Ian Smith wrote:
> In article <firstname.lastname@example.org>, 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
> >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
> 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.
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