How do you know what spokes to buy?

reilig

I have a steel road bike (Viking sprint, I think) which I bought cheaply. When the bug bit me, I decided to upgrade and I got a good bike on the BTW scheme.

The last time I was out on the steel bike, I broke 2 spokes. Its been hanging in the garage ever since. Anyway I had thoughts of using the steel bike on a turbo for the darker months ahead in my garage, so I want to get the wheel fixed.

So I have 2 questions really.

How do I know what replacement spokes to buy for the wheel? Will any 700c spoke fit it?

Secondly, the current wheel doesn't have a qr skewer on it, instead it has nuts - will I need to replace the current wheel with one with a QR skewer on it in order to use it with the turbo? (Thereby eliminating me need to replace the spokes )

Lumen

reilig wrote: »

Will any 700c spoke fit it?

No, you need ones the right length. The length depends on several things like hub dimensions, spoke pattern and ERD (effective rim diameter).

reilig

Lumen wrote: »

No, you need ones the right length. The length depends on several things like hub dimensions, spoke pattern and ERD (effective rim diameter).

Thanks Lumen,

I guess it requires a trip to the LBS to get the right length ones. LBS is great and all, and has fixed spokes at a very reasonable price for me in the past, just wanted to try to see if I could do it myself. I'd feel a bit awkward just buying the spokes from him to fix it myself

07Lapierre

reilig wrote: »

I have a steel road bike (Viking sprint, I think) which I bought cheaply. When the bug bit me, I decided to upgrade and I got a good bike on the BTW scheme.

The last time I was out on the steel bike, I broke 2 spokes. Its been hanging in the garage ever since. Anyway I had thoughts of using the steel bike on a turbo for the darker months ahead in my garage, so I want to get the wheel fixed.

So I have 2 questions really.

How do I know what replacement spokes to buy for the wheel? Will any 700c spoke fit it?

Secondly, the current wheel doesn't have a qr skewer on it, instead it has nuts - will I need to replace the current wheel with one with a QR skewer on it in order to use it with the turbo? (Thereby eliminating me need to replace the spokes )

Use a ruler/Tape measure and measure the exiting spokes?

reilig

07Lapierre wrote: »

Use a ruler/Tape measure and measure the exiting spokes?

Will that work?

I'll try it out.

Thanks for that!¬!

CillianL

I can build wheels myself so what I'll say is

1.Measure one of the spokes removed from the wheel from the tip of the thread to the centre of the end. If the wheels a 700C 3 cross pattern its probably a 292-294mm but always check in advance.

2.Cheap spokes are false economy. Most LBS's will stock cheap italian spokes (I know this from working there) which saves them money and costs you down the line. Buy Sapim or DT Swiss spokes. Cycleways stock Sapim spokes and the mechanics there have great technical knowledge if you need advice.

3. Be patient when truing the wheel, its a pain in the hole when you're learning

seamus

reilig wrote: »

Will that work?

I'll try it out.

Thanks for that!¬!

Yes and no.

Spokes tend to stretch over time which is why a new wheel often needs some minor adjustments after a little while and why rebuilding a wheel with old spokes is not recommended.

So if you measure the existing spokes it might be a little bit off. However, for the purposes you're talking about using the wheel, 1 or 2mm in the difference will still allow you to repair it. It won't be good enough for everyday road use, but fine for the turbo.

The spoke length is measured from the tip of the spoke to the inside of the elbow. It's an old steel wheel for use on a turbo - you don't need to go mad, a couple of standard stainless steel spokes in 2mm gauge will do fine. You should be able to get them from an LBS for next to nothing. You'll also need new nipples, again stainless steel is fine.

When you start using it again, if you find more spokes breaking, I'd be inclined to scrap it and start again - hold onto the wheel and get a new set of spokes if you fancy giving wheelbuilding a go, otherwise just replace it.

doozerie

seamus wrote: »

Spokes tend to stretch over time which is why a new wheel often needs some minor adjustments after a little while and why rebuilding a wheel with old spokes is not recommended.

This is getting into the realm of material science, of which I have sod all knowledge I'd have to say, but the suggestion that spokes stretch over time runs counter to what I understand. My understanding is that spokes may stretch a little (or a lot if the wheel builder isn't very good) when a wheel is being built or being worked on, but in use the stresses applied to spokes are significantly less and stretch is not an issue as such. Spokes that are stretched beyond their yield point (or whatever the appropriate phrase is) while the wheel is being worked on, are likely to break quite early on when in use.

In use, the tension on the spokes on the lower side of the wheel (the side in contact with the ground) slackens off so as a wheel rotates there is a constant variation in tension on the spokes. A spoke that has been weakened, by being tensioned beyond its yield point during the wheel build/maintenance, will eventually break. A spoke that has not been adequately tensioned in the first place will just work its way looser. So where spokes are becoming loose in use, I'd suspect that they were not properly tensioned to start with.

When building wheels myself I've sometimes had rims crack slightly at the nipple holes over time. I thought that maybe I was tensioning the spokes too much, so on my next build I used noticeably less tension. The build went fine, I pre-stressed the spokes, and used the wheel the next day on my commute bike. The 11km ride to work was fine, the 11km ride home was a race to get there before the wheel dismantled itself. Pretty much every spoke was flopping about like a soggy noodle by the time I reached my house, and the rim was quite, er, "mobile". In that case the issue was without doubt the lack of adequate tension in the spokes to start with so each time what tension was there was relieved during the wheel rotation, the nipples were "loose" enough to unthread just a little. The wheel went through many many rotations over those 22km, and even with what must have been a minute loosening of the spokes per rotation, it amounted to enough in total to deconstruct the wheel for me.

That's a very un-sciencey explanation, it may not be scientifically correct, but it fits with my understanding. So to my mind the idea that a spoke stretches "over time" while in use doesn't really make sense, at least not the idea that it stretches permanently (plastic deformation as opposed to elastic deformation) and by an amount that you could measure with a ruler. Basically, in my view a wheel needing re-truing is most likely due to the spokes having lost tension, rather than having stretched, and re-using spokes for a new wheel build should be fine as long as they were not overly stressed/stretched when they were used first time round.