I am having trouble with my nipples. Spokes too tight?

[andypugh]

I built myself a bike (well, it's probably more accurate to say that I assembled a bike) a couple of years ago.
I found some Mavic Cosmic Elite wheels in eBay, and fitted them.

All was OK until earlier this year, when a front spoke nipple broke going over a bump. Since then I have had a rear nipple fail, and yesterday another front one popped, this time on smooth ground just as I was setting off.

I have a sneaking suspicion that Mavic didn't actually build these wheels. As far as I can see they don't offer a through-axle version of the Cosmic Elite, and it seems that the spokes should be bladed too.
(Photo of the bike and wheels: https://photos.app.goo.gl/Vb47ZnftpGdTd4dy7 )
Also oddly, the barcode and part numbers draw a blank on the Mavic site.

So, I am wondering if the wheels have been built up from parts of other wheels (Maybe real Mavic parts, maybe not?) and maybe with too-high a spoke tension? I am no lightweight (85kg) but haven't really done that many miles (7 mile commute, about half the time)

Is it a daft idea to replace the broken nipple and then give each spoke a half-turn to reduce the tension?

[BFC]

Until the ongoing failures are understood it's not worth investing too much time or money. No experience of these specific parts so the rest is generic!

What is the nipple material and what environment has it been used in (ally nipples and salt do not get on!). Mature ally nipples do not respond well to using a spoke key on the square drive either. Brass is far more forgiving.

Measuring of current spoke tensions would be a good start, It is rare to get nipple failures from overtightening, more likely to be from flexing or other movement whilst riding - usually down to low tension. Can you lay your hands on a spoke tension gauge? Many builds suffer a reduction of tension with the tyre inflated, worth checking spoke tension in bare rim and fully inflated states

An informed tear down, inspection and rebuild is the most likely outcome, spokes can often be re used with new nipples - assuming no issues with the original build.

[LittleWheelsandBig]

https://road.cc/content/tech-news/mavic-warns-against-buying-fake-wheels-281435

Dunno if that applies to you but it is something to think about.

[andypugh]

https://road.cc/content/tech-news/mavic-warns-against-buying-fake-wheels-281435

It seems very likely, though the specific failure mode described isn't likely to affect me as these are aluminium rims and disc brakes.

The fatigue test failure rings true, however.

The bike hasn't been ridden extensively in rain and salt, I tend to wimp out and use the motorcycle in the wet (because it's easier to dress waterproofly)

The spokes are straight-pull, so not the J-bend ones alluded to in the article. The nipples are aluminium. The heads break off, leaving a perfectly serviceable spoke.
So far I have just been replacing the nipples from a bag of Sapim ones that I bought. (also aluminium)

(I have built wheels from scratch in the past, for a vintage motorcycle, so that part isn't a problem)

A spoke tension gauge would be a nice thing to have, but then how would one determine the correct tension?

[grams]

One other possibility is that it’s a wheel config originally sold as part of a bike rather than as a wheelset. They might offer an unusual combination to hit a price point for a contract with a bike manufacturer.

[LittleWheelsandBig]

Assuming the materials are fine, you can still pop the heads off nipples (fatigue) if the spokes are 1-2mm too short. The spoke should extend at least until the bottom of the screwdriver slot in the nipple.

[andypugh]

Assuming the materials are fine, you can still pop the heads off nipples (fatigue) if the spokes are 1-2mm too short. The spoke should extend at least until the bottom of the screwdriver slot in the nipple.

That's an interesting point. I suspect that they don't. But I would have to take the wheel back off and take the tyre off to find out. (And I have just got back in from swapping the nipple, doing exactly that)

FWIW, here is a picture of the fracture surface. It isn't telling me much:
https://photos.app.goo.gl/RQvhaud12Rex3PWF9

And here is a pic of the hub. I don't know enough to tell if this is genuine Mavic branding or not:
https://photos.app.goo.gl/8uYr6aooCpgYspua7

Actually, this also shows the broken nipple still on the end of the spoke, so it is possible to tell how far the spoke was through the nipple, and it looks about right.

[LittleWheelsandBig]

That points towards crap materials then, whether kosher or not.

[andypugh]

And here is a pic of the hub. I don't know enough to tell if this is genuine Mavic branding or not:
https://photos.app.goo.gl/8uYr6aooCpgYspua7

Maybe a giveaway is that the spokes have to pass through a round hole? There is no way to fit bladed spokes to this hub. And I think that real Mavic Cosmics always have bladed spokes?

[Hot Flatus]

As I think you  realise, you've bought fake wheels.  EBay is full of fake stuff, from frames to  SKS bearings to Shimano chains.

Cosmic hub flanges are different, drive and non drive, and as you know they are all bladed spoked.

