tornado60

I got a bike I want to mount a rack on. Problem is my disc brake is occupying the mount wholes on one side. Can I attach both to one using a longer screw?

cxwrench

What are you talking about? The rack only needs one hole per side and you have that one hole available. You just need a disc brake compatible rack.

BCRider

There's a threaded hole there. So it's perhaps blocking the hole but it's not being used. So you need to tweak the arms of the rack and get a spacer tube and a longer than usual screw. The only true problem might be if your rack wants to put one of the supports through the middle of the lump of the caliper body. If that's the case you might need to find a different disc compatible rack or figure out a more dramatic mod.

SoSmellyAir

I do not own a bike with disc brakes so the following is not a definite answer.

Common sense says no. Even if you get both the disc brake caliper and the rack mounted perfectly initially, any load thereafter on the rack may also shift the disc brake caliper and cause you braking issues.

jimc101

For a frame with the caliper mount on the seatstay, this is the only real option, frame designs for anything which may take a rack have moved to inboard/chainstay mounting, which don't use a disc specific rack

BCRider

That would be the wallet and shopping option for a solution. For those with some suitable tools some of the regular rack designs might be able to be modified.

oldbobcat

Good luck with that.

As long as you need to buy a rack, buy the right one for the job. Nearly all the major accessory vendors have them now, and most of them don't cost more than the wrong ones. It won't break or interfere with your brake. But, yeah, use the hole that the caliper isn't using.

For strength and ease of installation, I recommend this one: https://road.cc/content/review/bontr...isc-mik-295655

But I highly recommend cutting the "tails" off the seatstay connectors using a hacksaw or pipe cutter.

tornado60

I am wanting to make the rack I currently have work. This is a winter bike build so trying to do it using as many parts I already have as possible. Yes if all else fails I can buy one that will reach that inside slot. My question was if there was any reason why connecting all three in one slot would be a problem? I can keep the brake and frame the way they are now, and just add the rack to the outside.

FBinNY 

The problem with the simplest solution --- using a long screw for both brake and rack is two-fold.

1- Isolating the rack and caliper so both are independently secure. This is easily solved by using the screw more like a stud, and using a nut to secure the brake, then spacers or a second nut inside of the rack, finishing with a nut to hold the rack.

2- the bending moment the rack will apply to whatever hardware is holding it outboard of the frame eye. This isn't easily solved because both the frame and rack assume that any mount will have direct contact with the load on the screw being pure shear. Once the load is away from the eye, it creates bending moments on the screw which won't be up to the task. This is the killer, but might be solvable using a solid larger diameter (1/2" or more) spacer block between the brake and rack. Care must be taken to ensure that the spacer has a solid purchase on the caliper so it cannot deflect downward under load. Now, would be bending moments lever off the spacer's edge, changing to tension on the screw. Note, these tension loads will be more significant than the shear of conventional mounting, so a high strength allow bolt or cap screw is highly recommended.

FWIW- despite my suggestions which are about the possible, I'm not a fan of any weight bearing rack member being mounted indirectly to the frame. Besides the static load, one must consider dynamic loads of bicycles bouncing off potholes or other road hazards. Over the years, I've seen too many rack legs break or break loose on tours and the consequences are often much more severe than inconvenience. So, unless you're comfortable in the design and execution of any improvised solution, I urge you to go with a proven design made for the job.

In short, That you can doesn't mean that you should.

jimc101

Not really, having the disc on the seat stay as the OP has, means the rack needs to be far wider than a non-disc/normal rack to clear the caliper, you may get away with bending/spacing out a steel rack (it won't look good), but most low to mid-range racks are aluminum, and really don't like being bent, buy the time you have bent and broken an alu rack, you may as well have just bought a correctly spec'd one in the first place, as they should cost the same