Why Do I Keep Breaking Spokes?? Help

AllanM

Anyone offer any advice on why I keep breaking spokes?

I'm 95kg, 6'2" and pretty powerfull on the bike.

Yesterday I broke a spoke on my SS commuting bike 32spoke, 3 cross factory built Genesis hubs on Alex rims.

Today I broke a spoke on my road bike. wheels built by myself with ambrosio hubs on ambrosio excellence rims and Sapim race spokes, 36 spokes 3 cross. wheels are tensioned using a park tensiometer and are on the upper range of tensions for the spoke gauge. all spokes are within 10% of each other. this is the 4th non drive side spoke I've broken on this wheel. the wheel has only done probably 750 miles.

have broken multiple spokes on my CX bike too, hand built, 32 spoke 3 cross with sapim race spokes.

any wheelbuilders out there have any idea where i'm going wrong??

Help appreciated

Thanks

Allan

ugo.santalucia

You fatigue the spokes. I can't comment on your build unless I see it, but generally it's low tension that kill them. On your Park tool for Sapim race you are looking at a 23 reading on the drive side (with no tyre on) and whatever comes as a result on the NDS, 16 or so

maddog 2

too many right-handers. Do anti-clockwise rides from now on.

AllanM

Thanks for the reply Ugo

Just checked the wheel in question. The DS spokes are all between 23 & 25 on a Park tension meter and the NDS are around 21/22. checked on other "factory" built wheels and they all return roughly the same tension readings for DS and NDS.

I know that the spokes failing at the elbow is a classic fatigue failure resulting from not enough tension in the spokes but the readings above are all within the range for a 1.8mm round spoke. Is there any downside to tightening up the wheel to 26/27 DS and 24/25 NDS?? can't really think of anything else to try.

When the third spoke failed I was about 40 miles from the end of the Flanders Sportive but managed to ride till the end (beauty of 36 spokes) could this have damaged the remaining spokes making them fail quicker?? i.e. should I just re-lace the whole wheel?

Cheers

Allan

ugo.santalucia

In my experience I can't recall getting such a high reading on the NDS... you either have an asymmetric rim, which the Ambrosio is not or your gauge is not calibrated or the wheel is not dished or you don't measure the tension correctly (or you have different spokes).
Basically you are saying that you have 1400 Newton on the drive side and around 1000 N on the NDS, which doesn't stack up, as give or take the ratio has to be 2:1 and in your case is 1.4:1, which doesn't work.