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Who has filled alloy rim cracks with JB Weld (metal epoxy)?

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Who has filled alloy rim cracks with JB Weld (metal epoxy)?

Old 01-30-19, 11:10 AM
  #1  
masi61
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Who has filled alloy rim cracks with JB Weld (metal epoxy)?

Some of you may have seen my separate post about how my Dura Ace 7850 front wheel was leaking air through the weep holes preventing me from mounting tubeless tire on it. I assumed the issue was that I was using a generic valve. I had expected that using the proper Shimano front tubeless valve would take care of it. It didn't. And when I took it to the LBS they helped me identify the real culprit. The interior of the rim has a fine crack that is about 3" long!

I was seriously thinking of applying some "JB Weld" to the crack to see if I can seal up the rim extrusion to permit tubeless. I realized that this rim might be structurally compromised so, this wheel might turn out to be toast after all. But I plan to try this JB weld hack anyway just to see what happens. I spoke with my LBS mechanic and he said that the JB Weld was worth trying. He suggested taking a Dremel tool with a grinding stone to deepen the crack slightly to give more surface area for the metal epoxy to seal better.

So, I guess I would like to know - who has used "JB Weld" on an aluminum bike rim. Does this product have a use or am I just fooling myself?
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Old 01-30-19, 11:22 AM
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Just FYI: glue does not work well in tension.
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Old 01-30-19, 11:33 AM
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Originally Posted by masi61 View Post
Some of you may have seen my separate post about how my Dura Ace 7850 front wheel was leaking air through the weep holes preventing me from mounting tubeless tire on it. I assumed the issue was that I was using a generic valve. I had expected that using the proper Shimano front tubeless valve would take care of it. It didn't. And when I took it to the LBS they helped me identify the real culprit. The interior of the rim has a fine crack that is about 3" long!

I was seriously thinking of applying some "JB Weld" to the crack to see if I can seal up the rim extrusion to permit tubeless. I realized that this rim might be structurally compromised so, this wheel might turn out to be toast after all. But I plan to try this JB weld hack anyway just to see what happens. I spoke with my LBS mechanic and he said that the JB Weld was worth trying. He suggested taking a Dremel tool with a grinding stone to deepen the crack slightly to give more surface area for the metal epoxy to seal better.

So, I guess I would like to know - who has used "JB Weld" on an aluminum bike rim. Does this product have a use or am I just fooling myself?
A crack 3" long crossed from "might" to "is" long before it was 3" long.
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Old 01-30-19, 11:48 AM
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Do you have some photos of the crack?

For sealing, I'd be more apt to tape over it, which should give a little flex to the covering.

My guess is that pressurizing the tire will tend to open up the crack, and would be hard on something like your JB Weld.

Perhaps even flex from rolling will cause it to move.

Mark the ends of the crack to monitor for progression, and perhaps drill propagation stop holes in the ends.
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Old 01-30-19, 11:56 AM
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any survivors that tried this?

#1 , buy a new rim !!
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Old 01-30-19, 12:52 PM
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I am conservative, so I don't play with cracks in rims. maybe the crack falls gracefully or maybe it fails catastrophically. I don't want to play the odds

ymmv

PS FWIW my bike mechanic was just telling be about a study from I think USA cycling showing that tubeless road set up can induce cracks in rims. Best possible ride for road with out going to tubular is high end clincher with latex tubes.
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Old 01-30-19, 12:56 PM
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Originally Posted by fietsbob View Post
any survivors that tried this?

#1 , buy a new rim !!
Come on survivors, Iím counting on you!


So here is the requested picture...
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Old 01-30-19, 12:58 PM
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Are those Carbon/Aluminum rims? It might be fun to cut one open and look at Shimano's construction.

It may be that once the outer wall is compromised, there is little additional strength from the inner wall.
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Old 01-30-19, 01:08 PM
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Originally Posted by CliffordK View Post
Are those Carbon/Aluminum rims? It might be fun to cut one open and look at Shimano's construction.

It may be that once the outer wall is compromised, there is little additional strength from the inner wall.
No. Not the carbon/aluminum version just the aluminum tubeless one.
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Old 01-30-19, 01:10 PM
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Originally Posted by masi61 View Post


Come on survivors, Iím counting on you!


So here is the requested picture...
Doesn't look so bad, just a little fuzzy is all. Please post a video of your test rides.
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Old 01-30-19, 01:18 PM
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I've used JB Weld on a lot of things, but never on toast. I prefer amish butter and fruit preserves or honey. Seriously, I wouldn't ride that.
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Old 01-30-19, 01:19 PM
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I'd try the JB Weld, personally. As well as clamp the crack closed in some way while it dries. Might work, might not.
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Old 01-30-19, 01:45 PM
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Originally Posted by exmechanic89 View Post
I'd try the JB Weld, personally. As well as clamp the crack closed in some way while it dries. Might work, might not.
JB Weld has a tensile strength of 3900psi, aluminum (which has already failed), is in the range of 40, 000 to 45,000psi. Patching with a substance <1/10th as strong won't work.
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Old 01-30-19, 01:54 PM
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Originally Posted by FBOATSB View Post
I've used JB Weld on a lot of things, but never on toast. I prefer amish butter and fruit preserves or honey. Seriously, I wouldn't ride that.
OK, you win the thread.
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Old 01-30-19, 01:57 PM
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Tape may cover and re-seal better than your JB weld, especially if the crack expands.

