Fatbike Tubeless Setup: fun on a day off from work

In Blog by Eric Benjamin Comments

I’ve been putting off setting up my fatbike tubeless for some time now. I was going set it up using a tried and true homespun version for two reasons:

  1. No one has made a fatbike tubeless kit yet.
  2. A friend of mine (who is a sponsored racer and rides harder than I ever will) does all his wheels tubeless using this method with great success and it seemed fairly simple.

What could go wrong?

My Friday off was going to be in the high 60’s but very windy. It had rained the night before and the roads and trails were too muddy to ride. A road ride sounded as fun as some time on the trainer, no offense to roadies, all offense to Kansas paved roads. I had planned to do some good reading all day, but after taking the kids to school I went into the garage and looked at my Beargrease and thought. “Yes my friend, it is time.”

I took the computer into the garage to listen to Pandora radio on the big garage stereo, that every man should have, and turned on the space heaters. It was still pretty cold outside in the morning. I also needed the computer to read through an email conversation I had with Matt about his tubeless setup. I wanted to follow his directions to a T. He knows what he’s doing and I don’t have a tubeless tire anywhere in my garage, well besides the cars.

Some people have asked me why I would want tubeless tires. Two main reasons come to mind:

  1. taking some weight out of the wheels and
  2. flat protection.

The sealant will seal up any holes made by thorns or small rocks where with a tube you are changing a flat because of a tiny pinhole leak made by a thorn in the road. I really wanted flat protection as we have been getting more thorns on the roads in the Flint Hills with the hot, dry weather.

I had all my materials ready. Matt said he used something you can get at a hobby store called Mold Builder, a liquid latex used to make molds of 3-D objects mixed with window wiper fluid to thin it out and keep it from freezing. Those were my two ingredients. I had read online of complicated mixes and looked at the more expensive Stan’s sealant, but Matt assured me that this has been working in his tires for some eight years now without incident. When the package came in the mail, it wasn’t Mold Builder, but it was liquid latex, so I felt OK about it.

I had a container with a lid and pouring spout with lines of measurement on the side to use to make and store my sealant mix. Plus I asked my wife last time she was at the store to pick me up some cheap measuring spoons too. Probably shouldn’t use the family’s utensils for this.

As you can see, the latex is pretty thick, kind of like yogurt.

I read over Matt’s recipe of 5 heaping teaspoons of mold builder per 10 oz of window wiper fluid. I did that and shook it up. It seemed very watery to me and in the spirit of over doing things, I ended up going with 10 heaping teaspoons per 10 oz of wiper fluid. It was still watery so I felt good about it.

My morning consisted of good tunes, a heated (sort of) garage, coffee, gorilla tape, tire sealant, fat wheels and tires and a mission.

Wow, this is the first time I have taken the tires off the rims. Those are some big tubes. I had to hold the rim up to the little tire on my CX bike for comparison. As you can see, there is a nice, tight Surly rim strip in place. I left that on as it seemed that it would help with sealing this whole thing together. Plus I like the black color in the rim holes. Sorry, that sounded so dirty.

I bought these weeks ago in preparation for this adventure. I have seen some people use old valves they cut out of tubes, but I didn’t want to take any chances. These suckers aren’t cheap.

I took a nice large sip of coffee, sat close to the space heater and got started on taping up the rim with Gorilla tape. I suppose you could use regular duct tape, but Gorilla Tape is very strong and seems thicker than regular duct tape. I took my time to get it on the rim tight and flat.

One layer on the right and

another layer on the left. Then I

used a drill bit to make a nice hole for the valve stem.

At this point I thought two layers would suffice, but I texted Gersib to see what he thought. “Definitely do another layer down the middle,” he texted back. I did, but I cut the tape in half and taped over that middle seam. Um yeah, that puppy was going to be airtight, that’s for sure.

