bolt that goes through the brake pads. But I've had to replace that bolt too, as it's made of cheese.

I've seen harder cheese

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IanMSpencer | 3 years ago
1 like

Any decent quality bolt would do of the right length.

When I did bike repairs I ordered a few boxes of the things for repairs - refurbing old bikes, bolts could get quite corroded so I'd prefer using a new one (a new bolt can also be quite useful for re-tapping the thread in a slightly damaged frame fixing without going the hole hog with thread tappers which can be too aggressive).

Not sure where you can get individual ones at a reasonable price though.

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mike the bike | 3 years ago
2 likes

Wiggle supplied the wrong length bolts when I built my current 105-equipped bike.  They didn't have the correct length in stock so told me to order from SJS and they paid the bill, a shocking £7 each.

If it had been my money I would have found some handsome stainless substitutes at about 50p a throw.

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