rousseau

My spokes seemed a bit loose tonight. Why?

I rode a fair amount in March when the temps were sometimes below 0, and I also stored my bike in an unheated shed (though I kept the bike in a heated basement for January and February). Now the temps are generally above freezing. Is it possible that a transition from a month of lots of freezing air into the warmer spring air could potentially result in looser spokes, perhaps encouraged by riding in said above-freezing air?

Just curious. I admit I'm a physics idiot.

wants185s

No! But, could be the seed for another deflated football discussion. At least in that situation the numbers made a bit of sense.

rousseau

Thanks for the authoritative "No." Though I don't have a clue what you mean by your cryptic comment about a "deflated football." Is that physics related?

JonnyHK 

When I messed around and built a couple of wheels I did notice that the spoke tension altered when an inflated tyre was on the rim compared to a bare rim or a deflated tyre. I guessed that the inflated tyre was basically squeezing the rim smaller and the spoke tension was slightly lower.

wants185s

Sorry, guess you are not an NFL fan and familiar with the Patriots/Tom Brady issue last season where they were accused of playing with under inflated footballs to improve the QB's grip on the football. Google it if you like or are curious. Back to your wheels, there may be small changes in spoke tension from one condition to another as you describe due to the fact that your rims are aluminium or carbon and your spokes are steel (different coefficients of thermal expansion) plus the effect of tire pressure changes. But this is very small stuff. But more importantly if your spokes were properly tensioned last summer, regardless of the warming and cooling they experienced, they will come back to the same tension once you get back to the same temperatures this summer. Many of us have ridden through enough winters to confirm that the spoke tension change that may occur due to temperature change is so small that it has no effect on wheel performance. All that is not saying that something has not happened to your wheels. But if it has it was not because of temperature changes.

rousseau

I do build my own wheels. I thought they were properly tensioned when I built them two years ago, in that the driveside spokes on the rear wheel were basically as tight as they could possibly be, but I'm also a heavier guy, so I wonder if that might be the reason for the looser spokes?

Come to think of it, I do end up doing a retensioning every now and again. Maybe once per year. So, well...shrug.

rpenmanparker 

You have to consider the temperature effect on the rim and hub too. More than I feel like thinking about. What I do know is it has never made any difference.

Campag4life

Negligible rousseau.
Calculation is pretty easy. Coef. of thermal expansion X temp difference. Bottom line is C sub T is very small and the temp diff isn't enough to make a difference. Same with the rim and the hub. Proper wheel spoke tensioning in terms of elastic deformation of the spokes should easily encompass elastic tension in the spokes in cold weather...or your spoke tension is too low.

rpenmanparker 

Although there is good agreement among us that it makes no difference, still it makes sense to build your wheels at or near the mid-point of your most common riding temperatures. Or maybe what I really mean is that I'm really lucky that my situation just seems to work out that way. My house is say, low '70s. I don't ride colder than mid-50s or hotter than mid-90s and usually the limits are mid-60s and mid-80s. So my build temperature is just about centered between my riding extremes. You can't ask for better than that. Not that it matters...just sayin'.

Campag4life

No it doesn't. If you live in Canada and ride in the winter time, who wants to build their wheels in a freezing room...lol.
Ok to run slighltly higher than mid pt tensions if you know you are going to ride the bike at temps near freezing but again, amount of thermal expansion is miniscule for the temperature differential that humans can survive in. Not the same as a 200 deg F difference as with an internal combustion engine for example.

rpenmanparker 

I guess I should have included an emoticon like . I thought my restricted temperature range should have tipped everyone off I was just fooling around. Not only is the coefficient of thermal expansion small, but the temperature differential is really small too. We're on the same page here.

Lazyass

If temperature was going to affect spoke tension I would think they would loosen up in the cold when metal contracts.

rpenmanparker 

First approximation says the spoke gets shorter, therefore you are stretching it more and the tension goes up. But as said above, you also have to factor in the rim and hub changes.

wphamilton

Aluminum shrinks more than spokes or nipples material so I'd think it (spoke in the spoke hole) would get tighter in cold.

