Tyre pressure, have you checked yours lately?

[girishab]

yaa..even i had the same experience...i stuck to the pressure mentioned in the manual for ikon..it says 36psi in the front and 40psi in the rear when the car is fully loaded (4 adults)...the ride was so rattling that i felt it was worse than a bus..had it reduced to the "normal load" values of 30-32psi and the ride became so very comfortable..

by the way, does the tyre pressure differ depending on whether one is on alloys or normal wheels?

[Revvmaster]

Girish

Alloys vs steelwheels isn't the differentiating factor as much. Sticking to the pressures written on the door of your car or a +/- 2 psi difference should be acceptable. The 36 and 40 psi that you fit seems abnormal.

As Rehaan rightly mentioned, 28-32 is ideal for city conditions and 30-34 for highway.

Firestarter, your tyres are different from the stock VTEC tyres, both in terms of width as well as profile. Your readings might be slightly different and stick to the recommended pressures which your tyre fitter has recommended. Or visit a Honda workshop and calculate the same.

SLK, the readings on your cars seems abnormal. Unless it was taken when the sun was on its Zenith. The alto VXi, if i am not mistaken, runs on the same tyres as the Zen VXi - 145/80 R12. The burstability point on those tyres is 44 psi BTW.

Revv

[SLK]

Originally Posted by [b

Quote[/b] ]The burstability point on those tyres is 44 psi BTW.

Well they didn't burst!...
And just for info.... this was the pressure... when we got the car from the showroom!... something felt wrong with the steering!

How about a 48psi on a 800 with 145/70... MRF... ... even they didn't burst.

how about the Auto's!!!... have u seen their pressures??... probably u can put that air in 2 zen tyres!

[normally_crazy]

fellas,

after the servicing , the tyre pressures are usually high. God knows what kinda pressure gauages the service station guys have. this happened with my santro and the ikon too.....

till now whenever i have taken delivery after servicing , the tyre pressure is arnd 40 +- 2 psi.

so the 1st thing i do is go to the pump where i regularly check pressure and correct it.

cheers

[Revvmaster]

Originally Posted by [b

Quote[/b] ]ow about the Auto's!!!... have u seen their pressures??... probably u can put that air in 2 zen tyres!

Haha... a bit of trivia. If you want your Auto to run its meter faster, reduce the tyre pressure in your tyres. And watch yourself laugh to the bank.

Revv

[drifter]

Originally Posted by [b

Quote[/b] (SLK @ Nov. 02 2004,15:22)]how about the Auto's!!!... *have u seen their pressures??... *probably u can put that air in 2 zen tyres!

hence the secret behind their rock hard bone breaking ride.

Drifter

[Firestarter]

Hey i always felt that on highways your tyre pressure must br reduced slighlty to give space for air to expand this is contrary to what u guys are saying my personal experince is with higher tyrs pressure the car feels bouncy and has less grip hence my suggestion would be to lower your tyre pressure by 1or 2 psi incase of long drives in the city it does not matter to have them inflated by an extra 1 or 2 psi....

Comments pls

[normally_crazy]

Originally Posted by [b

Quote[/b] ]lower your tyre pressure by 1or 2 psi incase of long drives in the city it does not matter to have them inflated by an extra 1 or 2 psi....

i think vice versa. reducing pressure in the city gives u a better more comfortable ride...while on the highway its always better to have 2 psi more than what u have for ur city driving.

anyone clear out this confusion ?

cheers

[SLK]

Point is... If a tyre has perfect pressure... does reducing it improve the grip? No.

or say the tyre has excess pressure ... does reducing it improve the grip? Yes

And this is what I was saying.... in our country its hard to find a perfect tyre pressure gauge. Mostly our cars have excess pressure.... so if you reduce u feel its better!

If you give air the room to expand it'll get very hot due to lose friction at high speeds. and if it gets hot it expands a lot then u have a burst!

So according to me the best policy is to keep the manufacturer's recommended pressure at all times

ps: I remember seeing an article on Indiacar... about tyre pressures and grips... one should see that.

[aalaap]

Someone once told me that higher pressure may make the ride a wee bit uncomfortable, but it increases FE. What's your guys' take on this.. myth or fact?

What's the *ideal* (read: max FE) tyre pressure for the zen ?



- Aalaap

[Rehaan]

Originally Posted by [b

Quote[/b] (Firestarter @ Nov. 04 2004,17:02)]Hey i always felt that on highways your tyre pressure must br reduced slighlty to give space for air to expand

It has nothing to do with "letting the air expand".
The air is aldready compressed to a high degree.
It is a question of the higher pressure preventing the tire from flexing too much (at high speeds for a long duration) which causes heat which is bad for the tire.

