rpenmanparker 

Are the CTEs of different stainless steels more than a few % different anyway?

wphamilton

I'm not him but if we accept this page

[TABLE="class: large, width: 582"]
[TR]
[TD]Steel[/TD]
[TD]12.0[/TD]
[TD]6.7[/TD]
[/TR]
[TR]
[TD]Steel Stainless Austenitic (304)[/TD]
[TD]17.3[/TD]
[TD]9.6[/TD]
[/TR]
[TR]
[TD]Steel Stainless Austenitic (310)[/TD]
[TD]14.4[/TD]
[TD]8.0[/TD]
[/TR]
[TR]
[TD]Steel Stainless Austenitic (316)[/TD]
[TD]16.0[/TD]
[TD]8.9[/TD]
[/TR]
[TR]
[TD]Steel Stainless Ferritic (410)[/TD]
[TD]9.9[/TD]
[TD]5.5[/TD]
[/TR]
[/TABLE]
it makes a difference. I had chosen an Austenitic value to arrive at 1/7th turn equivalent, because my magnet didn't stick. I believe that RollCNY's Ferritic choice leads to a greater variance of equivalent to .3 turns when you account for 70° change.

but this page 9.8–25 5.4–14 Austenitic stainless steel shows CTE for one stainless steel up to even more than aluminum. Personally I have no idea which steel is in spokes.

rpenmanparker 

Wow, I would not have expected those differences.

Darth Lefty 

If you really want to panic about this, consider that the CTE of carbon fiber is next to nothing, and what that does to your indexing

lkngro

Materials expand as they get warmer, that's basic physics (Thermal expansion - Wikipedia, the free encyclopedia), so your answer is YES, your spokes SHOULD get looser. HOWEVER, would it be enough for you to notice? Most likely not. The expansion would be on the scale of fractions of a milimeter. Also, all of the other materials on your bike would expand as well, so it'll probably all offset. Though different materials expand different amounts per unit of temperature so there are way too many factors to account for, really.

Actually, your answer is yes. Practially, your answer is no.

This also explains why materials experience more stress at higher temperatures (aka Thermal Stress), just to give you a frame of reference.

RollCNY

You are absolutely right, I realized I forgot to multiply by degrees, but I was 25 miles into a ride when I realized it. For some reason, your original math felt off by an order of magnitude, so I didn't double check my math in my haste.

Sorry for the error.

wphamilton

It does feel off by an order of magnitude.

Maybe there's something else, choice of material, an assumption. But it would be great if in reality it does make a difference that none of us would have at first grasp expected.

Sixty Fiver

One should note that the temperature range in which road cyclists ride is too small to make a noticeable difference in spoke tension...

wphamilton

True, the 65°-75° range of road cyclists would just about account for my order of magnitude right there. But frozen tundra types who build wheels, ... why don't you just measure it one of those insanely cold mornings? Put this to rest.

Psimet2001 

You almost had me.

I was all...

Psimet2001 

Just reading through some of the posts now. Reminds me of a time when I had a class called 'Strength of Materials" and the final had a very similar question. The professor had gotten to the point where he thought, "all you guys have gotten soft - relying on your 'graphing cal-q-lay-Tors' and 'KOM-pu-turs'" so he filled the whole final with streams and reams of this kind of stuff and made it open book, open computer, open anything you want (before cell phones and internet).

I set the curve for both sections with the highest raw score - something like a 24. It ended up being a 116 with the curve. Turned out the answer for the change in overall length of the member was so small it was negligible due to sig figs and resolution of the measuring instruments. It was another one of those, "don't be an educated idiot" moments at college.

wphamilton

You mean you don't calibrate tension to the customer's climate? @Psimet2001

Hey, wouldn't that also change the dish of the rear wheel? Since the spokes are different lengths ... one might prefer to have his winter wheels built in the cold, or at least to the proportionally greater tension at room temperature ... how hard could it be to twist that extra 1/8th turn?

Sixty Fiver

Seriously... an old trick I learned to take all the build stresses and wind up out of wheels is to hang them over the wood stove in our shop after they were built which would heat them up to a few hundred degrees F and then let them cool down. This is a temperature wheels are not going to see unless you ride them on blistering descents where they can get hot enough to singe your fingers (or melt the glue off tubulars).

My partner called these 0/0 wheels and they were as perfect as a wheel can get, I have a few sets of these and they are built to an incredible tolerance of less than 2/1000... this is what happens when machinists build wheels.



I have measured out some of my personal wheels after the rims have worn out or been run many 10's of thousands of km and found they were still at their original build spec which could be as low as 5/1000 tolerances if the parts were right... many of these have seen hot summers, freezing winters, roads, and trails and taken a pounding.

wphamilton

Well there you go - if you would measure the tension both hot and cold next time, and put a thermometer to it, we wouldn't have to lay in bed at night thinking about it.

Bottom line, since you're being serious, is that you've found no issue with tension variation between seasons, whatever the number may be.

gc3

If the spokes are loose, blame....

big chainring 

I find that gallons of gas are bigger in the summer months. I get better gas mileage too, because a gallon of gas in summer is bigger than a gallon of gas in winter.

I wonder if in the winter if you have a heated garage and you go fill your tank at the gas station then drive home to the heated garage, does the gas expand and overflow out of the tank? Or what if you bought 50 gallons of gas in the middle of winter and stored it in a tank somewhere. Then when summer comes the gas would expand and then maybe you have 51 gallons of gas. So if you bought mass quantities of gas in the winter you could actually be making gas in the summer cause it would expand so much in the heat.