performance figures

@individual.net:
[...]

[...]

Ya know, it makes me feel proud, and just a little
bit humbled, to know that I can converse with and
draw knowledge from such a learned group of people
on a daily basis!

G

 

Not require, permit.

For whatever reason, ye olde timey racebikes sat the rider's arse
practically directly over the rear axle, making the bikes extremely
tail-heavy.

Further, the engines sat lower and further back than today, making the
front wheel's life even harder. Getting off the side of the bike would
only exacerbate that, as it moves even more weight lower down.

Lastly, and most importantly, a modern Kelso wheelbarrow you can buy for
$49 from Bunnings comes with a more advanced tyre than an early 60's GP
bike. Those guys didn't have the weight distribution nor rubber under
them to allow them to whip their bikes around the front contact patch
the way present-day racers do.

I find it very difficult to believe that anybody selling tyres for a
living would say something like that in the year 2005.

I find it even more difficult that someone who would appear to consider
himself a thinker on motorcycle dynamics would put enough stock into it
to repeat it.

<snip-bunch of stuff which might pertain to asphalt roads as they were
in the 1950's>

How much drainage-necessitated camber is there on even the most
sloppily-laid stretch of road, let alone along one along which you'd
attempt to set a speed record? A couple of degrees? What possible
combination of tyre width and CoM position could lead to a loss of
control severe enough to bring about a crash?

In the US, bikes race on the infields of NASCAR/CART/IRL ovals, and, in
a few places, run on the straight sections of the oval banking, without
drama.

 

I thought you'd decide not to argue any more!
("Waste of time", remember?)
Clem
~

 

You want learned go talk to IK or Hammo or Paulh or someone; I'm just here
for the bench-racing, jokes and arguments!
Honest-Clem
([Homer Simpson voice] It's pronounced "learnd")

 

You don't reckon aesthetics are the reason CBR250RRs and VTR250s have
similar-sized wheels to what FZR1000s used to need?
I think fat tyres are very much a fashion item!
Clem

 

Oh, that would be that 'Sarcasm' stuff I've heard so much about!

Who'd have thought I'd find some on aus.moto?


BF

 

I just bought a new wheelbarrow and the when pumping up the tyre I noticed
some writing on it which said "Not for Freeway Use". I'll have to think
about that next time I take my wheelbarrow on the road...

 

In aus.motorcycles on Sat, 15 Jan 2005 23:32:35 +1100

From an old mailing list posting:

==========

Motorcyclist Godfrey DiGiorgi spelled out the answer when he wrote on
an Internet newsgroup:

"Me old buddy aka Chris Conn, a GP racer from '58 to '68 who in '65 was
third man home behind Hailwood and Ago in the Senior at the IoM.

One night, we were sitting around at his place watching the Castrol 'History
of Motorcycle Racing' videos. They have film clips from as far back as
the early 'teens.

As the years progress, you see people hangin' off, not hangin' off, hanging
off again, etc. So I asked Chris about this and he rewound the tape so
we could watch things again.

To paraphrase:
"<BEGIN> You see in this segment, the tyres don't grip well enough to
really lean the bike over very far. This means that you can't really
corner all that fast, so the riders stay on the bike, tidy, to keep out
of the wind and not upset the grip.

<FF> Now, we see that the tires have improved, they stick quite well,
and the bike can lean over pretty good. So the rider has to hang off
a bit to get the cg in line with the contact patch or he'll ground stuff.

<FF> This next bit shows that the chassis has gotten better faster than
the tyres ... the bikes are leaned over to the tires' limit, still plenty
of ground clearance, so the rider stays in place.

<FF> Note the big Dustbin fairings ... they compromised ground clearance
so the riders try to hang off but must also try to stay behind the fairings.
Bloody dangerous in the wind, I tell you!

<FF> Here we go, getting into some serious power from Honda, MV, etc
.. The frames can't handle the power anymore, the chassis are wiggling
all over the place, and while tyres are improving, the riders try to
stay still as much as possible so not to upset the chassis, which is
jumping all over the place beneath them. Notice, though, that they're
adding a bit more body movement to the bike: controlling the steering
by moving the bars from their hips rather than their shoulders. Notice
also that the seats are way back on the bike so the rider can get enough
weight on the rear wheel so the tyre doesn't spin so much.

<FF> Ah, here we see your man Roberts and Sheene ... The tires are much
improved, the power is way up, the chassis are, well charitably, awful.
The engines are wide so they run out of ground clearance, the tyres are
sticking well so the poor blighters have to hang off like crazy to keep
the buggers on the track. They've got enough power that having their
knee and body in the air on the corners isn't going to cut their speed
any.

<FF> In this last segment, notice that the fast bikes, the 500s, have
all the power to spare so what the rider does in the corners with his
body is more how he feels comfortable keeping the ground clearance, cg,
and such aligned. His knee is in the wind to help turn the bike going
into the turn. He sits forward because that big sticky back tyre has
all the traction he wants and he can get the front wheel working better,
the chassis is stiff enough to flex only as much as the engineers deem
necessary. The less powerful classes, the 250 and 125, have plenty of
ground clearance, plenty of stick, plenty of traction so the riders tend
to stay more tucked in so they can eke a smidge more speed out where
ever they are... <END>"

=============

Zebee

 

In aus.motorcycles on Sat, 15 Jan 2005 23:32:35 +1100

What, you find it hard to believe that marketing would win over physics
on an expensive toy?

I find that hard to believe....

