I don’t know if a real 0 psi tire exists with a still resonnable weight. However, the fat bike tire are usually used at 4 psi. They are not light nor cheap but it makes for a smooth ride (too smooth for uni handling except on snow 
).
Well there’s always wheelchair rubber if you want 0 psi…
I have been playing a lot with tire pressure lately on all of my various 'cycles. With that in mind this is an interesting thread for sure.
If we look to Frank Berto’s article on road bike pressure for guidance we should be considering the rider weight, and mounted tire volume along with pressure. What he found for bicycles was that a 15% drop in the tire height with the weight of the rider gets you into the sweet spot between rolling resistance, comfort, and handling. In his method it is the actual width of the mounted tire under pressure that matters, and not the published width. This would therefore also take into account the rim width which we know has an effect on tire volume.
I’m not suggesting that the same 15% drop is appropriate for unicycles, and my guess is that the sweet spot for the drop will be different for a road going machine versus MUni. It would be interesting to see how the various numbers people are putting up on the board compare to drop as defined by mr. Berto.
My guess is that we won’t ever really know because we don’t have a standard way to measure it, and the possibility for consistent data is fairly weak. If riders who have many different tires on a few different size uni’s could somehow measure their own fleet to at least show if there is relative tire drop that would be a start.
tyre drop sounds more viable than saying there is a correct pressure.
only how would we ever accurately measure 15% ( or more for a uni ) sage in a tyre…?
I used to be a pump it up until it rolls good. Now i am go as low as you can go without sacrificing too much of anything.
Tubeless with the supergravity schwalbe enduro tyre allows me to get the most out of lower pressures, side wall strength and support, rolling resistance and ultimately grip. and grip without requiring a huge heavy wide rim.
I wont be surprised if the Muni industry changes rim and tyre arrays when the go towards this. I believe mostly tried and tested vigorously by BenNurse
If you want the best of muni re: tyre, rim and pressures. He has the experience dont hesitate to try anything he has done. so glad i did.
Muni just got BETTER!
like to thank…
KH for wonderful Unis
Ben Nurse for the inspirations
Stans for no more tubes! (throught chainreactioncycles dot com)
Schwalbe for Enduro tyres and the almightly Hans Dampf
Hmmm… That is an interesting article on tire drop and ties in with what I use on my ROAD bike with a 700x20 front, 700x23 back both at 100 psi. With me (130#) plus bike (<20#) and 2/3’s of my weight over the rear wheel the graph would agree with that pressure choice. On skinny tires like these my ride is quite harsh and road surface bumps and imperfections are all felt. But I ride my souped up twitchy road bike with steep angles and short wheelbase because its like a responsive race car : )
From an efficiency perspective on the ROAD bike the idea of not running the max rated psi of 130 on high end tires was that rather than bouncing up and down on the road surface the tire would to some extent roll through minor road irregularities.
All good stuff, but…
We’re talking MUNI here where there is less emphasis on efficiency and more on what makes a trail more rideable. I think a lot of us aim for that sweet spot of the lowest pressure that maintains enough tire shape integrity and/or is just enough to avoid 99.5% of rim strikes for our riding style.
I think my light weight and a tube is enough to keep the regular Hans Dampf side wall providing enough support. Some of the bigger riders are seeing that they can go too light on tire construction and the enduros are fulfilling their needs.
I do note that a couple of lighter riders are running higher pressures in the Duro than I do. My trails have lots of root gardens that bounce me off at higher pressures. As my skills have been improving I am getting better at negotiating these sections using my legs for suspension and have moved from the heavy 3.0 Duro to lighter 2.3x tires. Climbing is better on the lighter less rolling resistance tire set ups (as long as I can negotiate the trail bumps, roots and stones).
Definitely fun to experiment and challenge ones self.
pax
I still think that if we had a good way to measure drop it would offer a better point of comparison. It might be as easy as having someone measure the spindle to ground with your weight on the saddle, and the same measure with the unweighted uni. I will try it tomorrow. It would also eliminate the false data supplied by our pressure gauge. As long as the drop is correct it doesn’t matter what reading shows up on the gauge. It only matters that the pressure is consistent at any particular reading.
Okay, I’ll play along with some data…
130# rider Schwalbe 29x2.35 Hans Dampf snakeskin pacestar with tube. Measurements are from ground (hard concrete) to where the tire meets the rim.
17.3 psi (my preferred pressure plus or minus a couple of tenths on a digital guage) 56mm drops to 45mm. 20% drop.
16.4 psi (too low- I felt the rim a couple of times hitting some of the bigger roots this morning) 55mm drops to 43mm. 22% drop.
I’m running the 29-er as a light muni setup on an old Nimbus road 29 with the stock single wall RD2938 rim.
pax
enduro tyres for heavy riders
63kg am i a heavy weight class rider…interesting lol
Tubeless can can mush lower pressure than a light 29er tube if its a desire and a flat tyre specially with thicker sidewalls is almost never. Yet to be heard of on a tubeless uni.
any bike that is top end or in a race with experienced riders we find they convert and run tubeless and run relatively lower pressure according to the terrain on the day. speed is nothing without grip and reliability.
tubeless for maximum muni tyre pressure reliability, ( Kepping pressure and preventing flats ) and range ( psi range )
paxuni - end of the year a 29er Han in super grav will be available so keep an eye for it and try tubeless? Wouldnt like to be hitting rims specially with tube inside… and with the thicker walls you can safely run 16psi if you wanted