[zigzag]

the sticker on the hub looks non-genuine “mavic”, i’d be replacing nipples with brass ones or getting rid of the wheels.

[andypugh]

I have been chatting to Mavic, and they are suggesting fakery is afoot.

However, my choice of wheels is somewhat limited by my forks, so I will probably be sticking with the wheels and changing the nipples.

Specifically, my Chinese "gravel" frame has a 15mm through-axle. And there are not all that many 700c wheels with that axle.

Though, I could change the fork, it's not a pretty one...

[Hot Flatus]

You can get adaptors to change 12mm thru-axle wheels to 15mm

[BFC]

However, my choice of wheels is somewhat limited by my forks, so I will probably be sticking with the wheels and changing the nipples.

Another general rule - don't mix aluminium and brass nipples in the same wheel - it has the potential to create a galvanic circuit with one part becoming sacrificial. When they are all the same material they all rot at the same rate!

[PhilO]

You can get adaptors to change 12mm thru-axle wheels to 15mm

The other way round, Shirley?  To change a 12mm hub to 15mm would require the hole to be made bigger.  Some hubs have swappable adapters to allow different standards, but I doubt that is the case here.

[PhilO]

I have been chatting to Mavic, and they are suggesting fakery is afoot.

However, my choice of wheels is somewhat limited by my forks, so I will probably be sticking with the wheels and changing the nipples.

Specifically, my Chinese "gravel" frame has a 15mm through-axle. And there are not all that many 700c wheels with that axle.

Though, I could change the fork, it's not a pretty one...

A 29" MTB wheel should fit, provided you get the appropriate rim width.  Both 700c and 29er wheels use 622 bead diameter rims.

[Hot Flatus]

You can get adaptors to change 12mm thru-axle wheels to 15mm

The other way round, Shirley?  To change a 12mm hub to 15mm would require the hole to be made bigger.  Some hubs have swappable adapters to allow different standards, but I doubt that is the case here.

Doh. I've got covid brain. Of course you are correct

However...

https://forkmods.com/

Not cheap, and personally I wouldn't bother for a cheap brand less Chinese frame

[andypugh]

I bought a spoke tension gauge. (I only need the slightest provocation to buy a tool)
It looks like the front is at 130kgf each side, the rear is at 130 and 170 on the Drive Side.
Which seems a tad high, if one trusts the gauge.

I wonder if the local bike shop would let me compare what their gauge says with a specific spoke?

Anyway, a set of brass nipples (allegedy Halo) is on its way to me, and I will swap them all.

As for the through axle, thanks for the hint. I can easily make adaptors to reduce the hole and thread sizes. I really should have thought of that.
(I have a CNC lathe and mill, and a YouTube machining channel...)

[LittleWheelsandBig]

Aren’t you limited by the thru axle itself that threads into the frame or a replaceable nut?

[grams]

Easy enough to adapt the fork down to take a 12mm axle:

https://theradavist.com/2020/06/convert-your-15mm-ta-gravel-fork-into-12mm-with-jjpes-conversion-kits/

Obviously you’d make these if you have the equipment.

[sojournermike]

I have been chatting to Mavic, and they are suggesting fakery is afoot.

However, my choice of wheels is somewhat limited by my forks, so I will probably be sticking with the wheels and changing the nipples.

Specifically, my Chinese "gravel" frame has a 15mm through-axle. And there are not all that many 700c wheels with that axle.

Though, I could change the fork, it's not a pretty one...

I suspect you’ll be fine, but I’ve got a pair of hand built 700c wheels for 15mm through axle if you get stuck.

[BFC]

I bought a spoke tension gauge. (I only need the slightest provocation to buy a tool)
It looks like the front is at 130kgf each side, the rear is at 130 and 170 on the Drive Side.
Which seems a tad high, if one trusts the gauge.

I wonder if the local bike shop would let me compare what their gauge says with a specific spoke?

Anyway, a set of brass nipples (allegedy Halo) is on its way to me, and I will swap them all.

As for the through axle, thanks for the hint. I can easily make adaptors to reduce the hole and thread sizes. I really should have thought of that.
(I have a CNC lathe and mill, and a YouTube machining channel...)

Ask nicely at the LBS or just measure any wheels you and any mates may have (and trust!) to see what is normal for the spoke size on your tension gauge - larger sample size is better. I assume you have decent vernier or micrometer to go with the machines, to measure spoke diameter.
You may pick up some extra work whilst measuring mates wheels though!

Mavics traditional rims have a max of 130KgF, Pacenti rims have a minimum tension of 65KgF with the tyre inflated. Tension drop of 30% between initial bare rim build and tyre fitted and at max pressure (plus a bit extra?) is not unusual.

Inspect the rims (polish them!) for cracks if they have been exposed to 170KgF.