Good question Susan, unfortunately according to our friends at Wikipedia, they don't burn: http://en.wikipedia.org/wiki/Mag_wheels

I bet if you get them hot enough, they will burn. Just not "campfire hot", but REALLY hot. Sounds like a homework assignment for BLAST!

There is a bloke over here named Les Hiddens ( The Bush Tucker Man ). In one of his TV series he lit a fire as a signalling device, then did an aerial shot of the smoke. It was quite useless and hard to see. He suggested a signal mirror which he used and also showed an aerial shot, it was very effective. He did these experiments in the desert of Australia though, dont know about the results in the snow.

Most things are hard to see from a search aircraft. As you say the flash is the best. The way I have always heard the tyre burning thing referred to has been as a smoke signal to be seen from the ground. In the more remote regions of Austalia a smoke signal from a tyre is the best way to be spotted by someone on the ground. The best times to burn is at dawn or just before dusk. This is when Cockies (farmers/station owners) come out to look at their property. If they see any smoke at all you will have a visitor real soon!

I have heard it recommended that you should burn the tubes first and then the tyres after all the tubes are gone, that will give you five days of fires. Over here in the outback tubes are not uncommon because punctures are very common.

However the best way to stay found over here is to get a HT radio and join the VKS network. If you have trouble just radio and help will be on the way.

Been there, done that. It's VERY hard to get a mag wheel to start burning. The alloy used is ~95% magnesium so it will burn if you can ignite it. The problem was getting it hot enough. Magnesium is a good conductor of heat so the heat from any "point source" such as a propane torch and road flare was dissapated throughout the rest of the rim and so it never reached ignition temperature. Wood and rubber don't burn hot enough unless you have a BIG fire with a good wind blowing on it. A large amount of charcoal might do it, again if you have wind blowing on it (think a forge). Basically, anything most people carry in their car won't do the job.

A pound of thermite works though.
<img src="/images/graemlins/grin.gif" alt="" /> <img src="/images/graemlins/grin.gif" alt="" /> <img src="/images/graemlins/grin.gif" alt="" />

-Blast

Blast is correct, not that anyone would doubt that considering his area of expertise <img src="/images/graemlins/smile.gif" alt="" />

Now, if you could somehow turn that entire wheel into shavings, you'd have one heckuva signal flare...

"...if you could somehow turn that entire wheel into shavings..."

You could stay warm, using a file on that rim. And if you got a pile of aluminum shavings from a wheel, and had a rusty old hulk nearby you could file on...I'd better not go there...

As far as trying to take the tire off the rim, I just wouldn't. They are VERY difficult to do with a couple of prybars on a steel rim. On some of the alloys, because of the way the bead locks in, you're not doing it without the hydraulic bead breakers the tire shops use. However, cutting the sidewalls of even the best multi-plies is pretty easy. I would cut out a hole/strip big enough to pack in the wood or whatever flammable material you're using to light it up. I once cut out a couple of makeshift shoe soles in about 5 minutes just to see if I could. (cut out some soles, poke holes, add para cord and you've made sandals). A tip - angle the blade sideways when cutting the sidewall (or any heavy material for that matter), it lets the cut rubber offset so it's not just pinching the blade. Mucho easier!

As far as the alloy rims burning. I recall that in the earlier days of the new magnesium rims, there were some spectacular fires that couldn't be put out in some car races. "Magnesium" rims are not magnesium anymore because of that (and also because they would get micro fractures and cause the wheel to fail), they are aluminum alloys. Filing away to get some firestarting dust will just waste your time trying to light up aluminum dust.

Magnesium engine block fire + water
Here's a short video of what happens when you try to put out burning magnesiun with water. Makes you think those vehicles should come with a large warning for rescue personal. Sidenote: A CO2 extinguisher with also cause a really neat, uh, I mean bad reaction.

My theory about why magnesium engine catch on fire easier than mag wheels is the heat generated in an engine fire is much more contained and can't escape the engine compartment. The rims are exposed to the air and so the heat can radiate away.

-Blast

I have a VW bug with a Porsche mag engine in it burn one night, L.A. County Fire wouldn't believe that they couldn't put it out with water, in no time at all I had three lanes of I-5 flared off for all the equipment they rolled, they put a jillion gallons of water on it, and guess what, it burned forever. That was in about 1974, I think you can still see the burn marks on the pavement...