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What IS the deal with CF and cold weather?(5 posts)

What IS the deal with CF and cold weather?bill
Jan 5, 2004 8:52 AM
I've seen on this board several instances of people saying that CF should not be ridden in cold weather. This seems on the one hand reasonable -- cold makes plastic more brittle -- and absurd -- not only would this warning be common knowledge and splashed all over the frame, but CF forks, which are ubiquitous and about which no one worries, would be snapping all over the place.
What's the real deal here?
re: What IS the deal with CF and cold weather?pmf1
Jan 5, 2004 9:05 AM
It gets brittle and will shatter at temps below 32 degrees.

Same with heat. It'll melt at temps over 95.
So, when I rode my bike last winter in the teens, my forkbill
Jan 5, 2004 9:12 AM
shattered, and when I rode that 102 degree crit last summer, my fork actually melted?
I didn't notice that, but I don't always notice such things.
So, when I rode my bike last winter in the teens, my forkboyd2
Jan 5, 2004 9:30 AM
Consider that most of the satlilights in orbit have CF trusses that are exposed to dramatic heat/cold cycles every day. Deep spaceprobes also use carbon tubes. These tubes are not much diferent then the ones on our bikes.

I make carbon composite tanks for aerospace use and these are the rules that I live by:

1. Cold is never a problem, unless there is a thermal expansion mismatch between materials. Most often the problem is a carbon-aluminum joint. Aluminum expands quickly in the heat, but carbon does not change size much (if at all). This stresses Carbon/Aluminum joints.

2. Heat is only a problem when you get above the glass transition temp (Tg) for the resin that is used (other then CTE problems above). I have no idea what the Tg is for the resin/cure system that bike makers use, but I have never heard of one lower then 140f.

3. I have personally tested our tanks from -200F to 212F and not seen any problem with our carbon composite, other then a very predictable loss in strength above about 160F.

Take this info for what it is worth, considering I have no experience designing carbon bikes. I just could not imagine a mfg building a bike that could not take moderate temperature extremes. Also I have been riding my AL lugged carbon bike in <32F weather with no problems.
Hehehe, I couldn't resistpmf1
Jan 5, 2004 9:42 AM
When I bought my first carbon bike 12 years ago (a Kestrel 200 Sci), they were a relatively new technology. Everyone called it my "plastic bike". There was this "steel is real and its gotta be campy" guy at the office who I told that story to. He believed me.

It never snows in Missouri either -- it would kill the palm trees.

Ride your carbon bike with confidence, changes in temps have no effect on them. Its very tough stuff.