oh the pressure

I was wondering why the need to lower tyre pressures when a motorcycle is taken on a track and why that same need is not present during everyday street riding.
It seems to me that if you can shave four or five pounds off the weight of your wheels and tyres it would be just as likely that it would benefit on the street as well.

I think the need to lower pressure on the track is due to the fact that you are riding a lot harder and faster and the tyres heat up more raising the pressure. Lighter wheels will help with handling making turn in easier as there is less rotating mass. Centripetal force makes the wheels want to stay upright and go straight. Less weight means they are easier to push over. The lower weight will also put less force on the tyres and possibly keep them from getting as hot during hard riding.

I don't understand how you're equating tyre pressure with tyre/wheel weight. The weight difference between a tyre with 0 psi and one with 40 psi is almost unmeasurable (way less than 1% of the weight of the tyre).

Kuerbis

Does a few pounds of weight in rotating mass seem significant?
Swap over to a 520 chain and aluminium sprocket. I lost over 4 pounds doing that and it was amazingly different.
The only other things you can lighten other than changing to uber expensive wheels is titanium fasteners. Not a good cost to benefit ratio, IMO.
I have been told by just about everyone that the most significant upgrade spent was wheels. If you buy aftermarket wheels, some use non KTM drives so consider that before investing in many KTM sprockets as I did.

Try putting helium in your tyres.

So if you go to a lighter wheel, like the carbon fiber Dymags, You can raise your tyre pressures up and will still have the same weight?

your pulling our chain huh

if there was an emoticon with a smiley banging it head against something...... i would be using it!....... please tell me your joking .......

Here we have a saying"A pint a pound the world around" I you added four pounds to your tyre pressure i would assume that you added four pints of air to your tyre. I do not know how many pints a rear or front tyre holds and I am sure that it differs whether your at sea level or not but if the pressure were higher then it would be pushing on the earth more and therefore give you better traction. A tyre heats up upon hard use and raises the pressure and the amount air in the tyre causing it to be pressurized to the ground( or tarmac) giving better traction.
That is the way it seems to me.

This thread could end up as my Sticky of the Year

He HAS to be taking the piss.
No way you can convince me that someone is actually asking about the weight of air as related to a motorcycle tyre.
If he is, then I should think that tyre pressures and weights are the least of his riding problems.
I have never heard of that saying he references but we used to have another.
"The only stupid question is the one unasked."
I may have to disagree at the moment.
HOLY COW!

http://govbooktalk.gpo.gov/2010/04/27/“a-pint’s-a-pound-the-world-around”/
I do realise that the measurement is in regards to weight to volume. 16 ounces of liquid is 16 ounces of volume and weight. 16 ounces of weight is one pint of volume and one pound in weight. Why would it be better to have less weight( less volume of aire in the tyre) on the track and not on the street?

One more try.
16 fluid ounces of lead would weigh more than 16psi of helium.

Which is heavier? A pound of gold or a pound of feathers?

Geezz guys. Post like this will get me in trouble reading this stuff at work. LOL. I got tears in me eyes.. Great way to start the week. Thanks

...And there's 3 minutes of my life I can't get back...

GOOD LORD

What I am gathering know is rhat it is not the pressure as much as it is the volume of air in the tyre that causes it to be cooler or hotter at a certain speed. If you were on the street, you would not need your tyre to be as hot as you would need it on the track. The speeds and or forces are greatly increased on the track and if there was an abundance of air in the tyre it would cool the tyre down too much and keep it from getting as sticky as you would need. It is not important to get your tyre as sticky on the street so you put more aire in to help condition the aire in the tyre to keep it cool. More aire equalls more aire conditioning inside the tyre cause there is more aire flow inside the tyre when it is spinning.
Thanx,
By the way Ronin, my Mom told me that birds of the same feather flock together. That is quite possibly why my village called you first when they were trying to find me

There are quite a few rocket scientists in Los Alamos but I have a feeling Dribble is not one of them.... UNLESS....this is a belated april fools joke!

Nice one...

Reminds me about this female Navy sailor I was in Iraq with.
While talking about war atrocities she mentioned "those bombs we dropped on China".
I replied "You mean Hondashima and Kawasaki?"
She said "Yes, sir."
Whoooaaaa!!!!![/quote]


LOL....This day and age commonsense is a superpower.

Maybe we can explain correctly. It seems that this issue still is missunderstood.

On track lower pressure results in quicker warm up and higher temperature. There is a safe range as too hot will ruin the tyre and also produce hot scredding and you land on your backside. Some of you might have experienced that on a hot day at the tracks.
This lower pressure works also in winter as it makes your tyre warm up faster due to more flex in the carcass and bigger contact patch.
As you figured out by now this is not recommended for long excited rides in a hot climate as it will result in having to take a spare.
More pressure results in less flex in the carcass and slower warm up and less heat.

Idealy start wit a recommended pressure for track and go for a few rounds till the tyre is warm and you get to ride as expected. Then come in the pits and imediately check the pressure. The difference in between the two is the raise and the max should not exceed the manufectures recommendation!
Try to add air if the temp is too high and drop it if you need more heat in the tyre, again don't go lower than the recommended spec for that tyre!

Also make sure your suspension is set up properly as shitty damping will also stress the tyre and increase the temp, which will make your results useless. I could not believe the diffrence a proper suspension setup did for my bike and the tyre wear and temperature, recommended!

A bit of experimenting and keeping track of what the results are will help getting a ballpark setup for the next time.
And dribbel don't worry about the weight of the air, lay of the beer and burgers the night before this will make a bigger difference!

please mr dribble just think about this......

psi - pounds per square inch is a measure of pressure and cannot be directly equated to weight........ if you were to take your slightly crackers take on this to extremes then only super humans could ever become firemen or scuba divers...... their tanks are typical tested to between 2900 - 4400 psi ........ don't know many people that can run around with 2.2 of your american tons on there back????????

....

....checking out......

Have you been drinking no,,,,, ,,,,,out in the iradiated air direct from Japan,,,, ,,,,,,,it's worse in the morning when the air is "still",,,,,,good time to stay in and have a drink,,,,,,,

Dribble, this thread is so funny I'm prepared to ignore the sad reality of it and ask if you could do your version of an explanation of static and dynamic sag and a "how to" on suspension adjustment ( to compliment the handling of your now correctly adjusted tyre pressures ).

Thanks