performance figures

Hi
I am trying to find performance figures for an average superbike. Ie say
around 1000cc 0 to 100 mph time and for the same bike 100mph to 0 braking
time. This is to get an idea of the power output of an engine through the
rear tyre compared to the power output of double disks through the front
tyre.
I know the braking will be wind assisted but it may be possible
that the front--(Rossi style braking) tyre puts out more power-- Just a
physics argument!
I hope you guys can help
regards Dave R.

 

Definitely the front-brakes over the engine. (For 30sec or so until the
brakes overheat anyway).
GP bike can wash off 200kph in 100 meters but could never accellerate that
fast.

 

That was quick -- thanks for that-knobdoodle!!-- great numbers, which sort
of slightly makes most answers to the question, " why are superbike rear
tyres so fat compared to the front tyres"!
just a little puzzling- especially as I see it- fatter tyres increase the
lean angle of a bike over narrow tyres-- same speed- same bend!
Is that generally agreed with you guys.?
-- Dave R
Ruth & Dave
Tel:+64-09-2922112
Mob:+64-0212659939
Web: www.stationtostationcycletours.co.nz

 

Not too sure about that logic - considering that I can get to the edge
of my 180-section rear tyre but nowhere near the edge of the
considerably narrower front, tho it's probably more a funciton of the
different cross-sectional shapes of the tyres.

I think that you'll find that the width of front vs. back tyre is
related more to the handling characteristics than the
acceleration/deceleration potential.

But then again I could (and probably am) just talking bullshit.


FB.

 

Hi ya FB!
Interesting your practical experience. Must think about that one.
Give a thought to the lean angle being determined by the c of g of the bike
and rider through the point of contact with the road and the bend and the
speed.
Imagine a view of the rear tyre from close to the rear of the rear tyre and
draw a centreline through it with the bike upright and the line straight
down to the road, Now lean the bike- with a narrow tyre- the point of
contact is just inboard of that centre line-- now imagine a wider tyre-- the
point of contact moves further inboard. To maintain the same lean angle- ie
through the c of g and the point of contact, we lean over more!
I could be talking out of my arse but I think I am right
further to that-- if you have a bike and lower the c of g-- you will have to
lean the bike more-- same speed- same bend -same tyres-- use the above
diagram description and draw the lines.
regards Dave R

 

On Sat, 15 Jan 2005 16:21:08 +1300, "Ruth & Dave"

OK - i *think* i see your point, but this makes the huge assumption
that the narrower front tyre has the same proportional cross section
as the rear.

I currently ride with a Bridgestone BT020/BT012 combo, and the 020 on
the rear has a flatter profile than does the 012 on the front.

You''d reckon that this would make the rear turn at a different rate
than the front giving either over or understeer.

Some more anecdotal evidence - a mate of mine had a Firestorm with
BT020s front and rear, and he reckoned it handled like a piece of
shit. Changing to a 012 on the front transformed the bike, more so
than he thought could be explained by a different rubber compound. So
maybe there is something in the relationship between the two tyres'
shapes.

As far as the CofG issue you point out, I really think there are many
other variables to consider than just the width (and profile) of the
tyre - suspension settings front and back for instance (the CofG
doesn't often remain static in relation to the axles)? Tyre pressures
(flexing of the sidewalls, movement of the contact patch)? etc etc
etc.

But ignoring the other variables, I reckon you're probably right about
the way that lowering the CofG will increase your lean angle.

Think of the way gravity works on the cornering bike - you move the
CofG inboard to counteract the outward force trying to throw you off
the highside.

For a given corner/speed, you might need to move your CofG inwards by,
say, 30cms.

If your CofG is, say 30cms from the deck, you'll need to lean over by
45 degs.

If, on the other hand, your Cof G is 60cms from the ground, you'll
only have to lean over by - ummmmmm - a bit less than 45.




Probably.



FB.

 

Ok to me it sounds like your going into the corner toooo slow and then your
hard on the throttle on the way out.

I have got both the front and back too the edge and have found that the
harder I go into the start of the corner the closer you get it too the edge
of the front tyre.
I have found that if I go into a corner (Like u are) not as hard, but then
accelerate out of the corner I get to edge of my back but no where near my
the edge of my front. This would be because the weight would be at the back
of the bike suspension would be compressed, tyre compressed, front tyre u
would think would be more upright and not as compressed and would not be
leaned over as far (A guess). If I was u I would start putting a bit more
pace into when u going into corners as it seems to me you could go into them
alot harder and stop ridding like a sissy. (Obviously on the track not the
road)

 

I think that it might be the other way around. If you take the CofG below
the axal line
the bike will slide from under you. if you have a higher CofG you can get
the bike to
a greater angle before it trys to slide from under you. i think that it is
that trying to
throw you off that helps the grip of the tyres keeps them on the ground.

