Jarrett2

5200 miles on the wheel. What would cause this?

cracked.jpg

fietsbob

Metal fatigue.

FBinNY 

In simplest terms, metal fatigue or excess spoke tension, but it's not usually so simple.

Whenever I see stress cracking at the spoke holes, my first instinct is to say "too much spoke for the rim" meaning a combination of high spoke tension, and spokes that are too strong, or more precisely -- too resistant to giving under tension.

When loads change on structures, they adjust by distorting. Keeping it as simple as possible, let's say that the most deflection will occur in the weakest elements. So with light spokes and a stout rim, the spokes do most of the deflecting. With stronger spokes, the rim does more deflecting, and gives out sooner.

Looking at your photo I see a 2nd possible issue in the form of corrosion at he eyelets. If you ride in wet condition, especially near the coast or in winter, water wicks between the eyelet and rim. It carries in salts, and when it evaporates later on the salt is left there. Over time, these salts attack and corrode the rim, leading to pitting which concentrates stresses and accelerating the fatigue process. Corrosion related metal fatigue is well documented in aluminum, and of major concern to aircraft and other critical applications.

You can see the corrosion surrounding the unbroken eyelet in the photo.

Obviously, it's too late now, but in the future you want to wick in oil or highly thinned grease around spoke holes to prevent the water wicking which is at the root of the problem.

Tunnelrat81

Kudos for providing such a nice picture. Sorry about the wheel though.

-Jeremy

bradtx

This should have most checking their rims...thanks.

Brad

Jarrett2

Great info, thanks. The spoke is a DT Competition spoke. 2.0/1.8/2.0. The tension showed at 20 on my Park tension meter. I forget what that translates to, but well under the max for the rim. DS was ~20, NDS was ~15. I've had other rims with the same spokes in the 24-26 range on the DS.

I don't ride in the rain or near the ocean regularly. I did get caught in a rain storm on a long ride one day and spent about 30 miles riding in the rain. Other than that, all dry rides. I did do a 25 mile and 67 mile ride at the coast back in September. Other than that, all inland rides.

The builder said he would take a look at the rim and try and warranty it through DT Swiss. I assume that will take a while. I'm kicking around building a backup set of wheels in the meantime.

In anyone knows of any deals for similar built wheels, I would appreciate it.

I'm kicking around some H Plus Sons laced up to some 105 hubs. I really like the DT Swiss hubs, just getting tired of chewing up the cassette bodies.

Andrew R Stewart 

To be flip, I'd say about 5200 miles of riding did this.


At about 435 gm weight this is a fairly light weight rim. DT's application chart suggests it's a rim designed for riding performance and not longest life. But you probably already know that. I tend to look at rims like tires, they're wear items, although I would hope that one would last a number of years. If you're a big guy and/or ride pedaling squares then fatigue/stress is greater. If you climb out of the saddle (there are hills in TX, right?) a lot same thing. Andy.

ThermionicScott 

Per the table: 20 works out to 94 kgf, 15 to 58 kgf. https://www.parktool.com/assets/doc/p...le_3-21-14.pdf

Doesn't sound excessive to me.

Jarrett2

I am

I don't know what that means.

There are.

I am a big guy and my power meter tells me I'm hitting max power around 1000-1200 on each ride. I'm pretty sure that's when I'm trying to keep up with the little guys on the hills.

If 5200 miles is what I get out of a rim, so be it. I've never had one last this long before, so I'm trying to figure if this is just where they break for me or if this was something that should be replaced under a defect.

Thanks for the info.

Andrew R Stewart 

Pedaling squares means that the rider is not fluid in their motion. Lot's of up and down but little fore and aft effort in the pedals. Often with a lot of upper body use, twisting of the bars. Often rides "heavy" (meaning in the saddle a lot and not supporting the body with feet and hands much). Often uses a rear wheel fixed trainer stand in the off season (we call that winter up here in the North). (Why do I mention a trainer? because the rear wheel being held by the stand removes most all the feedback of the bike's side to side movement during pedaling and with the load it has reinforces the hammer style of riding instead of the spinny/floating style of riding).


