Schlumpf hubs: general discussion.

[turtle]

Originally Posted by From the Woods

And another concern is about shifting by accident. Does this happen often or never? I am thinking of riding technical XC/downhill trails where bumps may cause your foot to move on the pedal and then you shift... and... UPD

yes it happens, at least it did for me, not just once, several times... that's why on don't ride a schlumpf at the moment on my 26" (for a time i took the caps out and shifted gear bay hand...) an other reason was the weight, because i do alot of hiking in my muniing... ...but it looks like i'm going back to a schlumpf on the 26er...

[From the Woods]

Am I right if I assume that UPDs because of shifting by accident can be quite nasty? Another reason for wearing my protection gear

[turtle]

i'm not sure, but mostly when i shifted by accident it was from low to high gear, when it was really technical, with hopping, so it wasn't that nasty (means not in highspeed, but maybe nasty because of the unfriedly upd-terrain... if you know what i mean ), and it kinda shocked me everytime, because i wasn't ready for that...

[From the Woods]

Yes, I know what you mean What I was thinking about was the half rev (or how long does the shifting process last?) you are coasting after shifting. Isn't that an issue when you have a lot of pressure on the pedals?

[naturequack]

I've had two unintended shiftings in the two years I've had my Schlumpf. Both from low gear to high, and both with 165mm cranks. On the first one I was just riding down the street at a very modest speed and my heel hit the button just right. There was a fair amount of slop in the gears on that shift so I landed flat on my butt. Fortunately, I had my backpack on with my laptop in it. So my computer protected my valuable equipment (my butt) from serious damage.

On the second event I was riding pretty fast through town when I accidentally shifted into high gear. There was virtually no slop in that shift and I seemlessly shifted into high gear and kept riding. Woo Hoo! What a feeling!

Geoff

[munirocks]

A couple of things I have come across with my Schlumpfs:

- Serious mud can be problematic because it fills up the little screw in the shifter buttons. The dirt has to be taken out of there before any adjustments are tried on the screws.

- Accidental shifts haven't happened often but I think they are more likely to occur in technical terrain, which is where they are the most unpleasant...

- Sometimes the shifting happens at an unexpected time, quite a bit later than initiated, which can lead to UPDs. This is usually when shifting up.

- On my now retired 26er hub (waiting forever for the replacement) I noticed that sometimes when I did small drops (in low gear) the cranks would slip one slot further or something like that. I haven't ever heard of anyone else who experienced that, though.

- The 150mm cranks are fine for most of my rides but I am thinking about getting some 165s for steeper climbs. Accidental shifts would be pretty much impossible on those too, I guess, especially with not so large feet.

[siafirede]

Originally Posted by From the Woods

Yes, I know what you mean What I was thinking about was the half rev (or how long does the shifting process last?) you are coasting after shifting. Isn't that an issue when you have a lot of pressure on the pedals?

The shifting process (generally) takes 1/16th of a revolution. There is a thread called "Schlumpf shifting techniques" that describes some of the common things that happen when shifting. Sometimes when there is a lot of pressure and you shift, it will not engage right away until you change the pressure, it is hard to explain. There is a lot of input in that thread of the best ways to shift and ways to make shifting extremely predictable.

Shifting is very easy for me now. Your pedal choice and your shoe choice will also affect how easy/hard shifting is.

[hugo]

Originally Posted by From the Woods

Yes, I know what you mean What I was thinking about was the half rev (or how long does the shifting process last?) you are coasting after shifting. Isn't that an issue when you have a lot of pressure on the pedals?

As long as you have pressure on the pedals, the hub won't shift. The button basically initiates the shifting, but only when you release the pressure from the pedals, it will execute. That is one reason why there can be an unpredicable delay between hitting the button and changing the gear - possibly resulting in a UPD. The coasting can be up to 1/2 rev (at least it feels like that) or none at all. In most cases, when you reduce the pressure from the pedals before hitting the button, it shifts very smoothly without any delay (as said: in most cases, but not always).

I guess that you don't want to shift in rough terrain, usually you will stay in low gear and use the high gear only on nice surfaces where you can go fast.

I suggest you simply try it. You will need to make your own experience and simply get used to the way how it works.

[From the Woods]

I suggest you simply try it. You will need to make your own experience and simply get used to the way how it works.

Sure I will, but my new Schlumpf Uni is shipped today so I have a few days to wait left. And it really helps to talk about riding a GUni while waiting for it

As long as you have pressure on the pedals, the hub won't shift.

That's VERY good because the UPDs I was thinking about where with lots of pressure on the front pedal. When there would be a slop of about half a rev there would be nothing left than a faceplant

[hugo]

Originally Posted by From the Woods

That's VERY good because the UPDs I was thinking about where with lots of pressure on the front pedal. When there would be a slop of about half a rev there would be nothing left than a faceplant

But there's no guarantee for that. If you just release the pressure for a moment, to balance or whatever, it will shift.

[From the Woods]

If it gets a bit more technical or for riding single trails I will wear my fullface helmet. I will have to deal with that if it happens

[MuniSano]

As best I can recall I've only had a few accidental shifts. Like everybody else it was from low to high gear. Most often its because I'm concentrating while I'm riding rough terrain and my feet and ankle tend to "cheat" closure towards the cranks as I ride. I guess they move in enough that the side of my shoe begins to rub against the shift button and "pop" gear change! Typically no problem, it's just another UPD. And as its' from low-to-high I'm not going very fast anyhow...

I've had the opposite problem as well; not being able to shift into high gear. It is important to check your equipment periodically (if don't already). I was trying to shift up on the fly and I could tell the shift rod was moving but the high gear refused to engage! Turns out the frame bearing clamps on the knurled side of the hub were a tad loose so the high gear couldn't engage! It was a subtle thing as the wheel didn't feel loose in the frame.

Riding in high-gear I've never had a accidental down shift (now that could be dangerous).

[MuniSano]

As best I can recall I've only had a few accidental shifts. Like everybody else it was from low to high gear. Most often its because I'm concentrating while I'm riding rough terrain and my feet and ankle tend to "cheat" closure towards the cranks as I ride. I guess they move in enough that the side of my shoe begins to rub against the shift button and "pop" gear change! Typically no problem, it's just another UPD. And as its' from low-to-high I'm not going very fast anyhow...

I've had the opposite problem as well; not being able to shift into high gear. It is important to check your equipment periodically (if don't already). I was trying to shift up on the fly and I could tell the shift rod was moving but the high gear refused to engage! Turns out the frame bearing clamps on the knurled side of the hub were a tad loose so the high gear couldn't engage! It was a subtle thing as the wheel didn't feel loose in the frame.

Riding in high-gear I've never had a accidental down shift (now that could be dangerous).

[hugo]

Originally Posted by MuniSano

It is important to check your equipment periodically (if don't already). I was trying to shift up on the fly and I could tell the shift rod was moving but the high gear refused to engage! Turns out the frame bearing clamps on the knurled side of the hub were a tad loose so the high gear couldn't engage! It was a subtle thing as the wheel didn't feel loose in the frame.

There is a thread where the torque of the clamp screws was discussed. I think it is recommended to use 5 Nm, but on my KH29 it works very well with 4 Nm. There is also a warning that the bearings may get damaged when the torque is too high.
Unfortunately a torque wrench that starts at 2 or 3 Nm is quite expensive

[hugo]

Torque was discussed here