Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

Shimano Dynamo Hub faliure

Notices
Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

Shimano Dynamo Hub faliure

Old 03-16-22, 05:33 AM
  #1  
beetrootman
Member
Thread Starter
 
Join Date: Aug 2005
Posts: 32
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Shimano Dynamo Hub faliure

I just wanted to share some information on the failure of one of the newer Shimano Dynamo hubs, a DH-UR705-3D. It seized up on me and when I opened I found the magnets inside completely corroded and some had shattered.
Has anyone else had similar experiences? This is after only one winter riding with the hub (in Switzerland, temperatures can be below zero Celsius, the bike is stored indoors). Severe case of condensation inside the hub?
Shimano won't warranty it as I've opened it myself (which I kind of understand, but not that I think it makes much difference with a failure of this type).
Images below:

.
beetrootman is offline  
Old 03-16-22, 05:51 AM
  #2  
soyabean
Senior Member
 
soyabean's Avatar
 
Join Date: Feb 2022
Posts: 291
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 164 Post(s)
Liked 110 Times in 79 Posts
In my hometown, they throw so much salt on the roads, this kills everything metal, even aluminum.

So people have winter beater bikes and winter beater cars.

Not sure what they do over there where you are, but corrosion causes are always the same: water infiltration.

You can try your best with preventive measures like loads of grease/lube/inhibitors, wash the bike after each ride, and despite all that it still happens.

You got it easy. Should see what this does to some new ebikes are 1 winter as well.

soyabean is offline  
Likes For soyabean:
Old 03-16-22, 06:01 AM
  #3  
stevel610 
Senior Member
 
Join Date: Aug 2006
Location: Valley Forge: Birthplace of Freedom
Posts: 1,179

Bikes: Novara Safari, CAAD9, WABI Classic, WABI Thunder

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 324 Post(s)
Liked 376 Times in 197 Posts
I'd try to have it warranteed. Doesn't look normal.
__________________
Be watchful, stand firm in the faith, act like men, be strong. Let all that you do be done in love.
stevel610 is offline  
Old 03-16-22, 07:30 AM
  #4  
Bike Gremlin
Mostly harmless
 
Bike Gremlin's Avatar
 
Join Date: Nov 2010
Location: Novi Sad
Posts: 4,263

Bikes: Custom made on Scott Speedster frame, Custom made on a 1996. steel MTB frame (all but frame changed at least once in the past 20 years).

Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 1021 Post(s)
Liked 103 Times in 68 Posts
I've had good luck even with used (old) Shimano dynamo hubs, mostly with a solid axle, or with a quick release.
Recently, for my own bike, I risked buying a brand new one - with a quick release. What I did notice was cones being too tight from the factory, so I loosened them (yes, I understand magnets make it behave not like a normal hub, but it was still way too tight).

This problem however doesn't seem to have anything to do with bearing preload as far as I could tell. And I consider it unusual (someone please correct me if I'm wrong).
Those things are decently sealed to make any water or dirt intrusion more difficult.

Stupid questions, but just in case:
- Did you use any pressure washers on that hub?
- Do you store the bike indoors (condensation might play a part in that case - my bikes are stored outside, under a roof, but outside)?
Bike Gremlin is offline  
Old 03-16-22, 07:52 AM
  #5  
pdlamb
Senior Member
 
Join Date: Dec 2010
Location: northern Deep South
Posts: 7,776

Bikes: Fuji Touring, Novara Randonee

Mentioned: 33 Post(s)
Tagged: 0 Thread(s)
Quoted: 2012 Post(s)
Liked 1,258 Times in 801 Posts
My older Shimano dyno hub is still going strong after some 9 years' year-round commuting. However, it's stored in an unheated garage. That might make a difference; there's a theory that thermal cycling between cold and dry air, and warm and humid air, will suck moisture into the hub where it will condense and potentially corrode the innards (to use a technical term).

