Well yes, yes you can.
Whilst investigating a tyre system for my hardtails to help prevent flats and dinged rims. I looked at some of the options on the market and came to the conclusion that I could make that. Now the foam I used is not specially designed and formulated for MTB, but that doesn’t mean its not suitable for the application.
I used a closed cell foam, which is similar to yoga and old style camping mats, it is dense and light. It is also non absorbent, a crucial characteristic for something that will spend its life swimming in tyre sealant. I sourced some rolls online that looked like they could do the job, hit the order button and waited to see what would come.
The foam is easy to cut with a fresh scalpel blade, however, why cut it all by hand when you can use a laser to do the job for you?
A laser cutter is a computer controlled machine that uses a vector (fancy computer drawing) to guide a laser to either cut or engrave a surface.
I used Adobe Illustrator to create my design, refining and going through various drafts and iterations of the drawing. I worked through this drawing process before settling on something close to the final insert before making my first laser cuts.
I find I really need to hold a physical object to help make design decisions
When using a laser cutter you calibrate the laser for the material you are cutting, changing the speed or intensity of the laser until it cuts the material cleanly. Laser cutters are ideal for intricate designs or small run batch production, so cutting some foam wasn’t really stretching the machine.
With the machine dialled in, I then made a few test pieces. Whilst seeing and measuring designs in the software is useful, I find I really need to hold a physical object to help make design decisions. So after a few alterations to the drawings we were ready to go.
Once cut and hand assembled it was time to install and test a set.
Installation was a pain free affair, simply the normal process of setting up a tubeless tyre. The insert had the fringe benefit of helping hold the tyre bead against the rim, aiding with tubeless set up. I did use more sealant than usual, whilst the foam is non absorbent, placing the insert int he tyre did increase the internal surface area. So sealant would not go as far, hence more was required, I added 1oz more than normal.
Once fitted it was time to test it, I sessioned a rooty section of trail with some drops and sharp rocks. I dropped some PSI from the rear tyre to see how it would handle, the theory being that if the rim has some additional protection, I can run the tyre softer thus increasing grip and traction.
The tyre (a WTB Trailboss) held well on the roots and didn’t deflect, on the rocks it gripped predictably. I bottomed out my shock a few times but the rim went undinged. This gave me the confidence to try other lines, bunny hopping over roots into sharp rock sections ultimately going faster.
Throughout the tyre felt secure and didn’t feel like the sidewall was going to fold, even with lower than usual tyre pressure. I later changed the tyre to discover a few slight cuts into the foam, this would normally have been a good old ding on the rim. Now we cant say for sure that these hits would have dented the rim or punctured the tyre, but both the tyre and rim were fine.
You could argue that the inserts acted like a placebo, like a rock that keeps tigers away. You can’t prove its working, but I don’t see any tigers around. That said the simple piece of mind and extra confidence in a race situation is almost worth it in itself.
I don’t see how the added rim and tyre protection would be required on the front tyre. I have only installed them on rear tyres as that is where I have most need for protection, if I rode downhill I might have more need for inserts front and back.
So can you make your own tyre inserts? Yes you can, a little bit of time and work (and access to a laser cutter) and you can make a whole load for you and your friends, time rich and laser cutter poor? A steady hand and some scalpel blades will probably get the job done, although you’ll probably only want to make one.