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Cracks in the rim ...

Old 05-31-19, 09:52 AM
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CoogansBluff
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Cracks in the rim ...

Discovered this week that the back wheel on my road bike has small cracks near 3-4 of the spokes.

It's under warranty and can be replaced - albeit it in 2 weeks from the shop where I bought the bike. Wheel must be ordered. Not sure why that long, something about one of the Specialized warranty folks suddenly short-staffed.

Is it safe to ride for the next 2 weeks, IYO? I rode 32 miles yesterday without incident. The wheel is off true a little bit.



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Old 05-31-19, 10:13 AM
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I would not*, but I have several bikes.. by the entry..

* particularly if the front wheel ...

but I guess its a drive side rear with the pull through cracking..






....
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Old 05-31-19, 10:23 AM
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Originally Posted by fietsbob View Post
I would not*, but I have several bikes.. by the entry..

* particularly if the front wheel ...

but I guess its a drive side rear with the pull through cracking..






....

It is the back wheel, fwiw. ...

I've got a hybrid back that I can use, putting me back on the flat greenways, but I'd survive. Lucky to have to awesome long trails in the Raleigh area. ...

Sure would hate to park the road bike for 2 weeks, though.
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Old 05-31-19, 10:35 AM
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Probably OK to ride, but watch it. You might consider asking the shop if they have a loaner wheel.

If you continue to ride this, mark the currently cracked spokeholes with a magic marker. Now watch to see if the cracks grow or now holes start to crack. Monitor the progress. (I'm guessing these are all drive-side spokes. If they are non-drive-side spokes, this is less critical but I would not ride the wheel after a 1/4 of the drive side spokes have cracked.)

What we (fellow BFers) don't know is: are the spoke holes that cracked due to poor build and a few specific problem spokes in which case, the wheel may go on a long time untouched as a mediocre wheel or is this a wheel where the spokes were tensioned equally but too tight in which case you may be looking at an oncoming total failure of the rim and a collapse of the wheel. (The former is often due to inadequate spoke tension. Rarely catastrophic.)

If riding is important to you, I'd do the marking I suggested and I'd call the shop, tell them I need to ride, that I'll watch the wheel and could they set aside a loaner if I need it? That way, you come across as a customer who actually rides their bikes and not just a PITA. (Also keep in mind they operate on "bike shop time". A two week replacement usually take four.)

Ben
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Old 05-31-19, 12:49 PM
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You probably rode it for a few rides that way before noticing it. A few more won't hurt. Just keep an eye on it and keep a cell phone handy - in case you need to make the Call of Shame. If it goes completely, Duct Tape ain't gonna get you going again.
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Old 05-31-19, 02:12 PM
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I had similar cracks on the rear rim of my 2006 Roubais. These were 10 year old Mavic Open Sport rims. Someone said incorrect spoke tension, but since the wheels always stayed true, I never checked for that. There were two cracks on adjacent spokes, so I don't think they were drive side specific. I noticed it while cleaning the bike after a gear cable change. No idea how long they were broken, since the bike rode fine. I got a deal on a set of Reynolds Stratus Elites, so the cracked rim and it's partner are hanging on the garage wall. The Mavics are double wall construction, and might have been safe to ride but why chance it?
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Old 05-31-19, 03:30 PM
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spend $ for a backup wheel set Now, and then have 2 sets when the warrantee is fulfilled..

in a fortnight..
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Old 05-31-19, 03:31 PM
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Aluminum or other rim materials will eventually crack. The spoke tension is in constant change as you ride the bicycle. Once the damage is noticed it is better to wait for a replacement. I keep two sets of wheels for my tandem bicycle.
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Old 05-31-19, 03:51 PM
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Buy a spare wheelset now, and never have to worry about a bad wheel putting an end to your riding again. I've had these nipple-pull-throughs happen on several rim brands, but each time I simply put on the spare, and I'm riding again, and then bring the bad one to the LBS for a rebuild. I also typically keep more aggressive and wider tires on my spare wheelset, so I can swap the whole set in 60 seconds if I'm riding gravel that day.
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Old 05-31-19, 07:05 PM
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It is OK to ride if you enjoy walking long distances to get home.

Not really sure how anyone can "Keep an eye on it" while riding.

If a spoke pulls through then the rim is going to warp and might rub the chainstay or brakes.

I can take an Uber

Specialized must be sourcing rims from Bontrager, or they must be getting their rums from the same manufacturer.


-Tim-
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Old 06-01-19, 09:21 AM
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Originally Posted by CoogansBluff View Post
It is the back wheel, fwiw. ...

I've got a hybrid back that I can use, putting me back on the flat greenways, but I'd survive. Lucky to have to awesome long trails in the Raleigh area. ...

Sure would hate to park the road bike for 2 weeks, though.
First, ignore the people telling you to ďjust ride itĒ. The wheel wonít collapse (probably) but it canít stay true. The rim is needed to keep the tension on that spoke and with a broken rim, it will canít keep that tension. It will just wobble back and forth.

