I was cruising down a hill near my house in second gear tonight on my 36er Guni, just getting to some serious pace when the hub suddenly pops into this freewheel. I caught one step before I tucked into a roll on my hip and elbow, then sliding on my back. No serious injury but I chewed up the skin and muscle in those three areas.
The bigger concern is what to do about it. I have had my guni since the summer of 2008 and this has never happened. I keep it greased and it has been a very consistent performer for years. As soon as I picked up the uni after bouncing down the street it was back in gear and it seemed to shift fine.
This happened before when I first purchased the uni more than three years ago, but it always seemed to be in the process of shifting, never when I was cruising at speed in second gear. It eventually just stopped and it hasnât happened again in over three years.
The seems strange as well because the hub was under relatively little stress when the misfire occurred.
Iâd love to hear comments from people about this. Any ideas for addressing the misfire besides dismantling a brand new wheel build, (I just had it completely rebuilt) and mailing the hub to Switzerland? It seems to work fine now but I sure am skittish about getting on and gearing upâŠespecially downhill in traffic as I often do.
It is amazing how much trust we put in this equipment not to do precisely this.
(By the way, I did spend some time searching GUNI SHIFTING PROBLEM ect.. but feel free to point me toward a thread if I missed something.)
Check to see that your cranks are tight and installed correctly; a loose crank can creep out on the axle and press the button out far enough to go into neutral.
Since you write you just had it completely rebuilt, you must also have reinstalled everything recently. That probably has to do something with the present mishap. My number one guess is what Satch wrote already: a button not adjusted far enough out. Check your installation manual on the details. Crank creep (as suggested by Tom) would be my second guess: it could move the button out of the position where the gears are securely engaged. I would think itâs not the infamous bearing slip since the hub was under relatively little stress.
If itâs any of these three, it would make no sense sending the hub to Switzerland because you would âdestroyâ the evidence (and in a way, fix the problem) when building the hub out of the uni.
Possibility number four is that you unknowingly touched the low-gear button. With old design hubs, this might cause the hub to freewheel. The newer hubs should either stay in high or switch to low, not be stuck in between gears. However, if you suddenly switch to low gear, it might feel as freewheel for a short while.
As described in the above posts, if your wheel builder wasnât intimately familiar with this type of hub its possible that the shift buttons or sloppy crank installation could be the source of trouble. After you rule those things out, another thing to check:
âYou just had the wheel rebuiltâ
So who built your wheel for you??
I do recall something in the product specs for my geared hub (#359) that said and I donât recall the exact language, something like: âif the spoke tension is too high, it could distort the hub and cause bearing problemsâ. not sure if this could be the source of the problem you experienced, but Iâd at least go to your wheel builder and ask him/her to check the spoke tension with a spoke tension meter and make sure they are all about the same even tension all the way around the hub and make sure that the tension isnât higher than is recommended for 14g straight gauge spokes (or what ever spoke you used). My park spoke tension meter came with a chart to id the range of tension for different spoke types. When I built my Schlumpf 29er, I finished the wheel build in the exact middle of this range of acceptable tensions for the type of spoke I was using and all the spokes were at almost exactly the same reading.
An educated guess: the sort of sutuation that would cause your hub to âdistortâ under improper tension is more likely to be uneven tension where a couple or a larger group of spokes were left way too tight on one side pulls the hub out of round - and might cause a malfunction???
Slipping in high gear is usually the knurled bearing not being tight enough.
Also, it could be cause by excessively tight cranks (like way too high a torque value), and having the crank deform and get really close on the hub. But that is less likely. It is probably the first thing.
Oh yes, I should have mentioned that; definitely a common issue, especially if you hear a grinding noise when it freewheels. Although usually if it freewheels because the bearing holder isnât tight enough, you canât just hop back on and ride it in high gear; itâll just slip until you tighten the holder.
I appreciate all the feedback. I probably have 100 or miles on this wheel build without an issue prior to the big fall. It was built by the this guy that everyone in Denver metro pointed to when I made the rounds looking for someone to do it. It seemed like a competent job⊠I will have the tension checked. Great idea.
