tire pressure

Just wondering how you determine what tire pressure to use on your uni. I mainly street ride and run into small bumps/road surprises. Do you vary your tire pressure a lot?

If the tire feels to squishy, I add some air. If it needs to be squishier, I let some air out.

Higher tire pressure helps with idling. In order to stay on the uni while idling, I have to be able to pivot left and right while going forward and backward (I am still a novice idler). Low tire pressure adds friction while idling, making it harder to pivot.

High tire pressure makes everything more twitchy, due to the decrease in surface area of the tire which is touching the ground. Learning to control twitchiness means, I think, that we are controlling the unicycle.

I don’t have much experience riding on rough pavement at significant speed. It sounds like lowering tire pressure from the maximum…may have some safety advantage. I went for a long ride on my Muni with a street tire which was under lower pressure. I felt like the Muni was bobbing up and down, which was unpleasant.

For beginners learning to self-mount, lower tire pressure might help stabilize the uni during mounting. It’s nice to lower the tire pressure when learning to jump onto and off curbs. As skills progress, increasing tire pressure is practical for a larger repertoire of techniques.

Some of the videos of street riders show the tires flattening out during take-offs and landings. Their tire pressure may be higher than some may assume; they are placing serious pressure on their tires.

The following are generalizations regarding the progression from beginner to advanced unicyclist, based on many posts I’ve read on the forum.

  1. Crank length decreases.
  2. Seat height increases.
  3. Tire pressure increases.

This pretty much.

When I first started 36er riding, I put the TA tyre to its recommended max (32psi) which was FAR too low. I’m not intending to go 36er MUni’ing, so I just wanted it to be a fast road machine. I decided to ignore the recommendation, and jacked it up to 60PSI (Same as I run my 29er at on-road). It immediately felt much more twitchy, and a LOT smoother/less resistance. However, it bounced about all over the place on rough roads. I’ve settled on about 50PSI. Gives enough squish to handle the crap roads round here without it just bottoming out everytime I put pressure on the pedals.

For my 29er (Which is my ‘hybrid’, thoug in the new year I’m planning on turning it into a full MUni now I have the 36er for roading) I went through a similar process. But if I know it’s gonna be a day of nothing but off-road, I’ll just let some pressure out, and give it a bit more squish for the mud. I’m not too scientific about it, if it feels too soft I’ll add some more till it feels nice.

I also have a TA 36" tire on a Qu-Ax. I was running the tire at 32 PSI and tried the higher pressure of 50 PSI for a while. I did this because of advice posted somewhere on this forum. After experimenting a bit I find that the higher pressure has advantages if used on smooth terrain and for higher speeds but requires more active control which uses up some of your energy. The lower pressure has an advantage in this respect when riding on bumpy roads or uneven streets. With lower pressures the big wheel seems to be more tolerant to uneven road. If i relax and just make sure it keeps rolling i have spend less effort to control center of gravity. So at lower speeds with shorter, high speed crank lengths this may be a factor to consider.

I am amazed how much the feel of the 36" ride changes after minor adjustments in these parameters.

At work we are currently planning to build a wearable sensor suite for team sports (I am a teacher at a polytechnic). It may be interesting to adapt one to research this issue.

There was an interesting report put out by Schwalbe a while back that examined the relationship between tire pressure and rolling resistance on various surfaces (with various tires). It was a fairly lengthy document, but below is one graph from it that relates to this discussion. It illustrates the not-very-intuitive idea that while higher pressure reduces rolling resistance when road riding, lower pressure actually reduces it in the dirt. I’ve experimented with this (within my own limited scope), and found it correct for the type of riding I do.

tire pressure.JPG

Not surprising really. Higher pressure reduces the contact area. On a soft surface this makes it sink in further. More energy is used displacing the road material.

As far as rolling resistance is concerned i agree. But i was thinking about the energy expended to keep the unicycle upright. Higher tire pressure results in a stiffer suspension, which consists for a large part of the spring action formed by the tire. If you ride over a small block or tree root with low pressure tires you can just continue without too much trouble. On a high pressure tire you are propelled upwards and out of balance. requiring more effort for correction.

So compared to the advantage of having lower riding resistance the overall effort may be less. I haven’t found the optimum yet.

I am settling into it and it is higher than I originally expected. Riding broken pavement and streets on a 24 inch Maxxis DTH. I am currently up to about 50 psi (80 kg rider). This pressure used to launch me not long ago.

Dealing with the perturbations seems an ever changing skill. The disconnection between the uni roll and the inertia of my body continues to increase as I stumble across more options to drive through the rough bits.

These things are what makes the sport interesting. Sometimes you have what rockclimbers refer to as a high gravity day:)

I really need to look into the relationship between tire pressure and energy needed to maintain control on my 36er. I have found I seem to be exerting a lot of energy to maintain my balance with max psi in the Uni. Thanks for all the input.

If it makes you feel better, neither have I. I would prefer to run a lower pressure than I do for trail riding, but anything more than a 1’ drop get’s my rim a bit too close to bottoming out for me. Therefore, I’m in a constant state of riding too high of pressure, or bouncing my rim off of rocks.

I don’t have a tire gage but will get one tomorrow. I let some air out of my tire and had the best ride to date. Very easy to control and a noticeably smooth ride. Loved it! Thanks for all the help!

Each of my unis generally use them for a specific type of riding, so when I find the pressure I like I generally don’t change it. A different tire usually needs a different pressure to get a similar ride.

I use a digital Guage in 0.5 psi increments. My freestyle is usually at 30 psi one tire I needed 45 to get a similar ride. My Muni has really low pressure. Depending on the tire my ideal psi has varied from 11-13.5 psi.

This appears to be the thread for this. I have recently gotten a new tire and am trying to dial in the pressure for it. It is (or is like) this one. http://www.amazon.com/CST-Salvo-High-Protection-1-75-Inch/dp/ The profile is quite round, not peaked in the middle as the picture makes it appear.

My old tire was very heavy. It was two tires, actually, but I won’t bore you with the details of that here. It also was a 2.0" tire and was worn down to a rather flat profile. I was quite used to riding on it. I do road riding.

The new tire is obviously narrower, lighter, and rounder in profile, and I am having a hard time getting used to it. The thing is this. If I run it at a low pressure - say, 40 psi, I can handle it pretty well. I rode in Tour de Nash like that. I miss the flywheel effect which I was apparently using to my advantage. If I run it higher, my contact patch feels narrow and it offers little resistance to twisting. I also miss the flywheel effect which I was apparently using to my advantage with the heavier tire. It is a lot of work to maintain side-to-side balance. It feels kind of like I’m learning to ride again. Which is fine, if that’s the way it’s supposed to be. I’ll put in the work if it’s the right thing to do. I am not suffering from bounciness or an excessively rough ride, which are the usual indicators of running at too high of a pressure. I’m also not exceeding or even attaining the maximum rated pressure for the tire.

The obvious thing would be to run at low pressure, since that works. But, on the other hand, if I should be able to control the thing at higher pressures, perhaps that’s a direction I should go in to become a better rider.

Also, I seem to wear through tires quickly and have historically run at low pressures based on feel, not psi; so thinking that perhaps having too large of a contact patch causes scrubbing, thus excessive wear, leads me to look into higher pressures. I would also expect excessive pressure to cause concentrated wear in the center of the tread (but without as much scrubbing), so there’s that to consider too.