Bicycle Mechanics - When good rims go bad - is it a defect?

I have some wheel that use heavy bladed spokes.

The wheels developed cracks in the rims at the area where the spoke attaches.

Are these wheels defective in some way? Or is the cause of the cracks normal wear and tear of usage?

too much tension on the spokes or wear and tear depending on mileage. some bontrager wheelsets had this problem and it is a warranty issue.

This one is definitely from use but only after 5 yrs of solid use:
http://i35.tinypic.com/2d8m6go.jpg

either the rim wasn't up to the job, there was too much tension, or both.

I would say unless the cracks occour in the first 100 or so miles it is most likely normal wear and tear. unfortunatly not all of ride on glass smooth roads all the time and there are just too many variables to say it is a defect.

Usually from rough roads, pot holes, or jumping curbs.

I'm kind of surprised, the idea that a spoke-built wheel can fail at a tensioned point and it anyone would think it is "normal" wear and tear. One thing different from the picture posted above, the rims I am disappointed with had no reinforcing eyelet.

And if cracks are supposed to be from impact injuries than how is it they were all around the rim. At least in my case, I wasn't referring to a single spoke/eyelet crack, but several. Its been a month and no refund yet -we'll see.

Replace the wheel or just rebuild the one you have with a new rim, and go on with your life.

When I see this kind of failure, I chalk it up to the builder. Simply put, the spokes are over-stressing the rim because of excess spoke tension compared to the strength of the rim.

I have some wheel that use heavy bladed spokes.

The wheels developed cracks in the rims at the area where the spoke attaches.

Are these wheels defective in some way? Or is the cause of the cracks normal wear and tear of usage?

Yes, the wheel is defective but it's not the rim. Most likely the spokes are improperly tensioned. See below on which way.


This one is definitely from use but only after 5 yrs of solid use:


Fairly typical failure...if a spoke is going to pull out. After 5 years, I'd suspect a little too low tension which allows the spoke to flex in the rim. Aluminum doesn't like flexing and will eventually crack, like bending an aluminum can back and forth. Given the crustiness of the rim, I'd suspect some weakening of the aluminum due to chloride corrosion too.


either the rim wasn't up to the job, there was too much tension, or both.

If the rim fails early...like within a few hundred miles...I'd agree and say too much tension. You'll see star-shaped cracks around the eyelet. If the spoke fails like electrik's did, the mode of failure is much more complicated. A loose spoke can lead to the kind of failure in the picture because the wheel is constantly relaxing and applying tension.


Usually from rough roads, pot holes, or jumping curbs.

I doubt this highly. Rough roads, pot holes and curb jumping are going to cause other failures but not likely cracking of the rim eyelet. Pot holes are going to cause blips and damage to the braking track. Jumping curbs is likely to cause the rim to split down the middle on the inner surface of the rim (below the tube) because the localized forces are perpendicular to the rim's travel. Rough roads probably aren't going to do much at all or the damage may be some combination of what pot holes and curb jumping does.

What wheels are you talking about? Low spoke count wheels have to have more tension to compensate for the higher load on each spoke.
If the rim is anodized then that is the problem.
A wheel should come out of true when the spokes have too much tension.

I'm kind of surprised, the idea that a spoke-built wheel can fail at a tensioned point and it anyone would think it is "normal" wear and tear. One thing different from the picture posted above, the rims I am disappointed with had no reinforcing eyelet.

And if cracks are supposed to be from impact injuries than how is it they were all around the rim. At least in my case, I wasn't referring to a single spoke/eyelet crack, but several. Its been a month and no refund yet -we'll see.

It is not necessarily a defective rim because any aluminum part exposed to cyclic stresses will eventually crack and fail. The rim has fatigued. The problem can be worsened by excessive or inadequate tension or excessive load but will eventually happen even with the strongest aluminum rims.

Another thing that can worsen the problem is corrosion. Some grades of aluminum are subject to a condition called stress corrosion cracking. The stress of spoke tension makes the metal around the spoke hole more subject to corrosion, and once a pit starts to form, the location most susceptible to corrosion will be its vertex because that's where the stress is highest, so it will simply corrode through, in a line as if it has cracked.

A wheel should come out of true when the spokes have too much tension.While it's true that if you tighten a wheel to the point where it warps into a toroid shape, then back out so that it's straight again, that this yields the strongest wheel possible (as in it take the highest loads before going untrue). But it may not be the most durable wheel in terms of longevity. That's because the high static tension may load the area around the holes very high and the material will fatigue faster. It's a delicate balance between wheel-strength versus spoke & rim durability.

This is why I prefer to build wheels with double-butted spokes. These tend to have more elongation for the same tension and results in lower peak G-forces at the spoke-holes for any given road-condition. Interestingly enough, DB spokes also yields stronger wheels as well; the wheel can endure more and higher impact loads before going out of true (compared to same wheel with straight-gauge spokes.