Originally Posted by [b

Quote[/b] ]my personal experince is with higher tyrs pressure the car feels bouncy and has less grip

That is true, however there is a right balance you have to find. within the "highway range" of tire pressures. If you are doing an all out sprint to pune on the expressway you might want to go with a higher pressure like 34psi, whereas if you are doing a ghat road the car may feel more stable and comfortable on the corners with 30psi. And if you are doing an expressway & then ghats you might have to strike a compromise at 32psi.
These are subjective figures, but the point is that if you are running a low pressure like 26psi on a highway trip you are asking for trouble.

Originally Posted by [b

Quote[/b] ]If you give air the room to expand it'll get very hot due to lose friction at high speeds. and if it gets hot it expands a lot then u have a burst!

Well the burst is not really caused due to the air expanding a lot, more like the tire failing due to heat buildup.

Originally Posted by [b

Quote[/b] ]Someone once told me that higher pressure may make the ride a wee bit uncomfortable, but it increases FE. What's your guys' take on this.. myth or fact?

What's the *ideal* (read: max FE) tyre pressure for the zen ?

Fact.
However, like everything there is an ideal balance.
Higher tire pressure decreases your rolling resistance, (which makes it easier for the engine to move the car...which improves efficency).
Low pressure would increase the rolling resistance, and too high a pressure decrease the grip levels.

So in the end you are left with the usual spectrum of ~28-34psi, so if you want to suffer a bumpy ride you could run a higher pressure in the city, (might make ur steering a bit lighter as well as slightly dfferent handling characteristics.)

cheers
R

[Rtech]

Originally Posted by [b

Quote[/b] ]Quote (Firestarter @ Nov. 04 2004,17:02)
Hey i always felt that on highways your tyre pressure must br reduced slighlty to give space for air to expand

It has nothing to do with "letting the air expand".
The air is aldready compressed to a high degree.
It is a question of the higher pressure preventing the tire from flexing too much (at high speeds for a long duration) which causes heat which is bad for the tire.

I don't agree with rehaan on this. I remember reading that in an ACI issue some time back and i had to read it again to make sure I read it right the first time.

For sustained high speed driving, the best thing to do is lower the pressure by 1-2 psi. I have never ever in my years racing come across a situation where it is recomended to raise the pressure! Even on my bike, when I did a track day, we ride up, reduce the pressure by about 3-4psi and then go out on the circuit. If you don't do that, you're gonna overheat your tyres in a few laps.

The reasons behind ACI saying this were ludicrous - by filling more air, the tyre expands more hence will cool better (as more of the tyre is exposed to the surrounding air)! Hogwash!

We all know that you should never check the air in your tyres while they are hot. Well the reasoning is that heat buildup causes the pressure to increase. If you fill up 34psi and go for an expressway drive, by the end the pressure would have built up close to 40psi.

Sure underinflating your tyre will cause it to heat up too, but we're not talking of that here.

If you are going to be driving with sustained high speeds for long periods...the best thing you can do is reduce the pressure by 2-3psi from the manufacturer recomended pressures.

Rt

[Rehaan]

Hey Rtech,

I can understand why you would lower tire pressures for the track, however i still mantain m point of view that higher tire pressure is better for long runs.

I guess the question in point would be what exactly "higher" pressure means.... However i disagree with the concept of LOWERING tire pressure before a long highway run.
Could you provide some links and articles that have the same view?

I guess the point here is that theres a window of safe tire pressure (which we agree on i assume)...the window being pretty large.......but just to be on the safe side its better to go to the upper limit. (is what im saying)

cheers
R

[GTO]

For the circuit, push a bit of extra air into your tyres. This will prevent sidewall flex in the corners, providing better grip and a more stable car overall, at the expense of ride comfort. Check the owners' manual or inflation label (usually on the pillar at the driver's door) for the right high-speed tyre pressures your car needs, then add 3 to 4 psi to that.

Michelin Official Website

GTO

[Rtech]

Originally Posted by [b

Quote[/b] ]I can understand why you would lower tire pressures for the track, however i still mantain m point of view that higher tire pressure is better for long runs.

Well, one point of view is that on the street, you put run a couple of extra psi as the tyres don't warm up enough on regular runs. This way the extra pressure heats the tyre to its correct temperature.

Originally Posted by [b

Quote[/b] ]I guess the question in point would be what exactly "higher" pressure means.... However i disagree with the concept of LOWERING tire pressure before a long highway run.

Yup...the "higher" pressure would be subject to the car/tyre combo being run.

Originally Posted by [b

Quote[/b] ]Could you provide some links and articles that have the same view?

Haven't really searched, will do so and see, but what I'm talking from is real world driving. From my experiences, my tyres and my driving style, the lower pressure is best. I've tried both and I'll stick to running 29psi-30psi on my expressway runs instead of the specified 32psi.

GTO, well, I can provide a bunch of references supporting the lowering of tyre pressure before heading out on the track, but the best would be real world experience, trying all the possible set ups.

Surre, if you don't push, run a couple of psi more to heat up your tyres faster.

Rt