MisterP

I bought a 2017 Giant Defy Advanced Pro1 road bike a couple of years back. It was used- barely ridden- absolutely like new: basically the best bike I’ve ever owned. It came stock with Giant SLR1 carbon fiber wheels and I rode on these wheels for over a year with no problem. One day my rear wheel popped a spoke and I took it into REI to have it replaced. The bike tech called me the next day and said that something’s wrong with the wheel: he tried replacing the spoke and 2 other spokes would pop: he said he thinks the wheel is no good- I should check to see if it’s under warranty.
My question is: do CF rims just 'go' bad? I assume that spokes are popping means the wheel has gone really out of true? (I’d read that CF wheels don’t do that). It doesn’t make sense to me: I rode on these wheels a fair amount but not 'crazy' miles.
I’d really like to salvage this rim: I really like these wheels.
Any ideas or suggestions? I’m fairly mechanical, btw: don’t mind doing my own work.
Thanks in advance.
Giant SLR 1
Giant SLR 1
Giant SLR 1

Geepig

Ah, it is sad when our favoured things go bad...

Where are the spokes popping? Inside the nipple? At the hub end? Somewhere else?

I am not too surprised that more spokes are going at the same time, because whatever lies behind the first one popping might also have affected more of them.

I am interested why the mechanic believes it is the rim at fault.

jabbajabba

I have the same bike and had a similar issue with a single rear spoke.
It took 3 visits to a bike bike shop to fix.
It's been fine since the last fix, circa 300 miles ago.
In the end, they had to replace the spoke and nipple.
May be try a different bike shop.

cheesesandwich

Once my front wheel spoke broke, I sent to change all of them. Because I've read how 1 broken spoke can weaken the rest especially on race wheels where the spoke count are little.

MisterP

Hey JabbaJabba:
I’m encouraged to hear that: it doesn’t make sense to me that my wheel would just go bad without an incident or obvious signs of damage.
Did your shop explain what the remedy was? Just a spoke and a nipple?
Thanks for the info.

MisterP

Geepig:
looks like the spokes would break at or inside the nipple. Does that mean something?
thanks

alcjphil

Is it the spoke or the nipple that breaks? Very rare for a spoke to break at the nipple, but a nipple breaking could be a sign that the spokes are too short

jabbajabba

Hi,
1) The first fix was just to tighten the nipple. This didn't last a single ride.
2) The 2nd fix was a new spoke, same nipple. This lasted 1 ride.
3) The fix which worked involved taking the tyre off, rim tape off etc and fitting a new nipple and another new spoke. For some reason, the previous nipple wasn't seated correctly.
(Fix (3) was avoided at first in order to save the mess from tubeless sealant.)
It's been good since.

FYI, I'm in the UK and we have some shocking roads with large potholes. I suspect a very heavy impact caused the issue.
The bike is now 6000+ miles old and the issue happened circa 500 miles ago.
Wheels run true, are undamaged and seem very strong.
To date, the only other issue has been a failed front bearing which was a cheap fix.

Overall the bike is very good.

jabbajabba

I should add that my spoke came loose rather than snapped,

Andrew R Stewart 

Spoke breakage is nearly always from fatigue. The spoke goes through cycles of tightness and looseness with each wheel revolution. Much like the repeated bending of a paperclip. The looser the spokes are the greater the bending. Spokes (or their nipples) loosen when the amount of tension change for each wheel rotation is enough to have the spoke under so little/no tension at one point to no longer keep the nipple snug and stationary. The wheel needs enough spoke tension to allow this cyclic tension variation to remain in the spoke's elastic range. Spokes have a stretch (and to a degree so does the rim at the nipple hole) when properly tight. If the spoke untensions too much WRT it's stretch it will allow the nipple to move about and thus loosen. (This is why butted spokes which will stretch more for the same tension can result in a longer lasting wheel and less spoke issues)

Now a serious impact can deform the rim at a local point. The spoke at this point becomes loose and perhaps no longer stretched enough to remain tight during the cyclic tension swings. A rim that has too much "give" can have the same problem of detensioning spokes. Carbon is well known for not being compression resistant (carbon fiber is designed to be strong in tension, not compression, thus the various orientation of the fibers in structural uses). Like wood rims, some carbon rims have give in the nipple seat greater then other rims or then best. Early carbon rims were known to suffer from softening of spoke tensions over time as the nipples slowly deepened their seats.

Is this what's happening to the OP's wheel? I don't know but it's happened before with other wheels.

Additionally the greater dish of modern road wheels results in the non drive side spokes having far less tension then the drive side ones. So the non drive side spokes tend to suffer from more detensioning and breakage the drive side spokes do. On my own road bikes I build the rear end at 135mm to reduce the amount of dish, I use only butted spokes and (thank you) don't run carbon rims. The last broken spoke I had was in the 1970s.

The other topic I will bring up is the mention of warranty. If I read the OP's op correctly there is no warranty in effect any longer as the OP bought the bike used. Now the OP might be able to go to the person who sold him the bike and they can conspire to fool the LBS/Giant into believing the bike is still owned by the original buyer Or the LBS/Giant might extend a customer service solution which is not really the warranty the bike was sold with. But I know of no bike warranties that follow the bike, they are for the original purchaser IME. Andy

MisterP

ARS:
thanks for taking the time to share sure detailed information. I've been thinking of getting some tools to try and rebuild this wheel myself as a little project.

Andrew R Stewart 

Reusing a rim has both positives and drawbacks depending of a few factors. Since one of the aspects of a long lasting wheel is the sharing of the loads/stresses among as many spokes as possible the condition of the rim, independent of how ot looks when built up and fully tensioned, is VERY important. Many people think the "trueness" of a wheel speaks to the rim's condition. This is a false belief. I strongly suggest to check the rim's un tensioned condition before deciding to relace it with fresh spokes. One does this by bit by bit relaxing the overall spoke tension until the spokes no longer have any tension. Or to be more specific the spokes no longer are prodding the rim to move this or that way. The rim still needs to be as centered on the hub as possible but with only the rim's "natural" shape keeping it round and flat. Spin the loose wheel and watch the rim for deviation from round or flat. If the rim shows areas of untrueness then these areas will carry over to the rebuild as areas of differing spoke tensions as the spokes are tensioned to bring that rim back to what "looks" good but is actually is a poorly and unevenly tensioned wheel.

Another way to check a rim before lacing is to completely remove all the spokes and lay the rim against a known true/round rim/wheel. The two rims should be concentric and flat against each other all the way around. However having done this many times I can say that this is not a best method. It will show large issues but most of us don't have the eyes or experience to see the small deviations.

The time to do this is not minimal. This time to check is but one reason why many shops that still offer hand built wheels won't consider reusing a rim. The other reasons are about the shop's reputation and the customer being long term happy with the cost and reliability of that wheel. Andy