If you meant spoke tension, a ring contracts the same as a cylinder, or spokes, and an aluminum rim has a higher coefficient of expansion, so it does seem to me that the spoke tensions would get lower in cold.

rousseau

Whoa...so maybe there's something to this? I wish I could remember whether my spoke retensioning tends to happen in the spring or not. But either way, I think that perhaps my heavier build, putting a heavier load on the rims, probably has something to do with this a la straws and camels' backs.

wphamilton

I'm not 100% on that, but if I'm right about the way thermal expansion works on a hoop you can base it dimensionally on the radius of the hoop's circle. So the same thing as a spoke. Between an aluminum hoop vs stainless steel spoke I estimate a difference in thermal expansion of around .0000035 in/(in-°F). Still ball-parking, say 11 inches for the spoke and wheel radius, and guessing a nipple thread at 56 threads per inch, I get a loosening of around 1/7 turn worth for a 70°F difference. Honestly I wouldn't have expected any significant difference, but there it is - maybe something is off with my math.

The hub would shrink also reducing the effect, but from a smaller radius so a lesser amount. So it must be something less than 1/7 turn at least.

prathmann

So what material are your spokes and your rims made of?

Assuming steel and aluminum respectively, both would expand slightly with the warmer temperature, but aluminum has a higher coefficient of thermal expansion. So the radius of the aluminum rim should grow by a larger fraction than the length of the steel spokes which would result in a higher tension, not lower.

BoSoxYacht

there's really nothing to what you are thinking.

Perhaps the cold weather has frozen your brain and you are having hallucinations(just joking around).

If there was really anything to your theory, do you think you are the first to notice?

Sixty Fiver

This is part of the process of building, the final tension and adjustment gets done after the tyres get mounted and inflated as this can affect spoke tension a little.

wphamilton

I thought the same thing. Did you check my rough calculation, of < 1/7th turn looser if it's 70°F colder?

rpenmanparker 

I know of no traditional wheel building instruction that specifies final tensioning and truing after mounting and inflating tires. With traditional clinchers I have observed slight spoke tension reductions after mounting and inflating tires and tubes, but never a greater variation in tension from spoke to spoke or a loss of wheel true. As far as I know, the usual small reduction in tension is simply assumed to occur and accounted for in the bare wheel tension specifications.

The wheel has always been considered to be complete without any tire or tube mounted/inflated. Jobst Brandt specifically states that the wheel is ready to ride after it has been tensioned and trued in bare condition. Apparently lightweight rims and extremely tight tires (tubeless) rather than the inflation seem to be causing the extreme effects folks are now starting to observe. Perhaps also fewer spokes are too blame as the total compression due to spokes is proportional to the number of spokes when the same individual spoke tensions are used for any number of spokes. Stan's simply recommends higher spoke tensions at the outset rather than a retensioning after mounting and inflating the tire. Something new is going on apparently.

big chainring 

If you have problems with spoke tension due to weather change its best to put those wheels aside for a full cycle of seasons. It's like the wood you buy for your fireplace. It needs to season before you burn it. Same thing with spokes. If they are built into wheels the spokes need to season for a year. Otherwise you get spoke tensioning issues when the weather changes.

I typically build my wheels in a walk in meat freezer. Then when the wheels are exposed to the warm air outside they get a tempering. The expansion of the rim in relation to the spokes sets the ambient tension up a notch and tempers the spoke nipple creating a stiffer wheel.

rpenmanparker 

Bravo. You are clearly an MIT grad. You should have presented these results at a conference 10 years ago.

RollCNY

Your math is wrong. TPI of 56 means 0.018" per revolution. When I run the worst case #'s I can imagine (70°F, alum rim & ferritic stainless spoke for expansion ∆ of 6.8*10-6 in/in°F, 11.6" radius), I get 0.000079" difference, or 1/226th of a turn. And I don't think spokes are ferritic stainless.

Edit: i just stuck a magnet to a bundle of spokes, so they very well may be ferritic stainless.

wphamilton

Did you multiply by 70°? (6.8*10e-6 * 11.6* 70) =.0055

without 70°, 6.8e-6 * 11.6=0.00007888, your answer. So that would be per degree?