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Discussion Starter · #1 ·
My current winter bike has Mavic XM 819 rims. I am 250#, and in the warmer times of the year they have been robust, but, I have been having trouble the past few years with spokes coming loose when the temperature is below 0F.

The only thing I can think that causes this is the differential shrinkage rate of the spokes and the rim. Does anyone else have a similar experience with other aluminum rims at sub zero?

Does anyone have any experience with carbon rims at sub zero? They should not shrink when cold, which should lead to higher spoke tension. I know that graphite is used on things that must work well below -40F, which is my lower limit, but will the shrinkage of spokes cause issues?

Or, should I borrow a test chamber and measure the spoke tension as the wheels cool down to -40F?
 

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In theory, a 15ga spoke will elongate ~ .8mm when 100kgf of tension is applied. The differential shrinkage of aluminum vs steel will be ~.12mm in a temperature drop of 70 degrees. The result under those conditions is a spoke tension reduction ~ 15%.

I tip the scales at 210 and have never had an issue with low temps and my fat bike spokes, which are typically in the 80kgf range when built and often ridden in low temps.
 

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Are your wheels getting wet frequently and water is allowed to freeze in or around the nipples?
 

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I got a slightly different answer than Blue Cheesehead on the difference in contraction with that range of drop (mine was less than his) but not too far off. Otherwise I concur with him. It's possible that the issue is the nipples versus the spokes.

But you seriously ride down to -40*F???? I mean where does that even happen? I once went outside in like -10*F and went back in 3' later swearing I'd never go outside again. I'd go mountain biking in 20* if it was otherwise nice (and not windy) out, but you're made of hardier stuff than I am.
 

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I've ridden below zero F a few times, but never noticed any issues with spokes - although the noise of ice on the rims and riding on snow probably distracted me so I wouldn't have noticed if spoke tension was a problem.
 

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Discussion Starter · #7 ·
I am a year round commuter in Fargo ND. no, not a DUII. I just like to ride. The lowest I have ridden in is -30F. Sub zero is common. It is not a big deal if you have the correct clothing. Also, you need to use lubricants suitable for cold temperatures.

When I am riding in sub zero temperatures there is no liquid water out on the road. My garage is not heated, so when it is -30 in the morning, that is the temperature at which the wheels were stored.

The problem I am having is that the inserts which retain the spokes in the rims come loose. Maybe the cause is the insert to rim, or the spoke nipple to spoke as suggested by November Dave could be the issue.

I am in the process of building up a new winter commuter, and my question is do I have to spring for carbon wheels to prevent spokes coming loose.

What I am not hearing is that others are having trouble with conventional spoke / rim setups.
 

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I've never had a bike get that cold but I lock my junk commuter to a sign post all winter and it gets well below freezing, buried in snow, thawed and wet sometimes, refrozen, ect. Pretty much the worst winter can offer, some years, and never had a problem with wheels. (although I never check spoke tension).

Lots of people do the same in Montreal, Quebec City I know and I presume all over Northern Europe where it does get that cold so I think it would be a 'known problem' if that was just the way it is in those temps but I've never heard of it being an issue.

What do you mean by "inserts which retain the spokes". Washers? Unless I'm having a major brain freeze here there's typically spokes and nips and that's it (unless you have washers).
 

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I think the UST insert-to-rim interface is the cause of what you are experiencing. Not sure how to best moderate it but if it was me I would have considered some sort of a mild threadlocker to limit the movement of the UST insert when the wheel undergoes its expansion-contraction cycle during use under sub freezing conditions.
Of course this would require rebuilding the wheel but you are down that road any way. Regarding your question whether carbon is the way to avoid this, it may be a side benefit but the rest of the package does not warrant it. A regular (re: non UST) alloy rim should hold up fine for you.
 

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But you seriously ride down to -40*F???? I mean where does that even happen? I once went outside in like -10*F and went back in 3' later swearing I'd never go outside again. I'd go mountain biking in 20* if it was otherwise nice (and not windy) out, but you're made of hardier stuff than I am.
-40F is not that uncommon in the Dakotas, Minnesota and even northern Maine. The lowest temp I have personally experienced is -22F in Quebec. A fun thing to do in those temps is boil a pot of water, then take it outside and throw it up in the air and watch the resulting cloud and snow fall! I certainly wouldn't be biking in those temps. We usually wait till it goes up to -10F before we go out onto the xc ski trails!
 

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Discussion Starter · #11 ·
The insert is certainly the symptom. The question I have is what is the root cause? What I am hearing is that others in very cold places who are year round cyclists are NOT having the same issue with conventional rims and spokes. That does point to the one thing that is different: the nipple retaining insert to rim interface.

My old winter commuter is an ancient Ritchey mountain bike which is starting to develop rust spots. The replacement which is scheduled to arrive in bits and pieces over the next couple weeks is a Lynskey MT29 which should never corrode.

I don't want to have to spring for carbon wheels if I don't have to.
 

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The insert is certainly the symptom. The question I have is what is the root cause? What I am hearing is that others in very cold places who are year round cyclists are NOT having the same issue with conventional rims and spokes. That does point to the one thing that is different: the nipple retaining insert to rim interface.

My old winter commuter is an ancient Ritchey mountain bike which is starting to develop rust spots. The replacement which is scheduled to arrive in bits and pieces over the next couple weeks is a Lynskey MT29 which should never corrode.

I don't want to have to spring for carbon wheels if I don't have to.
Yeah, thats what I am thinking as well. Not sure what is the material the UST inserts are made off but apparently it does not shrink at the same rate as the rim alloy does when in subfreezing temps.

Alloy rims with brass nipples and steel spokes are reported to fare fine in very cold temperatures. Fortunatelly, I do not have personal experience down to these temperatures but I have not heard of any issues if the wheel was built with enough tension to begin with.
 

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IThe problem I am having is that the inserts which retain the spokes in the rims come loose.
They are called ferrules. And even if they are loose in the rim, the force of the spoke tension should keep them from moving. The only time you could tell they were loose is if the spokes were loose too.

I used to be a year-round commuter in Michigan and the lowest temp I experienced was -20 F (-28 C). I experienced no spoke loosening as a result. While the difference in coefficient of thermal expansion MIGHT explain your problem, it would only occur if the overall wheel tension was right at the lowest possible limit so that a the tiny difference in rim shrinkage and spoke shrinkage was pushing you over the limit. This is possible but highly doubtful.

I'm going with Occam's Razor: the simplest explanation is that it's coincidence.
 
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