I am thinking of getting a disc brake but what is the ideal rotor size?
160 +
Nimbus uses 178-180.
KH website recommends 160 mm or 180 mm (160 mm recommended)
The larger the rotor, the greater the heat dissipation, the longer you can ride the brake on a downhill before it fades.
The larger the rotor, the greater the weight too…
Has anyone tried a 2-piece rotor such as the Hope Floating Rotors (other mfgs are doing it too)?
They’re about 2wice the cost of a 1-piece rotor but at $40 they are in reach. The concept is to replace the center 2/3s or the rotor with an aluminum carrier. I am leary about the rivets that hold the carrier to the SS outer rotor. Clearance on uni disk brakes is always THE issue.
I set up a 180 or 183 mm hope ’ saw’ floating rotor on my KH G26
Can’t remember the exact number but it was on sale at LBS and looks awesome.
And yes clearance was difficult but doable. I needed to file the outside of bearing housing to get the rotor bolts to clear at 30nm torque on the crank setter
No matter how much truing of the disc I did
1 of the rivets was rubbing on the post to IS adaptor. The was fixed with a bit of work with a hand file. But ended up breaking down, filing more, and building this up seems like a hundred times. Also I had to use shorter bolts
So it is great bling and looks amazing. Plus the disc is great quality
Piece of kit. But my second schlumpf, I’m using a monolithic disc
Not worth the effort.
Thanks @FatLazyPig. That’s pretty much what I suspected. More work than it is worth.
I have a hard time imagining filing down a bearing housing on a KH frame. My frame is a Ti Triton, aint gonna happen.
Earlier today I ordered a set of Spirit cranks from UDC and a Hope single piece rotor/bolts from an online bike retailer. The Hope stuff is just so nice…
Yeah. I was a little upset to do all the filing. As I had a perfectly good KH 2011 frame. Which I replaced for a 2012 frame just so I didn’t need to do any filing.
Any way
I have seen write-ups of people filing material off their rotor bolts to spare their frame. but I think a better option might be to use countersunk rotor bolts. You’ll need to modify the rotor a little with a drill press, and buy new bolts. But should make clearance a lot easier
Or just get a disc hub and you can use any crank.
It’s not hard to build a wheel, and if you don’t want to try it, then have your LBS do it for ~$30.
I’ll bet the cost of the new cranks and frame were a whole lot more than a new hub and a wheel build 
But surely Kris will thank you for your support 
Maybe it’s on one of his two Schlumpfs…
Also, $30 for a wheel build is quite cheap. Sounds like a pretty cool LBS. (I build my own wheels, so not an issue for me.)
Mountainuni uses 180 mm rotors
Mountainuni uses 180 mm proprietary rotor. Nurse Ben will try and talk you into a full wheel build, but it’s not necessary. Any ISIS or Square Taper hub is compatible with the Mountainuni design, and will cost you far less. 
Yup, it’s a bad idea, I strongly recommend getting a crank based rotor (and a dremel tool, a couple files, a bottle of ibuprophen…)
If you haven’t built a wheel before, its quite a bit more difficult then using a dremel. (And swallowing pills for that matter).
I honestly like the fresh perpective you did relating to the issue. Genuinely had not been planning on that the moment I started exploring to obtain information and facts.
I sat down with my son when he was fourteen, gave him a set of paper instructions, made sure he started correctly, then let him go. I did the final truing, otherwise it was his wheel build.
Building a wheel is simple, but we make it out to be much more complicated than it really is. The OP bought a frame to avoid having to dremel his existing frame, all because the rotor clearance is an issue.
Granted, it sound slike he’s working with a Schlumpf, but I still think it’s a shame that there is a clearance issue to begin with esp since this is a new product, but then maybe there is no other way to make it work unless the Q factor is higher, such as on the Mountainuni set up.
No matter how you cut it, a crank based disc is a retro set up, the correct way to mount your disc if you have the time/money is to have it on the hub. In time all unis will be made that way, and most likely even Schlumpf will develop a hub mounted rotor.
I’m not trying to disparage Kris and others who have promoted this solution, it is a viable option, but the writing is on the wall…