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+--- Thread: Broken spokes -> NEAR DEATH EXPERIENCE!!! (/showthread.php?tid=4973)
RE: Broken spokes -> NEAR DEATH EXPERIENCE!!! - pekingduck - 05-20-2019
While we think of wire-spoke motorcycle and bicycle wheels as similar, the failure causes are very different. The informative book by Jobst Brandt in post 59 applies specifically to bicycles, where most failures are due to weight and fatigue.
Motorcycles can pull more than one G in either deceleration or acceleration. The area of concern to me is the bend in the spoke and how the spoke is not supported in the hub flange. In the picture below, the spokes are supported in the hub in the area below the red line. Spokes work fine in tension, but will fatigue when bent and unsupported.
The traditional spoke wheel has spokes bent at the hub flange, with spokes alternately bending on the inside and outside of the flange. The outside spoke have to be bent more than 90 degrees, the inside ones less than 90. Spoke failure is usually at the bend, and more often, the outside spokes.
In the picture below, you can see that the outside spokes rub against the hub flange, which actually gives them more support and strength. Also, when we think of spokes loosening, it is because the spoke is seating into the hub and the nipple into the rim, not because of spokes stretching or nipples unscrewing.
The black and the yellow arrows point to where the spoke will wear into the sharp edge of the hole causing the spokes to get looser. (It's like valves getting tighter, not because the cam or shim wore, but because the valve face seats into the valve seat)
The ideal is straight spokes, which the Triumph Bonneville went to in 2010 due to rear spoke breakage problems. Their spokes (although stainless) had similar long unsupported areas just like the earlier Honda.
RE: Broken spokes -> NEAR DEATH EXPERIENCE!!! - Bazbro_imp - 05-20-2019
Great posts on here and really good information. Thanks guys.
For information, my BMW R100R (1992 vintage) has straight spokes, out of the hub, in a straight line through the the edge of the rim. This also permits a tubeless tyres in a spoked rim. And that was 25+ years ago. Why everyone doesn't build wheels like this now, I don't know.
RE: Broken spokes -> NEAR DEATH EXPERIENCE!!! - pekingduck - 05-20-2019
(05-20-2019, 03:33 AM)Bazbro_imp Wrote: Great posts on here and really good information. Thanks guys.
For information, my BMW R100R (1992 vintage) has straight spokes, out of the hub, in a straight line through the the edge of the rim. This also permits a tubeless tyres in a spoked rim. And that was 25+ years ago. Why everyone doesn't build wheels like this now, I don't know.
If I remember right, no one knew how to true them, and BMW did not even sell individual spokes - they said if a wheel is damaged, replace it. Don't know if that has changed.
RE: Broken spokes -> NEAR DEATH EXPERIENCE!!! - Bazbro_imp - 05-20-2019
Wheel building and trueing is an art. It's not just a matter of tightening or replacing a spoke(s). I agree with BMW on this. If you have spoked wheel problems, take it to a wheelbuilder or your garage to get it repaired - it's too delicate a job to just blindly do yourself, imo. Tightening one spoke may overtighten/loosen another. or pull the wheel out of 'true'.
Here in the UK, courses are occasionally offered by wheelbuilders, in how to do the job. Seems a bit like turkeys voting for Christmas to me!
RE: Broken spokes -> NEAR DEATH EXPERIENCE!!! - jtopiso_imp - 05-20-2019
(05-20-2019, 12:08 AM)kennyw_imp Wrote:(05-19-2019, 05:30 PM)jtopiso_imp Wrote:(05-17-2019, 10:47 AM)The ferret_imp Wrote: That's a shame that happened.
Spoke breakage is not common but not rare either. The early Bonnevilles 2000-2003 had the issue so often the forums were asking for a recall. It happened to my 2003 Centenial Edition Bonnie as well. I went around a left hander and felt a pop, then more pops and the back end got all wobbly. Had probably a dozen or so broken spokes all together. Triumph thankfully paid for a new wheel.
Right now there is a internet blog of a guy on a BMW GS who's front wheel spokes all disintegrated on him. More reports of similar problems followed. They are wanting a recall on BMW spoked wheels.
Spokes are like the span of a bridge. EAch spoke shares and spreads the pressure between them. If one spoke goes, that puts extra pressure on the remaining spokes, which end up flexing more than they are designed and then another breaks, putting even more pressure on the remaining spokes. pretty soon it's a lost cause and most break.
Spokes look good, they flex making the ride softer, but they also sometimes break.
Well... spokes are like "stay-cables" on a bridge. The work in tension only, so they don't flex: they just stretch.
Preload on them has to be high enough so load cycles are small and fatigue is minimized (load will be small compared to tension, so cycle amplitude is small). If load is to high, you could have metal yield (so tension becomes VERY low), ir it can just snap (this depends on the alloy). In any case: spoke preload is VERY important.
Without knowing this case, I'd point the probable causes to be:
-wrong servicing (i.e. bad preload on spokes) -> most probable
-bad batch of spokes -> unlikely: we would have heard of more.
-corrosion failure -> unlikely: we would have heard of more.
-bad design -> VERY unlikely: spoke rim design is not exactly a new unknown technology
This is just my opinion, but if I had to bet... this failure can be from something very simple like a unit conversion problem from [Nm] to [lb·ft].
I'm glad nothing irreversible happened!