Why, for example, does a 250 Hornet need the same size tyre as a 600?

Not to say all wide tyres are too wide. But neither are they all just
right.

Zebee

 

A very apt choice of words, given what follows below, namely...

Not to dump on Cam's ride, but those bikes fit the label of "expensive
toy" better than most. The original Japan-only Hornet 250 scored its
180-section rear tyre precisely because it was pitched as a stylistic
statement for people on restricted licenses, who didn't take the
performance aspect of their motorcycling too seriously (if you're
confined to a Japanese inner city, you probably don't have all that much
choice in the matter, to be fair).

An interesting tidbit of pertinent information is this; in World
Superstock racing, where the bikes are very mildly modified litre
sportsbikes (shock, fork internals, full race system, remapped ECU,
compression upped by a maximum of a half a point over stock) running
commercially-available tyres, 2004 marked the first time 190-section
rear tyres began to be commonly used, ostensibly because the power
outputs of the '04 Blade and R1, and the ZX-10R, finally proved too much
for the 180-sections, used until then, to cope with over full race distance.

From that perspective, the 190-section rears, which have been
standard-fitment on open class sportsbikes for five years now, do remain
overkill. Personally, though, I'd sooner believe they're fitted to
increase tyre life and to dull steering just a bit so as to make street
riders more circumspect than just for fashion.

Something else to consider is this; my 600 rolls on a 5.5" rear rim and
180-section tyre as stock fitment. A 170 section will comfortably fit on
there, but if you compare identical tyres in 180 and 170-sections, it's
the 170-section which usually has a significantly flatter profile.

 

Not at all.

I think you maybe ignoring the context in which this was said.

Consider it being said when asked what advantages will I have if I go from a
160 to a 200 rear? It then makes perfect sense that it had been uttered.

Hammo

 

I'm only here so people believe I ride a bike. Besides, Sharkey writes all
my scripts.

H

 

Test rode a new Z1000 a couple of months ago, the bugger wouldnt hold a
line through turns without constant input, the rear tyre is a 190...
bloody NO doubt for markerting reasons... reading a few reviews and forums
that problem becomes soved using a 180 section rear...

HTH
JasonBW- Wollongong

 

: peter wrote:
: >
[.lots snipped.]

: or whether you're just spouting something which popped into your head as
you were typing it.

Which _you_ never do....

P

 

: Ruth & Dave wrote:
:
: > An Auckland tyre shop suggested to me
: > that aesthetics plays a big part in
: > tyre width to the expense of handling.
:
: I find it very difficult to believe that anybody selling tyres for a
: living would say something like that in the year 2005.

I think I remember hearing somewhere (very old hearsay) that once a tyre was
'proven' compound wise, the marketing guys got to choose which tread pattern
it was shipped with based on looks since different tread patterns have
neglible difference in tyre performance (water dispersion, traction etc).
Certain tread patterns look better than others and therefore sell better.

Just something I heard....

P

 

The bike in question comes with a quad-exit exhaust... the whole thing's
designed to be a stylistic statement first. Performance would sit some
way down the list of design priorities.

Sportsbikes, sports-tourers and tourers are built to perform a
particular function ahead of looking a certain way while they do it. The
concessions they make to looking good are relatively minor.
"Performance" nakeds and cruisers are more "lifestyle choice" machines,
and their dynamics suffer accordingly at the hands of the need to look
good, and the need to keep development costs down by raiding the
component shelves of higher-performance models.

 

In aus.motorcycles on Sun, 16 Jan 2005 02:10:39 GMT

I saw that in New Scientist and I think at least one bike mag.

Zebee

 

An Auckland tyre shop suggested to me-- Hi guys -- yes the guy in the shop did say this-- and he was one of the
few who did agree with tyre width reasoning. I used the statement to make
the point that the wider tyres are being sold by request from the owners of
some of these bikes cos it looks good. He does not market the concept of
looking good-- That is also what I am saying-- the bike looks good with the
big fat tyre.
Tyre profile surely is also affected by rim width-- go down a size in
tyre-- flatten the profile!!
I still stand by lowering c of g and widening tyre makes a bike handle
bad, it must lean more-- same speed same bend same bike narrower tyre-
higher c of g less bike lean angle.
Use a bubble level on a pushbike balanced on the flat --then
across a slope as in a previous posting-- then try that with your machines
and see which leans further-- tyre width-- low c of g.
Banked circuits help cornering- adverse cambers compound the tyre width
problem.

regards Dave R

 

I have no doubt of that. I've met no end of motorcycle industry
professionals who insist on applying early 1980's pub wisdom to
motorcycles 20 years newer in concept and engineering.

So what happens when you opt for a different model or brand of tyre,
with a different construction, and hence profile?

What in the name of all that countersteers are you blathering on about?

You go from stating the obvious in a tone which makes it seem like you
consider yourself to have been the first to stumble on the idea (low
bikes have to lean further than tall bikes; quick, patent that shit
before anyone else thinks of it)

Since you fail to quote exactly what you're replying to, it's only fair
to assume you completely missed the part about AMA racing being done on
the_straight_portions of NASACAR ovals.

These are straight sections of racetrack, they are often quite sharply
banked (definitely more so than any public road), and the racers have no
trouble traversing them at very high speed. There's no mention of
cornering here.

Maybe you should actually approach something made in the last
quarter-century, let alone ride one, before you put fingertip to
keyboard again.

Name one modern sports tyre.

 

'cos you're stretching a 10mm narrover bit of rubber
across the same rim, no?

G