Hey riders,
I tried searching past posts but could not find much specifically about folks’ experiences with using a 203mm disc brake rotor. I had to buy a new rotor and pads for my 27.5 Nimbus muni, having bent the old 180mm rotor (slightly, but irreparably) and also seemingly glazed over my pads. This had been my first experience with disc brakes on any cycle. I took the uni to the bike shop and told them I had lost a lot of brake responsiveness and there was also a lot of squealing that had not been there. The bike tech diagnosed probable glazed pads due to over-heating of rotor and maybe not having bedded them in properly, and recommended a larger rotor to deal with heat. Of course, he knows nothing about unicycles, but I took his advice. I am just now finishing up assembling, so I can’t report on the performance yet. Just thought I’d see what the community has to say on this. Thanks!
203mm? Yes, please!
Lots of alpine mountain unicyclists use 203mm. Kris Holm recommends this upgrade. All frames are strong enough for them (except for Quax’s RGB!). It’s a cheap and effective upgrade.
Bigger rotor also means more stopping power. I’d say the bike mechanic wa spot on for the advice. MTB has more weight and speed going downhill so their higher end equipment with help with uni physics quite a bit.
Overall if you did have a heating issue I think you’ll find this helps with it quite a bit, but also be aware you’ll have more stopping power when you’re next out.
Also @jaco_flans rides big rotors, he can probably give a bit more advice too.
Yeah I run a 203mm on my 36er and wouldn’t go any smaller. On my other wheels I’ve found it less necessary as I don’t ride them as often, and when I do, I don’t tend to use the brake as much.
Glazing over for most people on unicycles is not to do with overheating though, rather not bedding them in properly/being unable to due to the limited braking that people do. If you use the brake lightly and infrequently (or even frequently) then you’re likely to end up with squealing and limited braking power.
Do you know what type of pads you’ve got installed?
203mm disks are good, but it may not solve the glazing problem.
I’m currently fighting some light glazing with my freewheel, but it’s certainly not due to overheating them outright, my hills are fairly short. I believe that constant and too light use can be an issue too, I might just end up having to give them a light scuffing up every few rides.
I run a 203mm on my hatchet, I started with 180mm with 2 pot caliper and found it wasnt enough braking and needing to squeeze the lever harder than id like which resulted in clumsy braking.
203mm with a 4 pot shimano zee caliper i like as it has great modulation and no squel plus being a tart it looks better!!
I use shimano icetech rotors on my unicycles and MTB and find them squeel free.
I use 203 mm discs on my KH G29 and my KH 27,5 and I can highly recommend it. It is easy to change, you only need another adapter. I would also recommend good brakes, if Shimano SLX or higher.
resin pads. I use them plenty!
Took a nice ride and put the brake through its paces. I did take a handful of bedding in passes as instructed by a Park Tools vid (as best I could), and pouring water on calipers first as well. I don’t notice a big difference in braking power from the 180mm but hard to really say without doing a side-by-side comparison. Very pleased to have braking power again! Had some nice crashes lol 
What doesn’t kill you makes you a better uni rider? Thanks again for feedback!
This has nothing to do with 203mm rotors, but the first thing I did to get my brake rotor and pads to like each other was to take them on a walk. I walked about two miles, pushing the unicycle, while squeezing the brakes and forcing the wheel to roll. It wasn’t sure if it would do anything, but figured I could always replace the pads.
Before the walk, they would grab a bit in some places on the rotor. It seemed like the rotor was not perfectly straight. After the walk, the brake grab was consistent. That was on my 27.5 inch.
yes, I also run with a 203mm disc on several of my self made muni’s. it has more range before a lock up, and allows you to modulate the brake resistance more suited than others for long downhills
Sounds like a good idea. My rotor might have deformed a bit, they guys in my LBS tried their best to fix it but it still grabs sometimes. I’ll try that walk.
I’m not sure it really matters a whole lot on a unicycle. I’ve used all three of the most common rotor sizes and haven’t noticed any issues with any of them. I don’t think there’s any good reason not to go with 203mm rotors however and I’m trying to slowly standardize all my bikes and unis on them eventually. They do give you stronger braking and better heat dissipation, the weight penalty is minimal and the initial cost difference isn’t much.
At the same time however, I don’t think 95% of us will ever need more braking power than we can get from 160mm rotors. Just the nature of a unicycle means we are moving relatively slowly and applying relatively small forces to our brakes compared to bicyclists.
I run of my 26" Muni a 203 Rotor because the bike shop doesn’t have a 180mm Rotor. It’s good for ride with much breaking and a long road downhill. Better for the life time from the Rotor because it’s more Material for the breaking pads. But the Rotor is bigger and with the KH frame and a Kris Holm Dual Spirit Cranks the Rotor life dangerous because you can hit with it the rocks.