Monday, December 07, 2015

An alternative way to go fat tubeless.......starts with using a tube!

Ready for assembly
A good friend of the Barn told us about this method so we thought we'd give 'er a go and see how it works.

We will be working with a new Sun Ringle Mule Fut 80SL rim, which is tubeless compatible and a 45NRTH Husker Du 4.0 tire. (Yeah, I know, I'm missing the umlauts in "Fut", "Husker" and "Du.")  The rim has a cut out section in the center, like Surly's Holy Rolling Darryl, only square instead of round so we will leave the vinyl strip in place.

The original tube will be set aside as it isn't needed for this conversion but will make a good back up incase you need one out in the wild.

The secret ingredient for this recipe lies in  the tube section to make it work.  We are using a 24" x 2.4-2.75 Presta tube which has been cut
radially, down the back spine (opposite the valve side) and then splayed open.  Kinda like butterflying or spatchcocking a bird.
 Once that is done, you line your rim with the new tube inserting the valve in the valve hole as usual.  There will be some overlap of the tube on either side of the rim which will help us when it comes time to install the tire.  It will be removed once the tire is on and the bead is seated.  It will look something like this:

Now, depending upon how old your tire is, it may gone on easily, or your may have to battle with it a little, especially if it's our Husker Du.  Take your time, use a plastic tire lever if you need.  These rims don't have much of a valley in the center section so it doesn't really matter where the first bead is in relation to the rim.  Try to keep it in the center as you would with any tire change.  Once the first bead is on, make sure the tube is still placed evenly on the rim.

As you work the second bead onto the rim, take care to not gouge/cut/pinch the tube.  It can become tight as you work the last section on.  Try to pull the loose tube over and outside of the tire as you work the bead in place.  Take small sections and work them slowly.

Sometimes is helps to get the inner bead of the tire and tube lubed a bit.  We've had good success using Pedro's Bike Lust as a light lubricant to help seat the bead on stubborn tight tires.
Pedro's Bike Lust

 Once both sides of the tire are on the rim, it should look something like this.  Just for kicks, we wanted to see if we could get the tire to hold some air without any fluid, so we removed the valve core, grabbed the air chuck and blasted it up to 40ish PSI.....after a few loud and startling "POPS!", we noticed both beads had seated are were holding air.  It did lose some after a few minutes, but we were excited to see the beads had seated and it was holding air.

Next, we added about 8 oz. of Stan's tubeless tire sealant.  This amount is a rough guide, you may need a little more or less depending on how the bead/tube/tire is seating.  It tends to be less messy having the tire completely on the rim and fill the tire through the valve using a syringe, especially when trying to get the bead on this setup over the rim yet still have the tube flap hanging out.

Blasted the tire with the air chuck to seat the bead.  A little popping and hissing was heard while I removed the air chuck and pressed my finger over the open valve stem.  I quickly inserted the valve core and tightened it up, then added more air to compensate for what was lost during the valve core install.

I spun the wheel and to get the fluid all throughout the nooks and creavasses, then set it down to let it rest for a few minutes.  Once I didn't here any hissing of air escaping, I got a utility knife with a fresh blade and began to trim the excess tube flap that was hanging outside the rim/tire.  Using a fresh new blade is key, it doesn't take much pressure to trim the tube.  You really need to take your time and go slow so you are only cutting the tube.  I laid the knife against the side wall of the rim and used it as a guide keeping it at an angle to lessen the chance of cutting too deep.

After trimming both sides....and not slicing the side looked like this.....all trim and tubeless. 

This wheel set has been out on a couple rides now and is holding it's own.  Initially, the rear wasn't hold air and would lose pressure after about 24 hours.  I added a bit more fluid, spun and road the wheel and it's since held.  

The one unknown about this setup is just how easy or difficult it will be to keep that tube lined up when we have to change tires.  Having the extra flaps during the initial install made it easy to keep the tube aligned....not so sure it's gonna be that easy the next time.  But we'll blog that and let ya know.  Until then, keep the fat tire stoke high, and your PSI low!


Eric Anderson said...

Ghetto tubeless! I've done this and found it hard to do tire switches without using a new tube, unless you are pretty liberal with the amount of exposed tube "flap" on the outside of the rim. But then you lose the clean installation look. Works great though.

Anonymous said...

There's 3/4 of a tube left so how can it be tubeless?

Chaybo said...

Well, because the tube has been cut into a large, flat strip which no longer makes it a tube, correct?

If you were to look at Stan's tubeless conversion kit, you would see a very similar rubber strip that runs inside the rim, same as this, just really narrow.