Dear Dr. Science, Why is tire smoke white?

"Andy Sheehan, StreetsideStig" (AndySheehan-StreetsideStig)
11/24/2014 at 13:45 • Filed to: None

I'm wondering because when you light tires on fire, the smoke is black.

UPDATE: According to our esteemed Drs. Science in the comments, the burnout tire smoke is not actually smoke . It's a vapor. Sortof a tire steam, if you will. It's not a full combustion such as the tire fire above, but a superheating of the rubber. So it vaporizes.

Now we know. And knowing is half the battle. And battling is half the fun. Now I'm off to tell Matt Farah to change the title of his blog.

DISCUSSION (32)

RamblinRover Luxury-Yacht > Andy Sheehan, StreetsideStig
11/24/2014 at 13:52

Completeness of combustion, I would think. If a tire is burning after being set on fire, it's a hot flame that burns with insufficient oxygen to finish the very dense material that's being ignited. Thus, lots of carbon and complex carbon. If you're doing a burnout, the temp is high enough to semi-ignite material, but it's an external heat source (friction). The abrading and release of tire material isn't even really enough to completely burn what does burn, even ignoring the fact that a lot of what you'd see is really just vaporized from being worn off (and not burnt) rubber. Lots of breakdown products and vaporized tire, very little purified carbon.

Steve is equipped with Electronic Fool Injection > Andy Sheehan, StreetsideStig
11/24/2014 at 13:53

Because racecar.

Joshua "Dr. Science" Gilbert > Andy Sheehan, StreetsideStig
11/24/2014 at 13:55

You aren't combusting tires in a 'burnout.' The friction created mixes a lot of essentially melting rubber particles in the air, creating a white smoke. You aren't releasing energy by burning the rubber, fueling a fire. It is not sucking in oxygen as part of the burning process. Instead super hot rubber is mixing with air pulled around the tires by air pressure. Instead, if anything, you are releasing energy from the engine, through the driveshaft and tires onto the meeting area between the pavement and the tires. Since the energy's potential motion is being stopped (brakes preventing car from moving forward) the tires continue spinning against the 'weight' of the car's brakes. The wheels are in conflict with the static motion of the car and the pavement. The energy is being released into the tires, producing hot tires, hot pavement, and burnt rubber into the air.

Uh. This is entirely guessing on my part. Can I be Dr. Science?

Tohru > Andy Sheehan, StreetsideStig
11/24/2014 at 13:56

I dunno, in GTA 5 I can customize a car to have the tire smoke be white, black, red, yellow, green, orange...

pitstop_pitowski > Andy Sheehan, StreetsideStig
11/24/2014 at 13:57

RamblinRover is right, it is most likely the difference between early-stage heating for the coloring difference. I skimmed this long and advanced article about fires and smoke: http://www.fireengineering.com/articles/print…

MIATAAAA > Andy Sheehan, StreetsideStig
11/24/2014 at 13:58

Kinja'd!!!

Ferrari doing a burnout.

Hermann > Joshua "Dr. Science" Gilbert
11/24/2014 at 14:00

All in favor of allowing the title of Dr. Science to Joshua Gilbert say aye.

Joshua "Dr. Science" Gilbert > Hermann
11/24/2014 at 14:01

As long as Rambling Rover can be my "Research Assistant." We'll start our own MythBusters/Top Gear show. Basically Jalopnik in TV form.

Kinja'd!!!

OPPOsaurus WRX > Tohru
11/24/2014 at 14:03

Kinja'd!!!

not just GTA

lonestranger > RamblinRover Luxury-Yacht
11/24/2014 at 14:04

Not to mention a very lean "mixture", since each grain of rubber is surrounded by atmospheric air, supporting combustion. The solid tire on fire in comparison is "running rich", so-to-speak.

It's the same reason why over-fuelled diesel engines burn black smoke.

Sampsonite24-Earth's Least Likeliest Hero > Hermann
11/24/2014 at 14:04

Aye

Zerofret > Hermann
11/24/2014 at 14:04

aye

Twism > Hermann
11/24/2014 at 14:04

Aye!

