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Registered:
October 2003
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 tire pressure ??
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Sat, 26 February 2005 12:31
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im confused. i did a search about tire pressure and read that 3-5 psi off of the maximum tire pressure was optimal. i tried running 38psi in one of our cars and it felt peppier and had better steering response. i know the usual tire pressure is around 30 i just wanted to know whats the right pressure for 1st gens which balances grip and response. my tires are 205-60-13 on 13x7 rims. thanks
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Location:
Brisbane
Registered:
May 2002
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Re: tire pressure ??
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Sat, 26 February 2005 12:51
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1st gen what?
In any case, the "right" tyre pressure depends on a lot of things, such as what you're using the car for. Lower pressure (eg 30-ish) for a comfortable ride, higher pressure (up to 40) for sharp steering response and improved cornering stability, and even higher again if you're racing. I ran up to 45psi at the track when I had 14" wheels with giant sidewalls. When you have low profile tyres there's no need for such high pressures, but with higher profile tyres you need plenty of pressure to keep the sidewalls from wobbling around.
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Registered:
October 2003
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Re: tire pressure ??
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Sat, 26 February 2005 14:18
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whoops forgot to mention its a celica. itll be used as a weekend fun car with a little bit of city driving. so id guess 35 psi would be just right?
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Location:
Sydney
Registered:
June 2004
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Re: tire pressure ??
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Sat, 26 February 2005 17:42
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your best option would be to take it round your neighbourhood at different pressures to really notice the affects of the different rates in the tyres. being familiar with your local roads will allow you to really determine how they affect the drivability of your car at certain rates of pressure.
increasing/decreasing the pressure aint that hard at your local servo. different pressures are used for differnet reasons, 30psi is an all round even pressure that is for all sorts of driving. increasing/decreasing the pressures will affect the way the car handles, accelerates, brakes, etc. all these factor in to the equation when selecting a tyre pressure to suit.
also it is not just about putting the same amount of pressure into all 4 tyres. depending on the setup of your car (FWD, RWD or 4WD) and how it has been tuned you would need to test the car to determine the best pressures to have.
continuing on with the driveability of the car you could even have different pressures with each tyre. now this would be more in circuit racing scenarios but none the less i believe that tyre pressure is a MAJOR part of the car all round. you need to factor in that the tyre pressure of the car will change what happens when accelerating, cornering, braking, handling, tyre wear, brake wear, the change in temps caused by the different pressures on the tyres/pads/rotors.
further to this you would need to consider what rate springs you have and the type of dampers/shocks on the car.
for example on a RWD car increasing the pressures will allow cornering to be better but the downfall is that the rear end can slide out alot easier. reducing the pressure will increase the traction of the rear but is then compensated by the lack of cornerability (is that a real word?  ). so you would think that having a lower pressure on the rear than the front would be ideal true? well in essence yes but then you need to negotiate the ratio of the 2, basically how much more should the front have to the rear OR how much less the rear should have to the front. this ratio will determine the best setup for the car.
now once you have this ratio you can then easily manipulate the pressure dependent on what roads you will be driving on, the weather conditions and how you will be driving at that particular time. as for having 4 dfferent pressures in each tyre well we wont get into that now cause i doubt your talking bout circuit racing scenarios
at the end of the day tuning a car is not that easy and picking the right pressures is just as hard. most people tune their cars for MAX power output and torque and you would need to select the right tyre pressure based on how the car has been tuned and setup/configured, ie de-tuning your car slightly will allow you to increase the tyre pressure (maintaining traction) and hence better your cornering ability AND tuning it to its peak will require you to decrease tyre pressure to maintain traction but will reduce your cornering ability.
you need to decide and find a medium and then work from there. WELL THATS HOW I SEE IT ANYWAY 
PS cant wait to read the comments from this post 
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Location:
Sydney
Registered:
May 2004
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Re: tire pressure ??
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Sat, 26 February 2005 23:10
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when i got my car dyno tuned they increased the tire pressure to 40psi on the dyno. i noticd what they had done and kept driving around thinking it was all good. my tires were infact over inflated and wore out very uneven. I'd say keep your tire pressure between 30-34psi.
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Registered:
October 2003
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Re: tire pressure ??
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Sun, 27 February 2005 03:01
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wow comprehensive post fade-e thanks guys. ill just start experimenting then
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I Supported Toymods
Location:
Sydney
Registered:
December 2002
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Re: tire pressure ??
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Sun, 27 February 2005 12:22
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Toyo's website has a little table which will give you a rough idea of what pressure you should run... these figures are based on vehicle weight.
http://www.toyo.com.au/Pit%20Lane.htm
If you have a look at the Tech Info Bulletins on their website and they show how to more accurately work out the pressures based on vehicle weight, tyre profile etc. etc.
Personally I run 42 PSI when warm on all corners with 215/40/17's... I have experimented with tyre pressures and this just seems to feel the best for my setup.
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Location:
Hobart, Tas
Registered:
May 2002
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Re: tire pressure ??
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Mon, 28 February 2005 02:03
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| fade-e wrote on Sun, 27 February 2005 04:42 |
for example on a RWD car increasing the pressures will allow cornering to be better but the downfall is that the rear end can slide out alot easier.
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I disagree - to a certain point, more pressure= more grip. I'm talking 205/60 profiles on 14x7" rims, and the difference between 30psi and 34/36.
What you say is probably true for higher pressures though - if the tyre surface becomes convex, perhaps less grip from reduced contact pathc but better when cornering?
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Location:
Brisbane / Gold Coast
Registered:
May 2002
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Re: tire pressure ??
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Mon, 28 February 2005 02:10
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English = TYRE, guys.
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Location:
Sydney
Registered:
June 2004
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Re: tire pressure ??
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Mon, 28 February 2005 02:31
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| Stefan wrote on Mon, 28 February 2005 13:03 |
| fade-e wrote on Sun, 27 February 2005 04:42 |
for example on a RWD car increasing the pressures will allow cornering to be better but the downfall is that the rear end can slide out alot easier.
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I disagree - to a certain point, more pressure= more grip. I'm talking 205/60 profiles on 14x7" rims, and the difference between 30psi and 34/36.
What you say is probably true for higher pressures though - if the tyre surface becomes convex, perhaps less grip from reduced contact pathc but better when cornering?
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you are right but also consider that these pressures are COLD pressures and therefore when under normal driving conditions these pressures increase. therfore your 34/36 tyre will reach about 40 or so once warmed adnd heated from driving which could end up convexing the tyre and reducing the traction that you have.
this is why you see all tyre pressure rates at COLD tyre temps. therefore to maintain your optimal 34/36 pressure you need to fill them to 30psi when cold so that they get to 34/36 when warmed up.
this is why it is essential to test pressures. i even go to the extent to measure the pressure at cold and then measure it again after a small run around the local neighbourhood.
the problem is that alot of people (more mainstream drivers) see that their tyres are flat and pump it to 30psi. and then the next morning the get up and the tyre is flat again. thats cause the air inside has cooled and the pressure has dropped.
ITS ALL TRIAL AND ERROR, also for your style of driving those rates are gopod for you and not so good for others
cheers
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