Disc brakes - Inside vs Outside the frame

[ramackenzie]

Hi All,

My apologies if this has already been addressed in a previous thread, but I was not able to find anything.

Who has had the chance to run the new spirit cranks with a disc brake attached?
Have you had any troubles with the disc/calipers getting in the way? Obviously the possibility of this is higher than with hub-mounted discs.
Do you feel having the disc on the outside of the frame greatly increases the chances of the disc/calipers getting damaged while riding?

[GizmoDuck]

Originally Posted by ramackenzie

Hi All,

Who has had the chance to run the new spirit cranks with a disc brake attached?
Have you had any troubles with the disc/calipers getting in the way? Obviously the possibility of this is higher than with hub-mounted discs.
Do you feel having the disc on the outside of the frame greatly increases the chances of the disc/calipers getting damaged while riding?

I'm running the Spirit Cranks on a Schlumpf Hub with Triton Disc Frame.

Originally I had 1mm of clearance between the rotor bolts and my bearing caps.

For some I reason I can't explain, when my Schlumpf hub (2008 version) broke, the new hub I bought has less clearance (in fact zero clearance) with the frame bearing holders. That is despite the fact it has a longer axle than the 2008 version. It means the cranks must sit further in on the ISIS splines.

I managed to get about 10 microns (that's a guess) of daylight between the rotor bolts and the bearing caps by putting PVC tape on the splines so it doesn't sit all the way in. It's disconcerting should any of the bolts loosen- there is no room for error. I'll have to shave my beautiful Triton frame when I get home

But really- the Schlumpf hub should have a longer axle.

Aside from that- an inboard rotor looks more elegant, but I prefer an outboard one because it doesn't narrow your hub (which for a 36" makes it weaker and more flexy). Might not be an issue for smaller wheel sizes though.

As far as damage goes- so far so good. I imagine unless the disc landed on a rock, your pedals should take the impact first anyway. And you now have a big 180mm rotor protecting the frame (I'd rather ding my rotor than my frame).

[Nurse Ben]

Aside from the complications with running a disc brake with a Schlumpf hub, the inboard rotors work very well and have no "crank creap/alignment" issues that could effect outboard rotors.

I have three inboard setups, prev had a fourth but sold it (KH 26, D Brake, Oracle Hub). The three remaining inboard disc brakes are on an Oregon 26" and a Nimbus Stealth 36" both of which have 125mm bearing spacing, and a KH29 with a D Brake and Oracle Hub that is 100mm spacing. All work exceedingly well, I have not had a single problem with the spoke tension or wheel strength on the offset hubs nor the narrow flanges on the Oracle Hub. I ride all three unis off road and I weight. 200#.

The biggest differences are cost and time, but if you have the skills to rebuild your wheel then it is a push. A far as I can tell, the existing spokes on most wheels can be reused for an Oracle or Oregon hub. The cost of a disc hub and a shop rebuild is ~$50 USD more than the cost of buying a set of Spirit cranks.

Crank creap is a real issue, esp if you change cranks often. I find that swapping wheels does not require any disc brake adjustment on my inboard systems, whereas with an outboard system you would probably have to make caliper adjustments as each spindle/crank will be slightly different. I also have a lot of differnt ISIS cranks in my tool box, they vary widely in terms of offset and length and how they fit onto an ISIS hub. To run Spirits I would be limited to one crank, but they would work on any ISIS hub.

The outboard rotors are set out from the wheel ~3cm more than the inboard rotors. You probably won't have any problems with your rotor or caliper hitting the ground in either set up, though you may be more likely to hit your foot on the outboard rotor during a UPD. The rotors are easy to true, just flex them with your hand or use a truing tool.

Either system is fine and they are FAR BETTER than rim brakes for wet weather use and overall stopping power. They are also a whole lot less fiddly than Magura rim brakes. Check out the Magura MT2's, nice brakes, lightweight, easy to set up, pads can be removed without removing the caliper, the line angle is adjustable, the lines are easy to shorten, and they run on mineral oil.

But really- the Schlumpf hub should have a longer axle.

Yes, they were even a problem with the Moments and other ISIS cranks.

[DavidHood]

Originally Posted by ramackenzie

Disc brakes - Inside vs Outside the frame

You mean one of these versus one of these?

I can attest the difference in "feel" between a 26" Oracle (inboard disc) and a KH29 (outboard) is negligible to the point I wouldn't know which I were using if I did not look down. Smooth as butter same as when I learned to brake on a 36er Impulse (sold). The HS33 rim brake on my geared 36er (due to aforementioned complications) will grab and throw you over the handlebar even though it's got my favorite lever (Spooner) of the bunch. The Starfighter lever extension on a NB handle on my 26er is nice but I still like the feel of a Spooner in my hand.

[ramackenzie]

Originally Posted by Nurse Ben

To run Spirits I would be limited to one crank, but they would work on any ISIS hub.

I hadn't thought of that, that's definitely something to think about for the future.

A little off topic, but DavidHood: Based on these two pictures, and your "inventory signature", I noticed that your 29 has 150/125's, and your 26 has 165/137's. This seems a little backwards to me. I would have thought that generally as the wheel gets bigger, so do your cranks. Would it be safe to assume that you use the 29 for "easy-rolling less-hilly" XC rides, and the 26 for "technical and steep" all-mountain rides? I would think that the flip-flop in crank:wheel ratio would create a greater difference in the way each Muni rides.

[uniShark]

For retrofit of my KH29, I'm going outboard. Lower cost, lighter cranks upgrade, and no need for new wheel build are my reasons.

If I were starting with a new uni, I'd seriously be looking at an Oracle, esp for 24 and 26 wheel sizes.

I do think outboard is probably better for 36, and maybe even 29, due to potential wheel strength issues. No, I'm not aware of anyone actually folding a wheel because of the offset, but I wouldn't want to be the first, and peace of mind matters.

[DavidHood]

Originally Posted by ramackenzie

your 29 has 150/125's, and your 26 has 165/137's. This seems a little backwards to me. I would have thought that generally as the wheel gets bigger, so do your cranks. Would it be safe to assume that you use the 29 for "easy-rolling less-hilly" XC rides, and the 26 for "technical and steep" all-mountain rides?

I'm guilty on all counts. The 165/137 moments are held over from when I "tried" to MUni on my Impulse. I really should have gotten 165 Spirits when I got my KH29. Kentucky does not have any "easy-rolling less-hilly" XC. It's all roots/rocks and rarely flat. I'm still learning MUni so I need the 165 hole on my 26er. The 127 hole on my KH29 does spin VERY nicely on the asphalt paths but I have a 36er for touring so you may be seeing a set of 150/127mm Spirits on the trading post when I transition my 29er to full on MUni mode.

[Nurse Ben]

A little off topic, but DavidHood: Based on these two pictures, and your "inventory signature", I noticed that your 29 has 150/125's, and your 26 has 165/137's. This seems a little backwards to me.

It is backwards, but then what do you expect from a Kentucky unicyclist? All the Tenneessee inbreeding tends to gravitate North

[knoxuni]

hey not funny....

[uniShark]

Originally Posted by knoxuni

hey not funny....

Hmm, interesting objection from someone whose sig line pronounces their status as a dumbass.

[knoxuni]

its a joke :P

[haskinsc]

Has anyone considered the implications of repairing a broken spoke on inboard vs outboard hub? For inboard, the disc-side bearing must be removed in order to remove the rotor which must come off to get the old spoke out and the new one in. The outboard setup requires removal of the crank only. I've got an inboard setup and have fortunately not broken a spoke yet.