Iâm not sure why the button position would make a difference, but that that also seems fine. I remember initially I had a ton of problems getting the crank arms not too tight, just tight enough and i ended up resorting to locktight, at Corbinâs recommendation. I am going to re-install the crank arms as well
It just seems to different than the issues this hub had before. The neutral thing always seemed to happen when I was shifting, not cruising at high speed going down hill. I did not hit the button or put any particular tension on the hubâŠit just failed out of the blueâŠleaving me crumpled and bleeding on the pavement.
I am not too eager to see if it is going to happen again.
Yeah, that sounds odd. I would be sure to check your frame bolts and crank bolts first. The buttons wouldnât matter unless you did hit them slightly on the way down.
Otherwise, take it easy and ride high gear on some slight downhills with pads and a helmet and make sure you test it under pressure and spinning fast before you go down something like Lookout Mountain again!
That really sounds like the knurled bearing slipping in the housing. The first time it happened to me I thought the hub was bad! Turns out it just needed to be tightened and I was good to go.
I still use blue lock tight on my main crank bolts; they never come loose anymore, and I never retighten them. I think I use about 30 or 35 ftlbs of torque.
I suffered the âneutralâ thing last Saturday.
I wasnât shifting or doing anything strange. I was just pedaling in low gear when suddenly the gear went into âneutralâ mode and I fell down backwards. I hit the ground with my butt, back, elbows, and head (helmet). I didnât have the chance to dismount safely. The uni went ahead 5 or 6 meters.
It was a âluckyâ accident since I didnât get hurt (just a few scratches), and also the uni didnât hit anybody (it was in a park, in a flat surface).
But it could have been much worse should it had happened going downhill or in a street.
I noticed that my uni had 2 of the symptoms mentioned above:
The right crank was a bit loose
The right knob wasnât out far enough
I guess that my right crank pushed the button from the inside, and the gear went into neutral.
Quoting Tom âWhat could go wrong⊠if I do not keep the hub in proper maintenance?â. Well, very bad things⊠serious things could happen if we donât keep our hubs in proper conditions.
Iâve had that same thing happen; when the crank gets loose it starts to push the button outwards slowly, in a way that doesnât engage the shifting mechanism. Loose cranks on a Schlumpf is a immediate stop-and-repair problem.
Thanks to everyone posting back in 2011, this may provide the information I need to straighten out my 2012-era KH/Schlumpf hub. Still experimenting on trying to get high gear back and neutral out of the pictureâŠ
But so far, no. Bearings werenât loose, and Iâm still dealing with a loose part inside the hub. The shifting shaft (jackshaft?) came partially out while I was trying to remove the button with its threads locked to the shaft. The shaft ended up popping partway out of the hub, bringing a little tube with it. I put the tube back in, but I donât think things are right. That little tube appears to be what presses the spring, which is behind it. But I never saw a loose tube in there before, and I still canât get it to shift into high gear; I still only have 1:1 and neutral. If anyone has any suggestions Iâd love to hear from you!
Very helpful! Many thanks for sharing that. Gives me a better idea of whatâs going on in there. My little âtube/spacerâ, though itâs wider on one end, I still canât figure out if it matters which way it faces. Iâm going to agree with the photo that the wide end should go up against the spring. When all the bits are in there, the shifting rod seems to move more or less normally, but still only between 1:1 and neutral.
Iâve taken the wheel off the uni (itâs been in a bike stand until now). Took off the cranks to get a better look inside, but itâs still very hard to see or get tools in there. I have about 1/8â or 3.2mm of gap between the threads on the shifting rod and the threads for the axle rods. Every time I stick a tool in there, itâs contacting threads on both sides; not my favorite.
I havenât had a lot of time to work on that, between trips, family stuff and work happening on our house. Iâll mess around with it some more after we get back from this work-related conference weâre going to in San DiegoâŠ