On the other hand, if you have a hybrid it has the same sized wheels as the road bike so just swap wheels? You might have to swap cassettes and tires but doing that is mostly trivial.
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Old 06-01-19, 09:28 AM
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Originally Posted by Slightspeed View Post
I had similar cracks on the rear rim of my 2006 Roubais. These were 10 year old Mavic Open Sport rims. Someone said incorrect spoke tension, but since the wheels always stayed true, I never checked for that. There were two cracks on adjacent spokes, so I don't think they were drive side specific. I noticed it while cleaning the bike after a gear cable change. No idea how long they were broken, since the bike rode fine. I got a deal on a set of Reynolds Stratus Elites, so the cracked rim and it's partner are hanging on the garage wall. The Mavics are double wall construction, and might have been safe to ride but why chance it?
Yes, the cracking is due to incorrect spoke tension but not necessarily ďincorrectĒ in the way that most people think. Cracks can form from both low and high tension. Low tension allows the spoke bed to flex constantly which leads to cracking. High tension stresses the aluminum of the rim and leads to cracking. Two different mechanisms but the same result.

If your wheels (and CoogansBluffís) are OEM wheels, I would suspect that the tension is too low. I regularly run across OEM wheels on bikes that are improperly tensioned at my local co-op. Oddly, I run across a large number of OEM wheels that arenít dished properly. Iím even seeing a lot of front disc wheels that havenít been dished properly.
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Old 06-01-19, 07:57 PM
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Don’t ride it. Not worth the risk.

But then, I really like having teeth.
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Old 06-02-19, 05:34 AM
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When you interacted with your bike shop about this issue, did they bother to check the spoke tensions? If so, I'm curious about what they found.

Safe to ride? Depends on what safety means to you. On the rear wheel, if a spoke pulls through, you will feel it through the wobble that develops; however just a single spoke won't throw you off the bike. Once a single spoke goes, though, others will probably follow making the wobble so severe that the bike will be un-ridable.

When you get the new wheel, ask the bike shop to check the tensions.
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Old 06-02-19, 12:46 PM
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Originally Posted by Moe Zhoost View Post
When you interacted with your bike shop about this issue, did they bother to check the spoke tensions? If so, I'm curious about what they found.
They didn't check it. Glad some have mentioned that here. I'll be sure to ask about that when the new one comes in.
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Old 06-02-19, 08:46 PM
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Originally Posted by Moe Zhoost View Post
When you interacted with your bike shop about this issue, did they bother to check the spoke tensions? If so, I'm curious about what they found.
There would be no point. Once the spoke has broken through the rim, the tension is essentially zero. Itís a broken spoke or at least the near equivalent of a broken spoke.
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Old 06-03-19, 06:16 AM
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I had the same issue and only found it after breaking a spoke.
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Old 06-03-19, 06:55 AM
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Originally Posted by cyccommute View Post
Yes, the cracking is due to incorrect spoke tension but not necessarily “incorrect” in the way that most people think. Cracks can form from both low and high tension. Low tension allows the spoke bed to flex constantly which leads to cracking. High tension stresses the aluminum of the rim and leads to cracking. Two different mechanisms but the same result.
Originally Posted by RVH View Post
I had the same issue and only found it after breaking a spoke.
Low tension usually results in broken spokes - there are sometimes multitudes of broken spokes from a particular manufacturer's bikes from a single production year. These are sometimes blamed on a 'bad batch of spokes', but I believe it is usually a badly tensioned batch of wheels. As CC said, the same mechanism ('fatigue' as the wheel rotates and spokes move from minimum to maximum tension and back again) can cause cracks in the rim.

As for Specialized Warranty - as a vendor of mass manufactured items made by contract manufacturers, when there is a warranty issue it often involves thousands of bikes. A few years ago they were having problems with the freehub bodies on Specialized branded hubs. If you were one of the first few hundred to report the problem then you were sent a new freehub body in short order, but if yours failed later in the season, the NA distributors had no replacement parts left and you had to wait, unless your shop was kind enough to do some type of swap with non-Specialized-branded parts. This problem happens occasionally as companies try to cut the pennies they spend on parts they order from external vendors to maximise profits.

