Current Schlumpf hub + spirit cranks + disc brake modifications

[Fatlazypig]

I have a most recent available generation Schlumpf hub
plus spirit cranks and a disc brake on a 2012 KH frame.

these parts needed some modifications to get to work together and over time I am getting a little creaking noise from my right crank - Im presuming because of my under torquing of the crank bolt this side.

So I can think of a few strategies to employ to get these pieces to work together .

My question is which have you used and why. is it working out OK for you?

My feeling is I may need to adjust my approach.

A - filing down lateral wall of bearing housing
B - filing down of disc rotor bolts
C - deliberate under torquing of crank bolt
D - countersinking disc rotor and using replacement countersunk rotor bolts

So far I have employed A&C
torquing the bolt to 30NM
If you have some other strategies please add them to the list

[nickjb]

IMO c is bad idea and will lead to wear. I wouldn’t do d on a bike where the braking forces are higher and consequences of failure greater but it should be OK on a uni (unless you are a particularly spirited rider). I have thinned disk bolt heads before. You can’t remove much, and remember to grease them so they don’t seize.

[saskatchewanian]

I have done A and B. C is not a good idea as it will promote premature wear.

You will probably have to add some sort of spacer to snug the crank up to to keep it from creeping in further.

D sounds like a great idea.

Another thing you can do is trim back the crank itself. I don’t suggest doing this unless you are confident in your ability to keep it perfectly flat.

[Fatlazypig]

So is everyone else cranking that bad boy in to the full 50 Nm?

I’m not going really loose but 30-35, going up 1 Nm at a time while the wheel still turns. If it stops, I loosen. Pull the crank and start again
If I’m the only one doing this then I’ll find other ways to get this working

[Rowan]

@Fatlazypig

So is everyone else cranking that bad boy in to the full 50 Nm?

I’m not going really loose but 30-35, going up 1 Nm at a time while the wheel still turns. If it stops, I loosen. Pull the crank and start again
If I’m the only one doing this then I’ll find other ways to get this working

I had Tony Melton build my one and he used 30 Nm to make the brake fit.

@Tony's email to me

Some other things you need to know: the right hand bearing cap has been ground down to give it enough clearance for the rotor bolts. You may like to file down the inner face of the lefthand bearing caps to give the hub some more clearance. The left crank has been tightened to 50Nm and the right has been tightened to 30Nm and Loktited in place. The reason for the lower torque and loktite is that if right hand Spirit cranks are fully tightened the rotor bolts will rub terribly and enormous amounts of the outer face of the bearing caps need to be ground off.
The rotor rubs a little on the pads, which is quite normal and will reduce with useage. Every disc brake I’ve installed does this when new.

So maybe another strategy to try is loctite.
My one seems to be holding up OK so I haven’t checked the cranks yet. I’m not very good at using the brake!

[TonyMelton]

Since Rowan’s gKH36 I’ve built a second unicycle with schlumpf hub, Nimbus D’Brake and disc brake and again loctited on the right hand crank, with 30Nm of torque. This solution was recommended to me by Kris Holm. During the process of building this unicycle I tried putting the right crank on at full 50Nm of torque which caused the rotor bolts to meet the bearing face. It would not have worked without a lot of grinding. Since there are no spacers between the crank and bearing on the Schlumpf hub, high torques (such as 50Nm) pull the crank further and further along the axle. Apparently some Schlumpf hubs are worse for this than others.

I also found I had to grind/file down all inner bearing faces to provide sufficient clearance for the hub. If the bearing seal protectors rub even just a little they can fall off fairly quickly. Sufficient clearance is all the more important if its a geared muni you are building as grime and grit can easily get stuck between the frame and bearing seal causing annoying squeaking/rubbing sounds and helping the seals to fall off.

Had I known about countersinking disc rotor and using replacement countersunk rotor bolts at the time I would have done this too.

[UniMyra]

@Fatlazypig

D - countersinking disc rotor and using replacement countersunk rotor bolts

Does anyone know where I can get this?

[Eric_aus_Chemnitz]

@UniMyra

Does anyone know where I can get this?

The countersink tool or the bolts? Both shall be available in your local hardware store.

[UniMyra]

@Eric aus Chemnitz

The countersink tool or the bolts? Both shall be available in your local hardware store.

You need a tool? I’ve seen the bolts somwhere. I thought you could buy a rotor with countersunk holes in it that would fit.

[kunstrasen]

Bikes/mtb do not have the clearance issue. So all discs are with straight holes. You have to countersink the disc holes by yourself. Have you tried Shimano pan head screws? To my experience their head is pretty flat, so your could try them first.

[vookash]

@kunstrasen

Bikes/mtb do not have the clearance issue. So all discs are with straight holes. You have to countersink the disc holes by yourself. Have you tried Shimano pan head screws? To my experience their head is pretty flat, so your could try them first.

Any link to these pan head bolts? I’ve found something like this, but I’m not sure if they are flatter than regular ones: https://www.ebay.com/itm/Genuine-Shimano-XT-BR-M755-Disc-Brake-Rotor-Fixing-Bolts-6-pcs-Plates-3-pcs/221648999928?epid=1100002507&hash=item339b4f55f8:g:03QAAOSwg3FUo3GF

[kunstrasen]

Yes, something like this:

Shimano Befestigungsschraubensatz für Bremsscheibe SM-RT76 kaufen |...

I remember I measured the thickness of the head. Shimano was flatter than standard pan head bolts, but I do not recall the values. If neede I can measure again.