How to set up a fat bike tubeless

Editor’s note: Will this process work on your bike? I have no idea, so please don’t ask me. But since we get paid the big bucks to be human guinea pigs, we went ahead and tried it anyway. Caveat emptor and all that…

By Montana Miller. Photos by Adam Newman. 

Tubeless fat bike tires have quite a few benefits. They roll faster (by eliminating friction between the tire and tube), can be run at lower pressure without risk of pinch flatting, and are lighter.

Before we started, we had to weigh the wheels. There was some snow clinging to them, so we smacked it on the floor of the shop to make sure we were very precisely weighing them dry.

Then we started setting them up tubeless. We used:

• Gorilla Tape
• Old tubes with removable presta valve cores
• High density window insulation foam, 1/8th inch wide.
• Surly rim strip
• Sealant
• And an air compressor

On a single wall rim, like the Snowcats on Karen’s 616 test-bike, the Surly rim strip needs to be installed to fill in the cutouts in the rim. On a double wall rim, you could skip this step and go straight to tape.

Put the rim strip on first, then wrap the rim in a tight layer of duct tape. 

On the 45mm Snowcats we were able to use a single strip of tape. For 65mm to 100mm rims, wrap a strip down the middle, then a strip on each side, making sure the tape goes all the way to the edge of the rim.

On a rim that fits a tire decently tight, like most Surly rims, you can install the tire and go straight to inflating. But the Snowcats had a really loose interface with the Husker Du tires (it was so loose that the tire and tube almost fell off the rim when we deflated it), so we had to take some extra steps.

We still started with the rim strip and a layer of duct tape, then we wrapped a strip of high density widow insulating foam around both sides of the rim, leaving about 5mm between the edge of the rim and the foam. This creates a little groove for the bead of the tire to sit in so that it doesn’t pop off at low pressure. 

After the window foam was on, we wrapped the rim in another layer of duct tape.

Then we cut the valve out of the old tube, leaving a little bit of rubber around the valve stem, and popped it in.

We used the little nut to tighten the valve to the rim. Removed the valve core with a pair of needle-nose pliers, installed the tire, and used the compressor to inflate it.

The tire inflated right away with the foam groove, but if you’re just using duct tape, put a cam strap around the tire to get it tight enough for the first blast of air to seat the bead. The cam strap should be snug, but not so tight that it’s wrinkling the tire.

Once the tire is seated, go ahead and deflate it, then add some sealant, re-inflate, and make sure the bead is seated the whole way around. If it’s seated, shake the tire around to get the sealant into all the little cracks, then go ride it. It should be totally solid. We used this stuff from Orange Seal. Thanks Orange Seal! 

 

Even with just one or  two psi, the tire wouldn’t roll or burp.

And here are the weights:

Rear wheel with tube: 3,950 grams

Rear wheel tubeless: 3,850 grams

So even with three layers of duct tape, we saved 100 grams over a setup with tubes. And the foam made the tires fit on the rims tighter, so they should be more reliable at low pressure.

Input from test rider Karen Brooks:

But, you’re wondering, how does it work? The short answer is: awesome. I’ve only been able to take one short ride so far, but in that time, the tubeless set-up feels much more responsive and able to conform to the trail surface. Fat bike aficionados generally talk about the need to adjust tire pressure downward of "that basketball feeling," when the tires bounce too much, but for me that leads to the tires feeling like… deflated basketballs, somewhat dead.

Set up tubeless, they feel much more alive. Some of this "dead vs. alive" feeling is no doubt due to my relatively low weight. I’ll be eager to hear from some bigger folks how fat tubeless feels to them. I hope 616 doesn’t need their bike back too soon, as I’d like to try tubeless on some really rocky stuff. I bet it will work great. This may be the factor that tips fatbikes into the "yes, definitely" column for me.