Some time ago mine Pipifax hub broke after 1,5 year of use. Since i used to jump, land drops and ride muni in general warranty repair was not an option. I didn’t want to undo the wheel so i decided to fix the hub by my self.
Since the hub is quite nice and there is no other avaliable on the market, i think someone would need some advice how to fix this bad boy.
Disassemble the hub. This was most tricky part, since i could’t be sure what’s inside, but by try and error i’ve come up with idea to pull the spcecial bearing useing invasive bearing puller.
BTW pushing central pipe against hub housing didn’t worked.
Freewheel bearing needs to be drilled to create space for puller arms.
Removeing CSK25 bearing was quite simple we used some kind of puller with some extra metal prats involved.
While ordering new CSK25P bearing make sure it has cuts on inside and outside, if You miss that You will ned to spend some time with angle grinder, file and dremel (mini grinder).
You can consider repleacing standard bearing, but since mine was good i’ve keep old one and assemble the hub uesing long threaded rod nuts, big washers and metal pipe.
7. Squizing this hub went smooth with some grease. It’s easy to spot the moment when it’s ready since suddenly bolt start to resist.
8. Good as new:
Today i went for simple muni ride with 600m of elevation and it worked fine.
In general some special tools and some expirience are required. If You have any extra questions i’ll try to help unlike Qu-Ax. I’m convinced that other method should work too, i’ll try to simplyfy process next time CSK25P fails.
In conclusion main idea behind this hub is great since it’s simple.
Useing one size bigger bearing CSK35P would introduce some dimensionig problems but would come with extra torq resistance. I hope next QX frewheel hub will be better or will use some good ratchet mechanism.
It’s kinda sad that this hub can’t handle regular muni, but repairing process is reasonably simple and cheap.
Thank you for posting this up. Excellant explanation.
We (that is udc uk) have been dissapointed with the durability of the sprag bearing. On some hubs it just fails with very little use and no jumps. Others it lasts and lasts.
There is a special tool that we purchased from quax and instructions for removal of the bearing. We will make the tool available and share the instructions. This will help with the need to drill the bearing.
The best freewheel hub for durability I have seen was one that was fitted to a penny farthing. It was druid though. It had 2 bmx freewheels welded to the hub. This gave a surprising quick engagement.
I wonder… Shouldn’t it be possible to disassemble the Hub by supporting the flange (e.g. by using a tube) and then simply tap on the axle? This shold drive the bearing on the other side out of the aluminium body.
I also wonder if it would possible to use two of these one way bearings. The hub body would have to be modified with the help of a milling machine while the axle would have to have a tab (is that the right expression?) added that interlocks with the key of the bearing’s inner part. Could possibly be done using pins or bolts (unless you can weld), but I’m not sure if that setup could cope with the forces involved. But having two one way bearings could take some load, even if it probably won’t be the theoretical 50% due to tolerances. I suspect one would always take the initial load while the other would only kick in an take some load when the first one is starting to “deform” due to the stress.
Or am I completely off?
And thanks Roger for making the tool and instructions available to those plagued by their hubs breaking down.
I’ve tried to push the axle (from both sides) by useing questionable “press” (big srew in ,setal stand) but with no success, i suppouse it was due to pushing angles being bit off. In general i was advised that taping while dissasembling bearings is risky. Pushing by some kind of screw is much more safe.
I really like idea of useing two such bearings. Down side is that would require completly differend housing and some axle resizeing. (cluch bearing needs 25mm, q-axle is 24 if i remeber correctly). Load should be somehow distributed on two of those.
I was surprised when I learned that they were using it in this hub. Yes it’s a commercially available sprag clutch bearing which keeps the price a bit lower, but it’s very much not its intended use case and when you run the load calculations, outside its specifications too.
I don’t think CSK can take any blame for poor reliability here.
What you’re looking for is CSK25PP, the two Ps being the part that specifies keyways inside and out. As you found out, CSK25P just has the keyway on the inside.
I’ve not seen a Bicymple break yet, but I’ve got a wishlist if anyone were to look to make more specifically for unicycle use.
Instant engagement sprags is a great solution, but I suspect they’re never going to be cheap enough to make a moderately affordable freewheel hub with high reliability (as you need more sprags, which costs more, see Onyx racing’s hubs).