Some interesting info I've just found regarding spoked wheels:
http://poehali.net/attach/Bicycle_Wheel_-_Jobst_Brandt.pdf
You cannot rule the last three as unlikely without further investigation. I've seen all of these types of failures in my 20+ years as a mechanical engineer across many mature product lines and industries.
The fact Honda changed the spoke wheel design tells me they MAY have been aware of a design issue OR the change was to cut cost. However, since the materials used after the design change are more expensive, I doubt it was a cost cut.
Indeed: I can't rule anything out, but with the information we have, that's my guess. But it's just a guess.
Honda can change design or materials due to several reasons: cost, a design issue, or just because they wanted to offer something different, even if it's more expensive (if they think it adds value and they will sell more). E.g. double walled stainless headers are not there to correct any design issues, and they have to be more expensive to make.
And again: it can be anything, but if I had to put my money, I'd bet for wrong servicing.
Now I ask: how do they check preload on spokes? do they meassure torque on the nut or do they messure actual tension on the wire spoke?
Torque meassures are VERY dependant on how clean is the thread, the nut seat friction, and the calibration of the torque wrench. All this can add up to a lot of error (~30%). Sometimes all this doesn't matter, but... it could.
RE: Broken spokes -> NEAR DEATH EXPERIENCE!!! - alprider - 05-21-2019
(05-19-2019, 01:17 AM)pekingduck_imp Wrote: "What Alprider helpfully points out is the new wheel has an aluminum hub with 40 stainless spokes and the old wheel has 48 zinc plated spokes. "
Thanks very much for the translation and clarification. In the US market, we did not receive any CB1100s until 2013 and 2014, and they were all cast-wheel versions. We received no 2015 or 2016 models, and the only 2017 models we got were wire-wheel models (no RS models ever).
A check of the parts catalog shows that US wire-wheel models are 40-spoke, and presumably stainless. Still, if someone could put a magnet to their spokes, it would be nice to know.
made today a test with my olight flash light "baton S1" endcap...minimum our version are magnetic.... smile
RE: Broken spokes -> NEAR DEATH EXPERIENCE!!! - pekingduck - 05-21-2019
(05-21-2019, 04:29 AM)alprider_imp Wrote:(05-19-2019, 01:17 AM)pekingduck_imp Wrote: "What Alprider helpfully points out is the new wheel has an aluminum hub with 40 stainless spokes and the old wheel has 48 zinc plated spokes. "
Thanks very much for the translation and clarification. In the US market, we did not receive any CB1100s until 2013 and 2014, and they were all cast-wheel versions. We received no 2015 or 2016 models, and the only 2017 models we got were wire-wheel models (no RS models ever).
A check of the parts catalog shows that US wire-wheel models are 40-spoke, and presumably stainless. Still, if someone could put a magnet to their spokes, it would be nice to know.
made today a test with my olight flash light "baton S1" endcap...minimum our version are magnetic.... smile
made today a test with my olight flash light "baton S1" endcap...minimum our version are magnetic.... smile
Thanks for checking. So according to the website in Germany, the Press Release for the 2017 model says they have 40 stainless spokes, which I confirmed for the US model also. I assume then that your bike is pre-2017 then. Thanks for the info.
RE: Broken spokes -> NEAR DEATH EXPERIENCE!!! - alprider - 05-21-2019
hmmm i test it only by my 2017 modell.....bcos steinless is only start by 2017 modells...
RE: Broken spokes -> NEAR DEATH EXPERIENCE!!! - dave - 05-22-2019
Great video on the SS versus chrome plated spokes. Does anyone know what spoke material Honda used on their 1970's CB750's? I have a 1976 CB750F, and it's been sitting in my shed for over 20 years. The spokes are very rusted, and pitted. I thought I could clean them up, but that doesn't look like a good idea after watching this video. This bike has 123,000 miles on it (I am the original owner), and I never once had a problem with the spokes. I don't remember having to ever tighten them - I did check them a few times over the course of 22 years of riding it though.
RE: Broken spokes -> NEAR DEATH EXPERIENCE!!! - pekingduck - 05-22-2019
(05-22-2019, 12:26 PM)Dave_imp Wrote: Great video on the SS versus chrome plated spokes. Does anyone know what spoke material Honda used on their 1970's CB750's? I have a 1976 CB750F, and it's been sitting in my shed for over 20 years. The spokes are very rusted, and pitted. I thought I could clean them up, but that doesn't look like a good idea after watching this video. This bike has 123,000 miles on it (I am the original owner), and I never once had a problem with the spokes. I don't remember having to ever tighten them - I did check them a few times over the course of 22 years of riding it though.
The "Stainless steel versus chrome plated spokes" video misses two points.
First, the vast majority of spokes are cadmium or zinc plated. Throughout Honda's history, I cannot think of any bike that used chromed spokes (except possibly the 1976 GL1000 LTD which had gold colored or plated spokes), and only one that uses stainless spokes (2017 CB1100). That's likely true of most other bikes coming out of Asia (except Triumphs and some Royal Enfields).
Chromed spokes (or any chrome-plated or nickel-plated structural item) are subject to hydrogen embrittlement that makes the material much more prone to cracking and failure, amplified by it's movement. I doubt that most aftermarket chrome spokes are properly heat relieved.
Polished stainless steel can be almost as bright as chrome, but, like our stainless headers, doesn't stay nice forever.