But this reference to riding style is so old school... Andy.

FBinNY 

Though I don't call it that, I suspect that by "pedaling squares" Andy means pedaling such that power is applied in short high spikes, vs. through a longer arc of crank rotation. This is more common in low cadence or a sprinting style of pedaling, such as one may use for climbing in a higher gear.

Also, this style often involves rocking the bike side to side which introduces higher spoke load than just about anything else. Since you now mention that this wheel lasted beyond your historic average, I wonder why you would consider it defective in any way.

BTW- wheel life is a funny thing. BITD my riding circle included a ballerina (pro with the NYC Ballet) and gorilla (250#s built like a linebacker). I mention them because my gorilla friend rode like a dancer and never broke anything. But the ballerina was murder on her wheels --- go figure.

trailangel

How old is that rim? If you surf the web you come up with some people saying eyelet pull-out problem with this rim. They look painted. ? Back a few years ago.
I say this because, I just built the same asymmetric rim , but with 32 x3 CX-ray spokes.. to 110 on the DS. And I am older on the heavier side. Just at the Clyde cut off.
My rims look anodized instead of painted.
They are good rims. Please, no eyelet pullout for me.......

shelbyfv

That's a light rim and if you are a clyde it's a predictable failure. I'd try something more robust next time.

trailangel

Heavier people ride much lighter rim with no problems.

FBinNY 

+1

It's not that the rim is light, or the rider heavy.

It's how it's built, and the riding conditions.

440g is at the high end of rim weight for me, and I typically ride 300g tubular rims, and in 50 years have never has a rim failure unless crashed. (current weight near 200#s, and I also use these for touring with 25#s or so baggage)

Like Andy, I suspect that it's how the rider rides more than his weight, and though it's counter-intuitive, if the OP were to bring me these wheels and ask me to build a replacement. I wouldn't use a heavier rim, and instead go lighter on the spokes. (I'd also oil seal each eyelet even if he lived in the Sonora desert).

Jarrett2

I'm a pretty consistent 80-90 spinner. I let the gears do the work.

It's the first one I've had crack. Historically, I have issues with trueness and spoke breakage on a rim way before this. To the point that I just trash it.

This one I did not. It was just bulletproof right up to around 5,000 miles, then needed a touch up true or two. Then cracked.

So being my first crack, I wondered if that was unusual. It may just be the normal lifespan for me. Time will tell, I guess.

shelbyfv

DT Swiss specifies a 110kg weight limit for "system" with these rims. Maybe that means bike and rider on two wheels? I don't know. If so, that is well into clyde territory and I expect they are conservative in their rating. Hope your wheel builder will make it right for you.

fietsbob

So You going to buy a More conservative Higher spoke count wheel build next time ?

trailangel

Could you post a link for this information?

ThermionicScott 

Just out of curiosity, what rims do you use on your MTB commuter?

I ventured into 1.8/1.6/1.8 spokes on my last build, and am digging the results so far. Hope they keep making them.

shelbyfv

https://www.google.com/url?sa=t&rct=...,d.eWE&cad=rja It's a pdf and you need to scroll down to page 48 where they give specs for rims. If the link isn't right, just Google "DT Swiss rim weight limit" and it's the first choice. As I said, not sure what they mean by system weight limit.

Jarrett2

Would more spokes cause the rim to break less?

FBinNY 

The commuter uses old Mavic shallow profile double wall, single eyelet rims that are no longer made. I have no idea what they weigh, but like all my wheels are built with light spokes, and the original pair held up fine until I was broadsided at low speed.

Fortunately(?) the car hit me, not the bike, and pushed me across bending both wheels before slamming me to the pavement. This could have been much worse, but the only damage to me was a knot where the bumper caught my left calf and a massive hip/thigh bruise on the right. The only damage to the bike was warped wheels which I rebuilt.

I don't have another set of rims, so probably the next will be of some old Campys I have set aside.

ThermionicScott 

Rock on! Glad it wasn't worse.

trailangel

Thanks for that.. I see it.
242.5 lbs. ... rider plus bike.... I am under the limit!