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hi chaps,

looking for some feedback as I have my first trackday in the gtr.
Amazingly I havent been on track for nearly a year, whereas I used to go every 2/3 weeks, but such is life.

anyway, I want to make sure I get the best out of the gtr, so just wondering what some of you track veterans are doing re. tyre pressures, warm up/hotlaps and cool downs.

Is everyone letting air/ nitrogen out if the tyres start heating up?
Whats the ideal tyre pressure once heated?

Im going to bedford, so how many laps were you guys doing before coming back in especially considering the tranny temp oil needs watching?

Advice much appreciated as always
 

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Hi Peter,

I can't give any direct advice, but I don't think you'll see more than a couple of PSI increase over normal running tyre temperature as Nitrogen stays very similar in terms of pressure when heated.

Couple this to the fact they are run flats, so of course much stiffer, I think they will suffer much smaller temperature increases than a normal car would.

Given that the ambinet temperature is pretty cold at the moment, heating will probably be even less of an issue than it would normally.

Unless a tyre goes above 34PSI I'd probably leave them how they are. I have not tracked the car myself to see this first hand though, so might all be rubbish. Under fast road use I rarely get more than 3psi of extra pressure from stone cold though.
 

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Hi Peter,

I can't give any direct advice, but I don't think you'll see more than a couple of PSI increase over normal running tyre temperature as Nitrogen stays very similar in terms of pressure when heated.

Couple this to the fact they are run flats, so of course much stiffer, I think they will suffer much smaller temperature increases than a normal car would.

Given that the ambinet temperature is pretty cold at the moment, heating will probably be even less of an issue than it would normally.

Unless a tyre goes above 34PSI I'd probably leave them how they are. I have not tracked the car myself to see this first hand though, so might all be rubbish. Under fast road use I rarely get more than 3psi of extra pressure from stone cold though.
Sorry, but you're not accurate on pretty much every point.

1. Nitrogen expands just as much as any other gas does. The lack of expansion is a myth and is against the basic laws of physics (pv=nRT) . Air is 78% nitrogen anyway.

2. They heat up just like any other tyre, the heat is caused by stressing the tyre surface creating friction, not by the tire-wall bending.

3. The amount the tyres heat-up is pretty similar at most temperatures, they just take a bit longer to get to temperature as they start lower.

4. I've found it quite easy to gain 7-10psi on the track in the GTR, similar to other cars I've driven on track.

Obviously the effect will be greater the more laps you drive and the harder you drive.
 

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But the main point of using nitrogen rather than normal compressed air is it is not going to be contaminated with water vapour which will expand more dramatically as it boils than any pure gas?

I've not bothered to change pressures in the GT-R and have not noticed any major increase in understeer which is the normal indicator that the front tyres have overheated and overinflated themselves.

I've not been able to stay out for more than 12-15 minutes before tranny temps got to 119c and have mainly backed off before it went over 120c.

The standard brake pads have normally had enough by then anyway.

I always do a full cool down lap.
 

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I give it the beans on the straight bits, throw the anchors out just before the curvy bits and then apply beans when I'm half way through the curve.

Honestly, that's all there is to it.

;)
 

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Yep, tyre pressures are less of an issue.

Tranny temps and brake fade end my laps, and the number depends upon trackside temp and the track involved.

Keep the MFD showing oil and tranny temps and as soon as you get to 105 - 110 on the tranny, back off and cool down for 2 laps.

The usual stuff regards leaving the engine ticking over when you come in to the pits, with the handbrake off, gears in PARK.

Only other thing I'd say is if your rear number plate is stuck on, there is a chance that the exhaust temp will melt the adhesive and it'll fall off!
 

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Sorry, but you're not accurate on pretty much every point.

1. Nitrogen expands just as much as any other gas does. The lack of expansion is a myth and is against the basic laws of physics (pv=nRT) . Air is 78% nitrogen anyway.

2. They heat up just like any other tyre, the heat is caused by stressing the tyre surface creating friction, not by the tire-wall bending.

3. The amount the tyres heat-up is pretty similar at most temperatures, they just take a bit longer to get to temperature as they start lower.

4. I've found it quite easy to gain 7-10psi on the track in the GTR, similar to other cars I've driven on track.

Obviously the effect will be greater the more laps you drive and the harder you drive.
1) When comparing nitrogen and air against each other using the ideal gas law, the advantages of nitrogen look non-existent, but you must remember that ambient air contains a given level of moisture, and even more more when air is compressed as it would be in a tyre. If you have ever run an air compressor, when you let the pressure out at the end of the day, the moisture (water) comes out of the bottom along with the air as an illustration of this moisture build-up.

