Plate to fit a disc brake

[nobby]

I have a plate that P clips to the chain stay and takes the calliper for a disc brake.

Has anybody used, or is using one of these, or knows if they are safe, please?

[giropaul]

So the frame isn’t designed for disc brakes? Steel/ alloy might be worth the risk, but I wouldn’t. Carbon never ever. Frames for disc brakes are specifically designed for the stresses involved ( or at least, should be).

[LittleWheelsandBig]

I’ve seen disc brake adaptors mounted on seatstays with the mount extending a very long way up. Chainstays are stronger than seatstays but the applied forces relate to disc size and mounting location. If it was a beefy steel frame, I’d probably have not too many qualms about using one but would be dubious otherwise. What does this adaptor and frame look like anyway?

[Brucey]

this is a properly designed disc brake adaptor (A2Z);



it reacts the (potentially considerable) brake loads into the axle and one of the canti-bosses.

By comparison 'P clips round the seat stay' is not a phrase which inspires confidence.

cheers

[nobby]

I had it in my hand the other day and now I can't find it but I think I'll give it a miss after the explanations here.
Thank you all.

[grams]

They’re quite a common item on Ali Express, so someone must be buying them:

https://aliexpress.com/item/33007413535.html

I have one. It didn’t match the dropout shape on the bike I wanted to use it on, so it’s in a drawer somewhere.

Maybe all the others bought end up in the same place.

[DuncanM]

That looks insane, especially the picture of one on a carbon fork! I hope their photos have been flipped - they all seem to be mounted to the right side of the bike, meaning that instead of the braking force pushing into the stay, it's pulling away from the stay and potentially pivoting about the axle and putting all the force through the P clip.

[nobby]

They’re quite a common item on Ali Express, so someone must be buying them:

https://aliexpress.com/item/33007413535.html

I have one. It didn’t match the dropout shape on the bike I wanted to use it on, so it’s in a drawer somewhere.

Maybe all the others bought end up in the same place.

Well, the P clip and two holes seem familiar but that's all which doesn't mean that it isn't exactly the same. I've just been for another look and I'm now wondering if I threw it out. Ntw.

[PaulF]

I think the rear one is definitely flipped - the chain is obviously on the opposite side.

There's a good case for having the front brake on the right side of the fork; that way braking forces will push the wheel into the forks rather than ejecting it.

That said both the front and rear ones look very prone to getting knocked out of alignment and the rear one appears to be shimmed with blocks of wood! o:

[andyoxon]

They’re quite a common item on Ali Express, so someone must be buying them:

https://aliexpress.com/item/33007413535.html
...

One of those images apparently shows short wooden sticks under one of the brackets...   

[Torslanda]

Have only ever used two types of disc brake adapter.

The first is the Trek/Fisher unit that was designed to mount an ISO caliper to the rear dropout of a c.2000 frame.

The other is the A2Z adaptor which will fit 'any' frame - as long as it has a flat dropout.

I'm very dubious about the ability of band clips - which you would only use normally to mount bottle cages and so on - to dissipate the loads generated into thin walled tubing.

Based on nothing more than opinion but I won't use one.

[nobby]

Have only ever used two types of disc brake adapter.

The first is the Trek/Fisher unit that was designed to mount an ISO caliper to the rear dropout of a c.2000 frame.

The other is the A2Z adaptor which will fit 'any' frame - as long as it has a flat dropout.

I'm very dubious about the ability of band clips - which you would only use normally to mount bottle cages and so on - to dissipate the loads generated into thin walled tubing.

Based on nothing more than opinion but I won't use one.

I haven't found it but I have given up looking; to save myself from myself 

[LittleWheelsandBig]

That Aliexpress abomination looks like it has been ‘engineered’ using a crayon and guesswork.

[Mr Larrington]

I've got a different incarnation of the A2Z on the Towpath Bike, which has a Trek aluminium frame.  No issues in service save that you have to remove the q/r skewer entirely before taking the rear wheel out, with resultant loss of Jesus springs in the long grass.  It doesn't have the arm connecting to the canti boss.