Cannondale F500 rear wheel spokes

[surreypete]

Hi

I have a Cannondale F500 and the rear wheel keeps breaking spokes on the cassette side of the wheel, I took it to the bike shop and they said I need to replace the whole wheel but apart from sometimes popping spokes I can see nothing else wrong with it.

I brought a Hyperglide remover tool and took the cassette off and noticed a few of the spokes have damage near the hub, it looks like the chain has gone between the top cog and the spokes although I can never remember doing this.

The spokes on the non cassette side are all fine.

The rear wheel has a Coda hub, Mavic X221 rims and DT swiss champion 1.8mm spokes.

Would anyone know what length spokes I need on the cassette side of the wheel?

Cheers

Pete

[DaveM]

A couple questions are where are the spokes breaking (by the rim or the hub) and did the shop say why they think the wheel is toast? Is the wheel pretty straight with even tension or do you have to have some tight and some loose spokes in order to get it straight?

But aside from that, it probably makes sense to replace any spokes that show damage and see if it cures the problem. (There may be a bigger fatigue issue that this will not cure. But if so, it means relacing the whole wheel.) Easy enough once you have the cassette off. Measure your existing spokes to get the right size. If you were replacing all the spokes on the drive side, I'd maybe say go to 2.0/1.8 double butted. But I don't think you want to mix those and 1.8 straight on the same side.

[Joe_W]

Yeah, the dreaded chain drop (I assume the spokes break at the elbow, close to the hub, where they have been damaged)! Replace the damaged spokes (as Dave said) one at a time. If the spoke tension is OK on the wheel you will be able to do the exchange quite fast as you always only have one spoke to adjust.

However, if spokes break close to the rim, chances are a mistake was made when building the wheel you'll need to redo it from scratch. If you get a shop to do that, the cost in labor will probably exceed the price of a new wheel. I prefer using double butted spokes on my wheels, they make a stronger wheel than plain gauge spokes. Mixing different types of spokes is not really ok, but I have done it (nothing outlasts a temporary fix), it will work. I'd probably replace all drive side spokes with double butted, though.

Spoke length: http://www.wheelpro.co.uk/spokecalc/
Edit: or the one on the DT Swiss homepage

[surreypete]

Hi thanks for the replies.

I currently have one broken spoke thats gone at the hub end and there's about 4 that need to be replaced as they have visual damage to them about an inch away from the hub so it does look like the chain has done a bit of damage.

I tried a few shops the last time it broke a spoke and I got different verdicts, one said I need a new wheel as the rim was ovalised, the other stuck a new spoke in and it was trued up, it was running great till the latest spoke broke, now it's running buckled.

I was going to take a good original spoke out from the same side and measure the length, when measuring a spoke do you go from the end thread to the middle of the elbow or to the inner edge of the elbow where it comes out of the hub and goes towards the rim?