[Vid6639]

28psi seems fine since your tyres are low profile. keep the N2. youve already spent money for it. If the tyre completely deflates then put back in air.

till then doesnt make sense. lower should give you better ride. and cushion and prevent the sidewall from absorbing the shock.

[karthik247]

Huh!? RKS said to increase the pressure?? Guys!!

[Vid6639]

yeah what rks says is for the OE tyres. you have lower profile tyres on larger rims.

The volume inside is lesser so effectively it will be similar. more volume more pressure is ok. since less volume lesser pressure is needed to achieve the same inflation.

28psi is fine dude. I have a lancer which I keep 30psi on 195/60-14. Even if i put 28psi she is happy and gives a soft ride.

If you inflate a tyre more than its tightened and doesnt flex so wont absorb the bumps as well and the shock goes right to the suspension and tyre.

you are more likely to cut a tyre on higher psi than on lower as on lower it will just absorb the bump.

does that sound logical to you? hope it isn't confusing.

[karthik247]

Yep got it.....thanks dude. So i'll leave it at 28psi i guess

[kpzen]

Originally Posted by karthik247

Yep got it.....thanks dude. So i'll leave it at 28psi i guess

28psi is ok for those tyres in Swift....
I dont think bulging has anything to do with tyre pressure....Its the roads....


KP

[rks]

Originally Posted by karthik247

The recommended pressure for stock tyre (165/80 R14) is 32psi i think. I guess i'll get 30psi normal air unless u guys want me to keep the N2 and if it really does make a diff (which i don't think it does)

And does more pressure mean less grip?? I usually drive only in the city, maybe a max speed of 100kmph, very rarely hit the highways. So i need a balance btw handling/grip as well.

Substantial over-inflation may reduce the grip in wet/muddy/bumpy roads. For high-speed driving, Bridgesone India recommends over-inflation by 5 psi. This will reduce the sidewall deformation during high-speed cornering and give you much better grip under normal (dry) conditions.

If you feel N2 doesn't make a difference, then why the hassles? I would say switch to plain air. If you filled 28 psi when the tyres were hot or say, in mid-afternoon, then your cold pressures may be even less, say 27 psi. With air, you can always check the next morning when the tyres are cold, etc. With N2 I think you have to shell out money to check the pressures at the filling point. This is quite a hassle. I always carry a portable inflator and my own pressure gauge which I can use any time, any place.

You have upgraded from 165 to 205, which is a hefty upgrade. Another issue would be the width of your rims, which should be at least 5.5 J according to the carbibles website:

Car Bibles : The Wheel and Tyre Bible

I think 6J would be advised for 205 tyres. Narrow rims when combined with low tyre pressures will contribute subtantially to sidewall deformation and potential damage, especially in fast driving. Higher tyre pressures would be even more strongly indicated in this case.

See also the sections "Tyre pressures and gas mileage", "What's the correct tyre pressure", "The Max. pressure - 10% theory" in the above website. In general this guy advises operating at higher-than-recommended tyre pressures. I have followed his advice in my Santro, with good results. With stock-size tubeless tyres on steel rims, I am keeping my tyre pressures at 34-35 psi against the recommended 30 psi, for my regular Pune-Mumbai-Pune runs. After 10000 kms, the tyres are in very good shape with no uneven wear and the ride is not all that harsh either (or maybe I got used to it). The car has good pick-up and is eager to hit 130-140 kmph on the Expressway with excellent grip and steering response.

I have stock 4J rims, but as per the rim width calculator on the above website, the rim width should be at least 4.5J for the stock size tyres (155/70 R 13). So obviously that is another reason for my maintaining higher-than-recommended tyre pressures even with stock-size tyres. Apparently Hyundai has kept the rim size low to get ride comfort, may be to compensate for the stiff rear suspension of the Santro.

Ultimately it is up to you. I see that others disagree with me on tyre pressures. I personally would not operate below 32 psi for your specs.

[rks]

Originally Posted by kpzen

28psi is ok for those tyres in Swift....
I dont think bulging has anything to do with tyre pressure....Its the roads....

Low tyre pressures and/or narrow rims -> More sidewall deformation -> More sidewall damage (especially on bad roads or in high-speed driving). Of course it could also be a result of some freak manufacturing defect, etc. But in principle if you keep tyres at higher pressures, you will sacrifice some ride comfort and get better handling and less possibility of tyre damage, even when roads are bad.

[rks]

Originally Posted by vid6639

28psi seems fine since your tyres are low profile. keep the N2. youve already spent money for it. If the tyre completely deflates then put back in air.

till then doesnt make sense. lower should give you better ride. and cushion and prevent the sidewall from absorbing the shock.

No, this is wrong reasoning. Please see the Carbibles website that I quoted in my previous post. If tyres are low profile, you can afford to keep a lower pressure provided you have appropriately wide rims and *good* roads. On bad roads low profile tyres are prone to sidewall damage and higher tyre pressures are indicated from this point of view (obviously if you insist on not sacrificing ride comfort, then keep lower tyre pressures, but then be prepared to suffer as karthik did).

[Vid6639]

hey rks, agreed the logic what you say also holds true. but, the lesser psi for the lower profile is same as that higher for taller profile.

Even on the sidewall the way i see it is that if the pressure is lesser it will deform and absorb the shock. if it is hard then it will not be able to absorb that shock and not deform and may get cut. something like a crumple zone.

If your sidewall is already cut then theres nothing much you can do since a lower pressure will deform it more and a higher pressure may lead to more cuts as the tyre will bear the brunt.

I went through the website and I do agree with that but just a different angle i see it.

[karthik247]

I use 6.5JJ alloys... So then i'll keep 28psi, and just in case it falls, i'll fill air in it.

