Tyre Psi's For Colombo

SeanD · December 20, 2008

Hi guys, I have been inflating my tyres (Nissan N16) as per the manufacturer sticker pasted on the door for 33 in front and 30 at the back. However recently I was told by a friend that Lal Alawatte had told him (for the same make of car) to put around 28 for all 4 tyres as Colombo road conditions were not good to fill up the tyres and that he would get better mileage. Now I have not had any issues that I know of by doing more in front and less at the back as per the manufacturer sticker. I have not changed the tyre sizes or anything, everything is as the car was bought new.

Question is, how accurate is what he is telling? Should I switch to underinflating all 4 tyres, or wud this damage the tyres and have negative impact on fuel?

Many thanks.

GTAm · December 20, 2008

NO please don't. If you are happy with the ride stick with the manufacturers recomendations. I have never heard of under-inflating tyres to get better mileage. There are gurus and fake gurus. Nissan is the former

Pericles · December 20, 2008

Does sound a bit dodgy. It might give you more comfort in Colombo roads, but conventional wisdom says negative impact on fuel and tire wear.

NPP · December 21, 2008

same here...

the manual for vios says 33 for front and 30 for rear.

the ride will be bumby but surely better performance.

but my service station always pumps 28....

but wen i do it i do as as per the manual

ash · December 21, 2008

I consider under inflating the tyre is a no... no, in every aspect. You’ll loose fuel efficiency, more wear & tare on your tires, less performance, poor maneuverability, the only thing you get is better comfort. If you want comfort above all of the above points, then have a slightly less Psi on your tires.

According to some, Maximum tyre pressure - 10% is the best in economy & performance. (i.e. If your tyre indicates the maximum recommended tyre pressure as 40psi, then 40-10% = 36psi) Ya… in CMB roads it may be too rugged. I used to air them to 29-30. But since then I got a new pair of rubber, I do a 32 all around. Slightly hard but not too much I would say. I’ve tested with a tankful for the new economy. Definitely better than it used to be. Not enough evidence to prove it though. I think the new set of tyre has a lot in that increase as well.

Devinda_Z · December 21, 2008

under inflation caused the the tires to set a bigger contact patch with the road resulting in more friction - that will obviously result in the need for more power to propell the vehicle , thus causing an increase in fuel consumption

its best to stick with manufacturer specifications, but the rutty roads around town are certainly a worthy enough reason to deflate a bit if you feel the ride is excessivly harsh

Devinda_Z · December 21, 2008

ash said:
I consider under inflating the tyre is a no... no, in every aspect. You’ll loose fuel efficiency, more wear & tare on your tires, less performance, poor maneuverability, the only thing you get is better comfort. If you want comfort above all of the above points, then have a slightly less Psi on your tires.
According to some, Maximum tyre pressure - 10% is the best in economy & performance. (i.e. If your tyre indicates the maximum recommended tyre pressure as 40psi, then 40-10% = 36psi) Ya… in CMB roads it may be too rugged. I used to air them to 29-30. But since then I got a new pair of rubber, I do a 32 all around. Slightly hard but not too much I would say. I’ve tested with a tankful for the new economy. Definitely better than it used to be. Not enough evidence to prove it though. I think the new set of tyre has a lot in that increase as well.

i think those tires offer a lower degree of rolling resistance hence the possible increase in fuel efficiency

MasterDon · December 21, 2008

i go for 34PSI on goodyear eagle f1 205/40

Jayathu · December 22, 2008

The sticker on my P11 says, 2.2, 2.0 and 4.2, 4.2 kg/cm2.. An online conversion turns these values into,

2.2 = 31psi

2.0 = 28psi

4.2 = 59psi

Looks like the 4.2 value is a bit absurd.. Can't understand the sticker cos it's in Japanese and the only things I could read were these digits and the unit, kg/cm2..

Was wondering which are for front and which are for back and why would there be a difference in the left and right tires.. I currently have 17" low profiles and have been filling them upto 29psi based on advice from the A*W tech people, but now feel a little bit in doubt as to what the correct pressure is..

jerryda · December 22, 2008

Jayathu said:
The sticker on my P11 says, 2.2, 2.0 and 4.2, 4.2 kg/cm2.. An online conversion turns these values into,
2.2 = 31psi

2.0 = 28psi

4.2 = 59psi

Looks like the 4.2 value is a bit absurd.. Can't understand the sticker cos it's in Japanese and the only things I could read were these digits and the unit, kg/cm2..

Was wondering which are for front and which are for back and why would there be a difference in the left and right tires.. I currently have 17" low profiles and have been filling them upto 29psi based on advice from the A*W tech people, but now feel a little bit in doubt as to what the correct pressure is..

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=1

chana · December 22, 2008

Jayathu said:
The sticker on my P11 says, 2.2, 2.0 and 4.2, 4.2 kg/cm2.. An online conversion turns these values into,
2.2 = 31psi

2.0 = 28psi

4.2 = 59psi

Looks like the 4.2 value is a bit absurd.. Can't understand the sticker cos it's in Japanese and the only things I could read were these digits and the unit, kg/cm2..