The poll is unclear. Is it a defect? By all means; stop using the rim before the spokes pull out. Is it a manufacturing defect? No, any aluminum component which is repeatedly loaded then unloaded like a rolling wheel will eventually fatigue.

Should wheels fail this way? Well, they just will, unless you build them from steel and make it thick enough to stay below the fatigue limit, but then you have a very heavy wheel, and you'd just wear an aluminum rim out from braking anyway so there's no point in redesigning it for infinite life.

I guess I was biased against the wheels in general because the first wheel failed while at rest. I went to get on my bike one day and the wheel would not clear the brake pads.

The second wheel to fail - did in fact at least have several thousand miles of "hard use" - if you call a 170 pound rider riding over less than perfect chip-sealed roads "hard."

I think the point here is that at least four spoke holes were cracking in each case. I've damaged a single eyelet by hitting an expansion joint on lighter weight rims and accepted that as "catastrophic" single point damage - not a manufacturing error or defect.

I should also note, after the first wheel failed, I went around the other wheel and loosened spokes ever so slightly. I'm sure some of the other RCs here can find fault with that as well.

... the first wheel failed while at rest. Well, the wheel is a pre-stressed structure and basically reacts to riding by seeing less tension for the most affected spokes. So being at rest gets kind of a twisted meaning in this case.

...The second wheel to fail - did in fact at least have several thousand miles of "hard use" - if you call a 170 pound rider riding over less than perfect chip-sealed roads "hard."

Here's how it goes: heavily bladed=aero=low spoke count=racy=bling points=longevity not a priority

You might have heard of the phrase boutique wheels. For best durability - go dull. Plenty of spokes, no funny laces. Maybe a thinner gauge NDS, that's it.


I think the point here is that at least four spoke holes were cracking in each case. See above, it's (often) just a more marginal design. The risk for early failures(when compared to more conservative wheels) goes with the territory, like sports cars carrying higher premiums.


after the first wheel failed, I went around the other wheel and loosened spokes ever so slightly.
The lower the spoke count, the more delicate the balance becomes between maintaining enough tension on the NDS and not overstressing any other part of the design.

This one is definitely from use but only after 5 yrs of solid use:
http://i35.tinypic.com/2d8m6go.jpg

Have 3 sets of tubulars wheels laced like + 20 years ago and still perfect, and yes i did race and trained with 2 of them for more than 5 years.

Have 3 sets of tubulars wheels laced like + 20 years ago and still perfect, and yes i did race and trained with 2 of them for more than 5 years.I bet you kept them out of the snow and salt, or washed them very thoroughly after your rides. It's a case of stress corrosion cracking.

I would say unless the cracks occour in the first 100 or so miles it is most likely normal wear and tear. unfortunatly not all of ride on glass smooth roads all the time and there are just too many variables to say it is a defect.

No.

Hitting a pot-hole or jumping off a curb makes for a significant tension decrease in the bottom few spokes with negligible changes elsewhere in the rim.

While you might put a flat spot on the rim or even cause it to collapse if you get a big enough hit with side loading, you're not going to cause failures like the one illustrated.

Spoke breakage and rim-bed cracks come from fatigue, where the number of cycles which can be survived depends on average stress, magnitude of the stress cycles, and the materials/construction.

Where the rim is failing like that spoke tension is too high, there isn't enough material in the spoke bed, or there are material problems. Those are all defects whether they show physical effects in the first 100 miles, 1000 miles, or 10,000 miles although getting a warranty replacement may be difficult in the later cases.

Properly designed rims last until you wear out the braking surfaces or damage them in crashes.

Have 3 sets of tubulars wheels laced like + 20 years ago and still perfect, and yes i did race and trained with 2 of them for more than 5 years.

That rim was used off-road mtb, lifecycle for sure is shorter.

Worth updating- I put on the "third wheel" several weeks ago and it failed in less than 2000 miles of road use. I'm not going to check my logs but I would estimate that all three rear wheels combined supplied less than 8000 miles of service.

These are of course, cheap, very heavy wheels from a mail order company. I think what my point is in asking the poll was "If this in new technology" then how and why is this manufacturing technique even used when these wheels essentially offered only an increase in weight and no obvious advantage in any aspect of service?

OK great - new wheel - heavier, poor service life - but at least you have no reason to "true them" since they fail completely instead of "giving"........ yeah OK great stuff - my bad.....

Here is a revolutionary idea...

Lets build some wheels with 32 double butted spokes front and rear with good quality rims and eyeleted hubs and figure that if we use decent parts these wheels will come out lighter than a low spoke count wheel that needs a heavier rim to handle the higher spoke tensions.

I think that without these ultra high tensions the rim will probably survive and continue to be ride-able if a spoke breaks.

