[Coolman]

In my 2 week old Ritz VXi, I did not check the tire pressure as part of PDI. My bad, I presume. I kept an eye though during PDI and through the 2 weeks and the tires were looking normal - not low on air. I drove for about 350 kms in 2 weeks.

The Issue (Tire Pressure):

I went on a longish trip on Mysore Road yesterday (175 kms) and then on my way back, I felt like checking the tire pressure (this is after about 120 kms of driving - 85 TO journey, 1 hr break and then 35 FRO). When I checked the tire pressure at one of the fuel stations, to my dismay, the reading was 51 in all 4 tires. I don't understand and neither did the attendant. I told him they came like that from the Showroom, the car is hardly 2 weeks old.

I understand that the manufacture / dealer might over inflate the tyre by about 4-5 psi. And say, due to continuous highway driving (I wasn't going beyond 65 kmph) it increases by another 5-7 psi, the maximum it should have read was 42-45 psi. I can't believe it was 51 in all 4.

• Either the pressure gauge / pump was malfunctioning

OR

• The manufacturer had inflated it to ~ 42 and over the 2 weeks and then due to the continuous highway driving yesterday it went all the way 51. Beats me, though.

I immediately got it reduced to 33. No visible damage to the tires, but not sure if anything else has been impacted. However the EPS light turned on (Steering becomes hard) on a few occasions during this episode yesterday, and I had to stop my car and start it again (Will be posting in detail about this issue in Shashank's thread). As of now the EPS is normal, nonetheless, taking the vehicle to the Service Center today for inspection.

I read Shashank's thread:

http://www.team-bhp.com/forum/techni...-failures.html

Not sure if my problem is similar. Will keep you posted.

Thanks,
C_

[nilanjanray]

Originally Posted by Coolman

I went on a longish trip on Mysore Road yesterday (175 kms) and then on my way back, I felt like checking the tire pressure (this is after about 120 kms of driving - 85 TO journey, 1 hr break and then 35 FRO). When I checked the tire pressure at one of the fuel stations, to my dismay, the reading was 51 in all 4 tires. I don't understand and neither did the attendant. I told him they came like that from the Showroom, the car is hardly 2 weeks old.

Reopening this thread since I was doing some reading on air pressures for my upcoming highway drive.

@ Coolman: your tires were hot (after highway driving), so the reading would'nt be accurate - all recommended pressures are for cold readings. But seems the dealer overinflated the tyres significantly. Happens all the time when I take my vehicle to the ASC. One needs to be careful when other folks have touched the tyres.

Anyway, the Fortuner manual says 30 psi for all 4 tyres. For my previous highway trips (100 - 140 kmph fast driving, 10+ hours), I have used 32 psi and things worked fine. This time I was wondering whether I should increase the pressure to 33 or 34. I am still not sure. 32 has worked for me. Perhaps max I will use 33. Not more. Some folks drive with 6-7 psi increase over recommended pressures (perhaps for extra FE). I feel that such extreme increases are too dangerous.

Thoughts, folks? My tres have done 40K, I am favouring being conservative and increasing by 3 psi max rather than more.

Edit: read more articles, most are recommending 3-5 psi increase for sustained high speed (120 kmph) driving. Will stick to 33 psi.

[comfortablynumb]

Originally Posted by nilanjanray

Thoughts, folks? My tres have done 40K, I am favouring being conservative and increasing by 3 psi max rather than more.

Edit: read more articles, most are recommending 3-5 psi increase for sustained high speed (120 kmph) driving. Will stick to 33 psi.

IMO, tyre pressure should primarily depend on how loaded your vehicle is, and not the type of route. If you check any vehicle's manual, the recommended pressures will always depend on the laden and unladen weight and not on highway or city driving. I would strongly recommend sticking to the manual.

Just my $0.02!

Cheers,
Vikram

[nilanjanray]

Originally Posted by comfortablynumb

IMO, tyre pressure should primarily depend on how loaded your vehicle is, and not the type of route. If you check any vehicle's manual, the recommended pressures will always depend on the laden and unladen weight and not on highway or city driving. I would strongly recommend sticking to the manual.

Just my $0.02!

Cheers,
Vikram

I am aware of that. FYI, the Fortuner's manual doesn't mention about different tyre pressures for different levels of load.

Since I will be doing continuous high speed highway driving, the tyre pressure needs to be increased slightly. That is what my statement/semi-query was all about.

And what makes you say that the tyre pressure doesn't depend on the type of route? Depending on whether I am doing offroading in mud or sand, whether I am doing normal (city) driving or doing continuous high speed driving, the optimum tyre pressure will be different.

