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SRAM Spectro S7 hub spectacularly killed
Hi y'all,
I was riding around town yesterday on my 29er equipped with a SRAM Spectro S7 gearhub and 40/21 primary gearing. As I came to a short, steep uphill section of gravel alley, I downshifted to first gear and turned up my effort to climb the rise without having to get off and push. My hub said "pop!" and my pedals sagged out from underneath me. A quick triage operation established that instead of the usual [1-2-3-4-5-6-7] shift sequence, I was instead getting [N-N- N-4-4-4-4]. After the "event", there was no unusual noise, crunching, or balkiness in the hub-- just smooth freewheeling in both directions for gears 1-3 and normal 1:1 single-speed drive in gears 4-7. I hope to take apart the hub and do a postmortem soon. But until then, does anybody have a guess what let go inside, and whether it's a reasonably fixable issue? Chalo |
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#2
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SRAM Spectro S7 hub spectacularly killed
Chalo wrote:
Hi y'all, I was riding around town yesterday on my 29er equipped with a SRAM Spectro S7 gearhub and 40/21 primary gearing. As I came to a short, steep uphill section of gravel alley, I downshifted to first gear and turned up my effort to climb the rise without having to get off and push. My hub said "pop!" and my pedals sagged out from underneath me. A quick triage operation established that instead of the usual [1-2-3-4-5-6-7] shift sequence, I was instead getting [N-N- N-4-4-4-4]. After the "event", there was no unusual noise, crunching, or balkiness in the hub-- just smooth freewheeling in both directions for gears 1-3 and normal 1:1 single-speed drive in gears 4-7. I hope to take apart the hub and do a postmortem soon. But until then, does anybody have a guess what let go inside, and whether it's a reasonably fixable issue? Chalo It depends on what happened. If it's just one of the springs getting tangled or a ball cage coming apart & jamming it can probably be fixed. If any other piece of metal broke it's dead. Internal parts are not available in North America. There are fairly good diagrams available on the SRAM web site to help getting it all back together but you have to poke around a bit to find them. On the newer models you need an extra large (22mm?) cone wrench. Be careful of the phases of the planet gears when you put it back together, there's a spot on the top that needs to be in the same orentation for all 3 gears. Leland |
#3
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SRAM Spectro S7 hub spectacularly killed
On Apr 25, 12:51 pm, Chalo wrote:
Hi y'all, I was riding around town yesterday on my 29er equipped with a SRAM Spectro S7 gearhub and 40/21 primary gearing. As I came to a short, steep uphill section of gravel alley, I downshifted to first gear and turned up my effort to climb the rise without having to get off and push. My hub said "pop!" and my pedals sagged out from underneath me. A quick triage operation established that instead of the usual [1-2-3-4-5-6-7] shift sequence, I was instead getting [N-N- N-4-4-4-4]. After the "event", there was no unusual noise, crunching, or balkiness in the hub-- just smooth freewheeling in both directions for gears 1-3 and normal 1:1 single-speed drive in gears 4-7. I demand my money back, that was not spectacular. I wanted a description like a cartoon with loose wheels and random squirrels flying through a fog of bearings. Stinks though. Hope Leland's right-- could just be a simple spring. Good excuse to mess with it at any rate. |
#4
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SRAM Spectro S7 hub spectacularly killed
landotter wrote:
Chalo wrote: My hub said "pop!" and my pedals sagged out from underneath me. A quick triage operation established that instead of the usual [1-2-3-4-5-6-7] shift sequence, I was instead getting [N-N- N-4-4-4-4]. After the "event", there was no unusual noise, crunching, or balkiness in the hub-- just smooth freewheeling in both directions for gears 1-3 and normal 1:1 single-speed drive in gears 4-7. I demand my money back, that was not spectacular. I wanted a description like a cartoon with loose wheels and random squirrels flying through a fog of bearings. Fair enough. I could at least have had the decency to dive face-first off the bike for another round of haphazard DIY cosmetic surgery (complete with photos!!) I think of it as spectacular, though a better term might be "catastrophic", whenever a bike part dies with a bang instead of a whimper. Stinks though. Hope Leland's right-- could just be a simple spring. Good excuse to mess with it at any rate. It will be a good excuse to tear into it, and a good excuse to try out a new Alfine hub if that should prove necessary. (Complete with rear disc brake, natch.) If the money fairy smiles on me, it might even become "necessary" to "experiment" with another Rohloff hub. This bike is the temporarily de-electrified version of my 'lectric bike. If I can't fix it up to my complete satisfaction, then it will also be a good excuse to build yet another power-assist machine, stout as Vulcan's anvil. So it's all for the good, in its way. I'm sure my wife will come around to my way of thinking on this. Chalo |
