shelbyfv

^^^ I gather people have been able to figure out what you propose. I don't think language is the problem.

thook

despite how folks come across here, there is a reason they're advising against this. people have had problems trying to do what you're attempting. if you're intent, though, that's cool. but, do get a different fork. perhaps the surly 1x1 if you have a 1 1/8 steer tube/head set. at least that way IF the rear brake fails on you ...ie. crumbles the frame (and, it very well could)... you will have a definitely safe front mechanism with which to stop.
having said that, on the rear stays, if you know a welder, you could have a strut tacked in stretching at an angle from the seat stay to the chain stay that would reduce or eliminate the chances of failure. i have seen that done. just have someone use a TIG welder and not a MIG. either a flat plate or a section of tube

Eric F 

You have made it very clear that your knowledge of bicycle mechanics is worse than your knowledge of English terminology. Not one part of your plan is a good idea.

alo

It would be easier to just buy a bike with disk brakes.

But if you want to convert, I suggest:

Don't destroy your wheels. If necessary, buy new wheels, or all the parts to make new wheels, and build them. Then if it does not work as you hoped, you have the parts to convert it back. Keep all parts in case you want to convert it back.

You should be able to buy calipers with cables and brake levers. Pads are normally included.

When doing things like this, it may not work as well as hoped for. It may also work well. Whatever the outcome, it will be a learning experience.

I would just buy a bike with disk brakes.

But I like to experiment, and do things that many on this forum would never consider. For example:

I am running a motorcycle tube in my bicycle tire.

I am using motorcycle mirrors.

I have raised the handlebars on several bikes.

There are many other things I have tried. Too many to list them all. I have learnt some things were not a good idea. Other things I will continue to use, and do again if I get another bike.

jimc101

Why? if a rim can do rim brakes, it can do discs as well, only the hub is specific, back when discs started to be come more common, a lot of 'disc' rims were just rim brake rims without the braking surface being machined. until the manufacture got around to doing disc specific ones, have a few DT Swiss rims in both rim and disc versions exactly like this, they just added a 'd' at the end of the name of the rim, No issue with other brands and build several disc wheels on rim brake rims with no issues.

oldbobcat

To "upgrade" from rim brakes to disc brakes you need

• a way to mount the calipers to the frame
• a way to mount the rotors to the wheels

JB Weld does not work. You need a frame that has disc brake mounting posts or tabs. You need wheels that have hubs with a centerlock thread or six-bolt mounting holes for the rotors. Every other consideration is moot.

veganbikes

In case someone wanders into this thread and doesn't understand the OP (original poster) this is the worst way to go about things. If you need better braking make sure you have tried high quality pads and shoes from SwissStop or KoolStop (no one piece stuff please separate pad goes into a separate holder) and good quality cables and housing like Jagwire Elite Link or Pro, something compressionless with very slick stainless steel cables (ideally polished). I would also make sure you are running linear pull brakes of quality (sometimes referred to as V-brakes, a wholly owned Shimano trademark) with the correct levers and again something of quality. Finally make sure everything is properly set up by a professional.

Beyond that if your frame doesn't natively support disc brakes, you cannot run disc brakes and cheap disc brakes even if hydraulic isn't going to be better then a high quality linear pull brake with good components all over. Adaptors aren't designed by anyone who knows what they are doing, they are designed by folks who think like the OP and just think you can slap stuff on stuff and somehow it will work properly. You will at that point need to find a frame designed for disc brakes. If you have a decent quality steel frame that is straight in good condition and know a good frame builder they might be able to add IS mounts to the frame but at that point it can get expensive and won't really do much for you. More than likely you will have stopped at the linear pull brakes. Plus quick releases and disc brakes aren't always the most ideal combination certainly work fine and plenty of people have made it work but is not ideal especially if you plan on mountain biking.

Modern mountain bikes are freakin' awesome and if you haven't ridden one go for it. Yes vintage stuff is cool and we certainly did a lot with them but if you are having such upgraditis that you are wanting to try to add disc brakes to a frame not designed for it you need a new bike. Those old bikes aren't really going to do it for you at that point, don't toss it but maybe find some easier trails or convert to a drop bar tourer or have other fun with it or keep riding as is you clearly rode it at one point in the dirt, the dirt didn't really change we just found more of it and more technical stuff.

Russ Roth

Why? I know plenty of people who refer to items, myself included, as the front fork and the rear stays. Yes, I know the difference between seat and chain stays and I've never seen a rear fork or front stays, but the term is descriptive, especially when dealing with people who don't know the difference.

Your language is fine. If you are going ahead, as others mentioned, replace the fork. Speed doesn't matter, fold your fork and the ground comes up fast at any speed. Looking at the pics your dropouts aren't thick and probably a weak point for the extra stress put on them my a disc wheel. Also, as I mentioned, a bolt-on wheel in the back will hold the adapter better then quick release. Also might want to look into BMX parts, several companies now make retrofit adapters for disc to work with bmx bikes.

