Snapping bladed spokes...

Not sure what's going on but in the last fortnight I have snapped three aero spokes. I had them repaired at Condor and then the bloody things snapped again. Both times it's the drive side on the rear. Anyone got an idea why this might be happening. The bike isn't under any extreme weight.

well,

how many spokes, and what wheel/rim combo have you got?

for a scary moment I thought you meant these :-P

by "aero" do you mean "bladed" spokes?
how is the driveside rear laced? and is the dishing correct? this can be a pretty big factor in the amount of weight the wheel can take. bladed spokes are meant to be stronger and are used in a lot of high-end low spoke count wheels, so they really shouldn't be breaking.

i think the mavic ksyrium anniversarie road racing wheels are actually radially laced on the driveside (something i thought you were NEVER supposed to do) but they use bladed spokes and hold up to a fuckload of punishment.

kilgore_trout
i think the mavic ksyrium anniversarie road racing wheels are actually radially laced on the driveside (something i thought you were NEVER supposed to do)

eh, I think it was mostly myth! Aluminium hubs are sooo stiff compared to spokes/rims, that the drivetrain forces are pretty much applied to every spoke at the same time..

How many spokes have you got on that wheel Offwhite?

The wheels are campy shamals and 16 bladed spokes. The non drive side is radial and the drive side is crossed (sorry not sure of the technical term for this.)

hm.. Well to be honest I have no experience at all with bladed spokes, but I'd be scared to death riding a 16 spoked wheel in London.. I hope someone will prove me wrong, but aren't those proper racing wheels?

They are racing wheels, to be honest I'm considering selling them for something a little bit more sensible once I have had them respoked. I might have just been unlucky.

Yeah, a 16 spoke wheel isn't really suitable for road use unless you are super light. If the wheel was fixed and then still breaks spokes it sounds like the tension on the spokes wasn't correct after the repair.

Back to condor it is. Thinking about selling these once their repaired. Needing a solid wheelset for the winter

campy shimals should be relatively sturdy. i know people who play bike polo on them and they've held up fine.

i also know people who messenger on mavic ellipses on boston streets year round and haven't had a problem.

bike polo on shamals? they have too much money or sthg?

Offwhite The wheels are campy shamals and 16 bladed spokes. The non drive side is radial and the drive side is crossed (sorry not sure of the technical term for this.)

16 spokes, and they're laced asymetrically.

Hmm.

That's 8 radial spokes on the non-drive side bearing no torque load, just providing lateral strength and stiffness.

And then 8 spokes on the drive side in 1-cross bearing all of the torque load.

Yeah, they'd snap.

Looks like this right?

Too few spokes actually carrying load there.

Bike polo on shamals?!?!....What kind of poncey, left-leaning, non-contact, non-competitive game are you guys playing???...where someone would happily risk expensive 16 spoke race wheels??? still they look good right.

As I remember back when Shamals were reasonably trendy with real bike racers, there were quite a few incidents reported in the comic of them collapsing during races (often criteriums) and they fell out of favour, not long after the UCI introduced regulations on non-standard wheels....it's possible the UCI wwas prompted to do this specifically coz of Shamals failings, interestingly they don't appear on this list:

http://www.britishcycling.org.uk/News/2003/july/25_wheels.shtml

Someone lent me a pair for Good Friday once, they were smooth and fast I have to say, but not so hot on acceleration.

I used to race on 32H wheels.. fsck low spoke counts.
Shamals are also meant to have dodgy bearings.. maybe that's why winston tinks they're slow to accelerate?
There's an old comparison on Sheldon's site with loads of stats about wheel properties..

unxetas [quote]kilgore_trout
i think the mavic ksyrium anniversarie road racing wheels are actually radially laced on the driveside (something i thought you were NEVER supposed to do)

eh, I think it was mostly myth! Aluminium hubs are sooo stiff compared to spokes/rims, that the drivetrain forces are pretty much applied to every spoke at the same time..

How many spokes have you got on that wheel Offwhite?[/quote]

"A radial lacing has the highest lateral strength of any lacing pattern. This is covered in the RADIAL LACING INFORMATION chapter. A multi-speed rear wheel that is half radially laced, with the non drive side being the side with the radial lacing, can only have increased imbalance in the lateral strengths of the two sides of the wheel. The radial spokes on the non drive side will also need a lower build tension when compared to a standard wheel. Since radial lacing has the highest lateral strength, the spokes do not need to be as tight to counter the lateral forces from the drive side in order to achieve a true wheel. Also, with the non drive side spokes even looser than normal, the likelihood that the wheel will go out of true from road shock is increased."

cite http://www.geocities.com/spokeanwheel/lacingsr.htm

Yep and because you wnt to try and even out the differnece in tession between the drive side and non drive side it is better to have the radial on the drive side. (I assume this is a road bike wheel as there is no point to having asymetric lacing on a zero dish wheel)

So when I visit Condor again I should be asking them to relace the wheel with the drive side being radial, or should I ask for the whole thing to be laced radial. Thanks for the help guys much appreciated.

Never lace a rear wheel completely radially..... the will be little or no power transfer and they will be under so much tension that they will break

WTF!?

DO NOT PUT RADIAL ON A REAR

(unless you happen to have a lot of crossed spokes on there too)

Radial = Lateral stiffness
Crossed = Torque strength

Of course you want lateral stiffness, but this is a REAR wheel. Rear wheels are driven from the centre, they generate torque.
Torque = Rotational force.

Radial does nothing for rotating force, radial only helps lateral force.

When you ride fixed you generate far more torque than a roadie is likely to, and you're also generating it against the direction of the wheel when you brake.

You need more crossed spokes on your rear, not less.

My honest opinion: Dump that wheel if you're riding fixed. 16-hole is a bar minimum for the number of crossed spokes I would have on a rear.

If you want to mix radial and crossed spokes, get a 32h hub and rim and lace up a crows feet pattern or something.

But, NEVER EVER make a radial only rear. Nor even a majority radial rear. Only use radial on the front, or in a mix of crossed spokes. Rules for road bikes do not necessarily apply to fixed-wheel bikes.

Cheers guys. I was actually considering getting rid of both (F & R) once the repair has been done. Need something more suitable for the roads of Edinburgh when I move back. Anyone interested?

i might be interested...

Get them repaired in the same way as they were built. They are factory Shamals, not some random wheelbuild, and I wouldn't start messing with the lacing pattern on a pair of 16 spoke wheels. Once they're repaired then you can sell them for a bunch of money because they are quite sought after and then buy something more suitable for your use.

velocity boy - I know what your're saying about a full radial wheel on the rear being a bad idea, but Shamals were built by Campy to be track wheels so half radial might not be too bad. Remember that the rear is slightly dished as it is a single sided fixed hub at the centre.

kilgore_trout: Once Ive got them rebuilt Ill contact you.

Thanks again for all the help