The times said otherwise... but street tyres on a track, particularly Pirellis, seem to get hot and cause significant expansion. The readings were made on Wakefield, and i'm not the only one over those track days that had similar results.
V
Nytrogen in the Tires
- Thread starter zogger
- Start date
Mate, you're "scientific arguement" has no credability. You can not apply ideal gas laws to air. It's that simple. You can try and get partial pressures to give you another simplistic and idealised representation of the interactions in air... but again, you'd be wrong. If i get some time, i'll try and throw something together that may give a more accurate representation of air's response to heat under pressure at varying RH and external environmental conditions (include external temp, RH and barometric pressure). It'll be pretty rough as it's not my field of expertise... but a lot less assumption based than using idealised gas laws because they're simple and can be understood by high school kids. I do appreciate the effort you've gone to in trying to discredit my person experience by applying physics you can easily look up on the web. The efforts of a true keyboard warroir :thumbsup:
Claiming that, good or bad, you can't get street tyres to be subject to extreme deformation on the track is also misinformed or represent inexperience. Did the tyres hit 100degC? Don't know - i didn't record temp. Do the tyres turn, losing grip as the heat load increases? Yes, they do - something the wider temp tolerance on race tyres does not seem to give for good reason. Is 20minutes about the limit for street tyres on Wakefield? Yes, i've yet to meet anyone, pro driver or not, than can get more than 20 minutes on that track on street tyres without having them turn. It's quite possible that some of the disparity you think exists in my numbers is down to improvements in my driving style between sessions. Something i suggested in an earlier post. I do not agree that it accounts for any more than 3-4PSI.
The statement has also been made in this thread that my tyre pressures must have beeen 'wrong' to get such a big variation. They were wrong - i deliberately dropped air out of them when cold until i achieved my desired pressure when hot. This is what people do to slicks, when running air, to compensate for the expansion during a lap. When i left the tyres at my normal street pressure and completed a session, the pressure would increase in the tyres until i had a significant change in grip and, as already pointed out, the tyres construction then prevented any further deformation. Just like with a slick, the balance was to get pressure right when hot so that i could achieve better laps and lines. The net result was a 1 to 2 second difference between the wrong pressure and the right pressure... by my observations.
James G
Spool makes me drool.
- Location
- Bunbury, WA
- Car(s)
- '06 CW GTI 3DR
PV=nRT yeah....
i never applied ideal gas laws to air. duh. if you actually read my post i talked about two different tyres one filled ENTIRELY with o2 the other ENTIRELY with n2. in this situation ideal gas laws are a reasonable approximation of gas behaviour when heated. i never said it was an exact representation, just that even factoring in errors (which wouldn't be big given the similar physical properties of o2 and n2) what you saw could not be explained by the thermal properties of the constituent gases in air. we now find out that you were also letting air out of your tyres. 
personal experience < science. get over it.
blah blah, my science is wrong, whatever. let's see yours, explain what happened then. what the hell do i know, i only have a BSc, like a true keyboard warrior i only spent 4 years studying physics and chemistry. lets go mate, find some time and "throw something together that may give a more accurate representation of air's response to heat under pressure at varying RH and external environmental conditions (include external temp, RH and barometric pressure).." if you don't know why that statement is ridiculous seeing as how we're talking about relative pressure difference, you're gonna need a lot of time.
personal experience < science. get over it.blah blah, my science is wrong, whatever. let's see yours, explain what happened then. what the hell do i know, i only have a BSc, like a true keyboard warrior i only spent 4 years studying physics and chemistry. lets go mate, find some time and "throw something together that may give a more accurate representation of air's response to heat under pressure at varying RH and external environmental conditions (include external temp, RH and barometric pressure).." if you don't know why that statement is ridiculous seeing as how we're talking about relative pressure difference, you're gonna need a lot of time.
WhiteJames
Fun Nazi
- Location
- Sydney
- Car(s)
- VW Golf GTI MKV
Well,
It's good to see that everybody is getting anal about tyre pressures.
Of course tyres are the most important contact between your ride & the ground.
From experience: I have found that the Denver 17"/225/45 series seemed to hold pressure better than the Huff Reps 18"/225/40 series.
Not sure if it's the lower profile, or just the way the tyre has been placed on the rim. The difference is only marginal.
Being anal about tyre pressures of course is a good thing.
On my recent trip to the farm & Canberra, I did 1300km of driving and checked the pressure 4 times in 4 days:
1. Before commencement of journey.
2. Before Two man GTG with Dingah day after.
3. Before Canberra GTG day after that.
4. Before return to Sydney.
Pressures generally run at 36psi cold.
On my return to Sydney, I stopped by to see the Manager Kevin of Jobson Bridgestone Tyre Centre to have my tyres inspected for wear in deciding whether or not to have a wheel alignment after 5,000km of driving.
Tyre were rotated from to rear with wear pattern noted.
I'm running toe out (negative toe) of 0.2mm.
Standard specs for GTI is 0.0mm at front.
Manager Kevin & I will monitor wear patterns in decision to see if we go for a bit more toe out (negative toe) to aid turn in response.
