I'd like to hear some feedback on the pro's and con's of retro-fitting disc brakes to older (90's) steel frames not designed for them. Is it possible, desirable?
I've never done this, but I considered mounting disc brakes on an old Peugeot frame I have. brazing on a disc tab on the frame is relatively easy. On the other hand, putting a disc tab on a fork that was not designed for discs is potentially dangerous.
It's probably a bad idea since the chain stays and seat stays were not designed to take those type of loads from the braking force. You'll notice many non carbon frames have a brace between the seat stay and chain stay to strengthen them. I suppose a knowledgeable frame builder could add a brace to strengthen the area, but it just seems like a lot of effort and money when you could just get a new frame.
Rear bridge with brace is pretty easy to do unless you have some kind of weird dropout. If it has track ends then you might have to take the brake off to remove the wheel.
For the front, just buy a new fork.
If you know the right people and get lucky on eBay you might be able to do all this for $100 but realistically I could see this being $300+.
It is certainly possible and could be desirable depending on what you're converting. It's been done on a lot of mtb's. The thing is, as you are converting an old Peugeot road frame, there might not be much room. I would take the frame in question and toss a disc wheel in there and see how it all fits together. Is the rear spacing on the Peugeot 126 or 130? If it's 126, a 135 disc will be tough to get in there. The front is likely 1" headset and finding a road disc fork in compatible A-C and 1" will be interesting.
Anything is possible with enough money, but why? Good cantilever brakes set up properly work pretty darned well for a lot less money than you would spend potentially ruining your frame and/or making it unsafe by changing it to disc brakes.
earlethomas wrote:Actually, nalax, the bike I am considering is a Marin Bobcat Trail from the early 90's, but I don't have it yet...
Are you getting this bike for free or something? Changing a frame to accept discs is too much work, it would be a lot easier to just get a frame with disc brakes.
I've seen it done and honestly the frames just are not setup to take the exceptional stress level discs place on a bike. You can actually see the chain stay deform under heavy load. Definitely NOT a good idea on non-disc forks.
nalax wrote:Googled 1990's Marin Bobcat Trail. It's a low end mtb and would not be worth the $ to modify or upgrade.
The thread should have been locked after the response from nalax.
10 seconds of searching shows that these bikes sold for ~400USD new. The bike is at least 20 years old and worth less than most new tires. There is absolutely no acceptable reason to retrofit disc brakes to it.
