I have been running tubeless tires on many of my mountain bikes for several years now and I have always liked the results. The benefits of being able to run lower pressures and eliminate pinch flats has been great. I have the standard complaints – burping the tire on the trail, having to top off sealant, leaking beads, etc…. but for  me, the benefits have outweighed the negatives.

So, when the opportunity came along to test out Orange’s Subzero fat tire tubeless system I was pretty excited about it. If any bike can benefit from a tubeless conversion a fat tire bike is it. Why is that? Several reasons actually. It is a generally well accepted fact  that rolling weight – or wheel weight – is one of the most noticeable elements of a bike. You can shave a pound off your bike with Carbon bars, posts, and bobbles and bits. Add some ano titanium bolts throughout your rig and Voila! You have shaved some weight and made your steed look pretty bling. But if you shave a pound off your wheelset, now that is something you feel. It may not be as sexy as a carbon railed saddle dipped in unobtainum but boy will you feel it. The bike will accelerate faster and easier, and feel more nimble and agile.

This effect is multiplied on a fat tire bike. Cornering momentum on a fat tire bike is a very real and noticeable thing. The weight of these wheels want to keep the bike standing up and rolling straight. Overcoming that force requires equal parts finesse and muscle. Something else that becomes very apparent with a fat  tire is the friction created between the tube and the inner surface of the tire. These rigs are generally  run at very low pressures (5-15 psi) to create a smoother ride and a better tire/snow interface. At these pressures the tube has more ability to move within the tire creating stick and slip  from within. While minor, it still affects acceleration and handling. So, if ever a wheel could benefit from the upsides of tubeless, a fat tire is it.

I knew this would be an interesting trial right from the start. The following is a summary of my conversion experience with the conversion and the subsequent ride experience. An important note. In the mountain bike world its almost just assumed  that most rims and tires are now tubeless compatible. The tire beads and rims are designed to mate up and seal effectively right from the start. The majority of fat tire rims and tires are NOT designed as tubeless systems. This is new and still being figured out.

The Set Up:

2014 Salsa Beargrease

45 North Dillinger Tires

Surly Holy Rolling Darryl Rims

Procedure:

1. Remove original tires and tubes from the rim
2. Clean the rim surface with a dry cloth to remove and oil or dirt on the surface
3. Trim the existing rim strip to create a better sealing surface for the tubeless tape. This can be trimmed back with an razor blade. If you are looking to personalize your bike a little, now is a good time to replace that existing rim strip with a new colour or even a reflective tape. Once you get the tubeless system in you will want to minimize how much you unseat your tires from the rim. 
4. Carefully stretch and place the rim tape into place over top of the existing rim strip. Work the edges of the tape onto the rim. go slowly and make sure that the tape is smooth and sealed and there are no buckles in the tape.
5. Reinstall the tire and the tube. and inflate the tire to 20-25 psi. Work the tire around the rim to ensure the bead has set. Let the tire sit with pressure for an hour or two. the pressure from the tube will press the tape firmly into place and seat the tire bead onto the rim.
6. Remove only one side of the tire, leaving the bead set on the other side. Remove the tube.
7. Install the tubeless presta stem.
8. Put the tire back on the rim and re-seat the bead by inflating the tire. a medium to high volume air compressor is recommended for this. A standard home compressor should do fine. Work the tire to set the bead firmly.
9. Deflate the tire through the valve and remove the valve core. This can be don with a core remover or with a pair of needle nose pliers. Make sure the tire is fully deflated before removing the core or the pressure can shoot the core out while you unthread it – and it is a small part that is easily lost!
10. Load sealant into tire. I used 3-4 oz. per tire. I found the easiest method is to use a syringe that threads onto the valve stem but you can pour it in with a nozzle as well. The syringe is cleaner, simpler, and more accurate though. 
11. Reinstall valve core and inflate tire to 20-25 psi. Spin the tire repeatedly allowing sealant to work its way through the air channels. 
12. Allow the tire to sit over night. The tire may deflate the first few times. continue to reniflate and rotate the tire. listen for air leaks and rotate to that point to allow sealant to work its way through. This is normal. My tires bled down 4 times before finally seating in.

General Impression:

• Bead Seal – Getting the tire bead to seal was a bit of a trick. I tried multiple methods to try and create more sealing force in the tire and the one that worked the best was the method mentioned above. The real trick is having an air compressor that can dump a high enough volume of air into the tire fast enough to create a large pressure differential. If your compressor can’t keep up then the air will just slowly bleed out. As I mentioned, these rims/tires are not a tubeless design so seeing a great deal of sealant come through was not surprising. I assumed I would have to top the tire off with sealant and air multiple times before getting it to lock in.

• The Rim Strip – Orange’s rim tape was a little narrower than I would have liked. A few extra millimeters of width would have given me better coverage over the rim surface and may have sealed better. It was thin and light weight, which is a plus, but I felt like I could have used something with a stronger adhesive. As mentioned above – I used the tube to reset the bead and press the tape to the rim on my rear tire. However, on the front I pressed the tape on by hand only. after adding sealant to both I had leakage through the rim cut outs – which means sealant was working its way around the tape. I had less on the rear tire, which would imply the tape had a better seal, but there was still leakage.

• Valve Stems – The valve stems in the kit had an easily removed core which made adding sealant a breeze. However, I found the the sealing donuts provided did not create a 100% effective seal. No matter how much I cranked down the nut, I still had noticeable seepage through the valve hole.

• The First Ride – The front tire proved to be very leaky on the first ride. I rode 10 miles at the Kincaid STA trails and had to pump the tire several times. But, the tire sealed a little better each time. The first time was within the first 0.5 mi and the pressure was very low. The second time was about 1 mi later and still low. The third time was another 1.5-2 mi down the trail and only marginally low. After that I didn’t have inflate it again. When I finished the ride the pressure was slightly lower than my last top off. The rear tire held fine.

• The Second Ride: The bike went on loan for a short 5-10 mi loop and both tires were topped off before leaving. The rear tire proved a little more problematic on the second ride and lost pressure throughout but the front held much better.

• The Third Ride: Another 8 miles at Kincaid and I topped up the tires before leaving. No major losses but some leakage.

• Ride Quality: There was a noticeable improvement in ride quality. The bike handled much quicker and was very nimble. Acceleration and braking were improved and the overall experience felt faster and more controlled. The bike became more manageable and faster in the corners. weight savings are roughly 0.75 to 1 pound per tire depending on the existing tubes and the amount of sealant added.

Overall, I am quite happy with the ride improvement of the bike but I think the system will need a little more work to get it just right. My plan now is to add more sealant to see if that helps shut off the slow leaks. If that doesn’t help then I plan to rebuild the system with a different rim tape to see if that helps the overall effectiveness.

I have yet to test the seal in extreme low temperatures – which is suppose to be a benefit of the subzero system. Other sealants have been reported to freeze or solidify in very low temp ranges whereas this product is formulated for that environment. As my long term test continues I will evaluate that element as well.