Wheel trouble / Seeking opinions on what happened here

[bearfamily]

Howdy from a new guy. I'm a road biker/commuter in Atlanta, Ga and my bike has Bontrager wheels that are only about 13 months old (approx 6000 miles) and just last night I noticed that the rear wheel has a small tear in it in 2 places (right where the spoke enters the wheel itself). I noticed these tears about 3 or 4 days after I had the wheel trued and since the wheel is still relatively young, I find myself wondering if perhaps a couple of the spokes may have been over-tightened, resulting in the tears.

I took a couple of digital photos and since I'm not yet sure how to post photos to a thread (or if this is even an option) I posted the photos on a website and the link is here:

http://atlantatimemachine.com/wheel_trouble.htm

I've never seen wheels that exhibit this "tearing" problem. If anyone has thoughts on what may have caused this, I would be most eager to hear them.

Thanks!

Greg in Atlanta

 

[scotty72]

Geez, never seen that before.


Surely, an overtight spoke couldn't do that - could it? I'd have thought that the spoke itself would give out first before ripping in the rim. Then again, I'm no guru when it comes to this?

Might it be a dodgy or fatigued rim?

 

[boudreaux]

Could be a rim defect,or a ham fisted hack with a spoke wrench.

 

[philso]

amazing pics. a rim defect is certainly possible, but in that case, i'd guess the bike shop would have pointed it out up front. the fact that they didn't sounds like they had a part-time highschool kid do it and ruined your rims. difficult to prove though.

 

[artmichalek]

I've had it happen. About a thousand miles after the last time I let someone else true one of my wheels. You didn't specify, but I'm guessing those are the drive side spokes? The shop probably over tensioned them. Go back to the shop that did it and raise hell.

 

[John M]

. . . I find myself wondering if perhaps a couple of the spokes may have been over-tightened, resulting in the tears. Greg in Atlanta

Greg, you are right on the money!!! Do not ride that wheel. The rim is shot and must be replaced.

 

[JohnO]

The fact that it happened in more than one place tends to indicate overtorqued spokes. Rims can be defective, but a casting problem that occurred right beside two or three spoke holes... heck of a coincidence. Sounds more like a newbie wheel truing effort.

 

[gubaguba]

Well I agree no riding as the spoke will soon pull through the rim. I have only seen something similar one other time. I once was involved in an auto accident and my rim was badly damaged. Normally I would have had the wheel rebuilt but I was leaving on a charity ride (Boston to NY Aids Ride) and did not have time to rebuild it. So the local shop trued it up. The tension to pull the rim back in true was so great that the spoke pulled right through the rim similar to your photo during the ride. This was an extreme situation though and really I kind of expected something like that to happen. I'm uncertain why this would happen with your wheels.

 

[daveornee]

Howdy from a new guy. I'm a road biker/commuter in Atlanta, Ga and my bike has Bontrager wheels that are only about 13 months old (approx 6000 miles) and just last night I noticed that the rear wheel has a small tear in it in 2 places (right where the spoke enters the wheel itself). I noticed these tears about 3 or 4 days after I had the wheel trued and since the wheel is still relatively young, I find myself wondering if perhaps a couple of the spokes may have been over-tightened, resulting in the tears.

I took a couple of digital photos and since I'm not yet sure how to post photos to a thread (or if this is even an option) I posted the photos on a website and the link is here:

http://atlantatimemachine.com/wheel_trouble.htm

I've never seen wheels that exhibit this "tearing" problem. If anyone has thoughts on what may have caused this, I would be most eager to hear them.

Thanks!

Greg in Atlanta

I have seen wheels that have a small crack(s) near the spoke bed which relieves the tension at the affected spoke(s) and makes the wheel loose true and the spokes loose tension balance. If you then try to true up the wheel and regain the tension balance, you end up with a rim looking like the one in the picture. It is possible that the rim was shot before the shop even touched it and they should have called it to your attention. At this stage it may be hard to tell, unless there is oxidation in the "torn" cross section that would indicate that the rim was cracked for some time.
What ever you paid for truing/spoke tesnion balancing is wasted money. I would certainly visit the shop and ask what can be done in refunding that portion of your service cost. I would also ask the dealer about Trek's warranty policy on rim/wheel replacement.

