Keep breaking spokes??

[Conor]

Hi
I have a pair of Ambrosio f20 crono tubs 28 hole and have been having a lot of trouble with broken spokes, probably broke 10-12 spokes the last 2 years, ive got the wheel rebuilt 3 times since with new spokes but am just wondering now is 28 holes enough or should I go to 32 spokes, I'd be 70kg +-2kg.
Any advice?
Thanks

[sungod]

at that weight 28 should be fine

presumably this is happening on smooth roads?

you need to give a bit more info i think...

front or rear? how's it laced? which spokes/nipples?

[Conor]

Ye all happened on good roards, rear wheel is giving the trouble, sapim CX ray spokes and sapim nipples, the spoke pattern is double cross I think.
Also all spokes broke at hub

[bm0p700f]

Cx rays are not stiff enough for that build. Use Sapim force or DT Swiss alpine III and that will solve the problem.

[bm0p700f]

Cx rays are 2.0mm at the elbow. The spokes I suggested are 2.2mm at the elbow.

[racingcondor]

I'm similar to you (couple of kg lighter but not a lot in it) with Crono's built 28/28 to DA hubs on CX-Rays and I haven't broken a spoke in 3 years use even with the roads we have in the SE of England.

I do occasionally check spoke tension after finding that nipples unwound the first time I built them but haven't had any problems since. If I were you I'd take a look at the hub spacings and/or have someone else rebuild the wheel.

All that said, the wheels are pretty marginal. They ride beautifully but they're really not strong enough to race on (did it once, cornering was... intersting). If you're getting them rebuilt then a change of spokes is probably a good idea, the wheels aren't aero so CX-Rays are expensive for no real benefit (plus bm0p700f knows more about wheels than I do).

[bm0p700f]

Different riders load wheels in different ways. If they are not strong enough to race on then it wont take much to stating killing them. also 3 year of use could be 300 miles or 30,000 miles. high mileage means you treat them with kid gloves

I would personally say to ensure reliability the rider for a 28 spoke set of ambrosio F20 rims should be 60 kg or under (preferably under) above that the risk of something going wrong starts to go up from the very small to something that may actually happen to a certainty for some.

If you have to use a bladed spoke then the Sapim CX force is the one to go for but that is an OEM spoke and difficult to buy.

[F45]

So is this a case of a lack of lateral stiffness causing groups of spokes to detension (and thus accruing fatigue damage at the elbow) during hard, out of the saddle efforts, or is this a lack of radial stiffness detensioning the spoke at the bottom due to rim deflection?

What about poor build practice? If the elbows aren't cold set then they will be flexing more and fatiguing.

[Conor]

Thanks for the replies lads, id say the rim just isn't suited for me, I did a lot of hard riding and racing on them. The lad I bought them off never mentioned anything about them not being as strong.

[bm0p700f]

Well that sums it up them. If you want alloy tubular then have a set built with ambrosio nemesis or HED belgium C2. The HED rims in particular are very stiff and come in 24H and 28H drillings.

[kgt]

Crono f20 is not a stiff rim but at your weight there should be no problem.
I have used a pair of Mavic open 4 cd rims (32 holes) laced with cx ray spokes and I never had a problem even when I was 86kg.
I guess the one who built your wheels did not do a great job.

[bm0p700f]

It does not matter how well the o's wheels were built some riders will get problems with a build like that. It is not down to rider weight but how they are ridden. I would not build a f20 in 28H drilling for a rear wheel for anyone. While kgt, you may not have issue with your wheel another ride could just because they ride them different. This is not a slight on the P'S riding as I don't think the wheel you had was a good idea to begin with.

[racingcondor]

To expand on my experience a bit -
- If I were building them again I'd go 32/32
- With various wheelsets my 3 years has probably done around 6-8,000 miles
- Yes, I do baby them a bit. Roads are poor but I check spoke tension / true at the start of the summer and they mostly come out for long sportives etc where comfort is more important.
- Finally my bad experience racing on them could well have been a result of the overall bike. It was the only time I ride those wheels on that bike...

Sounds like the OP has had a lot less luck than I do with them though for whatever reason.

[Conor]

I'd say it was down to my riding style as bm0 said, I'd be the sort of lad who'd ride out of the saddle a lot and stick out fairly good power for my weight