Note... There is no cut or anything, its just a very small bulge. Hardly noticeable

[rks]

Originally Posted by vid6639

hey rks, agreed the logic what you say also holds true. but, the lesser psi for the lower profile is same as that higher for taller profile.

Even on the sidewall the way i see it is that if the pressure is lesser it will deform and absorb the shock. if it is hard then it will not be able to absorb that shock and not deform and may get cut. something like a crumple zone.

If your sidewall is already cut then theres nothing much you can do since a lower pressure will deform it more and a higher pressure may lead to more cuts as the tyre will bear the brunt.

I went through the website and I do agree with that but just a different angle i see it.

With *very* high tyre pressures, there is more possibility of the tyre getting damaged from an impact, say, with the pavement or a stone. But on the other hand, higher tyre pressures mean that there is less possibility of sidewall damage and poor handling due to excessive deformation of the sidewall on bad roads or in high-speed driving. Regarding impact damage, that is likely to happen if you over-inflate the tyres to the point where it is as hard as a rock. Here we are talking 3-5 psi, which is OK.

Lesser psi on low profile means you will get ride comfort but sacrifice some handling and risk tyre damage. Lesser psi on high profile means your handling will be *much* poorer, but as compared to a low profile tyre there is less chance of damage on bad roads. In high speed driving, lesser psi on a high profile can give dangerously poor handling, especially in cornering, and reduce tyre life due to excessive sidewall deformation.

So higher tyre pressures are indicated in the following scenarios:

(1) With low profile tyres on bad roads and/or narrow rims and/or high-speed driving

(2) With high profile tyres in high-speed driving.

[wolfinstein]

Mine lasted 50,000 KM and could have gone another 2 K more without any issues, But we were facing lot of punctures around the 50 K mark so we opted for a change. The Tyres were OEM Bridgestone Potenza' 2001-2005. Now running on Bridgestone Potenza G3 Tubeless.

On an average I get air checked and filled in all every 2 Weeks with an Average of 28 Psi- 30 Psi.

[kpzen]

Originally Posted by rks

Lesser psi on low profile means you will get ride comfort but sacrifice some handling and risk tyre damage. Lesser psi on high profile means your handling will be *much* poorer, but as compared to a low profile tyre there is less chance of damage on bad roads. In high speed driving, lesser psi on a high profile can give dangerously poor handling, especially in cornering, and reduce tyre life due to excessive sidewall deformation.

So higher tyre pressures are indicated in the following scenarios:

(1) With low profile tyres on bad roads and/or narrow rims and/or high-speed driving

(2) With high profile tyres in high-speed driving.

Whats the border line profile which will classify a tyre as low profile or high profile?? 55,60,65??

Originally Posted by wolfinstein

Mine lasted 50,000 KM and could have gone another 2 K more without any issues, But we were facing lot of punctures around the 50 K mark so we opted for a change. The Tyres were OEM Bridgestone Potenza' 2001-2005. Now running on Bridgestone Potenza G3 Tubeless.

On an average I get air checked and filled in all every 2 Weeks with an Average of 28 Psi- 30 Psi.

What size tyre?? profile??

[rks]

Originally Posted by kpzen

Whats the border line profile which will classify a tyre as low profile or high profile?? 55,60,65??

What I said is only qualitative. For Indian roads I think we can take 60 and below as low profile and 70 and above as high profile tyres. But this is only a crude approximation and may vary from person to person or from one road to another. I would regard my 155/70 tyres as of higher profile. I keep high tyre pressures mainly because of frequent high-speed driving (which is about 75-80 % of my driving). If I were confined to the city, I would probably keep the recommended 30 psi (or maybe 31 psi, to compensate for loss of air).

[iraghava]

Guys, let's not get into an argument here for the sake of it. A sidewall bulge can happen for a LOT of reasons including but not limited to Tyre Construction, Compound, Suspension condition, Road condition, tyre pressure etc.

Imagine that even on 155/70 R13 tyres on a stock Santro I had a sidewall tear, now that was a tyre defect & not related to pressures ok. So bulges & cuts can happen for so many reasons. My Goodyear F1's had 2 sidewall tears & 2 bulges in 30k kms while being properly inflated to 30 psi & being cared for regularly & on a good suspension. In the same conditions my Michelin XM1's have already lasted over 45k kms with only 28psi of pressure & have had no failures or bulges till now! And all this when the suspension on my car has not been at its best.

So let me re-iterate this once again for everyone's benefit:

1. Tyre failure/bulges can be caused by many reasons so look at all factors before blaming one. Also always remember on our road conditions low-profile tyres are VERY, VERY susceptible to failure even if all the factors are perfectly fine. It's no fault of the tyre or suspension though the fault lies with our roads & conditions.

2. Pressures - You should run what you find comfortable on your wheels. If at any point of time you feel that the ride is too bumpy or too relaxed change the pressure downwards or upwards respectively & then decide the exact pressure for your preferences. Also do a visual check regularly to see that none of your tyres is underinflated.

3. Looks - If you want the big rim Look then be prepared to pay for it in terms of poor ride & high-probability of tyre failures. A fellow member runs 17" on his Swift & by his own admission he has replaced 6 tyres on it already due to bulges & sidewall tears!!

4.Quality - Also be very aware of what quality tyres & alloys you use for your car since this can be a deciding factor. Always use the best possible components so as to minimise any chances of failures. And please stay away from Chinese tyre brands like Wanli, Ling Long etc. if they are cheap there is a good reason behind it.

And guys remember tyres are the most important parts of your beloved car, they are infact your only contact points to the road. So give them their due & don't be a miser in this department, this can be a very vital difference between you having an accident or not.

Be safe.