Recommended PSI

[0_Kewl]

My engine is located nearer to the driver side so the right side is always sinks lower as it is heavier.

 

It is worse when the driver is on the right too.

 

May be it was designed for left hand drive so the designer probably expecting the driver to be on the left to counter balance.

 

In that case, shall I pump more on the right since the load is higher?

 

Again, i'm not a vehicle designer, but based on common sense, I would think the answer to your question is no. Not recommended to mess about with different pressures for different tyres on the same vehicle, especially when its on the same axle (ie. front or rear). Just use the recommended pressures lah.

 

[Grix17]

Load index can be hard to read actually.

 

The normal rule of thumb I believe is increasing pressure by 2-3 psi for every inch upsized.

This applies to standard load (SL) tyres. For extra load (XL) tyres, not necessary to increase pressure.

 

Rules of thumb don't apply to everyone.

For good FC and sharper steering, slight overinflation by 1-2 psi is good.

Downside is possible wear in the centre of the tyre thread if overinflate too much.

 

My stock pressure for 17" was 250 kPa.

Upsizing to 18" on XL tyres I tried between 250-280 kPa.

250 felt sluggish. 275-280 less resistance but too firm. I found 260-270 just nice, depending on temperature.

Now on new 18" tyres, pumping 260 first.

 

My conclusion:

Try a range of pressures beginning with stock pressure.

See what feels best for your driving style.

[0_Kewl]

Load index can be hard to read actually.

 

But its right there on your sidewall. Your tyre pressure placard should also state i think.

 

The normal rule of thumb I believe is increasing pressure by 2-3 psi for every inch upsized.

This applies to standard load (SL) tyres. For extra load (XL) tyres, not necessary to increase pressure.

Rules of thumb don't apply to everyone.

 

You're entitled to your opinion but this is wrong.

 

Rules of thumb don't apply to everyone.

For good FC and sharper steering, slight overinflation by 1-2 psi is good.

Downside is possible wear in the centre of the tyre thread if overinflate too much.

 

Yours is a rule of thumb too. Difference is, my rule of thumb is industry rule of thumb. Yours is? Personal rule of thumb?

 

If you compare under-inflation and over-inflation...the lesser of two evils is over-inflation. Yes, you'll have better fuel consumption. Yes, you will also have better handling responsiveness. Yes, aquaplaning resistance is slightly better. BUT...do not overdo it. The downsides of excessive over-inflation is:

- accelerated tyre wear (specifically centre wear)

- harsher ride

- more susceptible to tyre damage

- accelerates wear of suspension components

 

My stock pressure for 17" was 250 kPa.

Upsizing to 18" on XL tyres I tried between 250-280 kPa.

250 felt sluggish. 275-280 less resistance but too firm. I found 260-270 just nice, depending on temperature.

Now on new 18" tyres, pumping 260 first.

 

My conclusion:

Try a range of pressures beginning with stock pressure.

See what feels best for your driving style.

 

If you're aware of the pros & cons of messing about with tyre pressure (wear, handling, cold pressure, hot pressure, over/understeer tendancies, comfort, low speed/load pressure, high speed/load pressure, etc.), then go right on ahead, but for the majority of motorists where it is a challenge just to have everyone pump at least their vehicle manufacturer's recommended pressures at least once a month, my advice is to just follow your vehicle manufacturer's recommended pressures.

Edited April 14, 2010 by 0_Kewl

[Beehive3783]

My own rule of thumb is to pump 80% of the tire's max rated pressure.

[Grix17]

Very elaborate answer.

 

But its right there on your sidewall. Your tyre pressure placard should also state i think.

 

You're entitled to your opinion but this is wrong.

 

I'm referring to air pressure according to load index when using tyres other than stock.

Anybody can read load index and check the table for maximum load.

Would you like to elaborate on how to calculate the new pressure when changing tyres?

 

 

Yours is a rule of thumb too. Difference is, my rule of thumb is industry rule of thumb. Yours is? Personal rule of thumb?

 

Yes, thank you for your professional advice.

And what is your rule of thumb for calculating pressure for different sizes?

Please elaborate. Don't just criticise my answer.

I would certainly like to know the correct method.

 

 

[Versatile]

Okay guys, change my PSI to 34...

[0_Kewl]

Very elaborate answer.

 

 

 

I'm referring to air pressure according to load index when using tyres other than stock.

Anybody can read load index and check the table for maximum load.

Would you like to elaborate on how to calculate the new pressure when changing tyres?

 

 

 

 

Yes, thank you for your professional advice.

And what is your rule of thumb for calculating pressure for different sizes?

Please elaborate. Don't just criticise my answer.

I would certainly like to know the correct method.

 

Already covered...see Post#8. Didn't cover what the guideline is if the new tyre's load index is lower than your OE one though....but the general rule anyhow is to not fit load and speed index lower than your OE tyre anyway.

 

Perhaps i'll write to the major manufacturers (except Michelin - cos i've already written to them and received a reply on this) just to triple confirm.

 

 

[Zuoom]

slight over is always better than under. (especially when people dun regularly check tyre pressure.)

 

you will have alittle more wear in the middle of the tyre thread, and maybe slightly less outright grip in the dry. wet on the other hand works in favour for the slightly over pumped tyre. on a positive note, you gain fuel mileage per tank. haha.

 

under inflated tyres have the possibility of getting overheated and then rapid deflate (more like shredding the tyre to bits as the sidewall goes.)

dangerous stuff if you are on a corner and the rear tyre goes. (it's usually a unrecoverable spin)

 

otherwise, consider using run-flat tyres. they are however alot more expensive n heavy.

