DT Swiss 240s Star Ratchet
My new in June bike came with the 240s rear hub w/36point ratchet.
I haven't even riden it all that much, but the star ratched (freehub panels) have striped.
I foun a LBS that had a set of 18point parks, and already I've heard it slip (spin) once. Now in riding in a sort of torque limited condition.
Anyone here know what would cause the ratchet in this hub to fail so early?
I have cleaned and re-lubed the hub and cassette body splines, and the springs seem to be in good condition.
Possibly the lube, although that wouldn't explain your first failure, when the hub should have been in factory condition. Those DT star ratchets need a really light grease. DT recommends using their own (which is spendy) and I've seen people post about using oil successfully, although what kind I don't recall. I've stuck with the DT grease, myself.
There is a fairly long thread somewhere on MTBR with a name like "catastrophic failure DT hub" that has a lot of this info on star ratchets and care/lubing. I'm on my phone at the moment, or I'd look for the link for you, but you should be able to find it.
"Back off, man. I'm a scientist." - Dr. Peter Venkman
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Thanks for the info. I'll look for the thread.
I'm using a synthetic motor oil in there now. I'll see how it does.
I use Slick Honey in mine and have had zero trouble. I take it apart, clean and relive it every three months which is probably overkill.
I have been using Progold EPX grease in mine and haven't had an issue. I will be re-greasing them soon since the last time I did was last winter.
Too much, or too thick, grease is the only reason I could imagine that would cause skipping on a DT-Swiss 240s hub (especially with the 18pt star ratchets) that was new in June and used in normal/average conditions.
My brand new 36t ratchet just failed
I purchased a new wheelset recently with DT350 hubs and the 36t ratchet. Put them on the bike a few weeks ago and loved them. But yesterday the ratchet stripped while I was out on a ride. It happened during a shift on level ground, and the hub suddenly went from working perfectly to not working at all, skipping with a loud knocking sound under any kind of load. I have less than 100 miles on this brand new hub and ratchet!
Originally Posted by reamer41
I had read that the 36t ratchet sacrificed some durability, but figured that meant I would get only five to ten thousand miles out of it. Failure in under 100 miles is obviously unacceptable.
The ratchet was well greased with a thin layer of the special DT Swiss pink grease. It was fairly quiet because I put a moderately thin layer of grease on it before the first install (it came with virtually no grease and the buzzing sound was immediately softer after the grease application). And yes, it was properly installed, with the springs in the correct direction etc., and there was virtually no drag in the hub (pedals never turned when freewheeling).
I verified on the trailside that the ratchet and freehub were properly installed and simply would not engage. After a 5 mile hike/coast back home, I opened up the hub for a look-see. The special pink grease had turned black at the ratchet contact points and there were a few very tiny sharp metal splinters visible in the grease between the ratchet teeth. Although the ratchets otherwise looked fine at first, upon cleaning them off it is clear that the sharp teeth are worn/sheared off by a tiny amount (less than 0.1mm) at the tops, and this is enough to prevent clean engagement. The ratchets still lock together, but it is no longer a clean lock and can be made to move by twisting them against each other with force. It isn't clear if this happened all at once in a catastrophic skip or was gradual, but as noted I had no engagement problems at all before the failure.
Fortunately, my wheel builder also sent me the stock 18t ratchet as a spare, so I will be back on the trail today. But none too happy about such an early failure. After riding bikes for most of my life and never suffering a freehub failure, I am more than a little disappointed in the vaunted Swiss engineering for which I paid a premium. I will contact DT Swiss and see what they can do for me. I'm hoping that my ratchet was simply part of the first lot manufactured, which I have read had a too-high failure rate. But in the future suppose I will have to pack an extra ratchet in my trail kit.
The way the DT swiss ratchets work is susceptible to the slightest amount of contamination (or even too much grease being used). Anything that stops the teeth fully engaging with each other will cause power transfer just through the ratchet teeth tips and they will break off. Once that happens, you've got a vicious cycle with those little splinters stopping proper engagement and more teeth getting chipped.
Unless you really need the extra POE run the 18 point.
That all makes sense, but:
Originally Posted by TigWorld
1) Everything was clean as a whistle in there, no contamination, and the proper light application of grease.
2) DT Swiss has already gotten back to me and is shipping me a new pair of 36t ratchets. They think the original pair was likely defective.
3) I really like the extra engagement. I needed it today when I needed to restart on a climb. And it helps in techy sections where you need to keep the pedals level.
People start throwing "user error" accusations around every time this comes up. DT doesn't even bother with that - they just kindly send out new ones. My 2nd set chipped too.
Originally Posted by Jfloren
DT Swiss 240 Star Ratchet
Great picture of the DT Swiss Star Ratchet.
Can you guys please send me any of these broken DT Swiss 240 Star Ratchets?
I do not care which model it is if the 36 or 18.
Thank you a lot
P.S. Some of the damage ( in addition to the heavy grease) might be caused by the 2 springs. They might be too week and do not engage enough pressure on the ratchets.