It's the moisture that causes the extra pressure change with temperature which the ideal gas law will not detect or account for. By using nitrogen it's totally dry, and so the moisture will not exist in the tyre. This is where the advantage comes from. The temperature change due to moisture does not exist with correctly filled nitrogen tyres.

2) Heat is caused by the tyre breaking friction (traction) yes, but it's also caused ina big way by the deformation of the metal section within the tyre. If you drive in a straight line, your tyres still get hot. This is down to the deformation of the tyre more than anything. A stiffer tyre, or one run at a higher pressure will show less of an increase in temperature when running. If the deformation of the tyre did not introduce heat, cars like the GT-R could just run around on skinny 195 tyres and still perform well.

3) A 10C day compared to a 30C day will show lower surface temperatures on the tyres. It's a contributing factor to the overall temperature, but you're right, on the average 10-12 minute track day session, you would probably see similar temperatures. The tyre deformation still generates the same amount of heat no matter what the ambient temperature.

4) I have not yet tracked my GT-R (still running in but I'm getting along nicely :thumbsup: ), but if you have seen 7-10 PSI change then that's more than I was expecting. I can't argue differently since I have not tried it myself. I'd put money on you seeing more like a 15PSI change with air alone though, especially on a lardy car like the GT-R :) I stand corrected about the temperature increase though - I didn't think it would be as high.

Sorry to the topic starter as this have drifted a little off topic. I hope you don't mind the discussion between Guy and I though.
 

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In practice though:

a. I ran my GT2 with nitrogen and also air and noticed no real difference between the amount of pressure gained on trackdays.

b. If you do drive hard on track you'll need to lower the pressures to keep grip optimum. At the end of the day you re-inflate the tyres when cold to drive home. I cannot imagine anyone here would carry a nitrogen canister with them so will likely do as I do which is use a small inflator. There's no way after that I'm going to drive to a tyre dealer each time and ask them to flush and refill all the tyres with nitrogen.

Regarding the points in the post above, yes tyres get warm in a straight-line, but nothing like they do on a trackday. Driving at 100mph+ on motorways/autobahns the tyres gain perhaps 0.1-0.2 bar. Driving on track they gain up to 0.5bar.
 

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[QUOTE}I've not bothered to change pressures in the GT-R and have not noticed any major increase in understeer which is the normal indicator that the front tyres have overheated and overinflated themselves.
Not driving it hard enough then !!! LOL

Mine under steered like a bitch at Bedford after 4 hot laps!! The pressures had gone up by 7 to 8 psi all round ! Always do warm up lap and a cool down lap. Much the same as my R33 GTR, however in that I REDUCE the tyre pressure (Toyo R888's) to about 25 psi so that the tyres are 30 ish when hot which I was told is the optimum operating pressure/temperature.
 

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Just get 0.3b off before entering track and inflate back when out. End of story :)
 

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Discussion Starter #11
great tips lads and dropping to opt pressures while hot was pretty much what i was expecting.

When re inflating, Im guessing there is no harm putting air and back in to mix with nitrogen?
Looks like the weather is settling so Im expecting a cold dry day

Cant wait.
 

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Nope, not as far as i know, or you could do what i did as i knew I would be doing lots of Track days and just let the Nitrogen out and put air in and then you know you can play around with the tyre pressures and not have to worry about the Nitrogen/air mix !!
 

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hi chaps,

looking for some feedback as I have my first trackday in the gtr.
Amazingly I havent been on track for nearly a year, whereas I used to go every 2/3 weeks, but such is life.
Check tyres and pressures, get in, foot on brake and press the red button. Warm her up and the thrash the grandmother out of her. Screw the tranny temps it is 300 odd quid for a fluid change - I had sooooooo much fun in mine at Goodwood this year I did not know what to do with myself.

Honestly drive it as fast as you can, when you have a bit of a gap behind you jump on the brakes mid corner (seriously, you may have to do it on the road one day you will be better off knowing what the car will do).

Throw it into corners and jump on the power - track days are great for learning what your can can do.

I would always get track day insurance and remember to let the car cool down on the cool down lap.

Other than that have fun and dont go out for the last lap of the day as there some tit that bins it.

Have a good one

Kp
 
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