After reading about that, and being quite happy with dyno lighting for winter commutes, I got another dyno hub for the spare bike a year later. The SON hub supposedly has a pressure equalization tube (or something like that) which catches the warm moist air and keeps the moisture from getting inside the hub.

Both mine are still working fine. But given the difference between my ambient storage and your inside storage, you might want to think about upgrading your hub to a SON.
pdlamb is online now  
Likes For pdlamb:
Old 03-16-22, 12:35 PM
  #6  
well biked 
biked well
 
well biked's Avatar
 
Join Date: Jul 2005
Posts: 7,414
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 117 Post(s)
Liked 105 Times in 61 Posts
I have used Shimano dynamo hubs for a few years on two or three different bikes, no problems so far. But I think your situation in Switzerland with the cold temps in the winter and indoor storage has created condensation inside the hub, and that's caused the failure due to rust and corrosion . As already mentioned, SON hubs have in their current design a feature that prevents this. My understanding is that earlier SON hubs were prone to this also, and so they improved the design to prevent it. SON dynamo hubs are pricey, but they are the gold standard for dynamo hubs. I think this rust-related failure inside your Shimano hub shows why a new SON hub might be worth the expense.
well biked is offline  
Old 03-16-22, 07:11 PM
  #7  
sweeks
Senior Member
 
sweeks's Avatar
 
Join Date: Sep 2004
Location: Chicago area
Posts: 2,156

Bikes: Airborne "Carpe Diem", Motobecane "Mirage", Trek 6000, Strida 2, Dahon "Helios XL", Dahon "Mu XL", Tern "Verge S11i"

Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 824 Post(s)
Liked 365 Times in 269 Posts
An early "Joule" hub, originally sold by Dahon, is similar in some ways to the Shimano dynohub. I had one of these hubs fail after a couple thousand miles. I was told it was not serviceable. Since I had a spare, I figured I had nothing to lose by trying to repair it. The process was documented HERE, and might be interesting.
On the subject of hubs "inhaling" moisture... the explanation makes sense, but I wonder how common this is. My Joule hub surely failed because of water incursion, but after its repair the problem has not recurred. I also have a SP dynohub on my folding commuter bike; the hub has over 10,000 miles on it. I'm riding in Chicago year-around; the bike is stored in an unheated garage at home, and indoors at work.
sweeks is offline  
Old 03-17-22, 04:59 AM
  #8  
beetrootman
Member
Thread Starter
 
Join Date: Aug 2005
Posts: 32
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Thanks for all the feedback. The bearings were fine in the hub, as was the wiring. My initial thought was that the easiest entry path for water would be along the wiring into the stator; the wiring didn't seem particularly well shielded. The link to the Joule hub is interesting. One thing I noticed is that the magnets in the Shimano hub are much thinner, and metallic in colour, perhaps a different composition? I think one of the reasons they shattered is because they are so thin. If they'd just rusted it would have been no problem to clean up the hub and get it running again.

What are people's thoughts on greasing / oiling the innards of the replacement hub with a thin layer to try and prevent the same problem reoccurring? (I have no qualms opening the new hub and voiding warranty as I believe in the right to repair / improve). Normally I service regular Shimano hubs before putting into to service because of lack of grease / over tightening of bearings from the factory.
beetrootman is offline  
Old 03-17-22, 06:27 AM
  #9  
dabac
Senior Member
 
Join Date: Mar 2008
Posts: 8,688
Mentioned: 46 Post(s)
Tagged: 0 Thread(s)
Quoted: 1073 Post(s)
Liked 289 Times in 216 Posts
It does look like you got some significant water in there, which I find somewhat surprising.
I've only had issues with one Shimmano dynohub, when one of the magnets came loose. It dragged and made a lot of noise, but didn't really damage anything. I disassembled and glued the magnet back on, and all was well.
Can't see anything wrong with a thin coat of grease.
dabac is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.