I'm having troubles imagining a catastrophic failure that could cause a crash, although you could have a front tire "blow-out", and generally at the least opportune moment.

Thick tape + tube-tire?

I'd have to look at your spokes and nipples carefully, but it is quite possible that an Ultegra 6700 or Ultegra 6800 rim would substitute.

Some of the 6700 rims were black.

Ultegra rim + Dura Ace decals?
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Old 01-30-19, 02:13 PM
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I'm tighter than an Amish tick. I draw the line at repairing rim cracks.
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Old 01-30-19, 02:21 PM
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Never used it myself, however I can only imagine negative things happening. It is like those adhesive backed tube patches from park tool, great to use in a pinch on the road but eventually they will fail. I have forgotten to replace the tube when I get home and it may take several weeks but sooner or later I have low air pressure on a ride and remember I was going to change the tube.

It may work for a bit but when it fails it could be catastrophic! Not a problem I want to have on a high speed descent!

YMMV
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Old 01-30-19, 02:22 PM
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If you just toodle around the neighborhood on your bike, I might try and fix it. No way I would ride that going any amount of speed.
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Old 01-30-19, 02:25 PM
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Don't do that. Do this!

That sir is a prime candidate.
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Old 01-30-19, 02:26 PM
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Wow.

I volunteer at a high-volume inner-city bike Co-op. I see really scary bike stuff on a daily basis, involving third-hand department store bikes ridden by zero-income folks with no other transportation options.

But your rim is one of the scariest, most life- threatening problem I've ever seen. Ticking time bomb.

So tire inflation pressures tend to push clincher rim walls apart, putting tension on rims. This is why clincher rims have max pressure ratings. As an aside, this is yet another deficiency in clincher wheel design (tubeless or tubed), and why tubulars are used exclusively at the elite levels of the sport - past, present, and forever.

This rim needs to be chopped up an buried deep into the trash. Please please please do not 'donate' this to a thrift store or bike Co-op. We wouldn't want one of our shop clients to use this and revive in a long-term coma ward in the year 2025 wondering: WTF??
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Old 01-30-19, 02:27 PM
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Originally Posted by CliffordK View Post
Tape may cover and re-seal better than your JB weld, especially if the crack expands.

I'm having troubles imagining a catastrophic failure that could cause a crash, although you could have a front tire "blow-out", and generally at the least opportune moment.
I have no trouble at all imagining someone getting hurt by a wheel splitting apart. There is a lot of stored energy, both in the wheel and the bike/rider, that when released suddenly can do a lot of damage fast.
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Old 01-30-19, 02:54 PM
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Originally Posted by dsbrantjr View Post
I have no trouble at all imagining someone getting hurt by a wheel splitting apart. There is a lot of stored energy, both in the wheel and the bike/rider, that when released suddenly can do a lot of damage fast.
Worn brake track failures aren't that uncommon, and often result in brakes bumping, or something similar, not always even causing flats.

Hmmm.... it has been a long time since I had a brake track failure, perhaps it was on the rear, as I frequently drag the rear on descents (and that was during the wicked hill commuting era).

My last blowout was definitely a rear, and quite uneventful, other than trying to boot a tire torn off of the bead and scramble to the nearest bike shop, hoping to replace the tire in 20 miles, not 80 miles left on my ride.

As mentioned, if I was to use the wheel, it would probably be with a tube.

Hard to say, I like to experiment, but as mentioned, I'd probably also look for a replacement rim or wheel.

One issue, if the rim was to burst, it would be a failure with no recovery. If the rider is 100 miles from home, it could make for a long walk.
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Old 01-31-19, 07:55 AM
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Back when I was a maintenance manager in heavy industry we used JB by the gallons but not on butt joints. Aviation uses specialized glues on aluminum but surely not on butt joints like what you have. Tig welding might be the only repair I would consider but that has several major problems. Having gone down on a curve after a front tire blow out I would only use that wheel with a new rim.
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Old 01-31-19, 10:41 AM
  #24  
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If you have to ask whether something is safe to ride, the answer is generally "no."
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Old 01-31-19, 11:06 AM
  #25  
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I haven't tried it,

but have tried enough of things like that to know that it won't work.

AFAS sudden death risk- if the crack reopens, which it will, then you have a flat tire. Not that life threatening.
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