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Discussion Starter · #1 ·
I had a bad wreck in a race and no spokes broke but some got pretty badly bent so I decided I should replace all bent spokes. The wheel is shimano R550, 20 spoke rear 16 front. I need to install 2 new non drive side spokes on the rear wheel and 1 spoke on the front wheel. I got the new spokes and nipples direct from shimano(cost an arm and a leg b/c you gotta order in packs of 5) but when I was talking to them they said to detension the whole wheel before replacing a spoke. That is what has me a bit scared, I've replaced spokes before but not on a high tension/low spoke wheel like these shimano ones. Is it really necessary to detension first? what will happen if I don't? Not like its going to taco the wheel, I don't think... I've seen people replace a spoke on a ksyrium without detensioning and it seemed fine.


thanks for the help,
herms
 

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Herms said:
I had a bad wreck in a race and no spokes broke but some got pretty badly bent so I decided I should replace all bent spokes. The wheel is shimano R550, 20 spoke rear 16 front. I need to install 2 new non drive side spokes on the rear wheel and 1 spoke on the front wheel. I got the new spokes and nipples direct from shimano(cost an arm and a leg b/c you gotta order in packs of 5) but when I was talking to them they said to detension the whole wheel before replacing a spoke. That is what has me a bit scared, I've replaced spokes before but not on a high tension/low spoke wheel like these shimano ones. Is it really necessary to detension first? what will happen if I don't? Not like its going to taco the wheel, I don't think... I've seen people replace a spoke on a ksyrium without detensioning and it seemed fine.
Instructions for servicing Shimano WH-R550 wheels (including single spoke replacement) can be found on the Shimano web site here. Although the instructions give final tension, they give no mention of detensioning other spokes.

I have done quite a few single spoke replacements, and never detensioned the other spokes first. I have no idea why this would need to be done.
 

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Discussion Starter · #3 ·
just talked to shimano again

They once again said that the tension needs to be decreased before replaceing a spoke. They said if you don't the tension will get all wacked out. Call them, they will tell you the same thing for any of their low spoke count wheels.
 

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Spoke replacement and de-tensioning

Herms said:
They once again said that the tension needs to be decreased before replaceing a spoke. They said if you don't the tension will get all wacked out. Call them, they will tell you the same thing for any of their low spoke count wheels.
This has not been my experience. Spokes are elastic members, and while their tensions may be affected by the tensions in adjacent spokes, they don't get "whacked out" if a spoke goes from full tension to zero tension (as when it breaks) and then a replacement spoke goes back up to full tension. Sometimes, when simply replacing a spoke, I haven't had adjust the other spokes at all.

If the spoke broke from the wheel being directly hit (as in a crash), then the spoke tensions may indeed have gotten knocked out of spec. due to the rim or spokes getting bent - but that occured during the wheel hit, and not from replacing the spoke. In either case, re-balancing the tension can be done without slackening the spokes first.

About the only time the spokes need to be completely detensioned is when you are doing a rim replacement (or attempting to unbend a bent rim). Otherwise it is unnecessary.
 

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Bad advice

Herms said:
They once again said that the tension needs to be decreased before replaceing a spoke. They said if you don't the tension will get all wacked out. Call them, they will tell you the same thing for any of their low spoke count wheels.
This is bad advice, possibly driven by ignorance on the part of whoever you talked to, and possibly driven by the desire to continue the mystique of "our wheels are so special that you can't even fix them yourself" marketing. As per Marc McM, I've replaced numerous single broken spokes and most times, just by bringing them to the same tension as the rest of the spokes, the wheel is perfectly true.
 

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I partially agree that you should back the tension off on the wheel before you replace the damaged spokes, here is why. When you loosen the spoke you are going to replace it may put the rim so far out of true that you may not be able to get the new spoke threaded onto the nipple. I am not saying it is definately what will happen but I have had that happen on very low spoke count wheels like the Rolf and Shimano Dura ace wheels.
 
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