Brake caliper allen key bolts stripped.

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largeallan
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Joined: 10 Jan 2010, 2:31pm
Location: Isle of Arran

Brake caliper allen key bolts stripped.

Post by largeallan »

HELP!! I've stripped out the head of the bolt that holds the caliper to the frame on tektro oryx cantilever style
brakes.They are a 5mm allen key button type head, obviously made of mild cheddar.
Can anyone tell me if these are a standard bolt on most bikes as I've now entered the minefield of buying bolts.
Where can I find suitable decent quality 'bike specific' replacements?

Thanks, Al
Jdsk
Posts: 24636
Joined: 5 Mar 2019, 5:42pm

Re: Brake caliper allen key bolts stripped.

Post by Jdsk »

1 Yes, they're probably standard. Check if they need some unthreaded shank.

2 Do you have a way of identifying the thread? Would you like some hints?

3 Trusted suppliers include:

SJS Cycles, which would support bike-specific discussion if needed:
https://www.sjscycles.co.uk/nuts-bolts/

Kayfast:
https://www.kayfast.co.uk

Namrick:
https://www.namrick.co.uk

Michael Lee:
https://www.finecheesesltd.co.uk/farmhouse-cheddar/

Jonathan
rjb
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Joined: 11 Jan 2007, 10:25am
Location: Somerset (originally 60/70's Plymouth)

Re: Brake caliper allen key bolts stripped.

Post by rjb »

Have you managed to remove the bolt. Sometimes hammering a tork bit into the head gives it sufficient purchase to enable removal. Flood it with penetrating lub before removal. Depending upon the mount you may be able to lub it from behind. The bolts are generally M6 threaded, widely available from several sources, Toolstation and Screwfix spring to mind as possibly being the most convenient. Try and get ones the same length as the ones you remove. You don't have to have an Allen bolt, a standard bolt will suffice, which you can remove with a spanner. :wink:
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
Barrowman
Posts: 441
Joined: 8 Jan 2022, 6:35pm

Re: Brake caliper allen key bolts stripped.

Post by Barrowman »

I generally use Stainless Steel rather than mild steel. Less prone to rusting in .
If you can't get a Torx drive to fit (as per prior post) you could carefully hacksaw a slot for a screwdriver or file flats (tricky, you need a file with a plain side to go up against the calliper) for a spanner .
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NATURAL ANKLING
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Re: Brake caliper allen key bolts stripped.

Post by NATURAL ANKLING »

Hi,
These were generally be M6 hexagon socket caphead screw.

I would generally say don't use stainless steel On critical safety components, but as they are M6 And generally in sheer force, You're probably going to be okay, they normally tighten into the aluminium disc caliper carrier.
Make sure the bolt is long enough and if there is a shouldered portion it doesn't foul in the thread.
Generally need 1 1/2 times the diameter of the thread insertion into the female component.
I find nowadays it's common practice for me to use low strength thread lock agent on a lot of bolts especially ones to do with breaking systems, not only does it retain the fastner but also it seals the thread so you don't get corrosion!
(The corrosion bit is a method that Brucey always recommended)

All bolts on the disc caliper mounting and the disc caliper carrier (bracket with four holes) should always have thread lock as standard, this would normally be a medium strength, and the specific bolts use normally come with thread lock agent already applied to the thread.

Always Good idea to use thread lock Agent and not over torque the bolts.

On the M6 bolts, if you apply a liberal coating of low strength threadlock agent, this is normally good enough to retain the bolts safely.
A-medium strength thread lock agent, should be applied with just enough fluid to retain the bolts safely.

Is it good idea to test out the theory so you know that the application will be reliable in future.
Clean the bolt threads apply thread lock agent leave for a few hours then make an attempt to remove.

You will soon get an idea of how much of the stuff to use.
On poor and low-grade stuff that's bicycle parts you might find an indication there is thread lock agent but it is insufficient due to poor quality of the threads to retain the bolts securely

On the net on the "Loctite" specification sheets there is a warning about size of thread!
On threads above 20 mm or thereabouts you will find that if you apply medium to high strength Loctite removing the bolt might prove impossible!
Applications and thread sizes are normally recommended on the lock tight website in the specifications.

Edit it for very poor grammar :oops:
Last edited by NATURAL ANKLING on 17 May 2022, 2:12pm, edited 1 time in total.
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Jdsk
Posts: 24636
Joined: 5 Mar 2019, 5:42pm

Re: Brake caliper allen key bolts stripped.

Post by Jdsk »

NATURAL ANKLING wrote: 17 May 2022, 2:00pmOn the M6 bolts, if you apply a liberal coating of low strength dreadlock agent, this is normally good enough to retain the bolts safely.
And would be very natty.

; - )

Jonathan
largeallan
Posts: 339
Joined: 10 Jan 2010, 2:31pm
Location: Isle of Arran

Re: Brake caliper allen key bolts stripped.

Post by largeallan »

Thanks for your help cats! I managed to get it out with mole grips. It was half out before I destroyed it.
The other three bolts seem fine.....anyway, I've ordered replacements all round.
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531colin
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Re: Brake caliper allen key bolts stripped.

Post by 531colin »

They are ordinary M6 bolts.....if you Google "cantilever brake stud bolts" you get loads of hits.
I recall somebody (might it have been Brucey?) posting on here that the "fragile" bit of this assembly isn't the bolt, but is in fact the boss the bolt screws into.
The bolt is M6.....the bit of the boss that the brake pivots on is 8mm diameter, so if everything is accurately made the boss has 1mm wall thickness, with the thread height in addition. .....thats not a great deal of metal to start hammering TORX bits into rounded-out Allen sockets.
I think a recommendation was to make sure the bolt went as far as possible into the fixing, certainly into the bit thats wider than 8mm (I think the next bit is 10mm!).....however, the bolts supplied with cantilever brakes aren't long enough to do this, and I have never seen a canti. brake stud fail by the 8mm diameter bit breaking.
(The old Mafac canti studs had a bent sheet metal base, with the stud peened over into the base.....the framebuilder was supposed to braze it all up, but this didn't always happen!)
I suspect in the days when mountain bikes had canti brakes, and it was the height of fashion to replace bolts with anodised ali ones, people used to use ali. bolts to retain canti brakes.....
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NATURAL ANKLING
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Joined: 24 Oct 2012, 10:43pm
Location: English Riviera

Re: Brake caliper allen key bolts stripped.

Post by NATURAL ANKLING »

Hi,
Forgive me I thought we were talking about disc calipers I must've had it on my mind :P

If we are talking about the M6 bolts that are used on cantilever brakes and "V" brakes.
Then these bolts are normally quite long but are threaded all the way up to under the head.
There is no real force on these bolts during operation, but if you left them off you probably lose the brake parts :mrgreen:
just make sure they're degreased on the threaded parts and you use some thread locking agent.

Like 531 Colin says M6 bolt with an eight mil spigot just gives 1 mm Of wall thickness.
So there's no need to get them up really tight as long as you've got some thread lock on there.
NA Thinks Just End 2 End Return + Bivvy - Some day Soon I hope
You'll Still Find Me At The Top Of A Hill
Please forgive the poor Grammar I blame it on my mobile and phat thinkers.
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