Dumb Ogre (and Troll, and ECR) rear brake question
Ok, so Surly says that the max rotor for the rear of the Ogre is 160mm, and requires the included adapter.
I'm not completely understanding this, but there's probably something I need to learn.
I'm running fenders and 60mm tires, so I have my axle set back with one set of monkey nuts. In this position, I can fit a 180mm rotor by just sliding the adapter forward in the slots. Is there something wrong with this arrangement?
Or alternatively, is there a reason one couldn't consider adding a standard spacer to allow 180mm or even 203mm rotors?
Or, finally, the Surly adapter looks a great deal like a lot of standard disc brake adapters. Does anyone know what the differences are, and if another adapter could be used to allow for larger rotors? Perhaps with modification?
Perhaps some of this is disc brakes 101, if so then that's what I need to understand better.
As long as you can get the caliper in the right place, you're golden.
I got a Troll recently, and I've been experimenting with this too. The frame has ample clearance for a 203mm rotor in the back, about 1/4" from the seatstay with the axle mounted all the way forward. I'm guessing that Surly opted not to support it because they don't want to manufacture/distribute 3 different brackets, especially when there's a prevalent attitude that almost no one "needs" a large rear rotor.
The Surly bracket is a bit different from regular caliper adapters in that its frame mounting holes are spaced differently than an IS standard mount, about 55mm apart. This is close enough that you can bolt a regular adapter to the frame (as shown in the photo you linked), but it ends up a bit crooked and I was not able to find a useful configuration with this method, using a few different adapter parts.
Moving the adapter forward in the rails should work, but at some point the caliper angle will be off. you're only looking at a 10mm difference for a 180mm rotor, so that case probably isn't a big deal.
Your thought to use regular spacers/adapters is right on- it worked perfectly for me. I stacked a front 203mm post/post mounting adapter on the Surly adapter. I'm not exactly sure which is the "right" way to mount the Surly bracket, but I've got it positioned to place the caliper closer to the chainstay, with the second adapter shifting it further in that direction. The bolt position corresponds to the axle position in the dropout, so I'd say the fit is just right.
Granted, I'm sure a bike mechanic would cringe at the sight of stacked caliper adapters. I'm considering JB-welding the two parts together or something, for some extra peace of mind.
Or alternatively is there a reason one would consider adding a standard spacer to allow 180mm or 203mm rotors? I don't see the point of adding the extra weight or complexity of messing around with adaptors. Every 160mm brake I've had on my Troll has had more than enough braking force to over power the traction available at the rear wheel.
Originally Posted by BATRG3
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