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I have a crack around the top mount hole of a Shimano Zee brake off my street/trials bike. I suspect it's been around for quite some time but I assumed the noise was pad rock (duh!) but it's held up.
crack:
So given that it's held up for so long with a crack in it (with a useless trials rider hopping the bike on the rearwheel) I'm thinking it would be a fine upgrade from mechanical disc brakes on my commuter. Even better if I repair it.
From quick research, and assuming it's made of some kind of aluminium alloy, the options seem to be glue/bond or TIG weld. I suspect welding would put too much stress on the caliper potentially rendering it unusable.
Oxidisation is a problem with bonding aluminium, so can't just squirt glue into the crack and clamp. Advice I saw was to grind out to remove layers of oxidization, and add more material in.
My loosely formed plan so far is to cut through the crack with a hacksaw, and glue a piece of aluminium strip of same width inside. Probably some kind of super glue.
Any holes in this plan that you see?
To reiterate, it just needs to be strong enough to assure me of its safety while on my daily commutes in the flatter parts of Kent, I'm not going to be sending it down Fort William 🙂
TBH, I'd just bolt it on and use it.
Well yes there is that, which in effect was good enough for the past year 😳
For a commuter snap. Maybe with a little chemical metal around the crack. Use the stuff on my kit cars all the time. Although nothing under serious load but its amazingly strong when set.
On the back of a commuter? Just use it.
The repair you suggest is a bunch of faffing about for little/no gain.
I'd seal it with some paint to stop the oxidation worsening, only use it on the back, use a big washer under the bolt head and find a brake mount that has the best supporting area for the underside.
TBH, I’d just bolt it on and use it.
This. You have no chance of repairing it. Just don't overtighten the bolt when you fit it.
Personally I'd bin it. Safety first second and third. You can already see that its spread.
How much is a new caliper?
Personally I’d bin it. Safety first second and third. You can already see that its spread.
For a proper MTB being used for proper MTB riding - absolutely agree.
On the back of the commuter I think that'd be fine, because loads are down and the mode of failure would be sub-critical.
Thanks for feedback.
paint to stop the oxidation worsening, a big washer under the bolt head
Sounds sensible... I want to use it on the front though! Still thinking about gluing something. Maybe a strip of metal on the side of the crack just to support it and help prevent it spreading. I'd need to upgrade the shifters on the commuter to go hydraulic anyway as currently the gear and brake levers are integrated in the same unit, so no rush.
On the front?!
Nope. Thats a step too far IMO.
Can you not swap the front and rear caliper so you have something safe at the front?
Maybe a strip of metal on the side of the crack just to support it and help prevent it spreading
You won't be able to repair it unless you weld it. Just buy a new caliper, they aren't that expensive.
You might be able to drill & tap then put an M3 grub screw or bolt at the side of the caliper mounting slot to keep the crack from splaying out as you tighten the caliper bolt down, careful you don't drill too deep though, judging by the recess left from the bolt head or undersized washer, overtightening caused that crack.
I’d glue a strip that’s bent around the whole square bit or even better bend a bit of metal going up the sides and over the top of it, with a hole for the screw glue it all over. Mind the threads though.
I had cracked lever clamp on an old set of hope xc pro’s. Local to me metal shop welded it for £5 I cleaned it up and used it for many more years.
No way I’d have that on the front in traffic. I’m not even sure the forces are lower on the road than mtb or trials
Yeah- not on my commute! Just bin it
A large washer to span the cracked area and it will probably be fine ,front or rear.
When you look at earlier mounts, for example I.S. on bombers, there really isnt much metal on them. They're quite thin and a bit flimsy looking, but they were fine and worked and to be honest, i cant remember ever hearing of such things shearing off or anything like that.
So the thick metal on the calipers today are probably more robust.
Aluminium oxidises very quickly so I'm not convinced that glue would be a good choice. Welding destroys the oxidised layer and is the better choice, but you'd probably need to heat sink the caliper to protect o-rings and seals
My choice would be the bin, but you could try a serrated washer if you're determined to re-use the caliper