What pressure for hopping ?

Hi !

I saw a guy hopping in a video and the tire seamed to be deflated for the
purpose… Is it recommended to lower the pressure when hopping in order
to create more rebound or more stability while trying to stay on the spot
? If so, what’s the recommended pressure (I know that tires do not have
the same rec. pressure but how much in % below recommended pressure ?)

Thanks in advance !

Christ.

'Gonna be a hopping weekend ! I just discovered I could do it not so badly
and I’m like a child !

In my experience it is a sort of trial and error method. You want just
enough pressure that the tire doesn’t bottom out against the rim when
hopping on the narrowest object you plan to hop on. If you frequently
flatten tubes with snakebites or dent rims then add air.

With the the wide variety of tires and their varying profiles I don’t
think you can simply say X% of recommended inflation is optimal.

Also, the riding surface makes a big difference. For hopping (not jumping)
on hard surfaces (like concrete) I usually keep the tire fully inflated.
On softer surfaces like mountain trails I’d deflate the tire some.

Jumping is a different story for me. I’m still working on being able to
jump. Seems to me that to maximize the height of the jump the tire
pressure should be such that the tire nearly bottoms out just as your legs
begin to extend into the jump.

I’ve been thinking about this lately though, and maybe someone can clarify
something for me. Take a basketball and inflate it 50%. Now Drop it from
6’. How high does it bounce? Now inflate the basketball to 100% and repeat
the exersise. It bounces higher right? Ok, now over inflate the ball to
120%. It will bounce even higher right? So, a fully inflated tire should
bounce higher? This seems counter to my experience. Why does it feel like
I can hop higher when the tire is partially deflated?

-mg

“Christian St-Pierre” <Christian.St-Pierre@fse.ulaval.ca> wrote in message
news:3BD0609C.2B66D442@fse.ulaval.ca
> Hi !
>
> I saw a guy hopping in a video and the tire seamed to be deflated for
> the purpose… Is it recommended to lower the pressure when hopping in
> order to create more rebound or more stability while trying to stay on
> the spot ? If so, what’s the recommended pressure (I know that tires do
> not have the same rec. pressure but how much in % below recommended
> pressure ?)
>
> Thanks in advance !
>
> Christ.
>
> 'Gonna be a hopping weekend ! I just discovered I could do it not so
> badly and I’m like a child !

Hi,

I have had the same questions. Also, can we consider tire pressure on inclined surfaces. My Gazz at 22psi feels like it folds easily on inclines when going up side ways. What pressure did Kris Holm run in the Santa Cruz scene in Universe? There were tons of inclined surfaces on those rocks.

If the tire feels like it is folding over then try more air and see how it
feels when side hopping the same incline. There is no right universal tire
pressure that works for everyone. It all depends on your weight, your
riding style, the tire, the rim, the terrain, etc. etc. Experiment and see
what works best for you in different situations. There is a little blurb
on http://www.muniac.com/tips.htm about tire pressure. It’s a little set
of questions that may help you find a tire pressure that works for you.
Ultimately it ends up being a mix of compromises. Enough air so you don’t
pinch flat or fold the tire and yet soft enough so you have good traction
and a controllable bounce when you hit roots and stuff.

john_childs

“teachndad” <forum.member@unicyclist.com>
>Hi,
>
> I have had the same questions. Also, can we consider tire pressure on
> inclined surfaces. My Gazz at 22psi feels like it folds easily on
> inclines when going up side ways. What pressure did Kris Holm run in the
> Santa Cruz scene in Universe? There were tons of inclined surfaces on
> those rocks.

It’s compression and rebound rate. With more pressure the compression rate
and rebound rate in the tire is much faster. With more pressure in the
tire you need to snap more quickly at the moment you jump to take
advantage of the rebound in the tire. With less pressure it is easier to
sync up with the rebound of the tire and you don’t have to snap as quickly
with the jump. For those of us without explosive fast twitch muscle fibers
it is easier to jump with less tire pressure.

john_childs

“Michael Grant” <michael_j_grant@yahoo.com> [snip]
> Jumping is a different story for me. I’m still working on being able to
> jump. Seems to me that to maximize the height of the jump the tire
pressure
> should be such that the tire nearly bottoms out just as your legs begin
> to extend into the jump.
>
> I’ve been thinking about this lately though, and maybe someone can
> clarify something for me. Take a basketball and inflate it 50%. Now
> Drop it from 6’. How high does it bounce? Now inflate the basketball to
> 100% and
repeat
> the exersise. It bounces higher right? Ok, now over inflate the ball to
> 120%. It will bounce even higher right? So, a fully inflated tire should
> bounce higher? This seems counter to my experience. Why does it feel
like
> I can hop higher when the tire is partially deflated?
>
> -mg