Tuesday, March 29, 2011

Sealant Corrosion?

Will the sealant corrode my rim? This is a real hot button issue among people who want to go tubeless. The big ruckus was started back in 2009 when Velonews printed these pictures, allegedly of rim corroded through use of sealants. (The picture above is not bicycle related!)

In recent months, Velonews followed up with information from Stan's saying that their is an infinitesimal amount of ammonia currently in his fluid, and that its composition has changed over the years it has been in production.
While the pictures from the first Velonews article are very scary, I have been using sealant on my road tubeless rims for four years now. If there has been any corrosion, I haven't seen it.  I have mostly been using Stan's, but I am also trying the Slime Pro product on one of my bicycles.

As an early adopter of road tubeless technology, my advice is to use your favorite sealant, relax, and enjoy the ride!


  1. Yes indeed, I have thousands of kilometers on Road Tubeless and sealant has saved the day several times.

  2. I'm riding a pair of Dura Ace C24's with Stan's. I definitely have noticed pitting in the rim bed. The pits are deeper near the valve stem hole, likely from sealant buildup. Any advice on how to stop the rim from getting more corrosive short of discontinuing the use of sealant?

    1. After two years my Campy Zonda two-way-fit front started needing refilling every ride so I pulled the Hutchinson Intensive tire off and found lots off corrosion pits on the black anodized rim. I cleaned the rim and fitted a new tire, since it was going to take a while to clean the Stan's guck out, and without putting more sealant in, the newly filled tire pressure dropped to zero in a matter of minutes. When I tested it in a water tank the air was escaping through the ventilation hole in the rim wall! Clearly, in one or more of those pits, the corrosion had eaten right through the rim!

      I am VERY unhappy. I cannot reliably use tubeless again on this rim! Now there's the rear to deal with and the pair of Zondas on my son's bike and the pair of DuraAce conversions on my wife's bike. I converted these three bikes purely for safety reasons - our rides are up and down the Niagara Escarpment and my son's riding is in the Hollywood hills - both areas have some pretty hairy descents.

      There seems to be no clear consensus as to what's going on here - Stan swears his sealant doesn't corrode rims. What is it then - the air? My bike has never been ridden in the rain. Do we just replace these $3000.00 worth of wheels every two years to continue the tubeless program? Cleaning out the Stan's periodically and refreshing would not have helped if the stuff is this corrosive.