Friday, October 7, 2016

What compounds soften rubber tires?

I'm a big fan of Tyler Rogoway, the defense journalist who blogs at the car-oriented website "The Drive." Thanks to a random clicking, I noticed this odd little story by Steve Cole Smith about NASCAR driver Tony Stewart being sued because of a dispute related to a racetrack that he owns: 
NASCAR Sprint Cup driver and team owner Tony Stewart appears to be headed back to court as part of a lawsuit filed against his Eldora Speedway, the dirt track in Ohio, and this one has nothing to do with the death of Kevin Ward, the New York sprint car driver who was killed when he charged Stewart’s still-moving sprint car during a race. 
This time, certifiably legendary dirt late model driver Scott Bloomquist, along with Jimmy Owens, Gregg Satterlee, Brandon Sheppard, and Ricky Thornton Jr., have sued Eldora, Stewart and sanctioning body UMP for damages that total $16.5 million. 
In dirt track racing, the softer the tires, the faster, and teams have been known to treat tires with chemicals that are readily available to make them softer. The makers of the chemicals label them as either difficult or impossible to detect, because using aftermarket additives on your tires is against the rules of most all sanctioning bodies, including UMP. The sanctioning body is controlled by World Racing Group, owner the World of Outlaws sprint car and late model series, and WRG was named in the suit as well.
So here's what I want to know - what kind of compounds will soften tire rubber? I'd think just about anything would, but how could it possibly be difficult to detect? (Also, aren't there straight property tests to detect if tire rubber was softened?) Random shows that some amateur racers use toluene (not a surprise), but how is that not detectable? 

I am so not a race fan, or someone who knows anything about cars - anyone out there know anything about this? 


  1. I race on road courses and hillclimbs but some people will bake or shave their tires or have special tire blankets in upper tier racing like Formula 1 and DTM, but need to be done on-track. With tire treatments, most home brews are some organic solvents like toluene/acetone/mineral spirits or even WD40 or PB Blaster (rust penetrator) if there's no sniff testing involved with their parc ferme inspections. With regards to the over-the-counter products that you can buy at places like Jegs and Summit, I have no idea what is in there as they claim you can't smell anything but most are supposed to be used days or weeks prior to the event, so perhaps they do have toluene and mineral spirits in there and thanks to them being VOCs, they will be undetectable days later. I've always wondered what was in them, but a quick search yields zero MSDS which is very surprising and honestly.

  2. I'm sure the manufacturers of chemical tire softeners would NEVER lie about their detectability.

  3. A comment from Canada. I know nothing about car racing, but in Canada these days most people switch their tire type from a nominal "all-season" radial to a "winter tire" when winter approacheth (i.e. yesterday, in Saskatchewan). This is a newer development (probably in the last ten years, people didn't do this when I was a kid). Winter tires are mandated by Provincial law in a number of provinces and have become pretty common (and strongly recommended) in the rest. They are specially formulated to be softer, so they still have some "grab" below 7 Celsius (yes, that is +7 C), where normal tire rubber gets too hard & glassy. Based on my experience driving in all kinds of terrible winter weather, they do make a difference. Hankook (Korean) and Hakkapeliitta (Finnish) are two of the big manufacturers. According to a random patent (Ryoji Kojima, "Rubber composition for winter tire, and winter tire, US Patent #20130030111 A1") found online "The present invention relates to a rubber composition for a winter tire which contains predetermined amounts of natural rubber, butadiene rubber, aromatic oil, silica, and carbon black, and also contains a specific silane coupling agent that includes a linking unit A represented by the following formula (1) and a linking unit B represented by the following formula (2) and has a predetermined content of the linking unit B." I'm not a chemist (just a physics guy), but it seems like there are plenty of volatiles in the mx which you could easily detect with mass spec or other means. Ditto for toluene of course. Never heard of anyone in Canada sloshing that on their tires just before the first snowfall, though.
    Mike Bradley

  4. Continuing from Michael Bradley's post. During the polymerisation of butadiene, the butadiene can polymerise either 1,4 or 1,2; increasing the proportion of the 1,2 polymer increases the softness of the tyre. This is done by adding something called a polar modifier to your anionic polymerisation reaction mixture.

  5. Cool! Thanks for the organic chem info, that's a bit out of my league.

  6. Tire warmers are legit. They don't soften tires any more than a tire would soften by itself when it gets hot during the race. Warmers allow you to go all out from the start without having to heat up tires by making a few slow laps.

    Bleach softens tires well. Probably by oxidizing some of the sulfur from cross-links. I've done that to an old tire by doing a smoky burnout in a puddle of bleach. Afterwards tire cooled down, tire remained really soft and all kids of debris were sticking to it.

    It should be trivial to detect any tampering by using a durometer, especially if everyone uses standard issue tire. No need to use a chemical detection method.

  7. Maybe I should ask my advisor!