I came a cropper

Why Smee?

Why must he suffer your penance?

28 is not too low and I would be interested as to what you claim to be
"ideal" an your rationale for it.

Hammo

 

Why do you care Hammo?
I don't
I gave my opinion.
don't like it?
.................

 

----Clang----

Do you have a problem?

It is your opinion and a crap one, especially as you suggested that "it
serves you right". That is a poor and lame thing to say.

Some bikes do well to have a lower PSI on the rear. The friction created at
that lower PSI creates a suitable pressure in the tyre.

Hammo

 

Sorry, Smee, but when I got the flat tyre between Mitta Mitta and Omeo
on the way to the GP last month, I could only reinflate it to about
12psi with the CO_2 cartridges in the repair kit, yet the back end
didn't feel overly sloppy in the super-tight stuff between Anglers Rest
and Omeo.

 

They re-surfaced a roads near me(UK) and they left more ridges in them
than as if it had been snowing and cars had made ruts in them.More
like ruddy tram lines!!!!

I avoid that road on my bike :/

 

Anyone had problems like this?

Weaving
(http://www2.ee.ic.ac.uk/cap/cappp/projects/2/files/weave_0_65.avi) is a
low frequency (2-3 Hz) oscillation of the whole vehicle[1]. It can
become unstable at higher speeds with fatal results.
Based on The control and stability analysis of two-wheeled road vehicles:
* The weave oscillations damp out once the rider reduced the roll angle.
* Tyre (tire) characteristics and inflation pressures are important
variables in the behaviour of the motorcycle at high speeds.
* From a stability point of view it is desirable to make the lateral
stiffness as large as possible, with the possibility of an optimum value
for the torsional stiffness of the rear frame.
* Common levels of lateral stiffness at the wheel spindle deteriorates
the wobble mode damping substantially with significant changes in the
wobble frequency as well, and slight reduction in the weave mode damping
at high speeds.
* Lateral distortion should be opposed as much as possible by locating
the front fork torsional axis as low as possible.
* The largest contribution to the weave damping came from the cornering
and camber stiffnesses and relaxation length of the rear tyre and not so
much from the same parameters of the front tyre.
* Amongst others, stiff frames, a long wheelbase, a long trail and a
flat steering head angle were found to increase weave mode damping.
* Degraded damping of the rear suspension, rear loading and increased
speed amplifies cornering weave tendencies.
* Rear load assemblies with appropriate stiffness and damping were
successful in damping out weave and wobble oscillations.

The only time I have ever experienced this is skipping a gear when
braking heavily and the engine compression forces the back wheel into a
semi-skid[2].

-sanbar

 

I've found, oddly enough, that flatter tyres tend to make the bike
follow tram tracks (etc) more, so it could indeed be some combination
of low tyre pressure and the asphalt repairs. Probably depends on
the bike, too, the GS feels like a drunken pig at 12psi. (and a
sober pig at correct tyre pressure)

I don't think it's much of a case to, you know, sue someone or anything
though since the falling off bit of it could have been avoided by either
a) better tyre maintenance b) better riding technique or c) slowing
down.

-----sharks

 

don't people know that you don't "rear brake only" when road riding?
guess not. no wonder he crashed.

 

Yep, every K100 I've ridden at speed (fast corners) with a worn rear shock.
The wallow never seems to eventuate into anything nasty, but it's very
disconcering till you learn to accept thats what the bike does. Mostly felt
through the rear, the front still felt stable. Fitting a rear shock with
adjustable damping like a Koni or better fixed it immediately. Never
happened in a straightline like the .avi, only when leant over at speed.

Al

 

Dickhead.

 

And? what are you gonna do about it?
Start another lecturing thread with psychobabble again?
Not interested

Not the zx12

cheers.

 

was it a zx12?

 

That's because GS can / is a drunken pig sometimes at PI - but we
still like him

Beer mate?

Johno

 

I do check my tire pressures before most rides of any distance or if the
bikes' been sitting for a while
I've got a couple of bikes registered at present and I've found that the
correct pressure is much more critical on the bigger tyres e.g.. 170 than on
the 120 (both rear sizes}
28 psi on the larger tyre makes a lot of difference to my bikes handling
{usually run 36} however the 120 can go down below 20 (usually 32} before I
notice anything amiss
Buy yourself a quality pressure gauge and a 12V super cheap pump and check
your tires at home before each ride or once a week if you ride daily
Oh and accept that your probably at fault in some way whenever you have an
off and learn how to avoid that particular incident in the future.

Cap. LT

 

No, but it was a bike with a similar wheelbase and weight distribution,
identical rear suspension layout and swingarm and rear wheel
construction, running less than half the rear pressure in question
without too much drama...

 

Interesting how different bikes handle with low tyre pressures.
The beemer will not handle well with low tyre pressures, in fact it gets
sloppy and wobbly.
Must be different with different bikes
I assume the zx12 would weigh considerably more than your little kwaka
though.

 

Wet weight of stock ZX-9R; 213kg.
Wet weight of stock ZX-12R; 248kg.

Stick me on a ZX9 and put someone like TB on a 12 and the two bike/rider
combinations will weigh the same.

 

yes but will the bike behave the same if the rear tyre was underpressured?

 

If the all-up weights were similar, what could cause them to behave
significantly different?

 

I have heard that EVEN with the correct pressure in the tyres, the
beemer will still not handle well... something to do with the water
they use in the tyres for ballast?? ;0

Beer mate?

Johno