On recommendation from my friend Roger, who is also building up a new fat bike, I decided to try some using some seam sealing tape designed for Tyvek installations as rim tape (MSDS). This is commonly known as “Tyvek Tape”, even though it isn’t actually made of Tyvek. It is actually a somewhat stretchy polypropylene tape with acrylic adhesive. At $11.98/roll it’s not exactly cheap, but with 50m of tape in a single roll there’s enough to do numerous wheelsets.
I’d intended to use Scotch 8898 tape for tubeless, but after looking at the Tyvek Tape I decided to give it a try and thus far I’m glad I did. On the DT Swiss BR 2250 wheels I first installed the DT Swiss Rim Strip, centering it between the locking bead seats (photo). I then laid one strip of tape with the edge in the bead seat, butted up against the vertical side of the rim. This was smoothed against the Rim Strip and a second piece was applied to the other side. After most of the wrinkles were smoothed I laid a third strip of tape down the center to cover any center wrinkles, pulling it taught as one normally does when installing any rim tape. This was smoothed into place with a rag and taping was considered complete (photo).
To ensure the tape was well bonded I then fitted a tire and tube, inflated to 20 PSI, and set the whole assembly in the sun to warm up and soften the adhesive. After 30 minutes or so I took the wheel out of the sun and set it in the basement to cool back down. Once cool I deflated the tube, unseated the tire from one side of the rim, and removed the tube. A Stan’s valve was then fitted into the rim, a plastic washer placed on the outside below the locknut, and everything tightened up. The valve core was removed and an air compressor and custom chuck was used to seat the tire. Four ounces of Stan’s Sealant was injected into the wheel via a syringe, the wheel closed up and reinflated, and the sealant shaken around the wheel.
The tape provided a nice, smooth surface for the tire bead to slide across, and after a few days the wheels (fitted with Panaracer Fat B Nimble 26 x 4.0 tires) are nicely holding air. This tape seems like a great, light-weight product for using on fat bike wheels. I’m glad I gave it a go, as the thinner, stretchy tape seems much easier to apply than the Scotch 8898. It seems to make a great seal and hold well, and was pretty easy to install.
I inadvertently ended up with a couple small puckers along the rim tape on the rear wheel, but I think this was due to either sticking the Tyvek tape to the rim tape with too much force, or possibly deflating the tubed wheel while still warm. I don’t believe I can correct it without completely removing the rim tape, so I’ll have to live with it.
UPDATE on 2015-Sep-22: Over the past few days the rear wheel — the one with the small puckers — lost all pressure. The root of the problem turned out to be adhesive used on the Tyvek tape. The acrylic adhesive is a bit gummy and softens with a bit of heat. My process of installing a tube, deflating the tube, then unseating half of the tire dislodges the tape leading to the puckering — which was a symptom of dislodged tape — and thus leaking. Using some tweezers I can unfold and put the tape back in the bead seat which allows a tubeless setup to hold, but this setup feels fragile. I think the combination of thin tape, soft adhesive, and very wide rim strip (resulting in not much adhesive being on the rim) allow this to happen.
While the wheels are currently holding 20 PSI reliably, I’m concerned about what may happen to the tape in hot weather or as regular tire maintenance needs to occur. I suspect that I may have to switch to a different tape some time down the line, maybe the rubber adhesive Scotch 8898. Doing this will be a pain, because of how solidly the acrylic adhesive sticks to the rim and rim strip… At this point I may have to get some new rim strips.
UPDATE on 2015-Sep-29: I’ve decided to move away from the Tyvek tape. The rear wheel deflated over the next few days in the same failure mode, and both of my friend Rodger’s wheels went flat when taken out in the sun. When disassembling and cleaning the wheel set I found the front beginning to suffer from the same issue, so it was only a matter of time before the tape became dislodged there and failed.
Because of the tenacity of the Tyvek adhesive I purchased another set of rim strips from eBay and cut the current ones. The rims were cleaned up with mineral spirits and set to dry. In a few days I’ll be trying them again with new strips and Scotch 8898. If that fails I’ll be trying FattyStripper Tubeless Solutions trim-to-fit latex rim strips.