I redrilled my hole, then I put the tube and tire back on the rim and

aired it up to 30 lbs and let it sit for about an hour to really get that tape to stick and flatten out. With a floor pump, it took what seemed like 15 minutes of pumping to get that fat tire aired up to 30 lbs.

As I aired up the tube, the tire looked very loose on the rim. There was absolutely no way I would get the tires to seal without a big burst of air. While I let the tape flatten out, I ran some errands including purchasing something every man should have in his garage – an air compressor.

Some manly men have these to use with their power tools and what not, but all I wanted to do was to air up some bicycle tires. Luckily I knew a guy working at the hardware store, so I asked him for help. I needed the correct adapters to go from the big nozzle down to a bicycle tire valve and, this little thing would be good enough to air up a bicycle tire right? I thought so. I got the smallest, least expensive one I could find. Surely it would be enough.

At first I was just going to do the front tire to see if I could get this to work before putting the strong grip of Gorilla Tape on my rear wheel. But things were going so well and now I had everything I needed so I figured, “What the hell.”  I did everything as above on this wheel too. But when trying to take the tire off after airing it back up to let the tape set, it would not come off. The beads had set into the rim with a hulk like grip. It took all I had, and a hammer to get the bead to come out. My hands are still sore. I have never seen a tire grip onto a wheel like that. That gave me hope that the bead would easily set and seal on these tires and wheels.

A vacuum was created as I let the air out of the tube.

I only popped one bead out of the rim to help seal the tire to the rim in the step to come. Having one bead already snug on the wheel would prove to be a big help in the final process.

How much sealant to pour into this huge tire? Matt suggested 8-12 ounces since some would be lost while trying to get it to seal. I went with 8. That seemed like plenty as I poured it in. Then came the really challenging part – getting the tire to seal to the rim.

As you can see, the bead of the tire on the right of the picture is already set and snug on the rim. I added air and watched and listened to it all leave the tire as fast as it went in. There were huge spaces between the tire and the rim, so using my feet and extra hand, I tried to get the tire against the rim as I pumped air in as fast as that little compressor could pump.

I turned and worked the tire a bit. The sealant is sticky and I turned the tire around a bit to get it everywhere. It seemed to help get the tire to stick to the rim. With feet and hands in place I added air again. As you can see below the right side of the tire is not against the rim and air was blowing out as quickly as I could put it in.

I think I was a little too deep in concentration to realize that Mikey was well within the blast range if the bead busted loose. But all was well as suddenly I got the amount of air going in to be greater than the amount coming out! Soon after that the tire pressed against the rim and I heard the PING! of the bead snapping into the rim. WOO HOO!!! Success! I put some more air in the tire and wobbled the tire around on it’s side to spread the sealant out and plug all the leaks. It didn’t take long before the tire sealed tight.

And as you can see, I only dripped a little bit of sealant on the floor in the whole process. Not bad.

I went out to ride on Sunday. It was a balmy 19 degrees or so when I left. I wanted to ride some gravel and headed west out of Emporia. So how did they feel you ask?

On first feelings, they felt lighter, but they also felt something more than just lighter. I can’t quite put my finger on it. They just felt like they were more nimble and easier spinning. That could be because the 1/2 pound tubes were no longer in the tires. But I remember awhile back that Matt Gersib described the benefits of tubeless and one of the things he said you’d lose by not having tubes was the friction of the tube against the tire. Basically I felt faster and more nimble and that’s a good thing.

Oh and one other thing that seems weird. I aired them up to a little under 10 pounds to ride on the road. At that pressure, they seemed harder than the same pressure with tubes. Even at five pounds, they didn’t feel as soft at that same pressure with tubes. Maybe one of you engineers can explain that.

The homemade sealant remained liquid, proved by shaking the tire and hearing it slosh around in there. And I have not had any leaks since the first seal of the tires. So far, so good! I ended up riding a 35 mile loop on a beautiful sunny, but cold winter day. There is something about riding in the cold that has an ethereal feeling to it. As long as you have the right gear (clothing) it is very pleasant to the senses.