so was cleaning the Stans 340 rims today and noticed cracks

[eddief]

a couple of hairline cracks where the nipples exit the rim on the back wheel. Think I read something about this issue a while back. Does this mean don't ride it or I will endanger my life, or is this just a symptom to do watchful waiting on?

[cmbicycles]

Definitely means don't ride it, not worth risking failure while riding.

[Elefantino]

a couple of hairline cracks where the nipples exit the rim on the back wheel. Think I read something about this issue a while back. Does this mean don't ride it or I will endanger my life, or is this just a symptom to do watchful waiting on?
http://www.gadgetmadness.com/archives/hammacher-lost-in-space-b9-robot.jpg

Danger, danger.

Don't ride them. Just don't. Hairline cracks never stay hairline cracks and could lead to catastrophic wheel failure. Replacing a rim is cheap. Surgery, or worse, is not..

[soulspinner]

They have had arash of those rims crack. If I got those rims Id get a 400 in back(ride 465s back, 415s front). But Im 170 lbs.

[Mark McM]

http://www.gadgetmadness.com/archives/hammacher-lost-in-space-b9-robot.jpg

Danger, danger.

Don't ride them. Just don't. Hairline cracks never stay hairline cracks and could lead to catastrophic wheel failure. Replacing a rim is cheap. Surgery, or worse, is not..

It's doubtful that a hairline rim crack could lead to a catastrophic wheel failure (unless the wheel is terribly under-built to start with). The affects of a crack around a spoke hole is basically like a slow-speed spoke breakage. As the crack grows, the spoke will lose tension and the rim may go out of true. The final result is as if the spoke broke - except that the spoke will not likely not flop around as it may if it really broke. So, the wheel would only fail catastrophically if it is already prone to catastrophic failure in the case of a spoke or nipple breakage.

Spoke hole cracks do not propagate completely through the rim, so the rim will not suddenly break in half. Fatigue cracks only form and grow under tension, but the rim cross-section is under net compression (from the agragate of the spokes pulling it inward). The only areas of the rim under high tension are the around the spoke holes (which is why this is where cracks form).

Your wheel with the spoke cracks will continue to loose spoke tension and go out of true as the cracks grow, and will eventually become unrideable - but it is a not an instantaneous event. You will have to replace the rim at some point, but you might still get a few miles out of it.

[Elefantino]

It's doubtful that a hairline rim crack could lead to a catastrophic wheel failure (unless the wheel is terribly under-built to start with). The affects of a crack around a spoke hole is basically like a slow-speed spoke breakage. As the crack grows, the spoke will lose tension and the rim may go out of true. The final result is as if the spoke broke - except that the spoke will not likely not flop around as it may if it really broke. So, the wheel would only fail catastrophically if it is already prone to catastrophic failure in the case of a spoke or nipple breakage.

Spoke hole cracks do not propagate completely through the rim, so the rim will not suddenly break in half. Fatigue cracks only form and grow under tension, but the rim cross-section is under net compression (from the agragate of the spokes pulling it inward). The only areas of the rim under high tension are the around the spoke holes (which is why this is where cracks form).

Your wheel with the spoke cracks will continue to loose spoke tension and go out of true as the cracks grow, and will eventually become unrideable - but it is a not an instantaneous event. You will have to replace the rim at some point, but you might still get a few miles out of it.
That's interesting because I've had some fellow riders tell me the same thing.

However, and I guess this is part of the equation, it depends on other factors we don't know about. Size and depth of the cracks, for one. Rider weight for another. On the advice of my team's prez, I recently de-rimmed a rear wheel because there were numerous hairline cracks on the both the DS and NDS. At pushing 200 pounds, I didn't want to take a chance on spokes going soft or pulling through mid-ride. (If I were 140 pounds, I probably wouldn't have given it a second thought.)

Would be interested to get ergott's perspex. What say you, Eric?

[gearguywb]

Cleaned mine last week and found some cracks as well.

That's what I get for cleaning them ;)

[Elefantino]

Cleaned mine last week and found some cracks as well.

That's what I get for cleaning them ;)
Dirt is a great adhesive.

[cmbicycles]

It's doubtful that a hairline rim crack could lead to a catastrophic wheel failure (unless the wheel is terribly under-built to start with). The affects of a crack around a spoke hole is basically like a slow-speed spoke breakage. As the crack grows, the spoke will lose tension and the rim may go out of true. The final result is as if the spoke broke - except that the spoke will not likely not flop around as it may if it really broke. So, the wheel would only fail catastrophically if it is already prone to catastrophic failure in the case of a spoke or nipple breakage.

