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View Poll Results: The best fuel
Reliance 15 6.98%
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Old 19th April 2006, 06:58   #46
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Quote:
Originally Posted by sharathjeppu
Currently I maintain 34 psi even in city with negligible difference in the drive comfort.
34psi seems rather high to me. There has to be ride differnrce between 29 and 34.
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Old 19th April 2006, 08:47   #47
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Question Slightly OT

Quote:
Originally Posted by sharathjeppu
Maruti reccommends 29 psi for the Swift ZXi in city and has specified in the manual that it can be increased by upto 5 psi for highway driving (Tubeless Tyres).
Hey aren't we supppose to fill slightly less air on highways since the air expands due to heat which is produced due to continues high speed running
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Old 19th April 2006, 09:02   #48
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Quote:
Originally Posted by Technocrat
Hey aren't we supppose to fill slightly less air on highways since the air expands due to heat which is produced due to continues high speed running
Actually its a viscious circle....
If you fill more Air.... the air would be tightly packed.. and won't heat up as much as if it was lose.
Just to strike the right balance its better to go with the exact recommended pressure.

Less Air is riskier than slightly more Air.
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Old 19th April 2006, 13:31   #49
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Quote:
Hey aren't we supppose to fill slightly less air on highways since the air expands due to heat which is produced due to continues high speed running
I do it the opposite way and I think thats correct. I fill up 2-3 psi more than normal which makes up for the higher flexing due to high speeds on the highway.
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Old 19th April 2006, 14:48   #50
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Shell! I think is the best!
Their service is best. The fuel quality was also not bad. And they even make sure that not a single drop of fuel is wasted while fuelling.

There're few Shell stations in Bangalore. None in my whole state (Kerala). I dunno about other cities.
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Old 19th April 2006, 15:10   #51
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Quote:
Originally Posted by Technocrat
Hey aren't we supppose to fill slightly less air on highways since the air expands due to heat which is produced due to continues high speed running
I think this changes when you have tubeless tyres I guess as they run cooler. But even the Maruti Showroom guys were quite surprised when I pointed out the same in the Swift Manual to them.
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Old 19th April 2006, 15:20   #52
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Quote:
Originally Posted by sharathjeppu
Also, the fuel efficiency is dependent on the Tyre Pressure. Maruti reccommends 29 psi for the Swift ZXi in city and has specified in the manual that it can be increased by upto 5 psi for highway driving (Tubeless Tyres). Currently I maintain 34 psi even in city with negligible difference in the drive comfort. So, is there any reason why Maruti reccommends 29 psi in the first place for the R14/70/185 tyres that they provide with the Swift ZXi ?
Sharath, The ride quality is entirely different when filling 28psi and 30 psi when i tried. Maruti engineer advised me to have 30psi for highway and 28psi for a smooth ride in city and short braking distance. But mileage drops by around 1KMPL with this difference.

Also by keeping 34 you are risking the tyres. When the pressure is more only the center portion of the tyre tend to grip the road and similarly only the edges when pressure is less. So make sure you maintain correct tyre pressure.

During highway ride the load on tyres are more. The aerodynamic characterisrics also apply extra load on tyres at high speed. So it is better to have extra 2-3 psi while on the highway.

Last edited by ksethuram : 19th April 2006 at 15:23.
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Old 19th April 2006, 15:53   #53
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Quote:
Originally Posted by Technocrat
Hey aren't we supppose to fill slightly less air on highways since the air expands due to heat which is produced due to continues high speed running
You too, Technocrat?

There have been numerous discussions over this earlier. It is recommended to fill 2-4psi higher on highways. Tyre bursts occur not due to excessive pressure in tyre, but due to rapid sidewall flex, causing internal heat building and resulting in tyre burst.
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Old 19th April 2006, 19:43   #54
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LOL yes mee too

Actually I have been hearing quite a few contradictory views on this so asked it, but I guess the confusion continues. Both views when presented sound logical.

Can you tell why should it be higher on Highways wont it make the ride bumpy ? also your braking would effect. I am aware & agree with the sidewall logic but then I also cant refuse the air expansion one.

Anyways this is a wrong thread to discuss this
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Old 19th April 2006, 20:10   #55
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Quote:
Originally Posted by Technocrat
Can you tell why should it be higher on Highways wont it make the ride bumpy ? also your braking would effect. I am aware & agree with the sidewall logic but then I also cant refuse the air expansion one.

Anyways this is a wrong thread to discuss this
My WagonR runs 33psi stock.... and any higher it feels like flying. So I never increase beyond that.

