How to restore broken rear disc brake mount in carbon frame?

Question

Look at the image:

Bike model is Rocky Mountain Vertex 990. The frame is broken in a way that it's impossible to install rear disc brake. Possibly there may be a frame deformation. Is it even possible to restore the broken parts and install the brake? How must does it cost and how the process looks like?

It's from local marketplace portal and seller wants $1050 for the bike (4500 PLN). Trying to figure if it's profitable to buy it even for parts.

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Update: Finally I purchased this bike and will see... I'm impressed of its lightness, maneuverability and behavior in terrain. I got few offers to fix the frame: $170, $230 and the most expensive for $280 with 2-year warranty. One company refused because it's too risky.

Answer 1

Why would you buy that bike?

The disc brake mount is gone, and I wouldn't trust any repair because brakes are a safety-critical item. If there's some part of frame you won't repair it's broken brake mounts.

1050 USD for used parts you have to remove from an existing bike doesn't sound like bargain. Also you will be getting whatever parts the bike has, not the parts you want. It's probably a far better idea to just buy new spare parts as you need them one by one. Then you will get exactly the parts that are best for your uses.

Answer 2

There are few hard-and-fast rules when buying used items, but there are plenty of things to consider.

1. Why does the seller not want to fix it? Perhaps it can't be fixed, or the repair would cost more than the replacement frame.
2. If it were repaired, could it break again in a similar way? Partially dependent on the quality of the repair, but some damage comes from poor design.
3. What else can go wrong? You're gambling the cost plus the repair cost that nothing else is wrong with the item. Perhaps the front disk brake mounts are of similar quality and are liable to do the same, so multiply the single repair cost by four and decide if its worthwhile.
4. Bikes are still being made - explore what else you can get for your money that doesn't have this liability. Add the price plus the repair cost, and possibly your time to organise all this.

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It's not all bad news. Some other options:

1. If the bike takes a rim brake on the rear wheel, you could simply fit a caliper brake and a cable-based rear brake lever. Not ideal, but workable. Some bike frames had V brake mounts too. Not possible on this example, but future readers might have a different setup.
2. If you choose to ride around without a rear brake, that would be inadvisable and dangerous to you and to others. Not recommended.
3. If the repair is too expensive but you already bought the bike, then you could part the bike out - seems it came with a SRAM X01 groupset but with Shimano XT hydraulic brakes, and some fancy Stan's wheels and a Rockshock fork. It may recoup some money to strip, clean and onsell parts. Or you could put the parts onto another of your own bikes.

Start by getting a quote for repair, from a carbon fibre repair specialist who is in your locality. They will definitely want to see the frame, so try and borrow it to take with you.