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Old 03-02-08, 10:44 PM   #1
lebowitz
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Rim damage

I found this damage today to my MA3 rim.

How dangerous is this for me to commute on this week? Do I run the risk of a catastrophic failure?

Is there are repair option? If not, I guess I would just switch rims, the wheel was undertensioned, not over tensioned. Could I up the tension on this wheel without exacerbating the damage?

Is there anything I can do to prevent this in the future?

Thanks!

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Old 03-02-08, 10:45 PM   #2
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Rim is 2.5 years old and I was a 215lbs clyde, now down to 191
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Old 03-02-08, 11:07 PM   #3
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Definitely replace that rim before riding it again!
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Old 03-02-08, 11:44 PM   #4
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If you tension up the spokes, the wheel will explode. You can see this by just squeezing the affected spokes and watching them pull the rest of the way through the rim. If you ride it at all you run the risk the rim will collapse completely.
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Old 03-02-08, 11:47 PM   #5
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Yikes!
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Old 03-03-08, 12:18 AM   #6
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thanks for the tips it will not see pavement until fixed!
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Old 03-03-08, 01:10 AM   #7
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Codswallop. I had TWO Velocity rims suffer spoke pull-through exactly like that, and rode for many kilometres afterwards, in fact with one rim having a hole the size of the pull-through area. The first was replaced under warranty, the second could have been but was too much trouble for me.

Just detension the spoke in question, or even remove it, adjust the tension on the spokes on either side to get the wheel reasonably true again, and you quite probably could keep commuting on it for the week and possibly a month or two.
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Old 03-03-08, 06:14 AM   #8
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Nothing's gonna "explode", but the rim needs to be replaced, obviously. Worst case scenario the spoke pulls out and could catch on something. It is possible, as has been suggested, to remove the spoke completely, adjust trueness as best as possible, and keep riding it for awhile longer.

BTW, has anyone been working on that wheel? That damage looks like a classic case of overtensioning.

To get back on my 'tensionmeter soapbox' again, this is the reason that tensionmeters are important. You can true up a wheel, pluck the spokes, and think everything is alright, only to discover the hard way that you have too much tension and your rim strokes-out.

Today's spokes are stronger than today's rims. If you don't know your rim's tension limits you can cause just the type of damage that your photo shows by overtensioning.

The same is true of pumping up your tires to their max psi. 160 psi may be within your tire's specs, but it may exceed your rim's specs. And that would be a 'catastrophic failure' waiting to happen.

If you have 2 components (e.g. spokes and rims; stem and steerer; tire and rim) never exceed the max spec. for the weakest component.

Bob
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Old 03-03-08, 10:01 AM   #9
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Oops. Too much tension. Park that wheel for sure. I could not agree with Bobby Lex more. A tension meter is very helpful in really bringing a wheel assembly to a decent place. I did not use one on my first wheel and nearly ended up like your photo. I later bought one and find it to be critical to a decent build.
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Old 03-03-08, 10:23 AM   #10
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Oops. Too much tension. Park that wheel for sure. I could not agree with Bobby Lex more. A tension meter is very helpful in really bringing a wheel assembly to a decent place.
I bought Park's tension gauge and 'evened-out' the spoke tension on one of my rims . . . just for practice. But I've searched everywhere I can think of and can not find info on WHAT THE TENSION SHOULD BE for my spokes/rims.

It's nice to be able to "measure" things [I own a machine shop] but I need more information on what 'numbers' I'm trying to reach.
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Old 03-03-08, 11:04 AM   #11
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I bought Park's tension gauge and 'evened-out' the spoke tension on one of my rims . . . just for practice. But I've searched everywhere I can think of and can not find info on WHAT THE TENSION SHOULD BE for my spokes/rims.
It's nice to be able to "measure" things [I own a machine shop] but I need more information on what 'numbers' I'm trying to reach.
Some rim manufacturers publish their max. tension specs. Some don't. You can try contacting them, or checking with your LBS.

Jobst Brandt (author of "The Bicycle Wheel") recommends increasing tension until the rim just starts to taco, then backing off a bit for the highest tension possible. But that scares the crap out of me, and IMO would likely lead to a lot of problems like the OP's.

Bob
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Old 03-03-08, 11:17 AM   #12
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I bought Park's tension gauge and 'evened-out' the spoke tension on one of my rims . . . just for practice. But I've searched everywhere I can think of and can not find info on WHAT THE TENSION SHOULD BE for my spokes/rims.

It's nice to be able to "measure" things [I own a machine shop] but I need more information on what 'numbers' I'm trying to reach.
Many seem to be in the 100 - 120 KGF range. I always use that if I cannot find the spec. Park's website lists some of them to give you a general idea. Try this link: http://www.parktool.com/repair/readhowto.asp?id=51

Look 3/4 down the page under tension recommendations
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Old 03-03-08, 11:19 AM   #13
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Jobst Brandt (author of "The Bicycle Wheel") recommends increasing tension until the rim just starts to taco, then backing off a bit for the highest tension possible. But that scares the crap out of me, and IMO would likely lead to a lot of problems like the OP's.

Bob

I have read that book and came to the same conclusion. For me, wheel building doe not include distructive testing.
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Old 03-03-08, 08:07 PM   #14
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For me, wheel building does not include distructive testing.
+1000!

Both a friend and my son-in-law had Trek factory wheels (on Klein-labeled bikes made after Trek bought Klein) fail the same way after about 10,000 miles, Neither rider is particularly large or heavy and I always assumed the wheels were over tensioned.
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Old 03-03-08, 08:38 PM   #15
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Nothing's gonna "explode", but the rim needs to be replaced, obviously. Worst case scenario the spoke pulls out and cause the rim to collapse, making it catch on the fork sending you over the handlebars.
fixed

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Old 03-03-08, 09:16 PM   #16
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From what I've read, the MA-3 is famous for that type of failure. Personally, I'd keep using it but obviously, it should be replaced as soon as possible.
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Old 03-03-08, 11:43 PM   #17
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Brandt published a treatise (is there any other way to describe his material?) on how the anodising can affect the durability of a wheel. He took aim in particular, if I remember rightly, at Mavic, and their reduced reliablity linked to anodising (compared with their non-anodised rims, I think).

I am still having a little trouble with that treatise (as I have with several of his others), especially after he was challenged to present his "scientific" findings on the relevant forum, and conveniently had mislaid them.

Anyway, I found it interesting that the Velocity rims I mentioned in my first post here, were both OS Aeroheads, and I suspect a combination of a suspect batch of aluminium extrusions and inappropriate tensioning contributed to the spoke pull-through.

I am with Hillrider in suggesting that Brandt's method of achieving optimum spoke tension through deformation of the rim through overtensioning, then backing off the nipples is not good practice these days. Personally, I think the "ping" test is as good as I need, and all my recently built wheels have done very well in a wide range of strenuous conditions. But I am old-school 36H, straight-guage.

Again, note, that the Velocity rims to which I refer were purchased as part of complete wheels, laced and tensioned by Velocity.
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