A recent General Discussion topic on the Global warming senario made me ask, Will it really crack at -10°? Some of the vinyl sources give Cold Crack Ratings of -10°, -20°, -30°, etc. One I fould had -60° The colder the rating, of course, the more expensive the vinyl; as much as &10 a yard range. Well I'm about as frugal (ok, cheap) as they come, but I sure don't want to get in my newly uphosltered car at -11° and have the -10° stuff crack. Also there is the issue of workability. The colder the rating also generally increases the thickness there by making sewing it together that much more of a challenge. I'm just wondering if this is a warning or simply a disclaimer (Might not crack, but sit at your own risk ) It rarely gets below -10° here and I don't see myself driving it when it does but there have been years when its gotten much colder. Do any home upholsterers have any experience on this?
Thanks,
Scott

Cold Crack ratings are based off of the ASTM spec (D1790-94; Brittleness Temperature of Plastic Sheeting by Impact).
Points from the spec read:
- brittlenss temperature is derived where 80% of specimens would pass 95% of the time
- testing is based on statistical calculation from a number of specimens

The test is an Impact test. Which means something, like a hammer, is dropped against a part that has been in a freezer for an hour.
The rating then describes the limit of the plastic/vinyl.
So a -20 cold crack rated vinyl would not shatter at -20 if you sat on it in the car, but you're pushing the envelope. The more aggresively you jump into the car, and the colder it is, the more likely it will crack.
A few things to keep in mind.
- The inside of the car is usually not as cold as the outside airtemp.
- The plasticizers that are mixed into the vinyl to keep it from cracking naturally leave (propogate out) of the vinyl over time. So a -20 degree vinyl today will probably only be -5 rated material in 5 years.
- What is the coldest your area sees, and what is the coldest you would use the car?
- I wouldn't use anything that isn't rated at least 0 degree cold crack.

Hope that helps.

Thanks, Ron. It didn't occur to me to look up ASTM. But thats exactly the info I was looking for (and half expected to hear). Like I said, I really don't PLAN to drive it in that extreme, and as you pointed out, it wouldn't necessarily be that cold inside. I Just know I only want to recover the seats one time. And you never know; In this economy, what I am building to be a daily driver, could end up being an ONLY driver, cuz I'll sell the Ram before I sell the Challenger! Better fix that heater core after all LOL