Tell me if this is a genius idea or stupidity

[mickle]

Adapters are never as good as something that doesn't require adapters. In the case of forks, while you can use an adapter on a normal fork built for rim brakes realize to that a fork built for disk brakes has the entire length of the leg reinforced not just near the dropout at two attachment points which is all the adapter is going to do, after prolonged use of a disk brake with a fork that only has an adapter you increase the odds of the fork failing. The same is true for the rear stay. In my opinion using an adapter is mickey mouse. When a disk brake is applied the front fork will twist a bit toward the rotor side, on road bikes, due to making them as light as possible, even disk brake forks are seeing more twisting, this isn't as evident in more stout bikes but even with mountain bikes they still had to reinforce the forks; this twisting thing is also one of the reasons why there is more issues with spokes breaking.

https://www.velonews.com/2017/04/bikes-and-tech/technical-faq-disc-brake-wear-fork-twist_434593

https://janheine.wordpress.com/2018/07/12/myth-12-disc-brakes-work-better-than-rim-brakes/

Now having said all of that the original poster said the brakes were be put on a touring bike to which I must assume he tours on. Touring in developed countries having disk brakes is not an issue should you need parts, but in third world countries finding parts for a disk brake system could be a huge issue; a V brake, or cantilever brake is much more simpler and parts would be easier to track down. Also with disk brakes if you're rotor gets bent you'll probably be walking, and if you're in a third world nation when that happens you will be walking for quite a ways.

Not an adaptor, a braze-on.

 

[T4tomo]

If it were front you were talking about, I'd say definite no no given the fork isn't designed for it, however a steel touring bike rear triangle won't have suhc issues.

Have you tried decent brake blocks, koolstop salmons or mixed compounds transformed the braking on my old Peugeot.

Discs aren't as forgiving as a drum brake in terms of being constantly used on a long drag, but if you have a.lever then you can pump it a bit and use alternately with the rim brakes.

If it doesn't work, you can just remove it all. Be mildly interested to see if it does work

 

[Deleted member 26715]

I actually don't understand your problem & why you are trying to do what you are trying to do, but if you use a disc brake which you are leaving on so it causes some friction, that will cause heat which will then cause the disc to expand which will then mean the friction will increases causing more heat, so you may find that once you have to put your brake on you will then ease it off, but the issue with that is the disc will then cool therefore meaning the drag will reduce so you have to put it back on.

 

[mickle]

Three brakes will always dissipate heat better than two.

 

[Deleted member 26715]

Sorry so this is not a trailing brake to be used on long descents but a 3rd functional brake to be used just like any other brake?

 

[Illaveago]

Could you get a secondhand pair of disc front forks which would fit your bike and then braze some mountings on for your favoured brakes ?

 

[winjim]

What I want someone to invent is a dynamo hub with variable drag (and therefore power generation) that could be used as part of a drag brake come energy recovery system. I am aware this doesn't answer your question.

 

[Illaveago]

I was thinking that a friction lever wouldn't be much use as once the brake was applied the brake material would wear and would then be less effective, allowing the bike to speed up. It would have to be a sprung loaded device that once applied would give a constant pressure to the brake.

 

[mickle]

I was thinking that a friction lever wouldn't be much use as once the brake was applied the brake material would wear and would then be less effective, allowing the bike to speed up. It would have to be a sprung loaded device that once applied would give a constant pressure to the brake.

I don't imagine there would be enough wear during one descent to have an effect on the brake's power. And even if it did I could just reach down and adjust it.

 

[mickle]

What I want someone to invent is a dynamo hub with variable drag (and therefore power generation) that could be used as part of a drag brake come energy recovery system. I am aware this doesn't answer your question.

KERS for bicycles.

 

[mickle]

Sorry so this is not a trailing brake to be used on long descents but a 3rd functional brake to be used just like any other brake?

Drag brake.

 

[winjim]

KERS for bicycles.

Exactly.

 

[TheDoctor]

If I'm reading Mickle correctly, he's wanting to have a disk brake at the rear, so considerations of the front fork are ill elephant.
My concern would be that back brakes are nearly always good enough to lock the back wheel anyway, unless I'm missing something.

 

[Deleted member 26715]

Drag brake.

Terminology I apologise, but my points still stand, the issue with using discs for this purpose will potentially be heat & disc expansion causing the 'drag' to increase as the disc warms up.

 

[froze]

Not an adaptor, a braze-on.

Not an adaptor, a braze-on.

Ok, but you would still have the same problem because it only reinforces the end portion of the dropout area and not the whole fork blade or rear stay if it's for the rear.