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-   -   Two Spoke / wheel / hub Questions (https://www.bikeforums.net/bicycle-mechanics/554884-two-spoke-wheel-hub-questions.html)

chrispe 06-23-09 07:29 PM

Two Spoke / wheel / hub Questions
 
I have a couple questions having to do with spokes/wheels.

The first is are hubs made for a very specific spoke diameter or a range of diametes. For example is a hub meant for only 1.8mm spokes and can't use 2.0mm or are these both close enough that they can be used in the same hub. My hub is an ultegra 6500 (9 speed) and I would like to know what size diameters are alright for it.

The second question which is kind of related to the first is whether or not it is alright to replace a spoke of a different diameter as a temporary fix when a spoke breaks. I know these probably bend a bit different when you hit a bump and its not ideal, but I'm just worried about any big problems.

This came up because I recently broke a spoke, but use my bike as my main form of transportation. It has 1.8mm straight gauge spokes, but the only spares I have are 2.0mm straight gauge. I bought the wheelset used and it turns out some of the spokes have already been replaced with 2.0mm straight gauge which concerns me a little, but I've had the wheels a while and they've been good except this one spoke. I plan to either rebuild the wheel soon or go through and make sure all the spoke are the same, but I'm just hoping this isn't and immediate problem and I can use the bike in the mean time.

vredstein 06-23-09 07:54 PM

Any spoke up to 2.0 thickness will have no problem fitting through the Ultegra hub. However, cramming 2.0 spokes through hubs with holes meant for 1.8 or 1.7 spokes would create stress points at both the spoke and hole.
I'd imagine that if a wheel has 31 butted spokes, adding a straight gauge spoke would affect the long term durability of that one spoke and probably a few nearby spokes.

interested 06-23-09 08:08 PM


Originally Posted by chrispe (Post 9154767)
I have a couple questions having to do with spokes/wheels.

The first is are hubs made for a very specific spoke diameter or a range of diametes. For example is a hub meant for only 1.8mm spokes and can't use 2.0mm or are these both close enough that they can be used in the same hub. My hub is an ultegra 6500 (9 speed) and I would like to know what size diameters are alright for it.

I think that your hub has a 2.4 mm spoke hole diameter. If you can fit the spoke in the spoke hole, it should be OK. Both 1.8 mm and 2 mm and 2/1.8 mm and 1.8/1.6 mm spokes are common and can be used with that hub.


Originally Posted by chrispe (Post 9154767)
The second question which is kind of related to the first is whether or not it is alright to replace a spoke of a different diameter as a temporary fix when a spoke breaks. I know these probably bend a bit different when you hit a bump and its not ideal, but I'm just worried about any big problems.

As a temporary fix, no problem.



Originally Posted by chrispe (Post 9154767)
This came up because I recently broke a spoke, but use my bike as my main form of transportation. It has 1.8mm straight gauge spokes, but the only spares I have are 2.0mm straight gauge. I bought the wheelset used and it turns out some of the spokes have already been replaced with 2.0mm straight gauge which concerns me a little, but I've had the wheels a while and they've been good except this one spoke. I plan to either rebuild the wheel soon or go through and make sure all the spoke are the same, but I'm just hoping this isn't and immediate problem and I can use the bike in the mean time.

The wheel may be fine for a long time if it was a good wheel to begin with, but there is a chance that there is uneven spoke tension in the wheel, something that unmatched spokes may exaggerate, and that this may lead to spoke breakage. It certainly is a worrying thing that several spokes already have been replaced and that yet another one is broken now. So if you experience problems, they are likely caused by old problems with how the wheel was built, rather than because you replaced a 1.8mm spoke with a 2 mm spoke.


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Regards


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