Bob Ross

I don't typically give my dirt bike -- which I tend to treat as an archetypal "beater bike" -- the kind of attention my nice road bikes get, and so I was way overdue for an inspection when I started checking out my wheels yesterday. Hmm... are those cracks on the rims around the spoke nipples on my rear wheel?






^^^Those are four different nipples randomly selected around the wheel. Some nipples have those lines radiating out fore and aft, other don't. [Update...and this data point seems like it might be pretty telling: Those lines/cracks are on the drive-side spokes only...but they are on every drive-side spoke!]

fwiw it's a two year old WTB STP i19 wheel w/ disc brakes that came stock on my Cannondale CAADX. Has about 6,000 miles on it, mostly pavement, maybe 20% not-too-gnarly dirt/gravel.

So, um, is this rim toast? In case this is germane: The front wheel is fine, has none of these marks.



Uh-oh...I think I know the answer, having just noticed this nipple:

CyclingFool95 

Toast, no - I don't think it would be good with butter. (sorry, bad dad joke)

But, it's ready for the trash.

shelbyfv

You didn't get much life out of that!

onsay99

If you are the original owner, check with your dealer. Lots of name brand bikes give
2 year warranties on wheels.

alcjphil

That is abnormal. Those wheels were either poorly built or the rims are defective. You should have a stern talk with the dealer who sold you the bike

Andrew R Stewart 

Rims are a disposable item, like tires but more costly. Andy

sweeks

Well, it would be better if you recycled it!

sweeks

I like the term "consumable" a bit better.

veganbikes

Not toast or even regular bread but certainly not something I would ride on. I would reach out to WTB or Crackandfail and see what they say on warranty.

cpach

Very dead. I checked and WTB warranty on alloy rims is 24 months from date of purchase. You may as well try contacting Cannondale and WTB but I wouldn't hold my breath. I'd put better odds on WTB.

This failure mode doesn't really have much to do with your riding. It's a bit of a combination of probably material quality of the rim and possibly overtensioning of the spokes.

Cheapest solution would be to have the wheel rebuilt with a rim of the same ERD. Best solution would be getting some nice handbuilt wheels on better rims with double butted spokes.

NoWhammies

Yeah, I'd be replacing that rim if I were you. As others have stated, check with your LBS in case there are any warranty issues.

GamblerGORD53

Looks like a poor design to me. That flat profile is bound to flex.
Now buy one that is pointed like my medium heavy duty Velocity Dyads. They have other narrower and lighter models.

Bob Ross

Hey, so bravo/thank you to everyone who suggested these might still be under warranty:

Turns out the warranty doesn't expire for another week! Seriously!
I reached out to WTB and they were pretty quick to respond with "Yep, that's covered under warranty, where do you want the replacement rim shipped?"

woodcraft

dedhed

Rim or wheel? If just a rim someone still has to lace it to the hub.

Bob Ross

Yeah, we're still hashing out the details. Rim only. Not clear whether yet they have to ship it to the shop where I originally bought the bike (that came with those wheels) in order to have the rebuild labor covered by the warranty. The dialog has begun.

adipe

the cracking sees to be precipitated by corrosion.
it could be that you used crap sealant.

stress corrosion. one helps the other.

be sure to build wheels with low tension variance. be sure to lube the nipples and the rim and that the surface is kept with some sort of corrosion inhibitor. at least basic lubricating oil needs to be put once in a while on each spoke as to get to replenish where the surfaces are prone to corrosion AND cracking.

Bob Ross

I don't use any sealant. Inner tubes ftw!

adipe

the rim was labeled tubeless compatible and i thought you used sealant.

anyway, be sure to prevent stress corrosion cracking.
galvanic corrosion is from direct contact of the nipples with the rim having no eyelets.

if using rims without eyelets in the future be sure to use lubricant with corrosion preventing additives not only when building the wheel (which is very, very important as it is very vulnerable to very small cracks at the surface when you turn the nipples, which adds shearing stress on the rim where the nipples make contact while friction occurs and residual torsional stress remains unless you turn the nipples back to eliminate that residual torsional stress) but also later, to prevent the ambiental chemicals interacting with the rim where it is in highest tensional stress - that's highest at where the nipples stop being visible. you do not need to relubricate the rim surface unless you need to work on the nipples but you need to apply something that prevents corrosion. they sell some things in auto stores meant for cleaning cars that has anticorrosion additives in them. you could use such stuff when cleaning the rim and maybe end up spraying something when you finish cleaning the rim whenever you care to clean the rim. i avoid cleaning the rim, i just let the greasy filth on and make sure the rim was greased from the start to prevent corrosion from initiating. i don't need the rims to shine, i don't need the bike to attract attention, just have the protecting film on the rim even if black goo builds up on top of it.

