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Old 05-10-2004, 11:31 AM   #1
STI-C-YA
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Default Slick Tires In Racing

Hi everyone!

I have this question. I'm racing my Sti in the circuit track every 45 days and I want to use slick tires for that. Someone told me that slick tires may damage the drive train of my car due to the amount of pressure that the car puts in it. I want to know if this is true because I also use my car for daily drivig and I dont want to damage it. Thanks
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Old 05-10-2004, 11:47 AM   #2
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Default Re: Slick Tires In Racing

Quote:
Originally posted by STI-C-YA
Hi everyone!

I have this question. I'm racing my Sti in the circuit track every 45 days and I want to use slick tires for that. Someone told me that slick tires may damage the drive train of my car due to the amount of pressure that the car puts in it. I want to know if this is true because I also use my car for daily drivig and I dont want to damage it. Thanks

track driving puts a whole lot of abuse on your car and may damage it, race tires or not.

however, the STI can put up with extremely sticky tires, that would be the last of my concerns.

a good track tire is the Kumho Victoracer. If you want to step up to something better and more expensive, then try the hoosier road race DOT tires. (R3S04s? I think they are called)

neither of these are techinically 'slicks' (they have token grooves), but most track day guys run tires like these.
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Old 05-10-2004, 02:42 PM   #3
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Default Re: Re: Slick Tires In Racing

Thanks a lot for your advise. I will like to know wich things I need to check after each race to try to keep the car in optimum conditions. Thanks
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Old 05-10-2004, 03:35 PM   #4
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Default Re: Re: Re: Slick Tires In Racing

Quote:
Originally posted by STI-C-YA
Thanks a lot for your advise. I will like to know wich things I need to check after each race to try to keep the car in optimum conditions. Thanks
brake pads
brake rotors

might want to step up to a good DOT4 brake fluid, might change your tranny and diff oil more often.

be sure to run high quality gasoline at the track, watch engine temps and such. If you can buy 100+ octane gas at the track it wouldn't be a bad idea.

Don't do too many hard laps in a row.
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Old 05-10-2004, 04:01 PM   #5
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Default



Thanks again. Actually I'm using Motul DOT 4 brake fluid, Red Line's Water Wetter along with a Crucial Racing Thermostat and 98 Octane Gas. I also have my Camber set to -1. What I been having are high raises in the preasure of the tires, sometimes more than 10 pounds. I heard someone said that inflating them with nitrogen will reduce this. Is it true?
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Old 05-10-2004, 09:54 PM   #6
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Quote:
Originally posted by STI-C-YA


Thanks again. Actually I'm using Motul DOT 4 brake fluid, Red Line's Water Wetter along with a Crucial Racing Thermostat and 98 Octane Gas. I also have my Camber set to -1. What I been having are high raises in the preasure of the tires, sometimes more than 10 pounds. I heard someone said that inflating them with nitrogen will reduce this. Is it true?
you can crank the camber all the way to -2.5 or so if you want =)
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Old 05-10-2004, 10:09 PM   #7
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Quote:
Originally posted by STI-C-YA
What I been having are high raises in the preasure of the tires, sometimes more than 10 pounds. I heard someone said that inflating them with nitrogen will reduce this. Is it true?
The pressure raising in tires comes from moisture in the air thats in the tires, filling them with an inert gas like nitrogen instead will get rid of the pressure fluxuation dramatically.
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Old 05-10-2004, 10:13 PM   #8
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Quote:
Originally posted by afpdl
The pressure raising in tires comes from moisture in the air thats in the tires, filling them with an inert gas like nitrogen instead will get rid of the pressure fluxuation dramatically.
]

PV = nRT

This s the ideal gas law, if temperature increases so will the product of pressure and volume.

I'm trying to figure out how moisture would effect the pressure rise due to temperature. I'm really not very clear on it. You have any links to info?

Thanks,
Dustin
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Old 05-10-2004, 10:33 PM   #9
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yep not moisture, just the good ole PV=nRT, nitrogen (a major component of breathable air, ~70%) is more temperature stable than oxygen (IIRC).


Do a few laps, your tires will heat up to operating temp and then adjust pressures. They will stay (or at least stay close) to that pressure when the tires are hot for subsequent laps.
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Old 05-10-2004, 10:57 PM   #10
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If you have moisture in your tires some of it will be in liquid form as small droplets on the inside of the tire for normal driving. Hard driving will heat these droplets into vapor, which makes a huge difference in the pressure in the tires. If you fill your tires at a typical gas station air line you can usually see water droplets coming out of the line when you start the air flowing. That water in your tires causes the pressure build up.
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Old 05-11-2004, 09:05 AM   #11
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Quote:
Originally posted by speedyHAM
If you have moisture in your tires some of it will be in liquid form as small droplets on the inside of the tire for normal driving. Hard driving will heat these droplets into vapor, which makes a huge difference in the pressure in the tires. If you fill your tires at a typical gas station air line you can usually see water droplets coming out of the line when you start the air flowing. That water in your tires causes the pressure build up.
This is the part that's not so clear. Water droplets represent a reduction in volume, water is essentially noncompressible at these pressures. When in turns to vapor you trade off that volume reduction for an increase in the n term of the ideal gas law. So does this produce a net increase in pressure???? And if so is it greater than the increase due to just the temperature change???
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Old 05-11-2004, 03:45 PM   #12
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Speedyham has the right of it...Rule of thumb #1 for thermodynamics, air is not an ideal gas and does not behave according to the ideal gas law (my professor used to mark problems with air wrong if we used the ideal gas law!) Too many impurities, like moisture which expands faster than gas when heated. That's why something like pure nitrogen works better...

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Old 05-11-2004, 03:54 PM   #13
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So, how different is dry air than nitrogen? Dry air is much easier to get than nitrogen.
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Old 05-11-2004, 05:46 PM   #14
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This gets more interesting with every reply
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Old 05-11-2004, 10:45 PM   #15
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Quote:
So, how different is dry air than nitrogen? Dry air is much easier to get than nitrogen.
With dry air, I have to work very, very hard to see much pressure increase. Like 10 laps per pound of increase.

Nitrogen may be better, but you have to be running stints longer than a sprint race to find out.
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