Yet Another Cycling Forum

General Category => Freewheeling => Tandems => Topic started by: 321up on November 06, 2017, 04:02:44 pm

Title: DT Swiss 540 Tandem rear hub - repair or replace?
Post by: 321up on November 06, 2017, 04:02:44 pm
Our DT Swiss rear hub has developed a fault.  It got us to our destination on Friday but we accepted a kind offer of a lift home rather than risk it failing completely and leaving us stranded.  I've not stripped it down yet but I suspect either the axle or wheel bearings are in the process of failing (I suspect the axle).  My plan would be to replace the axle and bearings, but by the time I've bought the parts & tools I wonder if it would be more cost effective and give greater reliability to replace the whole thing?  I'd probably replace it with another the same unless I can find something better.  I've read the DT Swiss technical manual but it's not clear if the ring nut needs to be removed to replace the drive side wheel bearing on this model (which requires a special tool).  Anyone have any practical experience/advice replacing the wheel bearings or axle on this model of hub?  Thanks, A.
Title: Re: DT Swiss 540 Tandem rear hub - repair or replace?
Post by: aidan.f on November 08, 2017, 10:47:42 pm
I have two dt swiss tandem hubs which have  'torn around the spoke holes'. I wonder whether the innards are the same as yours? Will have a check of model no.
Title: Re: DT Swiss 540 Tandem rear hub - repair or replace?
Post by: 321up on November 09, 2017, 09:40:39 am
Thanks Aidan.

Our hub is 145mm and is marked "P1566000 166 DTP F 1732".  Probably most the internals will be the same as the 135mm variant and the difference in axle length is probably achieved with different length adaptors on the end of the axle (i.e. it the axle assembly consists of three parts, the central part described as 'axle', and the end parts described as 'adaptors').  The plan is to attempt the repair myself.
Title: Re: DT Swiss 540 Tandem rear hub - repair or replace?
Post by: 321up on November 09, 2017, 12:29:00 pm
I've got the freehub off (just required a bit more force to pull it off than I had expected).  First thing I noticed was how clean it was internally, looks like the seals have worked perfectly.  The grease on the star ratchets was fine, just discoloured black due to normal wear.  Looks like hub side bearing on the freehub has at some point been turning against the axle (i.e. minimal wear caused on axle due to polishing of the surface), but the bearing itself seems to be turning freely.  The grease on both ends of the spacer between the freehub and wheel bearing (part 9 on generic diagram linked below) is black indicating that one (or both) bearings have been turning against it at some point (i.e. bearing seizure? but both currently turning freely).  Axle turns freely and true (i.e bearings seem ok and the axle isn't bent).  So superficially nothing thus far to explain the lack of rigidity in the hub (although a temporary bearing seizure could explain the screeching noises under load).  The first symptom we noticed was a very brief screeching noise whilst out the saddle on a moderate climb.  With 50km to go the screeching noise returned on a gentle climb (in the saddle this time), again intermittent but for longer durations.  The noise stopped when effort was reduced.  Time to investigate - I found that moderate side to side force at the top of the wheel would cause the disc rotor touch the pads either side - more movement than I would expect but I could not detect any rattle in the bearings and the screeching noise didn't sound like the disc rotor.  Also loading the wheel sideways appeared to cause a tiny movement in the cassette in the opposite direction (consistent with the axle flexing).  We decide it wasn't something a normal bike shop would have the parts to fix so continued to our destination riding as gently as possible.  So now I've got the cassette and spacer off I can see the axle - there appears to be a tiny fracture inline with the end of the spacer where it meets the freehub bearing (I'm surprised to find it here rather than inline with the wheel bearing so I guess that the spacer provides stiffness to the axle).  The fracture is also visible by looking down the inside of the axle (having removed the QR skewer), by shining light down the opposite end of the axle a black hairline is just about visible in the reflection of light off the inside of the axle (when I first saw this I thought it might be a cosmetic imperfection but now having found a corresponding hairline on the outer surface I think it's very likely to be a fracture).  Why the screeching noise?  Perhaps the flex in the partially fractured axle put unusual strain on the bearings or released the pressure applied by the spacer and allowed the bearings to spin on the axle?  Looks like we made the right decision accepting the lift home - thanks.  Time to discuss this with the supplier of the wheel and find out how good the DT Swiss 24 month warranty is. (
Title: Re: DT Swiss 540 Tandem rear hub - repair or replace?
Post by: Ian H on November 09, 2017, 12:37:50 pm
A cassette bearing can unexpectedly lock if the cage has broken up so that pieces are floating around loose. Prise a seal off to check.