 

[Balderick]

The fact that it happened in more than one place tends to indicate overtorqued spokes. Rims can be defective, but a casting problem that occurred right beside two or three spoke holes... heck of a coincidence. Sounds more like a newbie wheel truing effort.

It is quite a coincidence.

I had a puncture on the way to work this morning, and after I replaced the tube and refitted the tyre I checked the tyre was seated properly. I noticed what I thought was an odd scratch on the rear wheel. Closer examination disclosed similar cracks around 5 of the drive side spokes on my Ritchey OCR rear. The affected areas are very roughly equidistant around the rim. The rim has been used for training and racing, has not been crashed and have never needed truing or a spoke replaced - still straight as the day Ipicked them up from the bike shop. I weigh 109kg and like to sprint. The rims have travelled just over 8,000 km.

I'll be taking it back to the retailer I purchased them from, who will submit them to the supplier for a warranty claim. it will be interesting to see if the rim is replaced under warranty or not, especially when the rims were an upgrade from the Shimano 540 rims- that are the standard fitting for my bike (a Giant TCR 2 Composite) - due to my then greater body mass (123 kg).

 

[bearfamily]

Just a quick follow-up here from the originator of this thread.

The bike shop covered the wheel and replaced it free of charge. Obviously, I'm quite happpy. Thanks to all who helped out with answers.

 

[John M]

Just a quick follow-up here from the originator of this thread.

The bike shop covered the wheel and replaced it free of charge. Obviously, I'm quite happpy. Thanks to all who helped out with answers.

Good for them. Tell your friends about that shop. They deserve to be rewarded with future business for backing up their services/products.

 

[dhk]

Just a quick follow-up here from the originator of this thread.

The bike shop covered the wheel and replaced it free of charge. Obviously, I'm quite happpy. Thanks to all who helped out with answers.

I've had a rear rim fail like this also, after about 6000 miles. Believe it was an MA-40 rim, built with straight 14 gauge spokes by a local builder. It stayed true until the rim failed, so I really wasn't disappointed with the life of the wheel.

Seems to me this failure at this mileage could be more or less normal. As the braking surface of the rim wears thinner, the stresses from your weight, road conditions, and tire pressures build up right at the corner of the rim and result in the cracking.

Kudo's to your Trek dealer for replacing the wheel.

 

[artmichalek]

Seems to me this failure at this mileage could be more or less normal. As the braking surface of the rim wears thinner, the stresses from your weight, road conditions, and tire pressures build up right at the corner of the rim and result in the cracking.

It's not entirely a wear issue. Putting a corner feature like that on a lightweight rim is a bad idea in the first place. The way modern aluminum rims are extruded they're left with a highly elongated grain structure. This gives the rim a high bending strength, but once a crack nucleates in that corner there's very little to keep it from quickly propagating.

 

[dhk]

It's not entirely a wear issue. Putting a corner feature like that on a lightweight rim is a bad idea in the first place. The way modern aluminum rims are extruded they're left with a highly elongated grain structure. This gives the rim a high bending strength, but once a crack nucleates in that corner there's very little to keep it from quickly propagating.

Good point. Wear of the braking surface on a box-section rim may increase the bending stresses and likelihood of crack initiation at the corner, but if the corner feature can be avoided, that's even better. Do you think this is why so many rim designs today have gone "semi-aero" rather than the old box section?

 

[artmichalek]

Do you think this is why so many rim designs today have gone "semi-aero" rather than the old box section?

I think most of the reason is that the technology allows it. Box rims usually fail right at the spoke holes rather than out at the corners. Newer style wheels are getting pushed rather hard in terms of spoke tension and the way the rims are made. Getting an aero shape out of a rectangular aluminum billet requires a lot of deformation. Part of the reason why there's a +/- 15% variation in the weights of these rims is that the extruder dies wear very quickly. It's scary that the tolerances for such light parts can be so bad.