Schlumpf hubs: general discussion.

[MuniAddict]

Something VERY strange happened on my G26er ride today. Cruising along slowly in 1:1, I did a little two foot drop and as soon as I landed, it suddenly and accidentally shifted into high!

What's weird is that I just kept going like nothing happened! I think it shifted because my new Karvers have more padding near the shift button, but when I landed I also applied more down force to the pedals to roll out, which is probably why I didn't even skip a beat or get thrown off.

Then there was a steep uphill right after the drop, so I immediately downshifted and went on as usual. Amazing sequence of events that I could not purposely do again in a million years! Later, I moved the shift button a little closer in, and that took care of the accidental shift issue.

[nathan]

Ah, the old auto-shift feature! I was blazing along in high gear down a hill in India one time and didn't see a speed bump. It bounced me into the air and I landed ok, except I was now in low gear! No way could I pedal fast enough, so I crashed (not bad though). I am pretty sure it was the nice thick padding on my Karvers hitting the button. Nice job how you recovered without thinking about it!

---Nathan

[MuniAddict]

Originally Posted by nathan

Ah, the old auto-shift feature! I was blazing along in high gear down a hill in India one time and didn't see a speed bump. It bounced me into the air and I landed ok, except I was now in low gear! No way could I pedal fast enough, so I crashed (not bad though). I am pretty sure it was the nice thick padding on my Karvers hitting the button. Nice job how you recovered without thinking about it!

---Nathan

Ooh! Yeah, the dreaded High-to-low accidental shift is much scarier and potentially much higher risk of injury! I've tried shifting into low at too high a speed and as you experienced, could not "catch up" to the cadence required at that speed. Now I only downshift when I have slowed down to a reasonable speed.

[Tucson Uni]

Yes, I had a trip to Urgent Care for some stitches in my knee due to an accidental down-shift. I did a nice Superman dive onto a rocky trail. That was back when I was experimenting with the 125 holes on my cranks. Turns out that you don't want it to be too easy to shift.

[corbin]

Originally Posted by MuniAddict

I was having a conversation with a riding buddy yesterday about the 1:1.5 gearing ratio on the Schlumpf hub, saying that in high gear, a 26er becomes a virtual 39er. He said he doesn't think high gear adds 50% more wheel rotation to each pedal revolution, but maybe more like 33%. I was under the impression that 1:1.5 does mean that the wheel will rotate 50% more per pedal revolution, but now I'm not sure. My basic understanding was that if your pedaling cadence is the same in high as it was in 1:1, then you would be moving about 50% faster. Is this about right?

Mark your tire, and show him as you rotate it a half turn when in high gear.

corbin

[DavidHood]

Originally Posted by Tucson Uni

Turns out that you don't want it to be too easy to shift.

I don't have a problem with that! I wear (size 10) FiveTen's and use 150mm cranks so I have learned to ride my 36er on my toes. I've never had the guts (need the extra leverage in high gear) to switch to the 125mm hole. I was going to get myself a set (Kris unveils his new cranks tomorrow) of 137s (my all time favorite length for Cokering) to ease shifting. But, I've heard too many horror stories about accidental downshifts (something I never have to worry about with 150s) so I don't know. Decisions, decisions. Perhaps I'll wait out that "rumored" lightweight 36" tire so I can get everything done at once.

[Yeti]

Originally Posted by MuniAddict

I was having a conversation with a riding buddy yesterday about the 1:1.5 gearing ratio on the Schlumpf hub, saying that in high gear, a 26er becomes a virtual 39er. He said he doesn't think high gear adds 50% more wheel rotation to each pedal revolution, but maybe more like 33%. I was under the impression that 1:1.5 does mean that the wheel will rotate 50% more per pedal revolution, but now I'm not sure. My basic understanding was that if your pedaling cadence is the same in high as it was in 1:1, then you would be moving about 50% faster. Is this about right?

The exact ratio on high gear is 17/11, which is about 1.54. So yes, your assumption is correct.