and i have a strong distaste for non eyeleted rims because of all this.

give that rim to be recycled.

adipe

when one spoke on the drive side gets loose because the rim cracked the tension variance will be messed up and the cracks will develop in other places as well...

it very well be that the wheel had high tension variance, not only too high average tension.
corrosion contributed to cracks developing in use.

avoid low spoke count. better use a 32h or even 36h rim with butted spokes, like 1.8 DS and 1.5mm NDS....than 2mm plain gauge spokes on a 24h rim.

i'll give you a tip when using say DT Rev spokes and seeking high tension (like ~110kgf) on a front wheel non-dished wheel... press laterally on the wheel to temporarily lower spoke tensiion whenever you tighten the nipple and then turn it back a little to take torsional stress out of the spoke and rim bed. and if you care to put labels on the spokes watch every spoke turn as to turn it back just as to end up with every label aligned to where they initially were put - parallel with the wheel axle that is, perpendicular to the wheel as if they would have highest drag if they were to remain on the wheels in use.

adipe

when the wheel goes out of true and you seek to have it re-trued you might get the wheel with a higher spoke tension variance than it had from the start because that re-truing did not seek to bend the wheel back into shape (stress relieving etc) as to have the rim round if the spokes were taken off.

the goal is not to have a trued wheel at the cost of high spoke tension variance. because THAT IS the most probable cause of the rim cracking.
the goal is to have low spoke tension variance at the cost of the wheel not perfectly true. the goal is to balance the two at the end.

adipe

one more thing... having low spoke tension to begin with is the main reason the wheel goes out of true. and eventually it ends up cracking.
because when you get the wheel to be "repaired" it usually gets to someone who is not better qualified to do the harder job. it ends up cracking because tension variance after the wheel gets "fixed" is a mess, the spoke tension is all over the place.

some people have tools but never learn how to use them.
and then most people of those very few that really know how to do the job... will not tell you because you do not even realize that you need to learn those things and eventually ask politely.

it's most often hype (BS) that sells.

spokes at 4:30 and 7:30 get increased tension when spoke at 6:00 has its load reduced to zero;
the lower the average tension the higher this additional tension and amplitude of the fluctuation which means more fatigue stress.
the lower the spoke count the higher the additional stress and amplitude because fewer spokes work when the rim gets stretched and therefore the higher the temporary spoke tension on those spokes at 4:30 and 7:30.
higher spoke tension IF at low enough spoke tension variance prevents not only the wheel getting out of true but also prevents high fluctuation in tension and the wheel can be expected to last much longer.

watch:

adipe

here's how you inspect spoke tension variance: pluck all spokes for a flange; if you have more than a semitone variance between the minimum and the maximum tension then you have about 12% total spoke tension variance.

that's because spoke tension is a function of frequency at the power of two (squared)
semitone (n+1) has the frequency of semitone (n) times ~1,06. that would mean about 12% total spoke tension variance, if the minimum and the maximum would be as one semitone difference.
to be exact the number is 1,05998 (not exactly 1.06) but you can neglect the distant digits of 1.12356.. as well.

anyone should be able to compare two frequencies and detect if the difference is as if a semitone or a tone.

a good quality build should have +/- 5% spoke tension variance or so with a total radial/lateral runout of 0.1mm (+/-0.05mm)... OR higher runout (as a total radial/lateral runout of more than 0.1mm is certainly tolerable for most folks) for the benefit/goal of a more reliable wheel, with even less spoke tension variance. never the other way around.
a crappy build would make the wheel with low runout but at the cost of too much tension variance or overall higher runout and higher tension variance.

that's how you know if someone did a proper job when wheel building. just pluck the spokes and eyeball the runout. a sheet of most common printing paper (80gsm) is almost 0.1mm in thickness. radial runout is where it's at, more important in evaluating quality than lateral runout.

Barry2 

There’s an iPhone app for that !

No, really there is.

Barry

GamblerGORD53

I have a strong aversion to eyeleted rims because of this. ^^^^
Eyelets are the biggest CAUSE of corrosion and cracking. Putting a stiff ring around a weaker and usually rounded profile rim is a laughable solution. Plus the hole needs to be BIGGER to accommodate the eyelet. LOL . I agree too loose is worse than too tight.
My SA XL-FDD has 24,000 miles and looks like new. Black anodised Dyad rim, 2.3/ 2.0 WH spokes and locking brass nipples. There is ZERO chance of this going out of true. NO prep goop anywhere on my wheels. I actually way over tightened it at first, then backed it off twice. The nipple should settle into the bare Alu. This bike is 120 lbs on tour, up to 300 with me. I clean my bike when it gets dirty.
Who the hell makes square rims?? LOL
=====
I drill bigger holes for Schraeder valves too, no cracks there either.