(that explanation was brilliant, regardless of how true it was.)

Joshua "Dr. Science" Gilbert > Zerofret
11/24/2014 at 14:05

Kinja'd!!!

T5Killer > Joshua "Dr. Science" Gilbert
11/24/2014 at 14:07

Get in we're driving vaporware cars? :p

Jason Torchinsky > Andy Sheehan, StreetsideStig
11/24/2014 at 14:11

This is a great question! I'll start consulting SCIENCE!

RamblinRover Luxury-Yacht > lonestranger
11/24/2014 at 14:11

The white smoke is more related to the reason a car with bad rings burns white. Worse conditions for combustion + cooler temps = unburned material that isn't even even close to a carbon form - lots of water and long-chain still hydrogen-bearing stuff as transitory vapor.

$kaycog > Andy Sheehan, StreetsideStig
11/24/2014 at 14:15

Monte Carlos have red smoke burnouts.

RamblinRover Luxury-Yacht > Joshua "Dr. Science" Gilbert
11/24/2014 at 14:15

An excuse for tire fires? While no excuse is necessary, really, it does help to have one.

Hermann > Joshua "Dr. Science" Gilbert
11/24/2014 at 14:19

I'd watch an Automotive Mythbusters.

Mythbusters is awesome and they've done many car-related myths. But they seem to lack automotive knowledge and some stuff seems just stupid. Like trying to outrun a speed trap with a Murciélago at 120mph.

Andy Sheehan, StreetsideStig > Jason Torchinsky
11/24/2014 at 14:33

TELL SCIENCE WE'RE ALL COUNTING ON THEM!

Andy Sheehan, StreetsideStig > Joshua "Dr. Science" Gilbert
11/24/2014 at 14:37

Kneel, Joshua Gilbert. For your distinguished service to Oppo, I hereby dub thee Joshua Gilbert, Dr. Science! Rise, go forth to do science, and don't forget to change your username!

Steve Zissou > Andy Sheehan, StreetsideStig
11/24/2014 at 14:41

Wikipedia told me:

Technically the tire is not burning and the smoke is primarily a vapor (similar to steam). A tire that is set on fire will burn with a thick black smoke but that is rarely the result of a burnout.

doodon2whls > Andy Sheehan, StreetsideStig
11/24/2014 at 14:43

The smoke from spinning tires during a burnout or drift is _usually_ white or blue-ish white because you are superheating the rubber and oils in the tire, but not burning them (no combustion occurs). For example - candle smoke is white because the candle wax is melted into wax vapor and then immediately cools and condenses into a white 'smoke' which is actually microscopic oil droplets (anyone here vape ?). Acrobatic aircraft pump kerosene or another light oil into their exhaust pipe to leave a smoke trail. The oil is super heated into oil vapor and condenses into 'smoke' and produces the pretty trails.

At least one tire manufacturer (Kumho) has added chemicals to their rubber compound to produce colored smoke during burnouts and drifting. In this case, the Chemists developed a compound that would vaporize and condense into a colored smoke.

SO, to recap: Friction on the contact patch during burnouts and drifting superheats the rubber, which releases super heated oil vapors which quickly condenses back into thick white 'smoke' (microscopc oil droplets).

During combustion of tires in the open atmosphere (not in a furnace or incinerator), the rubber and oils are burnt at relatively low temperatures in an over-rich chemical combustion process which causes the acrid black smoke and bright orange flame. Tires can be used as fuel in an incinerator (or powerplant for example) if they are chopped finely enough and burned at a high enough temperature near stoichiometric conditions such that the material flashes to vapor and is burned completely.

Andy Sheehan, StreetsideStig > doodon2whls
11/24/2014 at 15:00

Dang! So our "tire smoke" isn't smoke at all, but rubber fog. I HAVE TO TELL MATT FARAH.

Great response. You are also Dr. Science. You and the other Dr. Science should start an institute.