P.S. I am surprised to see many members commenting that underinflation for high speed driving is ok. Please see these regarding why it is a good idea to increase tyre pressure slightly when on long high speed drives:

http://www.bridgestone.com.au/tyres/.../pressure.aspx
http://www.tiresafety.com/maint/maint_ipressure.asp
http://www.hankooktireusa.com/Serv/I...m=3&ChildNum=4
http://www.tirerack.com/tires/tirete....jsp?techid=72

Basically, for higher load and/or high sustained speed, the pressure needs to be increased slightly. How much, depends on vehicle manual (if they mention that) or general guidance e.g. most renowned websites call for 3-5 psi increase to minimise the effect of 'deflection' and heating when carrying heavy loads and/or sustained high speed driving.

[dhanushs]

Originally Posted by nilanjanray

P.S. I am surprised to see many members commenting that underinflation for high speed driving is ok...
... Basically, for higher load and/or high sustained speed, the pressure needs to be increased slightly.

Underinflation is definitely not recommended at speeds. The tyre flex will cause heating up and rupture of sidewall. Where as overinflation too is not recommended. As, even though reduced, there will be flex and too many molecules inside will cause tyre to again heat up!

IMO, go as per manufacturers recommendations for respective tyre sizes and loads. They recommend it for highways as well. Off roading is an entirely different thing.

[nilanjanray]

Originally Posted by dhanushs

Where as overinflation too is not recommended. As, even though reduced, there will be flex and too many molecules inside will cause tyre to again heat up!

I am talking about 2-3 psi increase from recommended pressure for sustained high-speed driving. Well within limits of tyre specs after considering the pressure increase due to heat etc.

[dhanushs]

Originally Posted by nilanjanray

I am talking about 2-3 psi increase from recommended pressure for sustained high-speed driving. Well within limits of tyre specs after considering the pressure increase due to heat etc.

Yes, 2-3 psi wont hurt. And I guess you have made the decision.

[S5157]

The manufacturer, while testing the vehicle would have considered the pressure increase during long highway trips and would have arrived at the optimum tyre pressure. If we increase it by few PSI in cold conditions the net increase would be much higher than recommended.

What are the benefits do we get by increasing the tyre pressure on highway?

For sand driving( read off roading) you have to reduce pressure for more traction, but for highway I am wondering what are the benefits of increased pressure?( Apart from FE due to less contact on road).

[CANPUSH]

Originally Posted by Coolman

The Issue (Tire Pressure):

I went on a longish trip on Mysore Road yesterday (175 kms) and then on my way back, I felt like checking the tire pressure (this is after about 120 kms of driving - 85 TO journey, 1 hr break and then 35 FRO). When I checked the tire pressure at one of the fuel stations, to my dismay, the reading was 51 in all 4 tires. I don't understand and neither did the attendant. I told him they came like that from the Showroom, the car is hardly 2 weeks old.

C_

Sorry for late reaction.

I believe it is standard practice in all dealerships to keep tire pressure on substantially higher side as the cars are likely to be stationary in stockyards for days together and lower pressure can damage the tire walls. Also in stationary mode the tires loose pressure much earlier than in moving condition.

[mb_jg]

What is the feasibility of purchasing a portable tyre inflator (the one you can plug into the cigarette lighter) & gauge & have the tyre pressure checked yourself? This way we don't have to depend on someone else for our safety!

I found some info here: http://shop.cardekho.com/car-accesso...+inflator.html

http://www.junglee.com/mn/search/jun...l_95hmtg1uy9_e

The pricing is pretty ok, considering you don't have to wait in a queue.

[Derezzed]

M Wagon R's recommended tire pressure is 32 psi. However on expressway trips I increase it by 2-3 psi before start of my trip. This has noticeably given me a better fuel economy (1-2 kmpl extra on highways) however at the cost of ride comfort. The ride becomes jarring whenever I hit the concrete section of the expressway and on the interlock brick road sections of Mumbai.

So I reduce the air pressure back to recommended after my highway run.

[Gansan]

During a better driving awareness workshop session conducted by Ford a year back, exclusively for TBHP members btw, we were told it would be good to increase the pressure by 8 PSI over the recommended one! Though it is my habit to keep 2 psi over the recommended level I was simply astonished by this! I never put it into practice though.

[sgiitk]

In the 1970's the AA of UK used to recommend a 2-3 psi higher pressure in radials for sustained highway cruising. I have not seen anything similar of late. I normally pump up to 2 psi above and then repump when I am 2psi below. Before any highway run I always check and top up the tyres.

[born_free]

Someone already mentioned that Maruti recommends increasing air pressure for Highway Driving
Attaching screenshot from owners manual for Wagon R, the point number 5 suggests to increase pressure by 5 PSI for High speed driving.
5 PSI increase seems to be on higher side, I generally go for 35 PSI which is 3 PSI more than recommended pressure for wagon R

[R2D2]

I add about 3 PSI to the tyres (10% over recommended pressure) when travelling long distances. IMO, slightly higher pressures reduce flexing, improve handling and most importantly help in preventing wheel and tyre damage (Michelins after all!) should I hit a pot hole (not the big ones, you're put of luck with them) at highway speeds. And, no, this extra tyre pressure has not been explicitly mentioned by the car manufacturer.