Ksyrium rim failure...

[onekgguy]

I was wiping down the back rim of my bike a couple nights ago and noticed not one but two cracks in the rim...here (http://kevinandtammy.net/images/ride_photos/mavic_ksyrium_rim_crack.jpg) and here. (http://kevinandtammy.net/images/ride_photos/mavic_ksyrium_crack_1.jpg) I figure the days for this rim out on the road are done but I intend to use it over the winter on my rollers. Or is that not a good idea?

My question to anybody with experience in this is what does rim failure look like when it happens from a stress fracture such as this? I'd hate for it to split wide open and cause a gash of some sort to my TruTrainer rollers but if that's unlikely to happen then I won't worry about it.

I'm not sure yet but I think I'll eventually have the wheel rebuilt and keep it as a spare.

I've liked the Ksyriums and have 24,000 on this pair with only 2-3 broken spokes in that time. Still, I may be considering something different as a replacement. Suggestions?

Thanks,

Kevin g

[Larry]

24,000 is fantastic!!!!!! Spend the money and buy a new pair. :hello: :hello:

[maxdog]

I usually prefer to go the custom hand built route these days, but I have to admit, I have a pair of sl premiums with over 10k on them, and I've never had to touch them. Nearly as true as the day I got them. Hat tip to Mavic.

[Louis]

Kevin,

Had you recently trued that wheel? Last time that happened to me was when I was messing with a wheel (I think it was an MA-2) and not paying much attention to the spoke tension.

I wouldn't think that it will stay true very long (if it isn't already way out of true) and on the trainer / rollers that might be pretty annoying.

Good Luck

[onekgguy]

Kevin,

Had you recently trued that wheel? Last time that happened to me was when I was messing with a wheel (I think it was an MA-2) and not paying much attention to the spoke tension.

I wouldn't think that it will stay true very long (if it isn't already way out of true) and on the trainer / rollers that might be pretty annoying.

Good Luck

Hi Louis,

I replaced a spoke a few thousand miles ago but other than that I haven't had to true them.

I've got some kind of mental instability because I enjoy riding my rollers. I've been known to do a couple century rides on them each winter. How sick is that?

Kevin g

[Peter P.]

Those kind of rim failures NEVER lead to a catastrophic event.

I've ridden and replaced many rims with cracks such as yours. They won't leave you stranded or damage your rollers.

[alancw3]

i am not a wheel builder however when i look at those cracks i would suspect the the spoke tension was to high. i once trued a rear wheel and unfortunately over tensioned several spokes and ended up with the exact same type of cracks.

[AngryScientist]

wow, 24k on a set of wheels is really getting your moneys worth IMO, with that track record, i wouldnt hesitate to buy another set, if i were you.

also, if the opposite wheel has the same mileage, id ditch it at this point too before it fails on you.

[onekgguy]

Those kind of rim failures NEVER lead to a catastrophic event.

I've ridden and replaced many rims with cracks such as yours. They won't leave you stranded or damage your rollers.

That's what I was hoping to hear. Thanks.

i am not a wheel builder however when i look at those cracks i would suspect the the spoke tension was to high. i once trued a rear wheel and unfortunately over tensioned several spokes and ended up with the exact same type of cracks.

Yes, the wheels are under quite a bit of tension but that's the nature of the beast with these. Aluminum will eventually fail and that's pretty much what I'm dealing with. I suspect there are many more cracks forming in the rim that aren't yet visible.

wow, 24k on a set of wheels is really getting your moneys worth IMO, with that track record, i wouldnt hesitate to buy another set, if i were you.

also, if the opposite wheel has the same mileage, id ditch it at this point too before it fails on you.

The front wheel appears fine but as you can imagine it's not subjected to the same forces as the rear wheel.

Kevin g

[Mikej]

What tire pressure do you run? Many cracks I've seen such as yours make me think too high of a psi was used. While it looks like high spoke tension, you have to think of how a wheel os loaded while spinning. 24K - I have a set around that myself - great wheels, no mattter wahat people say!

[godfrey1112000]

Just replaced the rear rim after 3 years, Joe Young builder, DT Swiss 1.1
30k, the hub cracked at the spoke and DT replaced at no charge
Joe inquired about the miles on the rime and we decide it was worth the $80 to start 2011 on a fresh rim

front rim is still original

I think I got my money's worth $0.00267 per mile

Happy Thanksgiving

[stephenmarklay]

You guys ride a lot!

[onekgguy]

What tire pressure do you run? Many cracks I've seen such as yours make me think too high of a psi was used. While it looks like high spoke tension, you have to think of how a wheel os loaded while spinning. 24K - I have a set around that myself - great wheels, no mattter wahat people say!

I'm at 100 psi and weigh around 153. The roads I ride on are generally smooth.

Yeah, the wheels have been great for me in spite of all the criticism I read about them. I just ride 'em.

Just replaced the rear rim after 3 years, Joe Young builder, DT Swiss 1.1
30k, the hub cracked at the spoke and DT replaced at no charge
Joe inquired about the miles on the rime and we decide it was worth the $80 to start 2011 on a fresh rim

front rim is still original

I think I got my money's worth $0.00267 per mile

Happy Thanksgiving

I'll say! Same to you

Kevin g

[AngryScientist]

just read a little of your blog onek, pretty good stuff. :beer:

[onekgguy]

just read a little of your blog onek, pretty good stuff. :beer:

Thanks. Best thought organizer there is other than my bike.

Kevin g

[maxdog]

So you like the Simplicity. I'm gonna need to replace mine soon, and that was one of my considered makes. The local hardware guys a dealer, so that works for me too, supporting a local business and all. They are a little pricey, but if you've got 25yrs on it, It might be worth the dough. Enjoy your winter.

[Mark McM]

i am not a wheel builder however when i look at those cracks i would suspect the the spoke tension was to high. i once trued a rear wheel and unfortunately over tensioned several spokes and ended up with the exact same type of cracks.

Careful there - excess tension is often used as an excuse for rim cracks (and spoke breakage), and while it is one variable in fatigue failures, it usually isn't the most important. Afterall, rims don't crack just sitting around, even if they have high spoke tensions. Other, and usually more important, variables are:

Wheel loading (i.e. how much weight and force the wheel must bear)

Number of loading cycles - each spoke, and the portion of the rim around it, is loaded cycled once per wheel revolution, or about 800 cycles/mile for a 700c wheel. So each wheel component experiences a million load cycles in only about 1,200 miles. A wheel with 24,000 miles has experienced 20 million load cycles

Alloy and temper of the aluminum rim

Stress-concentrations in the rim (either due to rim cross-sectional shape, or imperfections in the rim such as scratches and gauges).

A high static tension in the spokes will reduce the number of cycles to failure, but not by a whole lot compared to the other factors involved.

More often than not, high spoke tension is used as an excuse to cover-up poor design and manufacture of rims/wheels.

What tire pressure do you run? Many cracks I've seen such as yours make me think too high of a psi was used.

High tire pressure is unlikely to cause these types of cracks. Remember, fatigue cracks only occur under tension loads. Pneumatic air pressure can cause tension on the outer wall of a double wall rim, or on the inner surfaces of the sidewalls, but if anything, pneumatic pressure will create a compressive load on the spoke bed (pressure pushing outward on the bead will be balanced by pressure inward at the spoke bed).

[97CSI]

I'll take any decent wheel that gives me 24K of use. That's excellent.