Spoke hole cracks do not propagate completely through the rim, so the rim will not suddenly break in half. Fatigue cracks only form and grow under tension, but the rim cross-section is under net compression (from the agragate of the spokes pulling it inward). The only areas of the rim under high tension are the around the spoke holes (which is why this is where cracks form).

Your wheel with the spoke cracks will continue to loose spoke tension and go out of true as the cracks grow, and will eventually become unrideable - but it is a not an instantaneous event. You will have to replace the rim at some point, but you might still get a few miles out of it.

340s are a lightweight rim for starters, i.e. underbuilt for longevity, and are generally used where longevity is not the primary concern, so having several "hairline" cracks means that the aluminum has exceeded its useful life. No the crack will not likely spread through the entire rim... just the spoke bed where it supports the weight of the bike and rider. When the aluminum is uniformly structured, not broken, everything works as a unit but once the rim integrity starts to be compromised it fails at the weakest link. Hold an egg in your hand and you would be hard pressed to crush it exerting uniform pressure, crack the shell anywhere and do the same thing and your hand will be a gooey mess.

Bottom line is, Yes your rim will fail, it already has shown structural failure and the cracks are the proof of that. Catastrophic failure meaning total loss of the system, from which recovery is impossible... By definition... Is impossible to predict. On your wheel the spokes will pull out of the rim and it will go out of true or if the cracks are near enough to each other it will buckle, given enough help by riding conditions. How exactly it will affect you as the rider is outside my scope of practice, my crystal ball is in the shop. I would not chance my health or life on it, nor those i ride with. You already know you need to spend the money to replace it, replace it now and gain peace of mind, rather than push your luck to see how far you can ride the wheel.

[staggerwing]

Agree, time to replace rim.

On the good side, it is relatively easy to replace a rim when the original is whole. If you have never built a wheel before, this is an easy place to start, even if you take it to a shop for final tension and true.

Simply, purchase a new rim with the same ERD. Tape it to the old one at a couple of places, and move the spokes over one at a time.

Once you taco the original, it becomes harder. ;)

[eddief]

looks as if the 340 has a 592 erd and so does a Hed C2. wondering if any other light rims have that erd?

Agree, time to replace rim.

On the good side, it is relatively easy to replace a rim when the original is whole. If you have never built a wheel before, this is an easy place to start, even if you take it to a shop for final tension and true.

Simply, purchase a new rim with the same ERD. Tape it to the old one at a couple of places, and move the spokes over one at a time.

Once you taco the original, it becomes harder. ;)

[oldpotatoe]

a couple of hairline cracks where the nipples exit the rim on the back wheel. Think I read something about this issue a while back. Does this mean don't ride it or I will endanger my life, or is this just a symptom to do watchful waiting on?

Pulling eyelets out, VERY common on Stan's 340, particularly on early rims. Replace rim..use a stronger(heavier) one.

All that's gonna happen if ya ride it is the spoke will come out more, wheel will go way outta true. Probably isn't going to fail/collapse or anything like that.Should replace tho.

[notoriousdjw]

Stans replaced mine which were cracked on the drive-side rear spoke holes. The early 340s had a thinner spoke bed than the current rims. You can tell the rim vintage by looking at the 340 decals. New (http://www.paligap.cc/Stans-NoTubes-ZTR-Alpha-340-Rim_2840_p) vs. Old (http://www.spinlitecycling.com/images/Alpha340.jpg). I think the ERD changed from 591 to 592 as a result. That said I switched to Alpha 400s for the rear wheel just for a bit of added safety.

[pavel]

Dirt is a great adhesive.



load-bearing dirt imo

[jds108]

Stans replaced mine which were cracked on the drive-side rear spoke holes. The early 340s had a thinner spoke bed than the current rims. You can tell the rim vintage by looking at the 340 decals. New (http://www.paligap.cc/Stans-NoTubes-ZTR-Alpha-340-Rim_2840_p) vs. Old (http://www.spinlitecycling.com/images/Alpha340.jpg). I think the ERD changed from 591 to 592 as a result. That said I switched to Alpha 400s for the rear wheel just for a bit of added safety.

Thanks for the links to the pics, it's very useful. Now I know I've got the old version and I'll have to go check them.