Intro: Fat Tire Tubless Conversion
Bicycles have successfully used pneumatic tubes for a long time now but with them come some drawbacks. the extra weight of the tube probably being the least desirable. A company called Stan's No Tube came out with a system to get rid of the tube on a standard rim and tire by using a special rim strip and sealant solution which thickens when it comes in contact with the outside air. Since then many companies have come out with similar sealants and manufacturers have begun making wheels and tires designed to prevent air from escaping in conjunction with a sealant negating the need for the special rim strips. People have also found many less costly substitutes for the special rim strips made by Stan's.
The method I have seen most commonly used it to substitute the Stan's rim strips with Gorilla tape( a heavy duty form of duct /duck tape) and add the sealant.
When it comes to Fat Tire bikes there are some added challenges due to the width and shape of the rims. Here is how I took a commonly used technique and modified it slightly to overcome those.
Step 1: Overview
Fat bike rims have a very wide and flat profile compared to tubeless rims making it difficult to get the tire to set. or make a good seal along the edge of the rim. the images compare what the profile of a typical tubeless mountain bike rim looks like note the areas higher on each side where the tire can sit close to the edge of the rim. this shelf or bead seat, makes it easy to get an airtight seal around the outside of the rim even without any sealant in side the tire. Since the fat tire rims do not have these people have come up with several popular methods to recreate a place to enhance this seal. the 2 I read about the most are the "split tube method" in which you take a 24" bicycle tube, cut it in half and stretch it around the rim reusing the valve from the tube. this method seems to work well but there are a few drawbacks to it.
1) you have to have the tube sticking out around the rim making it visible from the outside
2) in order to change tires you have to repeat the whole process over again.
The other popular method uses weather stripping or plastic wire wrapped around the rim to create a bead seat. This is the method I started using when I came up with this alternative option.
I noticed the vent holes in the rim and realized the weather striping would not seal them so I thought of how to seal the holes and accomplish the goal of creating a bead seal. My solution was more tape but covering the rim with more of the 3" tape would just add back any weight I could hope to lose with the tube. So my thought was to just add a few wraps of narrower tape on either side. I measured it up, 2 wraps of 1 "tape adds.79mm 3-1.22mm of material.
Step 2: What You Need
- 2 rolls of 1" Gorilla to-go- tape
- 1 roll of "Tough and Wide" 3" gorilla tape
- 1 32 oz bottle of tire sealant (I used Stan's since I had it already)
- 1 set of Tubeless rim valves
- tire iron (you can probably get away without it since the tires are so loose
- air compressor
- lighter or torch
- air blow gun (not crucial but really helps)
- 3" piece of 1/4" ID clear vinyl tubing
The first step is to remove the tire and tube inside you will notice the protective/decorative rim strip found on fat tire bikes with drilled rims. I left mine as is but many people like to remove this and replace it with some more decorative duct tape. You may also see what inspired my to start this method, The 8 vent holes, 4 around the valve stem and 4 opposite that where the seam in the rim is. I believe these are drilled into the rims for venting the gasses when the rim was welded together but I could be wrong on this.
Step 4: Start Taping the Rim
The process is very simple, begin wrapping the on inch tape along the edge of the rim as close to the sidewall as possible without going over, staying straight and smooth. I started with the intention of 3 layers on each side. so after the first side I got 2 1/2layers on the other side. :-/ Being a little short doesn't hurt anything though so I continued with the 3" wide tape wrapping 2 layers of that (one is probably all you need after the sides but I went with more).
Step 5: Making the Hole for the Valve Stem
Now you should be left with you rim wrapped like a mummy in gorilla tape. it will be left wrinkly but the air pressure in the tires will soon take care of that.
I don't have a picture of the results unfortunately so you will have to trust me on this method. In order for you to easily be able to instal your valve stems you need a nice clean hole for them to fit. I found heating up the end of an awl and pushing it through the tape is good for this purpose. A Philips head screw driver can be used if you don't have an awl or just anything pointy and metal of the correct width.
Step 6: Setting the Bead
looking back this step is not crucial but i did it on both rims.
- All you do is put your tubes and tires back on and inflate them to around 20 or 30 psi. you may or may not hear a pop of the bead setting (I didn't)
- Then remove the tube from one side trying not to pull the tire from the bead on the opposite side
Note: I was unsuccessful at keeping one side of the tire seated during this and the next step so don't be horrified if the whole tire comes loose.
Step 7: Install the Valve Stems
the orange seal valves I purchased have o-rings on either side of the rim so pay attention to the instructions on the brand you use. Because the rims are flat inside and the valves are made for typical rims that are curved I had to re tighten the nut on the valves the next day with some long nose pliers.
Step 8: Add Sealant and Inflate
If you successfully removed the tube while keeping the tire on the rim you can proceed to pouring your sealant into the bottom of the tire, if not get one side of the tire wrapped around the rim then pour your sealant into the tire ( this may be hard to visualize but there are many instructional videos that explain better than I can.
How much Sealant seems to be a matter of opinion, in all the posts on forums and YouTube videos I have seen varying recommendations of how much sealant to use. many say use half a jug of sealant (16oz) others say 3 scoops of the measuring cup that came with it. I cut that down the middle and went with 4 scoops. I can't find what the exact measurement of each scoop is but if you go with about a third of a bottle you will have enough left over to add more in the future if you need it or if you knock over the bottle before starting the second wheel.
Inflating the tire:
Because of the volume of air these tires hold you have to get the air in quick which is why an air compressor is necessary. beyond that your typical tire inflator may not work.
I saw this trick on a YouTube video. Fitting a short piece of flexible tubing just wide enough to fit around the presta valve onto the end of a blow gun like the one in the picture makes a very simple inflator for presta valves. This system gets a lot more air into the tire making it easier to get the tire in the right spot to start holding air.
My front went on with no trouble at all the rear I had to play with a bit to get the air to start inflating it. I put some sealant on my finger and whetted the bead of the tire on both sides before adding air which helps get a seal started.
fill the tire up to about 35 PSI and spin it slowly while rotating it like a gyro to help get sealant to cover all surfaces. I could hear some fizzing for a little while after filling the tire so I just spun it some more until the fizzing stopped
you have tubeless tires!!!!!