Vince Canepa

I purchased a set of Dura Ace WH-7850-C24-TU tubeless wheels in March of 2010. The tires were installed by my (well respected) LBS. The rear slowly started to leak air after 6 months or so. By July of this year it would lose 2 bar overnight. At the same time I picked up a 10 mm cut in the rear tire so I had the same shop break down both wheels and tires, clean out the sealant, mount the new rear tire and remount the old front tire. The rear still had a slow leak which became worse. By November it would lose 4 bar overnight. Frustrated I tackled the diagnosis myself. I found the bead leaking on three areas, so I marked them on the brake track. I pulled off the rear tire and cleaned the rim. What I found was widespread corrosion, with moderate corrosion of the bead are where the leaks were occurring. I cleaned the rim thoroughly with Scotch Brite and remounted the tire. The bead was tight, but the tire would lose 4-5 bar overnight. On investigation I could hear air leaking into the void space between the carbon reinforcement and aluminum rim (when I put the drain holes in the carbon up to my ear). I removed the tire and spent some more time with Scotch Brite. I found 31 pits so severe that I considered them as suspect. Under a magnifier I found one pit with a tiny hole through the aluminum. The front is also corroded by not nearly as bad. Also, when I examined the bead area of the new rear tire I can see evidence in the form of impressions in the rubber of the bead area leading me to believe that the corrosion was there in July when I had the tires replaced/resealed at the LBS.

The only thing I can attribute this to is the sealant. Unfortunately I don't know what the LBS used and, due to the fact that this is the latest in a series of "missteps" by the LBS, I don't trust them to tell me the truth. Shimano has refused to warranty the wheels due to the use of sealant - they have a warning not to use "alkaline" sealants in their instructions. I am working with another LBS to have the rims replaced (the rims are NOT cheap). I really don't want to go through this again, not just because of the cost but my bike has been down since Thanksgiving.

I would appreciate any insights from folks here on BF. Please don't head off on a tangent about the merits/demerits of the tubeless system. I really want to hear about your experience using sealants in these rims. Shimano America told me they don't recommend sealants, but if I have to use it the guy on the phone said to use Caffelatex. Any problems with that product?