I will return to Jobson Bridgestone in 5,000km for wheel balance, rotation & another wear assessment to find the ideal between highway cruising & driving through the tight twisty corners, as I no longer do much city driving.
Now is that anal or what?
Another issue:
The money saved by using air, may buy you a tyre bleeder/pressure gauage, so as when the air filled tyre pressure rises for track use, you can bleed them back down to the preferred value.
Final issue:
More so for R32/S3 owners.
If you OEM tyres are speed rated at Y (92Y); would going down to 'W' (92W) give you more grip. I would think so as Y is rated at something like 300kph+ speed which is unlikely to be achieved for roadway use. 'W' is rated up to @ 270kph (I think) and should have softer sidewall construction.
So I'm thinking that the extra softeness of the sidewalls of the 92W being rated at only 270kph may give you extra grip - a bit like a drag car or Michelin Tyres.
It may be something for R32 owners to consider - going from 'Y' to 'W' is legal so long as your tyre outlet puts a sticker on front windscreen indicating that the vehicle is 'only rated to 270kph' and cannot be driven beyond this speed.
The 92W will also be cheaper.
I'm running a 92W on the GTI - but OEM is 91W - so I'm over on load rating and meet the same speed rating as OEM.
Cheers
WJ
It's good to see that everybody is getting anal about tyre pressures.
Of course tyres are the most important contact between your ride & the ground.
From experience: I have found that the Denver 17"/225/45 series seemed to hold pressure better than the Huff Reps 18"/225/40 series.
Not sure if it's the lower profile, or just the way the tyre has been placed on the rim. The difference is only marginal.
Being anal about tyre pressures of course is a good thing.
On my recent trip to the farm & Canberra, I did 1300km of driving and checked the pressure 4 times in 4 days:
1. Before commencement of journey.
2. Before Two man GTG with Dingah day after.
3. Before Canberra GTG day after that.
4. Before return to Sydney.
Pressures generally run at 36psi cold.
On my return to Sydney, I stopped by to see the Manager Kevin of Jobson Bridgestone Tyre Centre to have my tyres inspected for wear in deciding whether or not to have a wheel alignment after 5,000km of driving.
Tyre were rotated from to rear with wear pattern noted.
I'm running toe out (negative toe) of 0.2mm.
Standard specs for GTI is 0.0mm at front.
Manager Kevin & I will monitor wear patterns in decision to see if we go for a bit more toe out (negative toe) to aid turn in response.
I will return to Jobson Bridgestone in 5,000km for wheel balance, rotation & another wear assessment to find the ideal between highway cruising & driving through the tight twisty corners, as I no longer do much city driving.
Now is that anal or what?
Another issue:
The money saved by using air, may buy you a tyre bleeder/pressure gauage, so as when the air filled tyre pressure rises for track use, you can bleed them back down to the preferred value.
Final issue:
More so for R32/S3 owners.
If you OEM tyres are speed rated at Y (92Y); would going down to 'W' (92W) give you more grip. I would think so as Y is rated at something like 300kph+ speed which is unlikely to be achieved for roadway use. 'W' is rated up to @ 270kph (I think) and should have softer sidewall construction.
So I'm thinking that the extra softeness of the sidewalls of the 92W being rated at only 270kph may give you extra grip - a bit like a drag car or Michelin Tyres.
It may be something for R32 owners to consider - going from 'Y' to 'W' is legal so long as your tyre outlet puts a sticker on front windscreen indicating that the vehicle is 'only rated to 270kph' and cannot be driven beyond this speed.
The 92W will also be cheaper.
I'm running a 92W on the GTI - but OEM is 91W - so I'm over on load rating and meet the same speed rating as OEM.
Cheers
WJ
I take it you don't have any of your own experiments to validate your 'scientific' application of theories? And where did you get the concept that O2 was the dominant force in air? Was i being to subtle when i suggested that the interactions in air can't be described by one single bond??
And, for what it's worth, the air was being released from the tyres after taking pressure measurements using the same insturment every time... claimed to be calibrated to within 1% at the RH and temp i was using it. Does the release of pressure from my tyres somehoe invalidate the fact that the pressure increased to require the 'escape' t return to my preferred pressure? I'd love to hear your argument about that one...
OK... wang out. I have a B.E. in Electrical Engineering (specialising in Automation and robotics) and a B.Sc in Physics. When i get home (currently in Newcastle on a project), i'll happily wade through some of my old notes and text books to increase the size of my ePenis. It's been a few years (4 or so) since i've used them... so you'll just have to be patient while i discredit you, MK? After all... we can't have a difference of opinion when it comes to science. Science is all about who's right and wrong - who's more god like and who has the larger wang. :thumbsup:
Dingah
Crusty Aviator
- Location
- Canberra Airport
- Car(s)
- Audi SQ5
At last we're there - it's all about who has the biggest degree.
Well I use Celsius what about the rest of you guys and gals?
Dingah
Well I use Celsius what about the rest of you guys and gals?
Dingah
Dingah
Crusty Aviator
- Location
- Canberra Airport
- Car(s)
- Audi SQ5
James my dear chap, how are you?
