Friday, February 15, 2013

Fat tire tubeless conversions

Mountain bikers have been using various tubeless systems for years now to save weight, improve puncture resistance, and/or to reduce rolling resistance. There are various tubeless systems for various rims and tires, but nobody has a commercial tubeless kit for fat bikes. We found some fat-tubeless how-to advice on the internet, and decided to pair this advice with our own dead reckoning to roll our own fat tire tubeless kit.

Here's a fairly standard modern-day Surly fat rim, a Rolling Darryl in this case. This is a 82 mm wide single-wall rim with cutouts and a Surly PVC rim strip sized for this rim. The rim has a somewhat deep channel that we decided to fill with a strip of foam insulation. The ideal width is just barely wider than the cutouts, just enough to fill the rim channel. A little packing tape holds the foam in place.

Next, slightly inflate a really fat 24" tube and stretch it over the rim, putting the valve through the valve hole in the rim in the usual way. This one is labeled 24x2.4-2.75", which is wide enough for rims up to 100 mm. Once the tube is in place, start laying it open with scissors, as shown here.

After cutting the tube open, it should look like this.
Then put the tire on over the split tube such the the tube is between the tire bead and the hook of the rim. The tube should stick out the sides, like this.
Now pump up the tire to make sure the tire can seat on the rim with the tube pinched between the tire bead and the hook on the rim. It might be tricky to get the bead to seat since the air you pump in isn't contained by anything. An air compressor helps.

Once you've verified that the tire will bead and hold air without a tube, let the air out, and pour in some Stan's NoTubes sealant. We used three 2-oz scoops per tire. You can also use the injector to squirt sealant into the valve, but the high volume required makes this a tedious process. The funnel is faster.
As before, seat the bead and inflate the tire again, exercising care not to spill the sealant fluid. When you're confident that the tire is seated, shake and spin to ensure that the sealant works it's way into the nooks and crannies between the rim and tire to seal any potential leaks.
Finally, trim the protruding tube with a sharp razor or knife. Careful not to slash the sidewall on your $150 tire. When you're done, it will be difficult to know that this any different than a standard tube set-up.
Inflate the tires to near-max pressure (25ish psi) and wait a day or two to make sure they're holding air. Then go out and ride it:
I've been riding tubeless on my pugsley for a couple weeks now. Weight savings over the usual Surly 26x4 tubes is about 50g per wheel, which by itself is probably not worth the effort, especially since there are substantially lighter 26x2.7" tubes that seem to work for some people. Initially, my motivation was not weight savings, but puncture resistance, which will be nice for summer off-trail woods riding, the urban jungle, or vacations in the thorny desert. Now after some experience I'd add another motivation: I think the tires roll better, especially at squishy low pressure, since there is no tube flexing inside the tire to increase rolling resistance.

We could perform this service for you. Parts and labor for two fat wheels would run about $120.

For more on tubeless, see some of Stan's videos. I especially like the Puncture Demo video.


Anonymous said...

Jim - something doesn't square here (for me). How can you shave 50 grams from the total wheel weight if you still have a cut up tube, sealant, foam and packing tape still inside the tire? Seems like a lot of stuff that should add up to MORE weight if I'm calculating correctly.

Jim Thill said...

The Surly 26x4 tubes are pretty heavy, even compared to the stuff that goes into the tubeless set-up.

Dweendaddy said...

"it will be difficult to know that this any different than a standard tube set-up." Which is why I would find it hard to justify messing with that goop or paying someone $120 to do it.
But I love reading about it and will look forward to hearing about how you rock them this summer!

phaedrus said...

Maybe I'm misunderstanding something, but how is it more puncture resistant than a tire + tube? To puncture a tube, doesn't an object have to first go through the tire and if it goes through the tire, won't you have a flat at that point?

Jim Thill said...

Please watch the puncture demo video I linked at the end. This is how it's different than a tubed tire. This is why somebody might be willing to spend money to do it.

Anonymous said...

What handlebars are you running on your Pugs?

Jim Thill said...

Soma Clarence.

bsimon said...

Just got around to following these instructions tonight, minus the bubble wrap. Its a pretty easy job; caveats: I used 1) tubes with removable valve cores, 2) the injector tool, 3) an air compressor & 4) tires with miles on them. I'm not sure if new tires would be harder to seat. Thanks for the writeup Jim!

Erik Ross said...

$120???? Why do you have to be all the way in Minnesota?? I've gone through about 5 tubes since getting my Fatty and I'm struggling to get the tubeless system to hold air. I'll give your approach a try next.

Thanks for the tips.

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