To what extent can I safely over-inflate the uni tyre? I’m currently pretty
heavy (250 pounds) and the tyre gets squashed quite flat. Good traction I
suppose…
The tyre says “inflate to 40psi”.
http://www.foxholly.demon.co.uk ICQ# 30592054
Re: Over-inflation
There are several 20" bmx freestyle or flatlander tires available that are
rated at 65 psi and even up to 100 psi. Finding similar 24" tires will be
difficult but they may be around. Another option would be a 26" uni with a high
pressure MTB tire.
When going to the higher pressures make sure you have a high quality rim
and that the tire bead is properly seated. The rim that comes standard on
many (most?) unis is not what I would consider a high quality rim. If you
think you may have a questionable rim ask a bike shop for an opinion before
trying 100 psi.
Over-inflation is the norm on unicycles.
>To what extent can I safely over-inflate the uni tyre? I’m currently pretty
>heavy (250 pounds) and the tyre gets squashed quite flat. Good traction I
>suppose…
>
>The tyre says “inflate to 40psi”.
>
>Arnold the Aardvark
>===========================
>http://www.foxholly.demon.co.uk ICQ# 30592054
>
Get Your Private, Free Email at http://www.hotmail.com
RE: Over-inflation
Ian Smith wrote:
> In article <01bef133$c232fc60$d056989e@foxholly.demon.co.uk>, Arnold the
> Aardvark wrote:
>
> >To what extent can I safely over-inflate the uni tyre? I’m currently pretty
> >heavy (250 pounds) and the tyre gets squashed quite flat. Good traction I
> >suppose…
> >
> >The tyre says “inflate to 40psi”.
>
> In Europe (no idea what the liability issues are in the US) the reqirement is
> that the manufacturers have to inflate the tyre to twice its rated value and
> leave it for some time (can’t remember how long) and it has to not blow off
> the rim.
That’s true. But the problem with that “proof” of durability is that the tyre is
not used while inflated. Most damages occur while stressing the tyre, not while
storing it.
> On my unicycle I go up to about 2.5 times what it says sometimes. Generally
> I’m a bit under twice. Being naturally cautious, I don’t inflate it with my
> head pressed against the tyre (just in case) but nothing’s exploded yet.
I can confirm that. But overinflated tyres wear out much faster than not
overinflated ones. Especially the side walls will become cracks quite soon.
> It does over-load the side-walls and I’ve had a couple of tyres that the
> beading wripped from the side-wall (one quite suddenly, one over the course of
> a few days riding). This is entertaining 'cos sometimes the inner tube escapes
> through the hole and expands to about the size of a tractor tyre once it’s out
> - it’s like a giant anaconda desides to come rushing out the hole. I guess
> that if you’re unlucky at this point the tube explodes.
There may be another problem with overinflating tyres too much: more likely than
a damaged tyre or tube is a destroyed rim. Most cheap rims (as used for most
standard unicycles) are not durable enough to stand high pressures (>60 or
70psi), no matter of the stability of the tyre itself. The side walls of the
rims may bend to the outside (either slow or even by exploding). Be sure to use
quality rims (double walled, lots of spokes, quality manufacturing, especially
the welding, good material, no cheap steal). Good rims often come with a
statement of how much tyre pressure they are supposed to stand.
For my 20" uni I use a BMX double wall aluminium rim with 48 spokes and a tyre
that claims to stand pressures up to 100psi. I normaly inflate it to approx.
120psi and never got a problem with it. For my 24" uni I use a similar rim, but
I can’t find a high pressure tyre that’s white (for not setting up janitors at
gyms). So I use a 50psi tyre and inflate it to approx. 80 to 90psi. I have to
replace the tyre at least once a year, even if I use the uni sparely.
Best wishes,
Wolfgang
\\\|///
| ~ ~ |
(- 0 0 -) +----------oOOo-(_)-oOOo-----------------------------+
| |
| Dr. Wolfgang Stroessner |
| |
| e-mail: wolfgang.stroessner@sap.com |
| http://spectrum.mathematik.hu-berlin.de/~stroess | Oooo. |
±--------.oooO-----( )-----------------------------+ ( ) ) / \ ( (_/ _)
Re: Over-inflation
For muni it depends on the terrain. For hard packed trails and hard surface
riding I’ll pump up the tire to 50 psi or so. For softer trails, bumpy trails,
and cases where I want more traction I’ll drop it down to 30 or 40
psi. Lower pressures for offroad trails is generally better because it gives you
more traction and it makes it easier to roll over roots, rocks, etc. in the
trail. With high pressures you tend to bounce off the obstacle rather than
roll over it.
The people who are using the big fat downhill tires on the muni will do around
30 somthing psi (those big fat tires are low pressure jobbies).
So for muni, over-inflation is not always the norm.
