No seals in DT Swiss 240S hub

[tomli123001]

Hi guys. I bought my DT Swiss 240S rear hub. It has been great.

Yesterday, when I first time pulled it apart for service, I realized that there is no seal at all in the hub internal. No O-rings, no grease port, no lip seal and no rubber cap. I was using Shimano before, which has quite a few sealing mechanism there.

My question is how does the hub keep dirt out? Is no sealing worth the extra few grams of weight saving? I now start feeling the light weight stuff is not so durable, because the cassete already started biting into the alloy freehub body even XT cassete is used (the smallest cogs are not on carrier) :mmph:

 

[stacky]

The DT Swiss hubs use sealed bearings and also the axle adapters fit quite snugly to the hubs inner edge and stop dirt getting that far inside. They don't really need O-rings or extra seals really, how clean/dirty were the internals when you pulled it apart?
On the other hand, Shimano use a loose ball bearing system which is why they have the dust deals and adjustment nuts etc

 

[Binaural]

Hi guys. I bought my DT Swiss 240S rear hub. It has been great.

Yesterday, when I first time pulled it apart for service, I realized that there is no seal at all in the hub internal. No O-rings, no grease port, no lip seal and no rubber cap. I was using Shimano before, which has quite a few sealing mechanism there.

My question is how does the hub keep dirt out? Is no sealing worth the extra few grams of weight saving? I now start feeling the light weight stuff is not so durable, because the cassete already started biting into the alloy freehub body even XT cassete is used (the smallest cogs are not on carrier) :mmph:

There is a wiper seal on the exterior, and seals on the individual cartridge bearings on the 240 IIRC - I've attached a pic of when I took mine apart to replace the star ratchet mechanism. Only light sealing is required for cartridge bearings normally since otherwise they would have a bit too much drag. You might be used to the open bearings Shimano use in most of their hubs, which do need good-quality seals.



The only maintenance issues I've had with the 240s is when I broke the tip off the aforementioned star ratchet, which then got stuck between the meshing mechanisms and suddenly gave way, dumping me on my face in traffic and nearly getting me run over - on the flat, under light load. After replacing it I've not had problems ever again, but this single-point-of-failure is a key reason I'm staying away from this type of hub in the future.

 

[tomli123001]

The DT Swiss hubs use sealed bearings and also the axle adapters fit quite snugly to the hubs inner edge and stop dirt getting that far inside. They don't really need O-rings or extra seals really, how clean/dirty were the internals when you pulled it apart?
On the other hand, Shimano use a loose ball bearing system which is why they have the dust deals and adjustment nuts etc

Yes, that is very helpful. It wasn't that dirty in there, except some black stuff which is most likely the used grease. But then again I did not use it in terribly dirty or muddy trails either.

 

[tomli123001]

There is a wiper seal on the exterior, and seals on the individual cartridge bearings on the 240 IIRC - I've attached a pic of when I took mine apart to replace the star ratchet mechanism. Only light sealing is required for cartridge bearings normally since otherwise they would have a bit too much drag. You might be used to the open bearings Shimano use in most of their hubs, which do need good-quality seals.

View attachment 210197

The only maintenance issues I've had with the 240s is when I broke the tip off the aforementioned star ratchet, which then got stuck between the meshing mechanisms and suddenly gave way, dumping me on my face in traffic and nearly getting me run over - on the flat, under light load. After replacing it I've not had problems ever again, but this single-point-of-failure is a key reason I'm staying away from this type of hub in the future.

Nice photo Binaural. Thank you. Did you use the original 18T ratchet or the aftermarket 36T units? I heard that the 36T ones wear out a lot faster and chip easily on the tips. I though twin ratchet mechanism was supposed to be much more secured than traditional pawl system. I am sorry for the bad incident you had.

 

[udi]

A well designed traditional pawl system will tick forever, any issues would stem from a poor design.

I found the DT star ratchets worked fine though, they originally just used hardened steel which wore a little quickly, but soon upgraded to chromed ones which are a lot tougher. It's a shame you've heard of the 36T ones slipping, because I thought the 18T ones were a little slow to engage. Personally given the choice, I'd run/try the 36T ones anyway, don't all the new hubs come with them?

The other thing is, they run best with a very light grease or even a thick oil. Too much or too thick a grease will encourage slippage, I found that keeping the mechanism fairly clean and lightly oiled gave the best results.

As for the sealing, I never had a problem. The non-drive side should have a labyrinth/lip seal on the end cap, and the drive side should have an o-ring where it clips onto the axle. There should be another seal where the freehub body meets the main hub body. I haven't had a 240s rear (only front, and a bunch of 340/440 rears) so maybe yours is different, but I'd be surprised if it didn't have those seals.

 

[tomli123001]

A well designed traditional pawl system will tick forever, any issues would stem from a poor design.

I found the DT star ratchets worked fine though, they originally just used hardened steel which wore a little quickly, but soon upgraded to chromed ones which are a lot tougher. It's a shame you've heard of the 36T ones slipping, because I thought the 18T ones were a little slow to engage. Personally given the choice, I'd run/try the 36T ones anyway, don't all the new hubs come with them?

The other thing is, they run best with a very light grease or even a thick oil. Too much or too thick a grease will encourage slippage, I found that keeping the mechanism fairly clean and lightly oiled gave the best results.

As for the sealing, I never had a problem. The non-drive side should have a labyrinth/lip seal on the end cap, and the drive side should have an o-ring where it clips onto the axle. There should be another seal where the freehub body meets the main hub body. I haven't had a 240s rear (only front, and a bunch of 340/440 rears) so maybe yours is different, but I'd be surprised if it didn't have those seals.

Hi udi, Nope, no seals whatsoever. On chainreaction web description, it mentioned seals for 340s, but not for 240s. I had taken them apart twice now. Not sure about the non-drive side, but none with free hub body.

36t is only an upgrade not standard.

As for the 36t chipping, it is from mtbr forum here, http://forums.mtbr.com/29er-bikes/catastrophic-failure-dt-swiss-36-point-hub-602813.html
The 36t ratchet is hollow and maybe the forging is not as solid.