Smiley

 

Hmm ok, and your just after trouble.

Ok so I havn't done any trying, my friends arn't instructors and I wasn't
offered a job as one.

I said on the track, not the road if you read what I posted originally
instead of flying off the handle u would have seen this!!!
If you ride regularly on the track you should know each corner,
have turning points and entry speed, I have never seen oncoming cars on a
track. I was just offering advice from a track prospective as I said.

 

Bullshit. You've found no such thing. You're just making this up because
you want in on the discussion, and need an angle fast.

....and a pretty embarrasing one at that.

Do your front and rear tyres have the same profile?
Do they not distort when in contact with the ground?
Do bikes have hinges in the middle, so the front and rear lean separately?

Sound advice. Nothing's as embarrassing as leaving a safety margin on
corner entry and then finding no rough patches, tree debris or oncoming
cars on the way through.

 

Yeah, sure my scratching abilities are about a squillionth of what the
bike is capable of, and let's face it spending my saturday surfing the
net instead of riding isn't going to help

However, I still maintain that the different tyre profiles ate a major
contributing factor.

If you look at the tread surface on MY rear tyre (can't talk for
anybody else's tyre choice) there is a bit of a lip between the tread
surface and the sidewall.

The front, in comparison, also has a bit of a lip, but it's WAY less
pronounced.

I reckon that if I was to wear my front tyre to the edge of the tread
block, I'd be scraping the axle nuts.


BF

 

True,. but when optimally braking all the force is straight onto the middle
of the tyre and the more braking-force, the bigger the contact-patch
squishes.
Acceleration can happen over a range of angles and with a lot of sideways
(i.e non-helpful) forces so the back tyre has a much tougher job of it.
Clem

 

I'll believe that. Instructors seem to have this common trait of getting
uppity when you question their attempts to explain something they can
do, but can barely begin to understand.

No, I saw that. I ignored it because that makes your observations not
only incorrect, but irrelevant.

Nice to see your response pretty much comes down to "How dare you
question me?" instead of addressing the points I raise about tyre
profile and distortion.

 

I heard a commentator, at PI last October, say something about high
speed corners being harder on front tyres, whereas rears tyres cop a
hiding on tight low speed corners.

That kinda sits with what you're saying.

---
Cheers

PeterC [aka MildThing]
'81 Suzuki GS450-s
'87 BMW K100RT

www.dmcsc.org.au

 

I didn't see the point in arguing with you, regarless of what I say your
not going to listen so I don't see the point, I've seen you on this news
group arguing with other people with unfounded claims of your own trying to
call a red pen blue. Waste of time

 

OMG you just can't shut up.

 

That makes two opportunities wasted...

You say you don't see the point. That's quite correct, as the point
isn't to convince_me,_but anyone else who might be paying attention and
who might be interested to see whether you really have the first clue
about how tyres and suspension actually work, or whether you're just
spouting something which popped into your head as you were typing it.

 

Hi guys- I have been out on the piss
Some interesting stuff. Just a thought re old racers like
Agustini- Hailwood- Surtees.
They did not move around on the bikes as they do today. Perhaps today's
bikes and tyre profiles-- widths-- require it.
An Auckland tyre shop suggested to me that aesthetics plays a big
part in tyre width to the expense of handling.
A Kiwi guy cant remember his name-- built a special for a Kiwi
speed record, but as I understand it- he made it with a super low profile
and thus a low c of g and when he started off, the wide tyre profile
combined with the road camber made the bike virtually impossible to steer--
he did crash if I remember he was ok. He borrowed a Britten and broke the
record.
Look at the contact point of a wide tyre on road camber---
The bike must be lent over to go straight ahead especially with a low c of
g-- Draw the angles as I have explained in an earlier posting. put a
line--bubble level on your bike in a garage--flat floor- then roll it out on
to a slope- with the bike across the slope and balance the bike once again
and check the bubble-- the bike will lean into the slope just to stay
balanced- Yes tyre profile will effect this but generally fatter tyre --
more lean.-- lower the c of g -- more lean. build a speed machine with fat
tyres AND low c of g-looks good- fall off!!---
regards Dave R


Ruth & Dave
Tel:+64-09-2922112
Mob:+64-0212659939
Web: www.stationtostationcycletours.co.nz