Tire touches rim when I jump. NEED HELP!

I have been jumping around on my new Nimbus Trials and I’m trying to find out how much to inflate it. When I jump SI and pound my legs as hard as I can against the ground, it touches the rim. But the reality is: I never SI that hard and most of my jumping is SIF. So, regularly, I’d never really hit the rim, but I need to know if I should inflate my tire more.


inflate it so it squishes alittle bit. enough to propell you throught the air, but not to much or then you wont be able to jump. soo when you sif, your still gonna want to inflate it more… the only reason you dont THINK its touching rim is because you dont notice it.

bottom out your tyre enough and you will get a snake-bit puncture, do it some more and you will knock your wheel out of shape. Your tyre pressure should be enough that you never hit the rim in the course of your normal riding.

that’s the thing, when I ride regularly, I don’t hi the rim.

So what’s the question? You have already found the perfect mix for yourself.

Then take a pump around with you and change the typre pressure according to whatever you’re doing - problem solved.

thanks to joe2005, I now know that when I do my regular riding, I don’t hit the rim, so no problem.

but I have one more questions,

  1. the only time I might risk hitting the rim on my unicycle is when i do a freakishly large drop, does that happen to anybody?
    What I’m thinking I should do in that case is just increase my tire pressure before I do the drop.

What say you?

Also, where can I find out what my tire pressure is? My pump doesn’t tell you the psi.

Kinda like I just said…

also, when I do a pre hop before a SI hop, my tire barely (but does) touch the rim, should I inflate my tire. Keep in mind, I don’t normally do a big prehop before a SI

Inflate it gradually until it doesn’t touch the rim.

would somebody post a picture of how much their tire deflates when they do a big jump

I think that may be a bit tricky, to be honest… Just pump your tyre up so the rim doesn’t hit the ground on drops, then let it down after if you want.

here’s the thing,

I don’t know if what I’m feeling is the tire hitting the rim, or just a big rebound of the jump.

When I just went outside, I jumped with as much force as I could and I got massive air, but I’m not sure I’f my rim hit the ground. It felt like it might’ve hit but I also think it was just a rebound.

Now, regularly, I wouldn’t pound as hard. But I just can’t tell whether or not my uni’s rim hits the ground.

If it barely hits the rim, will the rim break?

Am I worrying to much :thinking: :thinking: :thinking: :thinking: :thinking:

That’s it right there. PSI numbers mean nothing, and a picture of the tire, if you could get it at the exact moment, which would be cool, would not be very useful. You can feel if/when your rim is hitting the ground and that’s what you have to avoid. The amount of pressure required to do that is not something anyone can know because it depends on your exact tire, rim, rider weight, temperature, altitude and how hard you jump/land.

So keep a pump nearby, and adjust as needed. With some practice you’ll have a pretty good idea of what you need most of the time. Also it’s better to put in more air than you need when pumping, then lower it to suit. Easier than pumping over and over…

but what i’m asking is, how to you know whether the impact your feeling is a rebound or the rim hitting the ground?

Well, you could ask someone to watch you do it and they will tell you.

if you are rimming hard enough to do damage (no jokes please) you will feel it as a sudden jolt where you suddenly stop moving down any further. Maybe try letting your tyre right down and doing it gently on purpose to see what I mean. It seems like your options are: pump it up for big drops, leave it pumped up enough for big drops all the time, or don’t do big drops. If you’re going to keep going up and down a tyre presure gauge would be really helpful so you don’t need to go through trial and error every time.

Do a small hop up w/ low pressure to make sure you are feeling the right thing, then up the pressure by 5 psi untill you don’t feel it anymore. Then reapeat w/ bigger hops up, and do the same w/ drops starting w/ smaller ones.

This should give you an idea how much you need for different situations. It’s better to err on a bit too much pressure so you don’t damage your rim.

I carry around a compact pump and a digital air pressure guage that give readings down to .5 psi. (not that I really need it that accurate, but it’s helpfull on my air seat :sunglasses: ).

Ok, you already know what it feels like when you bottom out, so its gonna feel about the same everytime.

Right now you are at the point where if you are regular riding, you are fine, but, if you put a decent force of a prehop down, you hit the rim. Now when you start doing bigger drops, not freakishly large, but around 4-5 feet, you will hit the rim.

So, just pump it up one or two more pumps from where you are at now.

John said PSI doesnt matter, and thats partially true. For me, for my tire, rim, my weight and how I ride, I do have a PSI number. It took a while to find it, cause I do a lot of drops, so I had to mess with a lot of pressure to still have bounce, and still be able to hold up to large drops, but I found it easily, and

Finding your point is very easy. Fill your tire up hard, then gradually let small amounts of air out untill you arent bottoming out, and you still have bounce.