Should I worry about cracks in rim alongside spoke holes ?

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tykeboy2003
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Should I worry about cracks in rim alongside spoke holes ?

Postby tykeboy2003 » 13 Jul 2019, 5:50pm

Whilst cleaning my Giant hybrid, I noticed cracks in the rim near the spokes. See picture. The bike has disks so I'm not worried about the rims failing whilst braking.
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Spinners
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Re: Should I worry about this?

Postby Spinners » 13 Jul 2019, 5:53pm

Gut-feeling = bin it.
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brynpoeth
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Re: Should I worry about this?

Postby brynpoeth » 13 Jul 2019, 6:20pm

The rims could fail while not breaking, damage could be more serious than one sees, time to replace them
Are they quite old?
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Paulatic
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Re: Should I worry about this?

Postby Paulatic » 13 Jul 2019, 6:27pm

Surely it could easily go while braking? I’d have thought that stopping force from the disc transfer down the spokes to the rim. Bin it !
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PT1029
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Re: Should I worry about this?

Postby PT1029 » 13 Jul 2019, 6:27pm

Usually when a rim like this fails, the spoke pulls through the rim, so in terms of riding the same as getting a broken spoke.
While I have never seen a rim loose its structural integrity when a spoke pulls through (ie, the rim stays round if some what out of true), its worth replacing sooner rather than later. Often other spoke holes will be cracking too.

Brucey
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Re: Should I worry about this?

Postby Brucey » 13 Jul 2019, 6:57pm

with or without disc brakes, IME the most likely place for such a crack is the rear driveside. If so, these spokes see loads that don't vary so much when the brakes are used (because the hub is not infinitely torsionally stiff) and as noted above the effect of the spoke pulling through will be about the same as a single spoke breakage. So it isn't very dangerous per se.

However cracks of any kind are bad news and they only ever get worse not better. You have three main options

1) replace rim/wheel
2) repair/reinforce
3) monitor whilst deciding between 1) and 2) above.


For monitoring you can mark the ends of the cracks with marker pen and look to replace the rim if they are growing at any rate.

In terms of reinforcement you can sometimes add a washer (bonded in with epoxy) beneath the head of the nipple and use a longer nipple so that the reinforced region doesn't show too much. This may mean that the rim is less likely to fail catastrophically, or very soon at all. If you want to re-use the (reinforced) rim where it sees less stress, you can build it into a disc-brake front wheel (with the crack on a RHS spoke, which sees both less static and dynamic tension variations) or into a non-disc brake derailleur rear wheel, so that the cracks are set on a LHS spoke. But it is very much more sensible to simply replace the rim with another one.

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mercalia
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Re: Should I worry about this?

Postby mercalia » 13 Jul 2019, 7:18pm

is there only one? Same thing happened to the stock wheels of my Dawes 1-Down. I only noticed when sitting on some grass and the sun caught the breaks. I saw one then saw lots of smaller ones. I would get a new rims or wheel as the rim is now broken

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tykeboy2003
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Re: Should I worry about this?

Postby tykeboy2003 » 13 Jul 2019, 7:52pm

Thanks for the replies.

It is the rear wheel, just had a look and there are several and all are on the drive side. They have been there for some time but I'm not sure if they've got worse. I'll start looking for a new wheel or rim.....

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tykeboy2003
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Re: Should I worry about cracks in rim alongside spoke holes ?

Postby tykeboy2003 » 13 Jul 2019, 8:42pm

Just ordered a pair of wheels suitable for disks (with cassette, I was thinking of replacing the cassette anyway) for £63.99.

nigelnightmare
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Re: Should I worry about cracks in rim alongside spoke holes ?

Postby nigelnightmare » 17 Jul 2019, 6:41pm

tykeboy2003 wrote:Whilst cleaning my Giant hybrid, I noticed cracks in the rim near the spokes. See picture. The bike has disks so I'm not worried about the rims failing whilst braking.



In a word YES, you should be worried.
As others have said "Time for new rims/wheels".

LollyKat
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Re: Should I worry about cracks in rim alongside spoke holes ?

Postby LollyKat » 17 Jul 2019, 9:13pm

Read the post above yours. :wink:

bgnukem
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Re: Should I worry about cracks in rim alongside spoke holes ?

Postby bgnukem » 18 Jul 2019, 1:31pm

Have to admit I've got the same issue with the rear wheel in my summer bike, a Giant Rapid.

I marked the ends of the cracks a while ago - there are 4-5 cracked spoke holes - and have been monitoring for growth since. The cracks have grown a bit but as yet there's no sign the spoke eyelets are starting to pull through and I'm going to keep riding it for a while.

Daft maybe, but I suspect it isn't going to fail catastrophically for a while yet. If the cracks were oriented laterally across the width of the rim I'd probably bin it but the circumferential cracking will result in a spoke eyelet pulling through at worst I reckon, rather than a dangerous rim failure.

I see a lot of people sailing closer to the wind with badly worn braking surfaces just waiting to cause rim sidewall failure under braking/descending!

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Re: Should I worry about cracks in rim alongside spoke holes ?

Postby Brucey » 18 Jul 2019, 1:41pm

bgnukem wrote:…. If the cracks were oriented laterally across the width of the rim I'd probably bin it....


why? Wheel rims have nigh-on this exact thing (a radial crack) anyway if they have a pinned joint. If the wheel has a reasonable tension in it there is a compressive force holding the rim together of approximately half a tonne, and a fatigue crack has a jaggy interface so the parts won't easily slide past one another even if the crack runs all the way. I've seen badly tensioned wheels crack radially and it normally takes multiple cracks running to completion before the wheel comes to grief.

FWIW it is only badly tensioned wheels that seem likely to crack radially; once retensioned I think the rate of cracking slows down enormously, if not actually stopping...?

cheers
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Mike Sales
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Re: Should I worry about cracks in rim alongside spoke holes ?

Postby Mike Sales » 18 Jul 2019, 1:46pm

Brucey wrote:Wheel rims have nigh-on this exact thing (a radial crack) anyway if they have a pinned joint. If the wheel has a reasonable tension in it there is a compressive force holding the rim together of approximately half a tonne, and a fatigue crack has a jaggy interface so the parts won't easily slide past one another even if the crack runs all the way. I've seen badly tensioned wheels crack radially and it normally takes multiple cracks running to completion before the wheel comes to grief.

FWIW it is only badly tensioned wheels that seem likely to crack radially; once retensioned I think the rate of cracking slows down enormously, if not actually stopping...?

cheers


The first rim I built into a wheel had a pinned joint and it was open about a millimetre. I took it back to the shop and they told me no problem, it will close up. As it did.

brynpoeth
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Re: Should I worry about cracks in rim alongside spoke holes ?

Postby brynpoeth » 19 Jul 2019, 5:15am

Tyres: one sees quite easily that they are wearing, rims: one may see if one looks carefully, chains: easy to see (I have a hub gear without chain tensioner)
Brake and gear cables: should they last indefinitely if checked and lubricated?

What about other parts, how may one check them?
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