What do people think about that?

Wait... this is how I still build wheels.

Aside from that...

The people who voted yes and no are wrong as wheels will fail at this point and many wheels suffer from this kind of damage and this can stem from design failure in the rim, a poor quality build, or impact damage that exceeds the wheel's capacity to make a saving roll.

Just helped my friend with a warranty issue for his Trek 520... it was fitted with those POS Bontrager Maverick rims with offset drilling and like so many others like them, these wheels developed cracks at nearly all the drive side eyelets after less than 1000 km of light use.

This was a design failure in the rim.

And when you build wheels you need to keep in mind that you have to build your wheels so that the build does not exceed the limits of the parts used... some rims will not handle the higher stresses needed for low spoke builds.

Older 36 spoke rims don't need the same uber high tension as lower spoke count wheels as more spokes are sharing the load... I have had old single wall Araya rims last until the sidewalls were too thin to ride and without eyelets they held up fine.

What do people think about that?

I - and my 1375g 28 spoke wheelset - agree.

^^^^^ + 1. I just trashed a cheapo Avenir "Equation" 20-spoke rear wheel when a HUB flange failed around the spoke hole. Good riddance; I broke so many spokes on that wheel that I took to carrying a spare spoke in my seatpost and a "hypercracker" (on-the-road cassette lock ring tool) in the seat bag. Stoopid design, the flanges didn't even go around the whole circumference of the hub, there were just little "ears" sticking up for each spoke hole. Recipe for early failure. THAT DAY, an old-school Shimano 600 hub with (DT?) db spokes with a Matrix rim from before the deep-vee aero days showed up on craigslist. Rim was even made in the US. Back on the road in one day. 28-36 spokes FTW.

This is why I can't figure out why many wheel manufacturers now go with such fancy, flashy designs that builders in the 80's and 90's avoided like the plague becuase of reliability problems. Everyone now seems think that all new high performance bikes need radial spoking, sub 28 spoke counts and more new/usual proprietary hub and spoke designs and I noticed many people having wheel problems that seems to be related to this trend. You can only design so close to the limits of the wheel material's ultimate stregnth and design envelope or you will see a lot of problems out there like this rim cracking. I really don't thing most riders will feel the difference between a new 18 bladed spoked radially laced new wheel and maybe a classic 28 oval spoke 3 or 2 cross wheel from the mid 80's early 90's on the road. the design on wheels on the newest bikes today seems to be just all marketing and flash to sell it to wide eyed, tech hungry gear heads.
Heck, I think I spend more time riding than my college age nephew these days because he's always having to re-true the fancy radial laced wheels on his new bikes constantly and we ride the same roads. Never mind the wheels he had already mothballed in our garage cause they "broke" on him.
JMOs

Chombi

This is why I can't figure out why many wheel manufacturers now go with such fancy, flashy designs that builders in the 80's and 90's avoided like the plague .....

There are two ways to design and spec bikes and hardware. You can design it for riding, or for selling, and the two often aren't the same. It's hard to get folks excited about good fundamental product. It has to be NEW, and IMPROVED, and have all kinds of marketing buzzwords. In a product as highly evolved as a bicycle, being new and different often means abandoning proven concepts, and is sometimes counter productive.

That doesn't mean that improvement is impossible and all new stuff is junk, but it does mean that new isn't necessarily improved, and buyers also have to decide if a given product, no matter how good it is is suited to their purpose. Low spoke wheels are more aero, and make sence for serious competitors who ride at speeds where they can benefit, vs someone who actually pays for his won stuff, doesn't ride at 25+mph, and is more interested in durability.

I guess I was biased against the wheels in general because the first wheel failed while at rest. I went to get on my bike one day and the wheel would not clear the brake pads.

The second wheel to fail - did in fact at least have several thousand miles of "hard use" - if you call a 170 pound rider riding over less than perfect chip-sealed roads "hard."

I think the point here is that at least four spoke holes were cracking in each case. I've damaged a single eyelet by hitting an expansion joint on lighter weight rims and accepted that as "catastrophic" single point damage - not a manufacturing error or defect.

I should also note, after the first wheel failed, I went around the other wheel and loosened spokes ever so slightly. I'm sure some of the other RCs here can find fault with that as well.
I ride about 14,00 miles a year on two different bikes. The tourer has seen loads of me and gear as high as 240 pounds and the wheels have over 40,000 miles on them. The only problem with them was when I rode without a spoke protector and dropped the chain. I notched the 9 spokes on the outside and one failed. I no longer ride without a spoke protector and have not broken any other spokes.
The other bike's back wheel began to show cracks around the eyelets after over 60,000 miles. The rim was an Open Pro with hard anodizing. I have replaced it with an Open Sport and after over 30,000 miles it is OK. My wheels are all tensioned to 110kg with my Wheelsmith tensiometer.