Save your fat tire

02/12/2017

If you’ve ridden your bike in the Agreement Forest post-snowstorm you’d know you’ve got to let a bit (okay a lot) of tire pressure out to maximise your bike’s traction. You will inevitably start having an awesome time after freeing a few psi, but then there comes that horrible thunk. Hopefully it’s not a thunk-hiss. Yup, the rocks are still buried in that snow. Repeat this process enough times and even the toughest tire (or worse your rim) will give up the ghost. If you’ve owned a fat bike you know that the cost for one or two tires could easily set you back a few hundred – Damn.

Well, there is a cheap DIY solution the folks at HAFTA have been testing over the last few months and we’d like to share it with you. Turn those thunks into gentle thuds and save your sidewalls. This setup does require that you already be running tubeless, sorry about that if you’re not.

Disclaimer: Please exercise care and examine each step below. Take a moment to see if it seems safe to you, if not then stop. We make no guarantees about the safety of the below system and it might void your tire warranty or something. The onus is on you! 

Okay, to set this up you’ll need:

  • 1 sheet of dense closed-cell foam (it must be closed-cell otherwise it swells with sealant) – 10mm thick material is a good width. A cheap camping mattress pad can work, but if you can find denser foam it will be better. Yoga mat is too thin 🙂
  • 2 or 4 zipties
  • 1  ruler or callipers
  • 1  box cutter

Step 1: Measure the width of your inflated rear tire at its widest point and the width of the rim.

Step 2: Remove your rear tire from the frame and deflate it until there is enough air inside that it holds its shape, but is easily deformed by your hand. Place the wheel on a nearby set of carpeted stairs such that the disc rotor is facing downwards into the space between the two steps. On the down step or up step, line the lower edge of the rim up with the edge of that step. Make sure only the rim is contacting the steps, not your spokes or disc rotor. Stand on the top of the wheel and use the other foot to progressively weight the tire until it unseats. It might go bang and you might slip, so be ready for that – Hold onto the railing and use shoes.

Step 3: Mark and cut a strip of the closed cell-foam sheet at a width somewhere between the rim width and the tire’s maximum width. The strip must be greater than the rim width and less than the tire’s width in order to resist snake bites and sidewall cuts while not interfering with the tire’s sidewall.

Step 4: Eye up the circumference of the foam strip to the tire’s circumference at its widest point. If your foam strip is not long enough, cut another one and use some zip-ties to append it to the first one. Make sure the fit won’t interfere with the tire’s sidewall through its diameter being too short or long. Try and line that foam strip up to where the tire is widest.

Step 5: Cut some notches in the foam strip so air and tire sealant can float freely between the tread and rim. This will also relive interaction between the foam-strip and sidewall under normal riding.

Step 6: Zip-tie the strip into a circle. Careful with the ends of the zip-ties, don’t leave sharp edges.

Step 7: Put that bad boy back in the tire, add a bit more sealant as the foam will absorb a bit on it’s surface. Reseat the tire, inflate and rock out.

There are lots of brands doing this with nice foam and custom stuff (Huck Norris, Flat tire defender), but no options for the fat tires yet. This will probably add a bit of rolling resistance and weight to your tire, but they’re fat bike tires and it’s rocky out there.

Cheers!