Bump Bump Bump — One Very Loose Spoke on Rear Wheel
12-06-11, 04:45 PM
#1
you guys ridin'?
Thread Starter
Bump Bump Bump — One Very Loose Spoke on Rear Wheel
I could feel a subtle but periodic thump coming from my rear wheel, transmitted up my seat stays to my saddle. I sensed this around the time I installed new tires. Thinking it was related to the tires, I switched back to my old ones. The thump was still there.
I observed the wheel while riding and noticed one spoke on the left side that bowed outward more the the rest. Sure enough, it was incredibly loose; however, the wheel ran true. I have not yet adjusted spoke tension and re-trued the wheel, but...
Would having a wheel that basically runs true but has one spoke (effectively) missing produce the phenomenon that I am experiencing? [This may be a good question for Jobst Brandt!] Has anyone experienced something similar? Thanks!
I observed the wheel while riding and noticed one spoke on the left side that bowed outward more the the rest. Sure enough, it was incredibly loose; however, the wheel ran true. I have not yet adjusted spoke tension and re-trued the wheel, but...
Would having a wheel that basically runs true but has one spoke (effectively) missing produce the phenomenon that I am experiencing? [This may be a good question for Jobst Brandt!] Has anyone experienced something similar? Thanks!
12-06-11, 06:06 PM
#2
Senior Member
Join Date: Oct 2007
Location: West Yorkshire, United Kingdom
Posts: 5,773
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 453 Post(s)
Liked 104 Times
in
87 Posts
having one spoke loose or missing can cause this, especially with low spoke count wheels. just replace, true and it should be fine.
12-06-11, 07:44 PM
#3
Roadkill
Join Date: Sep 2004
Location: East Tennessee
Posts: 858
Bikes: 2002 Lightspeed Classic; 2010 Pedalforce RS
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
I would guess a bent rim (flat spot) causing the loose spoke and the bump.
12-06-11, 08:42 PM
#6
30 YR Wrench
Join Date: Aug 2005
Location: Oxford, OH
Posts: 2,006
Bikes: Waterford R-33, Madone 6.5, Trek 520
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 3 Times
in
2 Posts
This wheel was not properly equilibrated so that all spokes on a given side share the load equally, so absent any kind of spoke retention compound on the spoke or in the nipple, the unloaded spoke unscrewed itself.
The fix is simple: assuming the rim is not bent, using some form of tension measurement, balance the tensions, then using very small turns, bring the wheel back true and round.
The fix is simple: assuming the rim is not bent, using some form of tension measurement, balance the tensions, then using very small turns, bring the wheel back true and round.
12-07-11, 02:06 AM
#7
Senior Member
Join Date: Mar 2008
Posts: 8,688
Mentioned: 46 Post(s)
Tagged: 0 Thread(s)
Quoted: 1074 Post(s)
Liked 295 Times
in
222 Posts
If it runs true, but creates a bump, and it isn't the tire, then it pretty much has to be a flat spot. Bringing the spoke back to tension will in all likelihood promote the overall life of the wheel, but will not get rid of the flat spot. Some have reported being able to bend back flat spots, but I've never had any luck with that.
In theory, it could be a high spot as well. But you won't get a high spot from only one spoke dropping out. Maybe it's been there all the time and you've just recently picked up on it. Basically not associated with the loose spoke.
In theory, it could be a high spot as well. But you won't get a high spot from only one spoke dropping out. Maybe it's been there all the time and you've just recently picked up on it. Basically not associated with the loose spoke.
12-07-11, 10:23 AM
#8
Roadkill
Join Date: Sep 2004
Location: East Tennessee
Posts: 858
Bikes: 2002 Lightspeed Classic; 2010 Pedalforce RS
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
If it runs true, but creates a bump, and it isn't the tire, then it pretty much has to be a flat spot. Bringing the spoke back to tension will in all likelihood promote the overall life of the wheel, but will not get rid of the flat spot. Some have reported being able to bend back flat spots, but I've never had any luck with that.
But, after about 500 miles, the rim started to fail at the former flat spot and I replaced it.
With the OP's rim with less of a flat spot, he might get away with straightening the rim, but I would just replace it.
12-07-11, 10:31 AM
#9
Constant tinkerer
Correct me if I'm wrong but I think the thump the OP is describing isn't the rim but rather the spoke flopping around every revolution. I had a 36x3 wheel that did this, but that was before I knew anything about mechanics so it was never fixed. Wheel was straight and true at the time.
OP: just get the wheel re-tensioned and trued, should be a simple repair.
OP: just get the wheel re-tensioned and trued, should be a simple repair.
12-07-11, 11:01 AM
#10
Banned.
Join Date: Apr 2011
Posts: 937
Bikes: CCM Torino 76
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
Funny... I have had wheels with multiple broken or missing spokes and felt nothing, but a slightly out-of-true, or slightly improperly seated tire can almost always be felt through the saddle.
12-07-11, 02:07 PM
#11
you guys ridin'?
Thread Starter
Now that's the kind of stuff I was looking for! The subtle thump that I was experiencing MAY have actually been from the spoke buckling with each revolution due to inadequate tension. It was only really perceptible on really smooth pavement. That particular spoke happened to be adjacent to section of the rim where it is joined and I was concerned that it might have something to do with the joint failing.
12-07-11, 02:30 PM
#12
Banned
Wheel maintenance was skipped for too long. that includes tensioning and truing.
If the rim has a seam rather than welded, there is a set of pins across that gap
and the aluminum extrusions are rolled in compression, they don't 'come apart'
Further, the spokes pull together increasing the compression across the seam.
If the rim has a seam rather than welded, there is a set of pins across that gap
and the aluminum extrusions are rolled in compression, they don't 'come apart'
Further, the spokes pull together increasing the compression across the seam.
Last edited by fietsbob; 12-07-11 at 02:35 PM.
12-08-11, 06:56 AM
#13
Senior Member
Join Date: Mar 2008
Posts: 8,688
Mentioned: 46 Post(s)
Tagged: 0 Thread(s)
Quoted: 1074 Post(s)
Liked 295 Times
in
222 Posts
Unlikely. With double-walled rims (which yours are), the spoke would be free to move quite a bit down/out before encountering any resistance. Perhaps if the nipple has seized to the rim, which in itself also is unlikely.
12-11-11, 07:01 AM
#15
you guys ridin'?
Thread Starter
My bad — On close inspection (in the truing stand) I have found a very localized "flat" spot on the rim, right at the point where it was joined. Also, there is some evidence of damage (perhaps from a pothole) as there is a slight notch in one side of the rim in this location.