It seems that a lot of bike companies don't actually expect their bikes to be ridden, and this attitude often pays off... say Manufacturer X saves $5 on each bike it equips with a certain cost-cutting part, but that part is expected to have a 20% failure rate. Manufacturer X sells 200,000 bikes per year with that part, so this decision saved them $1,000,000 during production. Manufacturer X knows that 50% of its bikes are only ridden a couple of times before being moved to the back of the garage as a dust collector, so they only expect 10% of those cheap parts to come back. They probably also expect not all people will realize that they can get a free replacement under warranty, or will otherwise chose to fix the part on their own - maybe another 50%. So of the 40,000 potential defective parts they need to replace, they expect to be held responsible for about 5,000. This is all worked into the initial cost of the bike. In the OP's case, they probably got wheels from a vendor who delivered at a substantial discount, but they underestimated the number of failures and are having a hard time keeping up.
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Old 06-03-19, 07:03 AM
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Originally Posted by Wilfred Laurier View Post
It seems that a lot of bike companies don't actually expect their bikes to be ridden, and this attitude often pays off... say Manufacturer X saves $5 on each bike it equips with a certain cost-cutting part, but that part is expected to have a 20% failure rate. Manufacturer X sells 200,000 bikes per year with that part, so this decision saved them $1,000,000 during production. Manufacturer X knows that 50% of its bikes are only ridden a couple of times before being moved to the back of the garage as a dust collector, so they only expect 10% of those cheap parts to come back. They probably also expect not all people will realize that they can get a free replacement under warranty, or will otherwise chose to fix the part on their own - maybe another 50%. So of the 40,000 potential defective parts they need to replace, they expect to be held responsible for about 5,000. This is all worked into the initial cost of the bike. In the OP's case, they probably got wheels from a vendor who delivered at a substantial discount, but they underestimated the number of failures and are having a hard time keeping up.
Good insights. Thanks.
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Old 06-03-19, 08:08 AM
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Originally Posted by cyccommute View Post
There would be no point. Once the spoke has broken through the rim, the tension is essentially zero. Itís a broken spoke or at least the near equivalent of a broken spoke.
Any additional information is never pointless. It may not be useful but you won't know that until you have it. Tension patterns on the spokes that have not broken through may be a clue to why it happened, though I understand why this is not important to some.
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Old 06-03-19, 05:52 PM
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Originally Posted by Moe Zhoost View Post
Any additional information is never pointless. It may not be useful but you won't know that until you have it. Tension patterns on the spokes that have not broken through may be a clue to why it happened, though I understand why this is not important to some.
If you wanted to make an analysis of the rim, it might be worth measuring the tension. But unless you are going to try solve a problem of production of rims, the tension on the other spokes is pointless for a single wheel. Even for a production problem, there are probably better ways of analyzing the rim than measuring the spoke tension on the remaining spokes.
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Old 06-04-19, 09:29 AM
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Originally Posted by cyccommute View Post
If you wanted to make an analysis of the rim, it might be worth measuring the tension. But unless you are going to try solve a problem of production of rims, the tension on the other spokes is pointless for a single wheel. Even for a production problem, there are probably better ways of analyzing the rim than measuring the spoke tension on the remaining spokes.
Don't overthink it. It's all about curiosity, mate. The only pointless query is the one not explored.
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Old 06-04-19, 11:18 AM
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Originally Posted by Moe Zhoost View Post
Don't overthink it. It's all about curiosity, mate. The only pointless query is the one not explored.
There are lots and lots of pointless queries that donít need to be explored and there are lots of people who insist on exploring them. If you want to pursue them for your own edification, feel free. But donít expect to get much useful information from testing the tension on the remaining spokes of a broken wheel. The tension on the remaining spokes arenít the same as they were before the wheel broke and the tension on the broken part of the wheel wonít tell you anything that you can use later. Itís broken. The tension is zero. ĎNuf said.
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Old 06-04-19, 11:36 AM
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Originally Posted by cyccommute View Post
There are lots and lots of pointless queries that donít need to be explored and there are lots of people who insist on exploring them. If you want to pursue them for your own edification, feel free. But donít expect to get much useful information from testing the tension on the remaining spokes of a broken wheel. The tension on the remaining spokes arenít the same as they were before the wheel broke and the tension on the broken part of the wheel wonít tell you anything that you can use later. Itís broken. The tension is zero. ĎNuf said.
Your opinions are welcome and worth considering if you can validate them. Let me know when you do. Thanks, mate.
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Old 06-04-19, 02:41 PM
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Originally Posted by cyccommute View Post
...The tension on the remaining spokes arenít the same as they were before the wheel broke and the tension on the broken part of the wheel wonít tell you anything that you can use later. Itís broken. The tension is zero. ĎNuf said.
You should grab your tensiometer and test that theory.

I have 8 cracked holes, all drive side, rear wheel. My Park tensiometer shows they all still have pretty good tension, and relative to the non-cracked DS spokes it's difficult to ascertain if they've even lost much tension from original truing tension. I measured 90-120 kg-f on both cracked and non-cracked spokes. IIRC they were originally tensioned 100-120 kg-f, but that was 5,000-10,000 miles ago. I have rear rim brake and the wheel has never gone out of true much even with the cracks.

I believe all the cracks developed about the same time, shortly after I started using a 26x2.0" tire inflated to 80psi, an unusually wide/HP combination for my use. My theory is that wide tires spread the rim walls more than smaller tires, especially at higher pressure. The whole rim is deflected slightly and the spoke bed area is pulled away from the hub, which causes a significant increase in spoke tension, and results in failures along the spoke holes, i.e. spoke cracks.

OP, I've ridden my cracked rear rim for a few thousand miles now, it does not seem to be getting any worse. My cracks look more like the image in #6 than yours in #1. I've got spare rims and wheels and can rebuild, but I've just left it because it appears to be functioning fine even with 8 cracked holes, and it makes for an easy experiment. If it were a front wheel I would change it for safety reasons.
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