Tyre pressures.. Again.

After I was done crying that image out of my eyes and the swelling came down, id say trailer that! There is no way to put that on one wheel bearing!

 

I have heard the top racers in 2 and 4 wheel use nitrogen to help keep the expansion fluctuation down. And they make sure that there is no moisture as that can also change pressure quickly. Not sure if its true or not. I just use a calibrated gauge and check pressure the moment I get to the pits for an accurate hot reading. Dunlop gp211 slicks have strange numbers they recommend but they sure seem to be right on. I think it was 23lbs hot for the front. On my street bikes I run a little under whats printed on the tire as I have heard that listing is for 2 up riding. I seem to get better mpg this way and handling is fine.

 

But do ya think 40psi with her in the saddle would absorb those bumps you keep running over?

 

Simply: NO!

I dont think having 40psi in two tires under her would help. The f'n shock and spring will be permanently damaged by the extreme load.

 

QUick searh came up with this.

http://www.popularmechanics.com/cars/how-to/repair-questions/4302788

 

There ya go.. If ya think all that will make you go faster then do it. Those gas laws apply to gasses not specific gasses or gas mixtures. I would also like to think that the various tire manufacturers know more about their tires than we do.

Aside from flying cars which are a regular feature of Mechanics Illustrated, cyber weapons that will shoot the balls off a kangaroo at 7,000 miles and their most famous bit that calculated that 144mph was the fastest speed attainable by any vehicle in a quarter mile. Later that week,,,,, SoCal racer Art Chrisman knocked that one out of the park.

Bottled gas is dry. A K bottle of N2 is a bunch.. X cu ft @ 22-2300 psia.

Kind of theoretical but useable is the passing of helium gas through quartz to measure partial vacuum leaks.

Plugging some numbers into the gas laws to form an equation and solution, I think one would have to crank in the temperature of the tarmac, the ambient temp and the cooling effect of the gas expanding and losing energy then being compressed forcing the molecules closer together producing increases in temperature. That heat would then be absorbed (laws of thermodynamics) by the carcass of the tire.

This could lead one to think that it's stuff like that that makes the fast guys fast.. IMO the fast guys would be fast anyway..

 

Thanks for the reply Billy. I think that more than the nitrogen being effected less by temp that not having moisture in the tire is even more important. I'm not ooking for nitrogen to helping me going faster at the track, just not having to deal with large pressure varriances as much. More of a confidence builder not worrying about high pressures and landing on my head. Lol.

 

Don't forget the other big "selling point" of Nitrogen is the larger molecules that don't seep out over time like Oxygen can. I'm not saying it makes any difference or that I agree one way or the other, just throwing it out there.

 

Landing on one's head is never good.. Ya don't need one of those bigass K bottles of N2 to do your own research and you will know that it's dry. The purging thing is interesting. If you go ahead with all this, keep us apprised.

 

Tis true! That's why the fast guys have the big bottles and cojones. Keep those percentages or better said those. partial pressures in mind. There is probably some data on internal temps of the gas in tires at rest and in use. Water vapor is another factor not so much in seepage but overall pressure buildup.

Heat transfer from brake rotors could have some effect as well.

For the scientific view on molecule size best to defer to the pros:

http://www.getnitrogen.org/pdf/graham.pdf

 

I've just read your post and all the replies and I couldn't agree with you more. The manufacturers spend £millions on R&D and come up with a bike and a spec. We riders then spend next to nothing, second guess the experts and think we have better answers! Sometimes people do of course have better answers, but in most cases with tyre pressures and suspension settings you should go with the manual - unless you really know what you're doing.

The problem is that non-technicians read something on a forum or down the pub and decide to give it a try, resulting in similar experiences to yours. My own experiences are that every time I've made adjustments to the recommended settings I've always gone back to the manual's settings. Moral of the story? They're there for a reason!!

Your own handling issues could be a combination of many things and tyre pressures are only one variable. Suspension settings, head race bearings,rear wheel bearings, tyre wear, different brands front and rear, road surface irregularities, air temperature, your own body weight and your own perceptions all contribute to a 'not quite right' feeling. My suggestion would be to check everything you can, adjust back to factory settings and go from there. A decent TP gauge is also essential and the fact that it's digital doesn't necessarily mean it's accurate. You can't expect to make dramatic improvements to handling by altering just one thing.

Keep trying!

 

In summer at the track it's easier to deal with pressure fluctuations. Off the tire warmers and out onto a hot track. In the cooler temps off the warmers and onto a cold track can drop the pressure and the colder tires have less grip. Have to be careful for a few laps trying to build some heat back in them. As soon as I pit I check pressure even before my helmet is off. Warmers immediately back on.