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Old 6th April 2005, 15:16   #61
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An excellent resource for tyre pressures at various loads and speeds. I believe, it is for Australia, where conditions will be similar to India (hot climate).
I dunno if an increase by 8 psi (over the rec pressure) is a good idea. Maybe it is but, i wouldn't bet on anything above 4 psi (over rec pressure).

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Old 6th April 2005, 22:32   #62
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Obviously for the stock tyres the car manufacturer's recommendations hold good. However if we upgrade the tyres, will those numbers still hold good?
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Old 6th April 2005, 22:33   #63
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Obviously for the stock tyres the car manufacturer's recommendations hold good. However if we upgrade the tyres, will those numbers still hold good?
Yup, i still use the original 29 psi in my new tyres. But, change it, depending on how the car is gonna be driven.

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Old 7th April 2005, 03:34   #64
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Quote:
Originally Posted by Shan2nu
I'm in the habit of keeping 30-31 at the front and 29 at the rear.

Shan2nu

shan2nu,

keeping the front tire pressures higher then the rear tire pressure will give u a lot of understeer in the entry and exit of the corners!!! Dunno how come u are comfortable with it!!
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Old 7th April 2005, 08:14   #65
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Quote:
Originally Posted by amitoj
i thot one shd keep lower pressure only when more than normal grip on the road is required... for example dusty terrain... or wet surface.
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Hey Amitoj,

As pointed out aldready, tire pressure must be increased before a long high-speed journey.
Its mostly the flex in the sidewalls (and friction between tube and sidewall) that builds up the heat and causes tire failure. This is more likely to happen at a lower tire pressure since that would let the sidewall flex more.

Anyway, the reason i am quoting your post is because i wanted to specify that on a wet surface you would want to run a normal/higher pressure. Since, the larger your contact patch is, the more likely you are to aquaplane.

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Old 7th April 2005, 09:47   #66
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also when u upsize your tires ,its more of a trial and error when it comes to maintaining the proper tire pressures.
about 145/80r12 ,maruti says 24 psi,but i used to fill about 27psi.
but when i went for 155/65r13 ,27 psi seemed to be less as ,there were black bands on the outer edges of the tires ,which suggest underinflation.so i used to keep 30-32psi.


now with the 165/60r13 ,i feel 28-31 is ideal.



and amitoj,

during the rains it is better to stick to the slightly lower air pressures to reduce the risk of aquaplaning.by lower ,i dont mean lower than the manufacturer recommended.u can stick to whatever is mentioned on the sticker on the driver side.
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Old 7th April 2005, 10:43   #67
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Quote:
keeping the front tire pressures higher then the rear tire pressure will give u a lot of understeer in the entry and exit of the corners!!! Dunno how come u are comfortable with it!!
Believe it or not, it doesn't. infact it kills understeer. I went through a few websites and they said that increasing the front tyre pressure actually helps the car turn into corners.

low front tyre pressure results in understeer, and low rear tyre pressure in oversteer.


Ofcourse using too much pressure will create understeer but, a diff of 2 psi wont, you'll love the way the car enters into corners. Try it.

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Old 7th April 2005, 11:12   #68
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Hmm... thanks rehaan, satya... regarding the pressure in rains... wotever i do i will NOT keep it lower than recommended during rains.
during rains i anyways slow down a lot... coz if god forbid i have to brake suddenly, then i might stop without causing any damage but i cant say the same for the guy behind me!!
It has been raining on n off here for the past few days and not a single day has passed when I havent been witness to a 2 wheeler banging into a car. Something about this weather jus makes the two wheelers go even more rash!!

Cheers
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Old 7th April 2005, 14:11   #69
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Quote:
Originally Posted by Shan2nu
Believe it or not, it doesn't. infact it kills understeer. I went through a few websites and they said that increasing the front tyre pressure actually helps the car turn into corners.

low front tyre pressure results in understeer, and low rear tyre pressure in oversteer.


Ofcourse using too much pressure will create understeer but, a diff of 2 psi wont, you'll love the way the car enters into corners. Try it.

Shan2nu

hhmm.... never heard this before, its like going against the laws of physics..! coz we have tried it on the track also played around a lot with tire pressures....!! Since increasing the Psi on the front tires will reduce ur contact patch... in the front hence causing understeer...!!Well let me still try this on the road cars and see .... u never know it may just help me overcome understeer!

Last edited by jigarmuni : 7th April 2005 at 14:12.
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Old 7th April 2005, 15:06   #70
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Well let me still try this on the road cars and see .... u never know it may just help me overcome understeer!
Yes, it works pretty well on my car though. I've driven Rush's Vtec on the twisties and i know for sure that my Vtec doesn't understeer to that extent. It has to be the tyre pressure, since i got the supenssion checked and they're perfectly alright.

Not just the 195s, even the old 175s used to make the car oversteer.

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Old 7th April 2005, 16:00   #71
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So shan, I guess you've got rid of the snap oversteer now
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Old 7th April 2005, 16:05   #72
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Quote:
So shan, I guess you've got rid of the snap oversteer now
It wasn't snap oversteer, it was more like lift off oversteer. And yes, the car still doesn't understeer. With the new tyres, it's more neutral now.

but tell you what, i've got a fixed gear (for the Vtec) for almost each and every turn on the Hubli-Ankola road. If i take a 3rd gear turn in 5th (at the same speed, the car isn't able to hold a tight line and can stray away, a bit.

So, i guess my gear selection also adds to the way the car turns.

Shan2nu

Last edited by Shan2nu : 7th April 2005 at 16:09.
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Old 7th April 2005, 18:45   #73
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Quote:
Originally Posted by Shan2nu

So, i guess my gear selection also adds to the way the car turns.

Shan2nu

Yeha shan2nu surely it makes a big difference!!! If u are in a lower gear then u are producing more torque from the engine, this torque is delivered to ur front wheels, which in turn will tend to understeer much more compared to driving in a higher gear!! where else if u just tap ur brakes while u are turning, will give a little bit of a drift to ur car, which we help overcome that understeer quite nicely!
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Old 7th April 2005, 18:54   #74
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coz we have tried it on the track also played around a lot with tire pressures....!!
Which race track are you talking about? And what car was this on?

Yup, i always trust downshift to the right gear and rpm. Nothing better than that. It even makes the Wagon R look good. LOL

Tried toe-heel braking but still need a lot of practice with that.

Shan2nu

Last edited by Shan2nu : 7th April 2005 at 18:56.
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Old 7th April 2005, 21:10   #75
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Quote:
Originally Posted by GTO
I have gotten with me an amazing digital tyre pressure gauge from the states which is dead accurate.........
seen discrepancies of upto 10 psi between petrol pumps.
From my experience in instrumentation, the digital gauges do not always mean accurate readings. I have two of these (one bought in US and other in UAE)and each reads different from the other. I even tried to get them calibrated against a test gauge but was not successful (BTW and for info, even these digital instruments need regular calibration. Without calibration, there accuracy is as good (or bad) as the analog ones).

Regarding the petrol pump gauges, as you have already mentioned, the less said the better.

Ultimately I have realized that it is very difficult to know the exact actual tyre pressure with the kind of intruments we have. And thats why I dont think much about the exact pressure required. I just try to keep the pressure in the vicinity of the recommended numbers, as measured by one of my guages (which I think is more accurate than the other ), and pray that it is OK.
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