Wheel build and spoke breaking...

seweryn

Hi Guys,

My Friend has a small problem with his own wheel that he built himself. The front wheel is laced radially with 20 nr CX-Ray spokes on Hope Pro3 Hub and with Stans 340 rim. The rider weight is only 72-75kg, however the spokes break at the hub / J-bend section during off saddle efforts. The tension between spokes is within 10-15% uniformity.

My theory and the way I would fix the problem would be to change the spoke type for a more flexible spoke or lacing pattern to 1 or 2-cross, or both. Also, the spoke washers may be a good idea here. However, I will appreciate your comments and help on this.

Smokin Joe

Spokes work in tension so the way the wheel is laced would have no bearing on the load on the spokes. I've never used a tension meter so I don't know how close a tolerance you need between spokes but 15% does sound like a lot.

dgunthor

crossed spokes will be a lot stronger, radial looks nice but in reality crossed is better

brettjmcc

He's breaking spokes on the front?

My understanding was that you should have tensions equal, not within 10-15%. If you built the front to 100kgf, then 15% would mean one spoke potentially at 85kgf. How have you determined

a/ the variance
b/ you are measuring the tension properly

trailflow

Spokes too short ?

Smokin Joe

dgunthor wrote:

crossed spokes will be a lot stronger, radial looks nice but in reality crossed is better

No they won't. As I said above, whether spokes are crossed or not makes no difference to the load they have to bear.

seweryn

Thank you for all responses. I will update if we find the solution for the problem finally.

ugo.santalucia

Measuring exact tension in CX Ray is not that easy as they fall in the high deflection zone (low reading) in pretty much all meters. You need a good calibration to get a reasonably accurate value...

seweryn

ugo.santalucia wrote:

Measuring exact tension in CX Ray is not that easy as they fall in the high deflection zone (low reading) in pretty much all meters. You need a good calibration to get a reasonably accurate value...

Thanks Ugo. The tension meter used is the Park Tool TM-1. I believe changing the spoke type should help making the wheel reliable? Or how to make it unbreakable is the question...

brettjmcc

The TM-1 will read low. I copied hypster's design and built myself a calibration meter. I still question why you have so much variation in the spoke tension though

ugo.santalucia

brettjmcc wrote:

. I still question why you have so much variation in the spoke tension though

There is no need for willy waving, a total variation of 15% is perfectly fine and normal if that means the lowest is 85 and the highest is 100 and on average they are somewhere in the 90s.

If that means the lowest is 85 and the highest is 115 then it is a different story, but that's not 15%

dgunthor

Smokin Joe wrote:

dgunthor wrote:

crossed spokes will be a lot stronger, radial looks nice but in reality crossed is better

No they won't. As I said above, whether spokes are crossed or not makes no difference to the load they have to bear.

have to disagree with you as i had a 28 hole radial front which went out of true easily, relaced in 2 crossed and no issues. crossed means the spokes support eachother surely, similar to crossmembers in scaffolding

apreading

I think crossed spreads the load over more spokes, whereas radial has just a single spoke under peak pressure.

Smokin Joe

apreading wrote:

I think crossed spreads the load over more spokes, whereas radial has just a single spoke under peak pressure.

How?

Spokes work ONLY in tension. Think about it.

Smokin Joe

dgunthor wrote:

Smokin Joe wrote:

dgunthor wrote:

crossed spokes will be a lot stronger, radial looks nice but in reality crossed is better

No they won't. As I said above, whether spokes are crossed or not makes no difference to the load they have to bear.

have to disagree with you as i had a 28 hole radial front which went out of true easily, relaced in 2 crossed and no issues. crossed means the spokes support eachother surely, similar to crossmembers in scaffolding

No they do not. As for your radial going out of true that was down to poor build quality. I spent five years up to recently riding a self built 28 spoke radial and it never missed a beat.