Originally Posted by corbin

Mark your tire, and show him as you rotate it a half turn when in high gear.

You don't need a special mark. Just take the valve for reference.

[Klaas Bil]

Originally Posted by MuniAddict

I was having a conversation with a riding buddy yesterday about the 1:1.5 gearing ratio on the Schlumpf hub, saying that in high gear, a 26er becomes a virtual 39er. He said he doesn't think high gear adds 50% more wheel rotation to each pedal revolution, but maybe more like 33%. I was under the impression that 1:1.5 does mean that the wheel will rotate 50% more per pedal revolution, but now I'm not sure. My basic understanding was that if your pedaling cadence is the same in high as it was in 1:1, then you would be moving about 50% faster. Is this about right?

On the risk of adding to the confusion (or introducing new confusion), there is also a ratio of close to 33% involved. If you take the high gear as the basic riding mode of a Schlumpf, then if you switch to low gear and keep the same cadence, you'll be going about 33% slower.

Or, on a related note, if you switch from low gear to high gear but don't increase your speed, your cadence will be about 33% slower.

[svzurich]

I have the previous model of KH26 frame, and KH Spirit cranks on order. I am wondering if those combined with a UCM and 180mm offset would work well/safely with my KH/S hub.

I am hoping that I can just pick up a 160-203mm disc brake (160mm preferably) as my LBS and use discs on the KH/S wheel without needing a new frame. Paying $58 for the UCM and offset seems better than buying a new KH26 frame and still having the current one to store.

Kimmie, still learning this stuff.

[Fatlazypig]

Basically it can be made to work
However you will likely need to do some filing on the outside of the
Right bearing housing
The bolts holding the disc to the crank are 'likely' to catch
Honestly I don't know how close it will be. My stuff is on order too

However being a not very handy Andy, and with my workshop being my kitchen table. I have gone for the new 2012 frame. Which has a redesigned slimmer bearing housing so should clear without any modifications

[svzurich]

I went ahead and ordered the UCM with 180mm offset. I'll give it a try. If I do end up going with a new KH26 frame (mine is only a month old, ouch), I'll direct the UCM to the KH20 instead.

[nathan]

We ordered a couple of the brake kits from Compulsion Cycles and they came in today (Spirit cranks, D'Brake adapter and Avid Elixir 5 brakes). We're planning to install tomorrow night into existing (pre-2012) KH36 frames and I'll post on how it works.

---Nathan

[svzurich]

All 4 of my DH Spirit cranks just arrived from Compulsion Cycles! They seem much lighter to me, 25% makes a nice difference in weight. I look forward to seeing how the D'Break and that set performs for you.

I intend to order a new KH36 with a KH/S hub of its own in a few weeks.

[DavidHood]

Originally Posted by svzurich

I intend to order a new KH36 with a KH/S hub of its own in a few weeks.

I cannot recommend enough having Bronson Silva (of Silva Cycles) build your geared 36er. He was kind enough to ride it a few times so he could retighten the cranks again. You may be a master mechanic. I'm not. I've never so much as took a wrench to it in one year and well over 1000 miles. I've only had to add grease. I would also recommend Magura rim brakes. Leave those discs to the mountain unicycles. Just my $0.02 worth.

[svzurich]

I spoke with Bronson Silva in April about it. The guni wheel I bought from Ben is solidly constructed, and that came from Bronson as well. Joe Lind of Compulsion also offered to build the KH36 Guni.

It will be getting disc brakes. My intent is to commute on it. I think riding 13+ miles each way in Las Vegas will benefit from the disc's smooth operation.

I am a novice all around when it comes to mechanics. I trust myself with pedals and cranks, even wheel switch outs, seat post cutting, and tire changes. I do not trust myself with truing, wheel construction, welding, or grinding. Adding grease is fine. I can figure out how to add a disc brake with a KH/S hub (dreading it), but I think I will go to a LBS for that.