Sidewall logic is not the only one... and is more applicable to tubed tyres .... since the tube and tyre rub against each other on flexing sidewall and heat up.

Think about friction caused by air circulation inside the tyre.
Take funny example.... you fill tyre with sand.... the tyre inflates fully, though there is more scope to put in sand to tighten it.
When you drive with lose sand ... its lose particles cause friction and HEAT.
Same happens with air though at faster rotation speeds.
So more Air less fristion between air modecules.
(also with less air there is more tyre friction with road again more heat)

That said low pressure would cause too much friction.... and tyre would heat up.
Tyre blow-outs are not only because of air expansion.... its also heat that makes the rubber weak.

Now about Higher pressure....
too high a pressure means less grip.... so again a problem.
but friction inside (air circulation) and with road would be less so less heat.

My conclusion:
if your car has a good recommended pressure... like Wagon R (33psi)... or Alto (30psi)... stick to it under all circumstances.
but if your car has an unusually low pressure for ride quality... like zen (24psi)... its better to put some more Air for the highway.

PS: the right thread exists.... someone please find it.. i'll paste this there

Last edited by SLK : 19th April 2006 at 20:12.
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Old 19th April 2006, 23:10   #56
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The Wagon R Manual did not reccommend changing Tyre pressure for the Highway where as the Swift Manual explicitly states that I can incease the tyre pressure by about 5 psi for the highway. Which means that it can be increased from 33 psi to 38 psi for the LXi and the VXi and from 29 psi to 34 psi for the ZXi. Why is this applicable only for the tubeless tyres? Also why is the lower tyre pressure reccommended for the wider tyre of the ZXi?
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Old 19th April 2006, 23:56   #57
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Quote:
Originally Posted by sharathjeppu
The Wagon R Manual did not reccommend changing Tyre pressure for the Highway where as the Swift Manual explicitly states that I can incease the tyre pressure by about 5 psi for the highway. Which means that it can be increased from 33 psi to 38 psi for the LXi and the VXi and from 29 psi to 34 psi for the ZXi. Why is this applicable only for the tubeless tyres? Also why is the lower tyre pressure reccommended for the wider tyre of the ZXi?
I can't be sure but.. 38psi.. still sounds... too much. Any other car with runs on 38psi?

Why only for tubeless?
Maybe b'coz tubeless don't lose shape like the tubed. And they are softer, tent to flex more!

Why different pressure for Zxi?
Maybe B'coz Vxi/ Lxi .. have thinner tyres that require more Air to reduce excess sideward movement.... (if you see, 80 profile tyres look like balloons )

BTW I got hold of the SWIFT manual and it does say "If continous high speed driving is required, increase tyres pressure by 5 psi over recommended inflation pressure."

Last edited by SLK : 19th April 2006 at 23:58.
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Old 20th April 2006, 09:05   #58
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@SLK: Great explaination dude Am glad that I havent ben palying much with tyre pressure hehe.

Guys SLK has already explained why you need different tyre pressure for tube & tubeless

Btw If we are talking about Swift then MUL has themsellf accepted that the stock tyres on Swift are not good, how do I know one of my friend used to work for Car India & the recent shoot out where they test drove quite a few cars the Swift didnt handle as it was expected to on Ghats & MUL gave an explaination that its due to the tyres. Now hows that for a premium car, some one should sue MUL

Last edited by Technocrat : 20th April 2006 at 09:09.
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Old 20th April 2006, 15:24   #59
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Quote:
Originally Posted by Technocrat
@

Btw If we are talking about Swift then MUL has themsellf accepted that the stock tyres on Swift are not good, how do I know one of my friend used to work for Car India & the recent shoot out where they test drove quite a few cars the Swift didnt handle as it was expected to on Ghats & MUL gave an explaination that its due to the tyres. Now hows that for a premium car, some one should sue MUL
Any idea of the tyre was the JK Tornado used in the LXi/VXi or the JK Vectra used in the ZXi.
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Old 20th April 2006, 16:14   #60
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Quote:
Originally Posted by Technocrat
Can you tell why should it be higher on Highways wont it make the ride bumpy ? also your braking would effect. I am aware & agree with the sidewall logic but then I also cant refuse the air expansion one.

a) On highways, you are driver faster effectively heating up tyres more than in city. If you have less pressure, you might blow up.
b) Ride will be affected in city, but on highways, road is better quality so it doesn't matter much.
c) Incidently at higher speeds, the ride quality improves rather than worsening.
d) Handling doesn't go for a toss till you heavily over-inflate it. (Definitely not by 2 psi). In fact, it becomes crisper.
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