“Greg House” <ghouse@southwind.REMOVEME.net> wrote
>John Childs wrote in message <19990830045248.40248.qmail@hotmail.com>…
>
> >Over-inflation is the norm on unicycles.
>
>Does this also apply to a Muni? What’s commonly done off the road?
>
>Greg
>
>
Get Your Private, Free Email at http://www.hotmail.com
Re: Over-inflation
Arnold the Aardvark wrote:
>
> To what extent can I safely over-inflate the uni tyre? I’m currently pretty
> heavy (250 pounds) and the tyre gets squashed quite flat. Good traction I
> suppose…
>
> The tyre says “inflate to 40psi”.
___________ =========================================== ___ /_/ / / / /
Kevin Gilbertson - <a href="mailto:mail@gilby.com">mailto:mail@gilby.com</a> / _ '/ / / _'\_ / Unicycling
T-shirts at <a href="http://www.gilby.com/">http://www.gilby.com/</a> \_ /_/_/,___/ / ICQ: 12611076 AIM/AOL:
IamGilby /\/ /__________/ Unicycled Across Minnesota to help others!
\__/ ================================================Re: Over-inflation
Arnold the Aardvark (aardvark@foxholly.demon.co.uk) wrote:
: The tyre says “inflate to 40psi”.
We run our wheels at between 50 and 70 PSI depending on which one it is. I pump
them up with a trackpump with gauge, more accurate than a garage forecourt one
and less likley to explode your tire.If pumping with a hand pump, then its till
the tire is V solid and can’t be squashed by thumb presure on the centre of the
tire. Or till I get bored of pumping and think that’l do :-). All our tires say
on them, 35psi or similar, I just ignore it now as I find the uni more
responsive with more presure.
have fun sarah
Re: Over-inflation
I sympathize with your problem. I wiegh 225 but at one point I was 265. I
generally will inflate a tire which suggests 40 pounds to about 60 pounds with
no ill effects. I did have one tire failure becuase of this practice but it
usually is okay. I can find tires which suggest 40-65 pounds of pressure which
will usually hold 75 pounds.
Re: Over-inflation
Thanks for all the advice, everyone. I won’t worry too much about using high
pressure, and I’ll let you know when I get a life threatening blow-out 
Given the current evidence from my practice sessions, I suspect I will
weigh quite a lot less in the near future. And I thought two wheels were
good for me…
http://www.foxholly.demon.co.uk ICQ# 30592054
Re: Over-inflation
In article <01bef133$c232fc60$d056989e@foxholly.demon.co.uk>, Arnold the
Aardvark wrote:
>To what extent can I safely over-inflate the uni tyre? I’m currently pretty
>heavy (250 pounds) and the tyre gets squashed quite flat. Good traction I
>suppose…
>
>The tyre says “inflate to 40psi”.
In Europe (no idea what the liability issues are in the US) the reqirement
is that the manufacturers have to inflate the tyre to twice its rated value
and leave it for some time (can’t remember how long) and it has to not blow
off the rim.
On my unicycle I go up to about 2.5 times what it says sometimes. Generally I’m
a bit under twice. Being naturally cautious, I don’t inflate it with my head
pressed against the tyre (just in case) but nothing’s exploded yet.
It does over-load the side-walls and I’ve had a couple of tyres that the beading
wripped from the side-wall (one quite suddenly, one over the course of a few
days riding). This is entertaining 'cos sometimes the inner tube escapes through
the hole and expands to about the size of a tractor tyre once it’s out - it’s
like a giant anaconda desides to come rushing out the hole. I guess that if
you’re unlucky at this point the tube explodes.
|\ /| Opinions expressed in this post are my own, and do
|o o| not reflect the views of Amos, my mbu puffer fish.
|/ | (His view is that small snails are very tasty.)
Amos now on the web at http://www.achrn.demon.co.uk/amos.html
Re: Over-inflation
John Childs wrote in message <19990830045248.40248.qmail@hotmail.com>…
>Over-inflation is the norm on unicycles.
Does this also apply to a Muni? What’s commonly done off the road?
Greg
Re: Over-inflation
When you pump a uni tire to 80# then put a 225 pound rump on the seat, wonder
what the pressure goes up to?
Joe Mayers Unicycle1@home.com
Re: Over-inflation
100 psi!!! I thought 50 would be pushing it. It must ring like a bell.
Thanks.
http://www.foxholly.demon.co.uk ICQ# 30592054
Re: Over-inflation
>When you pump a uni tire to 80# then put a 225 pound rump on the seat, wonder
>what the pressure goes up to?
psi = pounds per square inches if you add weight the pressure stays the same but
the square inches increase with a 225 lb. man on unicycle weighing 10 lbs,
with a tire with air at 80 psi.
