I have some problem with the brake on my KH26, the disc scratches the pads. Tried to fix it by bending the disc, but the scratch comes back after a few rides (even without using the brake).
LBS says there are some play between the frame and the wheel, and actually I can feel the play by wiggling the wheel (around the yaw axis); but the LBS guys say they’ve never dealt with a unicycle, so they are not sure how to fix it.
not an expert by any means but it sounds like the inside of bearings themselves are where the play would be. being that the rotor is direct to the hub and the brakes are on the frame the only way you will get movement would be if the bearings are moving internally. But it could just be the brakes closing in on the rotor, even though your not using them I guess they could move enough to rub.
Are you sure it’s the brake pads that are causing the scratching sound?
I had an issue for a long time with a scratching sound - but only when pushing hard - and I thought it was the twist between the wheel and frame that caused the pads to rub the disc.
It turned out to be the brake caliper was hitting the backside of the KH Spirit cranks (it left a visible scratch on the backside of the cranks after a while). So I changed to another slimmer caliper with better clearance between caliper and crank and the issue went away…
If you feel play between frame and wheel could it be that it’s the bearings on the Schlumpf hub that is worn. Maybe you can feel it if removing the wheel and try to twist the bearing by hand.
Are you using the “crank stop feature” of the (Generation 4) Schlumpf hub to prevent that cranks are creeping on the ISIS interface? (I assume it’s just a small ring similar to a regular on an ISIS hub that stops the crank from moving inwards when tightening the crank bolt but I have never owned a Schlumpf hub so don’t know if it looks different)
Also adjusting hydraulic disc brakes to make them perfectly aligned can be tricky in my opinion. Even my brakes that I consider to be “silent” makes a tiny rubbing sound that I can hear when listening careful in a silent environment inside my house (outside it’s unnoticeable). However it does not seem to cause any braking effect that I can detect while spinning the wheel.
In my opinion you don’t need perfection. As long as the brakes are silent when riding and you don’t feel any braking effect. 99,8% silence from disc brakes are enough but obviously your local bike store/mechanic might have a different view.
Sadly I would say yes - meaning to keep your hub in good shape you’ll want to 1) stop trying to use / install the disc brake and 2) get a replacement spacer/stop.
I think you should be able to do that by contacting Florian as there’s likely stock and should be fair cheap plus easy to ship.
Without it you’re not really benefiting from the design of that 800 series hub.
Sadly me personally I’d simply not risk running an outboard brake - crank stop or no:
It feels like a way to wear out your hub’s internals before their time.
Still given you’re got it set up this way, getting the stop and using that is probably your fastest option to get it up and running semi-safely.
I feel bad for being the a bit doom laden here, but I’d always be slightly weary of a solution from a LBS - as I just feel they’re never going to know as much as uni-folk do regarding the dos and don’ts for these hubs.
I’ve got it back from LBS. Seems the problem was with the axle bolts, one of them (on the disc side) was worn out and cannot be tightened to a required torque (40-50Nm according to the user manual). They swapped the two bolts so the good one is on the disc side. I’m not quite sure about that but anyhow the play disappeared, and the disc does not rub any more. I’ve ordered a new bolt to replace the worn one.