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Rim Crack

Old 01-28-08, 10:22 PM
  #1  
jmb
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Rim Crack

I have seen cracks from spoke but any ideas as to the cause of this crack?
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Old 01-28-08, 10:36 PM
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Too high, or uneven spoke tension, old age of rim, overweight rider, potholes or any combination of these
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Old 01-28-08, 11:14 PM
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That crack looks rather straight. Are you sure it's not the seam?
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Old 01-28-08, 11:40 PM
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Originally Posted by urbanknight View Post
That crack looks rather straight. Are you sure it's not the seam?
+1

It's right under the label, which is usually directly opposite the valvestem hole. Sun rims, in my experience, don't finish the seam off very nicely
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Old 01-29-08, 06:59 AM
  #5  
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+1+1
thats a seam crack,...I have a matching one
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Old 01-29-08, 07:06 AM
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+1 that's the seam of the rim. That is to say, it's not a crack (or probably not one) unless the seam has separated. If the seam has separated, you should be able to pull the rim apart by pulling left and right if you have the rim in your hands as pictured.
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Old 01-29-08, 07:39 AM
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Originally Posted by bmalmquist View Post
+1 that's the seam of the rim. That is to say, it's not a crack (or probably not one) unless the seam has separated. If the seam has separated, you should be able to pull the rim apart by pulling left and right if you have the rim in your hands as pictured.
That won't be possible. There's approximately 2,000lbs of force at that seam. The only purpose for it being welded or pinned is for ease of wheel building.
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Old 01-29-08, 08:13 AM
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Right, but if it's broken in two, you'd be able to pull it apart . . .
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Old 01-29-08, 08:15 AM
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The cause of that crack/seam is the manufacturing process.
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Old 01-29-08, 08:37 AM
  #10  
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Unless there is another crack by the spoke holes, what you show is just the seam where the rim has been joined. Not a problem unless it creates uneven braking; even then the region can be gently leveled.
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Old 01-29-08, 08:43 AM
  #11  
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Thanks for input everyone , yes crack is most likely the seam but it was not previously visible .
reckon +1+1
Maybe this is normal for a CR18 rim
"that's a seam crack,...I have a matching one "
reckon-Are you still using the wheel with seam crack ?
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Old 01-29-08, 09:13 AM
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Originally Posted by jmb View Post
Thanks for input everyone , yes crack is most likely the seam but it was not previously visible .

reckon-Are you still using the wheel with seam crack ?
That's how it was when it was brand new, so yes. 20 years ago, almost all rims looked like your picture above. Only recently did they start machining and welding over the seam so you couldn't see it (it's still there though).

fwiw Sun rims are still good rims. I raced on plenty of them before and they tend to be light but durable. The seam shouldn't be a concern unless it is actually coming apart as mentioned above.
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Old 01-29-08, 10:28 AM
  #13  
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Originally Posted by urbanknight View Post
That's how it was when it was brand new, so yes. 20 years ago, almost all rims looked like your picture above. Only recently did they start machining and welding over the seam so you couldn't see it (it's still there though).

fwiw Sun rims are still good rims. I raced on plenty of them before and they tend to be light but durable. The seam shouldn't be a concern unless it is actually coming apart as mentioned above.
Ok again thanks .I guess i will find something else to obsess about.
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Old 01-29-08, 12:06 PM
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Originally Posted by jmb View Post
Thanks for input everyone , yes crack is most likely the seam but it was not previously visible .

reckon-Are you still using the wheel with seam crack ?
why no, I took it off, and tossed it remembering the last time I rode a rim with a crack in it:

it was a lovely sunny day, and I thought "hey!, it's so nice out I think I'll ride home for lunch", and set out on a typical 2.3 mile all out sprint to my house (I work in a shop: only a 30 minute lunch "hour") I hit the intersection at top speed (prolly only 20mph) and hit a bump, the front tire exploded, then the rim did the same, and I took a nice 25 foot long slide across the intersection.

while limping home bleeding I thought to myself "ya think I maybe should have replaced that rim"? and then "I wonder where I left the tylenol" and then "I wonder where I left the demerol?"

so no, I try and avoid cracked rims whenever possible
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Old 01-29-08, 01:26 PM
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Originally Posted by bmalmquist
+1 that's the seam of the rim. That is to say, it's not a crack (or probably not one) unless the seam has separated. If the seam has separated, you should be able to pull the rim apart by pulling left and right if you have the rim in your hands as pictured.
Originally Posted by mcmurryjohn
That won't be possible. There's approximately 2,000lbs of force at that seam. The only purpose for it being welded or pinned is for ease of wheel building.
Originally Posted by bmalmquist View Post
Right, but if it's broken in two, you'd be able to pull it apart . . .
If it's a rim seam (as you said) and the hoop ends are not attached (separated, as you said), you cannot just pull the rim apart for the reason I explained above.
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Old 01-29-08, 02:43 PM
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ok
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Old 01-29-08, 05:51 PM
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OK bmalmquist cant pull it apart so must be just the seam.
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Old 01-30-08, 01:05 AM
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Reckon,
We want a full sized pic of your avatar.
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Old 01-30-08, 01:12 AM
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Originally Posted by WNG View Post
Reckon,
We want a full sized pic of your avatar.
+1

Regards,
J T
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