2.9375 square inches of tire will be in contact with the ground.
You can actually weigh a car by finding the sum of all the tires area touching
the ground X tire pressures.
Jeff
Re: Over-inflation
In article <JN_y3.8237$k4.185370@news4.giganews.com>, “Joe Mayers”
<Acadian@eatel.net> wrote:
> When you pump a uni tire to 80# then put a 225 pound rump on the seat, wonder
> what the pressure goes up to?
Easy enough to find out. All you need is a unicycle, an air pressure gauge (with
someone to use it), something to hold on to, and a 225 pound rump.
Ask the someone to use the gauge to measure the pressure in the tire. Put the
rump on the unicycle seat (holding on to the something to remain stationary).
Ask the someone to use the gauge again. Remove the rump. Ask the someone to use
the gauge yet again (to verify that testing didn’t allow too much air out of
the tire).
Let us know how it turns out. I would attempt this, but I don’t have easy access
to a 225 pound rump.
Jim
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you don’t.
RE: Over-inflation
> >Over-inflation is the norm on unicycles.
>
> Does this also apply to a Muni? What’s commonly done off the road?
Though I agree over-inflation is usually the norm, it does not necessarily apply
for MUni and for slippery floors.
When I MUni I have a “normal” sized tire (26" x 1.75 or so). the relative
narrowness of this tire, in relation to the rocks and drops I’m using it on,
force me to keep a lot of air in it, still around 60# or so. Some people ride
with lower, but their terrain may not be as radical. We have a lot of what I
call “tire popper” rocks on our trails, and if you come down on one the wrong
way, instant puncture.
Soon I will have a Gazzaloddi 2.6" tire, which should allow me to lower the
pressure. Bruce Bundy has a 3.0" Gazzaloddi on his MUni, and runs it at 26-29#.
And he can pretty much jump to (or from) the moon.
You can order the 2.6" Gazzaloddi from UnicycleSource:
http://www.unicyclesource.com/Gazzaloddi_Downhill_Tires32525.html
Stay on top, John Foss, the Uni-Cyclone
Re: Over-inflation
Well on mine it says 45psi I went to the pump and obediently as it say in the
FAQ of this group overinflated it to 55psi. Then I went to a bike shop to get a
new screw for my seat post and they said the gas stations are notorious for
being wrong and it was 70psi. All in all I still found this to not be as solid
underneath me.
Hey maybe I’ll even ask some of the guru’s here, how should it look from above
if it has any give does it take away from the unicycling experience , does it
make it harder to ride or maneuver
Jack
Arnold the Aardvark <aardvark@foxholly.demon.co.uk> wrote in message
news:01bef190$5090bcc0$d056989e@foxholly.demon.co.uk…
> 100 psi!!! I thought 50 would be pushing it. It must ring like a bell.
>
> Thanks.
>
> Arnold the Aardvark
> ===========================
> http://www.foxholly.demon.co.uk ICQ# 30592054
Re: Over-inflation
Is this including the knobby tire, or assuming the tire is smooth?
Just kidding! I’m just impressed that someone had the audacity to actually
calculate this tidbit for us.
Thanks, Shane
> psi = pounds per square inches if you add weight the pressure stays the same
> but the square inches increase with a 225 lb. man on unicycle weighing 10
> lbs, with a tire with air at 80 psi.
>
> 2.9375 square inches of tire will be in contact with the ground.
>
> You can actually weigh a car by finding the sum of all the tires area touching
> the ground X tire pressures.
>
> Jeff
Re: Over-inflation
Jack Goodman (jgoodman@notar.on.ca) wrote:
: Well on mine it says 45psi I went to the pump and obediently as it say in the
: FAQ of this group overinflated it to 55psi. Then I went to a bike shop to get
: a new screw for my seat post and they said the gas stations are notorious for
: being wrong and it was 70psi. All in all I still found this to not be as solid
: underneath me.
: Hey maybe I’ll even ask some of the guru’s here, how should it look from above
: if it has any give does it take away from the unicycling experience , does it
: make it harder to ride or maneuver
Hardly - it is a case of horses for courses. Different riding situations require
different pressures. Long-distance riding on tarmac will need high pressures (to
minimise the rolling resistance) but even this will give the tyre some squash
Other circumstances such as MUni in soft mud or hockey in gyms with really
slippery floors call for a softer tyre. At Eurocycle this year one of the halls
we were playing hockey in was really difficult to turn sharply in and I ended up
with my tyre at about 25-30 psi and this helped the grip no end.
That’s my tuppeny on the subject despite not being a guru!
–
Paul Selwood paul@vimes.u-net.com
Re: Over-inflation
>Is this including the knobby tire, or assuming the tire is smooth?
I believe it’s assuming the tire is smooth. Jeff
Re: Over-inflation
bite me