To put your mind at rest on our comparison runs I was running 36psi cold too.
I note your Toe in vs Toe out comments with interest - in my experience on Bargearse the fat Ford, increasing its Toe-in tended to increase the level of nervousness off-centre - does that follow from your experience in the Golf?
Di:iono: ngah
Capercat
It's a chuck-about
- Location
- Location :)
WJ, I'm thinking of buying Michelin's PS'2 225 17 45 91Y
My current OEM Conti's are 91W, are you saying the 91Y Mich have a harder side wall = less grip?
My current OEM Conti's are 91W, are you saying the 91Y Mich have a harder side wall = less grip?
-mission-
Direkt Schalt Getriebe
- Location
- Location: Location:
- Car(s)
- MY07 Golf GTI
WOW when are some of you blokes getting a call up for a F1 team ??? Knowing so much about tire pressures etc - you'd be a valuable asset to Ferrari and co.
:bellyroll:
:bellyroll:
-mission-
Direkt Schalt Getriebe
- Location
- Location: Location:
- Car(s)
- MY07 Golf GTI
Will Kelvin help? :yikes:
WhiteJames
Fun Nazi
- Location
- Sydney
- Car(s)
- VW Golf GTI MKV
Rocco,
It's difficult to say.
Michelin traditionally have softer side walls than the other brands.
That's what makes them grippy & comfortable at the same time.
They are also noted for being notably good in the dry.
The EVO 2007 tyre test performed with Golf GTI had the following rankings:
1. Goodyear F1 asymmetrical
2. Vredestein Ultrac Sessanta
3. Conti CS3
4. Bridgestone Potenza RE050-A
5. Michellin PS2
6. Pirelli PZero Nero
7. Kuhmo Ecsta STP KU31
8. Dunlop Sport Maxx
9. Yokohama S.Drive
Point is: I think there are better tyres out there for a lot less money.
If you're boss is paying for them - fine.
If you pay for them; I reckon the Goodyear F1 Asymetrical or Bridgestone RE001 Potenza Adrenalin - why? They are designed to work with lowered sports vehicles with extra negative camber.
Michelin PS2 are like $600.
I think the Conti CS3 are better at $495.
My first choice was Goodyear F1 asymmetrical due to -20mm ride height & -1.0 negative camber. I found with the CS2 that they worn unevenly. Haven't had this problem with the asymmertical RE001. RE001 are not OEM tyre so they are a bit noisier & ride a bit harder.
Goodyear F1 or RE001 could be had for @ $290-$360.
The Conti @ $495 or Michelin PS2 at $600 are not twice as good as the other brands. The Goodyear is likely to be better than both for wet & dry.
Good to hear from you Dingah.
I'm fine.
To answer your question - Yes.
The toe out (-.0.2mm) I run at the front is only marginal - but does have a notable effect - esp at higher speed.
When the outside tyre is turning into a corner, the inside wheel is acting like a brake which helps pull the car into the corner.
Great for tight twisties; but at high speed you have to have your wits about you.
After another 5,000km - I will check wear to see if I can get away with more toe out. I doubt it though - as more toe out (negative toe) will start to wear the tyres unevenly, causing more wear on the inside edges.
Interestingly - I experimented with the tyre pressure once going to 18"/7.5"/225/40 series tyres. I thought I would require more pressure.
I ran them as high as 39 psi - but found too much understeer at low speed turns; and too much oversteer in higher speed turns.
Now I run them at the same pressure as I ran the 17" Denvers - 36psi cold.
The heavier huff wheel does make the ride more supple & refined; but counteracts with a brittle feeling at low speed in city with less tyre & more wheel.
Cheers
WJ
Dingah
Crusty Aviator
- Location
- Canberra Airport
- Car(s)
- Audi SQ5
again, you don't seem to understand what you're talking about. it has nothing to do with 'bonds' or about which gas is more 'dominant'. what you saw cannot be explained by the difference in gases in your tyres. also i don't need an experiment, you don't seem to understand that air pressure vs temp at constant volume has already been graphed! how do you think they work out fuel maps? the results do not agree with what you say you saw.
or it could just be that you exaggerated and when it was pointed out to you, you wouldn't accept it so you kept edging out on that limb, pursued by someone who doesn't know how to let go of an argument... there is no way an air filled tyre can rise in pressure 6 times more than a tyre with just nitrogen in it only as a result of heating. the problem you have is that even if we account for you doing something different on each run, the temp change required to cause such a change in pressure is such that your tyres would likely have melted. this is because, for our purposes, pressure approximately varies with temperature.
i'm done here. if you'd like to continue, let's get someone to act as a second and we'll each put up $10. all you have to do to collect is explain, using established physics, how a street legal tyre filled with air can be heated such as to give a pressure change 600% greater than the same tyre filled with n2, initial pressures and change in temperature being equal in both tyres. tell you what, you can even apply twice as much heat to either tyre if you want.
if you do that and take my money, i'd like you to tell me where you got your degrees because i'll want to send my kids there. for future reference, regardless of if you win or lose, i'll buy you a beer if we ever meet up, to show there's no hard feelings.