Was wondering which are for front and which are for back and why would there be a difference in the left and right tires.. I currently have 17" low profiles and have been filling them upto 29psi based on advice from the A*W tech people, but now feel a little bit in doubt as to what the correct pressure is..

31psi - Front

28psi - Rear

59psi - Spare Tyre

Jayathu · December 22, 2008

chana said:
31psi - Front
28psi - Rear

59psi - Spare Tyre

Ok.. but what bemuses me is that there are two 4.2 entries...

chana · December 22, 2008

Jayathu said:
Ok.. but what bemuses me is that there are two 4.2 entries...

Could you post a picture of the label? Somebody who understands Japanese will help you.

Jayathu · December 22, 2008

chana said:
Could you post a picture of the label? Somebody who understands Japanese will help you.

Will do

Jayathu · December 23, 2008

chana said:
Could you post a picture of the label? Somebody who understands Japanese will help you.

Managed to get a pic with my phone..

The Japanese is not all that clear but shows the four values which I mentioned.. Hope somebody can decode it..

Devinda_Z · December 23, 2008

Jayathu said:
I currently have 17" low profiles and have been filling them upto 29psi based on advice from the A*W tech people, but now feel a little bit in doubt as to what the correct pressure is..

that seems fine

when refering to the factory suggested pressure you need to take into account that fact that they aren't stock tires and the rim is a good 2" larger!

over inflating with rims that big on our rutty road is not a good idea

to be perfectly honest i run lesser pressure on 16"s

Jayathu · December 23, 2008

Devinda_Z said:
that seems fine
when refering to the factory suggested pressure you need to take into account that fact that they aren't stock tires and the rim is a good 2" larger!

over inflating with rims that big on our rutty road is not a good idea

to be perfectly honest i run lesser pressure on 16"s

But, wouldn't our darned roads damage the rims if the tires are under inflated.. I thought, lower the profile higher the tyre pressure should be to avoid rim damages..

Devinda_Z · December 23, 2008

Jayathu said:
But, wouldn't our darned roads damage the rims if the tires are under inflated.. I thought, lower the profile higher the tyre pressure should be to avoid rim damages..

the greater degree of streess would be transfered over onto the suspension system by running with excessively high pressure

i wouldn't say underinflate but personally i keep it to just a tad bit under manufacturer specification

jerryda · December 23, 2008

Jayathu said:
Managed to get a pic with my phone..

The Japanese is not all that clear but shows the four values which I mentioned.. Hope somebody can decode it..

4.2 is the inflation pressure of the spare tyre when used at the front or the rear.

http://www.drive.com.au/Editorial/ArticleD...?ArticleID=5178

Edited December 23, 2008 by jerryda

Jayathu · December 23, 2008

jerryda said:
4.2 is the inflation pressure of the spare tyre when used at the front or the rear.

Thanks Jerryda.. It then boils down to 31 at the front and 28 at the back. To be on the safer side as Devinda mentioned, 30 at the front and 28 at the back would be ideal me believe.

Also the specified spare tyre pressure applies for the stock (smaller) spare tyre, isn't it..? Currently I use the standard 15" tyre which was originally fitted to the car and later replaced by the low profiles.. So fill it up with 30 would be OK, I presume.

Edited December 23, 2008 by Jayathu

jerryda · December 23, 2008

Jayathu said:
Thanks Jerryda.. It then boils down to 31 at the front and 28 at the back. To be on the safer side as Devinda mentioned, 30 at the front and 28 at the back would be ideal me believe.
Also the specified spare tyre pressure applies for the stock (smaller) spare tyre, isn't it..? Currently I use the standard 15" tyre which was originally fitted to the car and later replaced by the low profiles.. So fill it up with 30 would be OK, I presume.

http://www.tirerack.com/tires/tiretech/tec...e.jsp?techid=72

http://www.tirerack.com/tires/tiretech/tec...e.jsp?techid=35

Edited December 23, 2008 by jerryda

JadeyBlitzen · December 23, 2008

i always stick with the manufacturers claims cos my car already has a rather bumpy ride. so im happy with 30 psi. but then again a 5psi increase would do wonders to ur fuel bills. cos there's a smaller contact patch with over inflated tyres and since the sidewall is held up as straight as possible there's lesser rolling resistance. which slightly increases the performance as well. not just that. you'll appreciate the sharper handling. on the minus side you'll have to live with a relatively bumpy ride and the tyre life could be slightly reduced and also u'll have less grip off the line. as for lal alawatte i think he's talking bollocks. i never liked his attitude anyways.

MasterDon · December 23, 2008

GTAm said:
There are gurus and fake gurus.

amen to that....the potatoland man is a bit of a hot head...must be all the tv fame...i've heard of him being rude and impolite to even his paying customers

JadeyBlitzen · December 24, 2008

HelRazor said:
amen to that....the potatoland man is a bit of a hot head...must be all the tv fame...i've heard of him being rude and impolite to even his paying customers

thats exactly my point. i once heard he had a go at a customer and he's asked "do you know who i am?" and the customer said "yea alahena or sumthing"