#5
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SRAM Spectro S7 hub spectacularly killed
Chalo wrote:
Hi y'all, I was riding around town yesterday on my 29er equipped with a SRAM Spectro S7 gearhub and 40/21 primary gearing. As I came to a short, steep uphill section of gravel alley, I downshifted to first gear and turned up my effort to climb the rise without having to get off and push. My hub said "pop!" and my pedals sagged out from underneath me. A quick triage operation established that instead of the usual [1-2-3-4-5-6-7] shift sequence, I was instead getting [N-N- N-4-4-4-4]. After the "event", there was no unusual noise, crunching, or balkiness in the hub-- just smooth freewheeling in both directions for gears 1-3 and normal 1:1 single-speed drive in gears 4-7. I hope to take apart the hub and do a postmortem soon. But until then, does anybody have a guess what let go inside, and whether it's a reasonably fixable issue? Chalo all these hubs have torque specs, which you can easily exceed. this should therefore not really be at all surprising. |
#6
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SRAM Spectro S7 hub spectacularly killed
jim beam wrote:
Chalo wrote: I hope to take apart the hub and do a postmortem soon. But until then, does anybody have a guess what let go inside, and whether it's a reasonably fixable issue? all these hubs have torque specs, which you can easily exceed. this should therefore not really be at all surprising. I've been riding on various gearhubs for about ten years. This is the first one I've busted up internally (though certainly not the first one I've had some trouble with). If a bike part has a capacity rating, I generally exceed it. I'm used to that. I try to stick with stuff whose real capacity is known to exceed its rating, or whose useful lifespan and failure characteristics are otherwise acceptable. A couple of weeks ago, I wasted an 8/9 speed cassette body, while using a modest 36t ring. In that case, my pedals didn't fall away-- rather the thing crunched and then stopped freewheeling. I suppose I could limit myself to trials-proven single freewheels or (worse yet) fixed gearing, but where's the fun in that? Chalo |
#7
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SRAM Spectro S7 hub spectacularly killed
Chalo Wrote: Hi y'all, I was riding around town yesterday on my 29er equipped with a SRAM Spectro S7 gearhub and 40/21 primary gearing. As I came to a short, steep uphill section of gravel alley, I downshifted to first gear and turned up my effort to climb the rise without having to get off and push. My hub said "pop!" and my pedals sagged out from underneath me. A quick triage operation established that instead of the usual [1-2-3-4-5-6-7] shift sequence, I was instead getting [N-N- N-4-4-4-4]. After the "event", there was no unusual noise, crunching, or balkiness in the hub-- just smooth freewheeling in both directions for gears 1-3 and normal 1:1 single-speed drive in gears 4-7. I hope to take apart the hub and do a postmortem soon. But until then, does anybody have a guess what let go inside, and whether it's a reasonably fixable issue? Chalo OK,I'll bite. Here's my guess. I'm betting the spring that allows the ring gear to move toward the drive side to engage the hub pawls in the high gears was already weak. Then you were putting massive torque to the pedals in first gear when the only feeble interface in an otherwise robust hub failed. That would be the teeny weeny clutch teeth that engage the coupler gear to the ring gear in gears 1 through 3. This failure would not be related to the weak spring, but the spring is the only way I could explain direct drive in your top 4. If the ring gear pawls fail to engage the hub when you shift to gears 5 to 7, the planet carrier pawls will drive the hub. With the clutch engaged to the planetary carrier, you have direct drive. Dan Burkhart www.boomerbicycle.ca -- Dan Burkhart |
#8
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SRAM Spectro S7 hub spectacularly killed
Per Chalo:
If a bike part has a capacity rating, I generally exceed it. I'm used to that. Have you managed to toast a Rohloff hub yet? -- PeteCresswell |
#9
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SRAM Spectro S7 hub spectacularly killed
PeteCresswell wrote:
Per Chalo: If a bike part has a capacity rating, I generally exceed it. I'm used to that. Have you managed to toast a Rohloff hub yet? Nope. I've had no mechanical problems at all with my Rohloff hub. The only repair I have had to make has been to replace the rubber cuff on the shifter when it unstuck and worked loose. The Rohloff Speedhub is specifically approved for tandem use. It has a specified minimum gearing ratio of 38/16 for single bikes and 40/16 for tandems. I put 44/16 on mine just to be on the safe side. I'm not only heavy without being debilitated, but I use 205mm cranks on that bike, which effectively lowers the ratio of the primary gearing. Chalo |
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