DiabloScott

Did you read that somewhere legitimate? With disc brakes, during braking, the hub sort of winds up so the pulling spokes see less tension and the pushing spokes see more tension. This doesn't happen with rim brakes - but the spokes do see similar tension change with pedaling forces.

I've never seen "disk brake" rims list this as a feature, and I don't think it's necessary.

thook

i had to look that up, myself. some disc rims are advertised as being reinforced. can't say how necessary it is. not all disc rims are advertised having the reinforcement. i would say, though, as long as pimpman's rims are eyeletted, they should be fine. plenty of wheelsets sold as being compatible with rim or disc brakes

as for "front fork" terminology, sheldon here uses the reference....as well as rear fork end

https://sheldonbrown.com/frame-spacing.html

maybe english isn't his first language, though <<<caca eating grin>>>

oldbobcat

Banded bolt-on disc brake mounts will never withstand the torque to stay in alignment with the rotors. And then there's the problem of rotor-less wheels.

So why are we advising on a project that is destined to failure?

DiabloScott

It's slightly less precarious than that other method of braking... jamming your foot between the rear wheel and the downtube.
But yeah, this forum needs a thread on catastrophic results of folks who did something BF Mechanics posters warned against...with photos of broken stuff and blood... then we could just link and get smug.

Speak for yourself, spindly legs. ​​​​​​​

oldbobcat

My, but some of us have such high estimations of our wattage;

Hey, I made my point. Carry on down the rabbit hole.

thook

hey @PimpMan. I just did some reading over at mtbr.com. Check out this video. Might help you in your madness

csport

OK, so you know what you are doing and why. I shutdown and say nothing about forks failing, rotor rub, wheel ejecting from the dropouts etc.

You asked about other possible problems:

• The hub width (spacing) may not match, especially if the rear was 6 speed. Article: https://www.sheldonbrown.com/frame-spacing.html The hubs you linked are 135mm/100mm rear/front.
• Cassette vs frewheel: https://www.sheldonbrown.com/free-k7.html The ones you listed are frewheel (Aliexpress listing incorrectly spells it as flywheel). Check what you have.
• As people said, the mounts probably need bolt-on hubs, these are quick release.
• Amount of cable pull. Article: https://www.sheldonbrown.com/canti-direct.html#compat Aliexpress listing says "line pull"; probably they mean "linear pull" -- this is the synonym of "long pull".
• Maybe something else we missed.

Geepig

Ah, life in a plug and play world fuelled by aliexpress, anything seems possible.

Moe Zhoost

Yeah it sounds a bit redundant, but there is precedent for the term fork to be applied to the rear, as implied by the "fork ends" used on track frames.

dabac

+1

While there is greater force on the spokes in a disc brake wheel during braking, it is evenly distributed to half the number of spokes in the wheel. So split over 16 spokes for a 32-spoke wheel. Which means that the increase for each spoke and their attachment points isn’t much, even during a full-on stoppie.
But sure, if you have a wheel that’s kinda marginal already to begin with, maybe a few overtensioned spokes, then maybe the extra load from (hard) braking can be enough to snap something.
As could the extra load from any ride related mishap.

alo

For those who said it can't be done, or it is too difficult, or it wont be strong enough, here is an example of doing it. So it can be done. Of course, anyone doing this needs to be creative and adapt, as each bike may be different.

70sSanO

Conversion threads like these were popular years ago. I never really followed them closely, but I vaguely recall the solution was getting a disc compatible fork, like a Kona P2, and using a brace between the seat and chain stay.

The rear setup seemed to be the biggest issue as few, if anyone, would use an existing rim brake fork. Not sure if a brace and a strut to the original brake post, like the one in the posted video, will work well enough.

Of course the best solution is probably a disc front and rim rear since most braking is done by the front brake. That was, and is more common, as rim brake suspension forks are pretty non-existent.

Not cost effective on a cheap bike, but a solution for a high end vintage mtb.

John

DiabloScott

Yeah, I've seen respectable people post the same thing - even Dave Moulton in his blog once.
But it's a little like describing the driver's side steering wheel.

Amt0571

Don't do that unless you're willing to pay for facial reconstruction, a dentist or a coffin.

If you want powerful brakes with that fork, use magura hydraulic rim brakes. But whatever you do, don't mount disc brakes on a fork that's not designed for it.

Moe Zhoost

Which side is the driver's side?

Koyote

Personally, I am all in favor of PimpMan mounting this disc brakes to his non-disc frameset. And I think he should test his new setup by riding down an extremely steep hill.

If nothing else, it will get rid of some of the dross on bf.

Russ Roth

Nothing like wishing someone ill will for wanting to follow their own path. It might not be the best idea, and its at his own risk; so why wish harm?