ASK MBACTION – Going Tubeless and Shock Troubles


Q: I recently bought a new NS Snabb frame because I hate running bikes every- body else has. So far the build is coming along part by part. My question is about the upper shock mount. I’m not a fan of RockShox rear shocks. They don’t have as many adjustments as Fox shocks like the Float X. I’m still undecided about what I’m going to do in that department. What bothers me most is the mounting on the upper shock mount. Is there a spacer kit to get away from the upper mount and make it eye/eye mounting? Cane Creek has the spacers, but I can’t find a threaded sleeve to be able to use the stock bolts that screw into the stock shock. Is it worth having a buddy at a machine shop mill out the spacers, sleeve and tap sleeve to accept the factory bolts?

—Joe, who’s not a factory rider and is willing to do the work himself

A: We’re sure there are many riders with this same quandary. Fox is planning to launch a full line of metric and Trunnion mount shocks. If you like the Float X as you mentioned, that would be our suggestion. If you’re dead set on the Cane Creek, you could certainly have your buddy machine some spacers. It will likely work, especially if your guy is good with a lathe, but that mod will certainly void your warranty.


Q: I’m a total newbie to tubeless, and I’m finally taking the plunge. I’m having trou- ble, though, and thought maybe you could help. I have Bontrager Race tubeless-ready wheels. It’s a fairly old ride—a 2007 Trek Fuel EX8. The rims have some sort of greenish lining in them, and I was told that they are sealed rims. I was also told that I didn’t need rim strips in there, just Stans. So, I pulled the trigger and I’ve got one tire installed. It’s holding air, and I heard it pop into place, but if I pump it up too much, air leaks out of the valve stem (also Stan’s valve stems). What am I doing wrong? Any suggestions?

—Adam, who can’t hold the air

A: We’ve run into this problem in the past, as well as on a number of wheels. It sounds like the rims are indeed sealed, so that’s not your problem. It may be that those Stan’s valves are not mating well with the rims and creating a good seal. There are many valve types and shapes out there, and this combo is simply not getting along with the rim. We’d recommend trying a different valve shape first. Since your Stan’s valves are fairly square, for example, try a different aftermarket valve that has a more conical shape. This should give you the seal you need and prevent the leaking.

Ideally, though, you should use the valves that the rims and rim strips were designed to work with. Bontrager typically sends its test bikes to us with tubeless conversion kits that always include valves. Any Trek dealer will likely have a few of the real Bontrager valves on hand, and that is likely the best solution.

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