 

since we are in Singapore. this place experience quite a bit of rain. so, we should ideally be bias to wet weather issue. ie: water.

 

A Taste of Tire Testing

 

Switching to the car with the new front/worn rears (as the tire shop suggested), we again approached 55 mph. Suddenly, the car snapped its tail out, and we were beyond oversteer and well into an off-pavement excursion. We were no longer drivers, but passengers in a car spinning out of control. We tried a second time. Even when anticipating the moment the car would break loose, there was no time to correct for the slide because it happened so fast. By the third attempt, we finally learned how to regain control of the car.

 

The problem is that, in reality, you don't get three chances to avoid an accident. Next time you buy two new tires, insist that they go on the rear, not the front of your car. It doesn't matter if it's an all-, front-, or rear-wheel-drive car: Always put the fresh ones on the back.

 

Read more: http://www.motortrend.com/features/consume...l#ixzz0jArxZOd1

via : http://www.celicasg.org/index.php?topic=222.0

 

[Grix17]

Already covered...see Post#8. Didn't cover what the guideline is if the new tyre's load index is lower than your OE one though....but the general rule anyhow is to not fit load and speed index lower than your OE tyre anyway.

 

Okay, your Post #8 says:

 

"When you upsize, it is important to note the load index of your OE tyre spec vis-a-vis your new upsized tyre. If the load index on your new tyre is the same or higher, then you're ok to follow the pressure recommendations as the OE tyre. Its only if your upsized tyre has a lower load index than the OE tyre that you have to compensate with additional pressure."

 

Somehow, I read something elsewhere about the calculation but I really didn't quite understand it.

I like to be precise with numbers, well cos I teach Math. Haha.

Your guide is simple to understand. Sorry I missed it.

Anyway, I never go below my OE pressure of 250 kPa even with XL tyres.

 

 

[Jeleburacer]

Sorry but these terms are very very hard to understand. However, i will try to catch/understand what you mean.

 

Anyway, the default PSI that came with the rim is 31-32. I've pumped to 38 PSI as per recommended by RedPlanet. I'm pretty worried whether is it good or bad to pump in 38 PSI.

 

Will it decrease the tire's performance? As i do some hard cornering at times, will there be any side effect?

what car? FF or FR? 215* 45*17 33psi should be fine. Singapore road temperature is high it result

psi increase. If you are drifter higher psi the best....

[0_Kewl]

slight over is always better than under. (especially when people dun regularly check tyre pressure.)

 

you will have alittle more wear in the middle of the tyre thread, and maybe slightly less outright grip in the dry. wet on the other hand works in favour for the slightly over pumped tyre. on a positive note, you gain fuel mileage per tank. haha.

 

under inflated tyres have the possibility of getting overheated and then rapid deflate (more like shredding the tyre to bits as the sidewall goes.)

dangerous stuff if you are on a corner and the rear tyre goes. (it's usually a unrecoverable spin)

 

otherwise, consider using run-flat tyres. they are however alot more expensive n heavy.

 

since we are in Singapore. this place experience quite a bit of rain. so, we should ideally be bias to wet weather issue. ie: water.

 

You're quite right on the above, except for the run-flat solution. Its just not practical. Why? Cos other than cost of tyres where you rightly point out that run-flat tyres typically cost more than regular radial tyres, the other important component is the rim. Run-flat tyres need special rims in order to actually run flat (EH2 rims to be specific). If you whack run-flats on standard rims (H2), and you run flat...the tyre will probably come off the rim and you'll be running nowhere plus probably damage the rim too.

 

EH = extended hump

H = hump

2 = both sides of the rim

[Redplanet]

Do NOT pump at 38psi just because RedPlanet said that he's using 38psi! Good god! He/she is a f-ing wanker to just say 38 works for him. 38 might be ok for him but what vehicle is he driving and what size tyres does he have?! Its not all the same you know? If I was driving a Lamborghini Gallardo, my recommended pressures would be 44psi. A Porsche Cayman S is 29psi (front) & 36 psi (rear). A Toyota Camry is 32psi.

 

Look in your vehicle owners manual. It will tell you how much to pump. Based on my data, the recommended pressure for the old Avante is 32psi...i think.

 

Now when you have your recommended pressure (which is 'cold' pressure), you will most probably drive to the petrol station to top up yes? Once you get there, you will need to add an additional 3-4psi (equivalent in kpa is 25kpa). Why? This is to compensate for expansion of air in your tyres due to heat buildup from driving to the pump. Trust me. If you want to know why, check in to White Circles for a detailed explanation...it'll be up this week or next.

 

Hey f--king arse. I can't bloody say what works for me eh? Where in my posts did i tell TS to follow? Bloody shitstirrer.

[0_Kewl]

Hey f--king arse. I can't bloody say what works for me eh? Where in my posts did i tell TS to follow? Bloody shitstirrer.

 

Well he did follow you didn't he?

[Teddy123]

I would like to share with all the Singapore drivers old & young and help you with this piece of information.

 

Basic

Just get in between the range of not low and high for tire pressure.

 

Tire size 15" or 16" or 17" compare to 18" or 19"or 20" or 21" 22" is different.

 

Another car compare to another is also different because of the weight and everything is different.

 

If your on stock (bmw stock is 17", toyota stock is 15", Kia stock is 14" for e.g) BIG QUESTION MARK ?

 

Solution: Just read read read your drivers manual or check the driver side tab on the door for recommend air pressure&pump ,5min & its done.

 

Problem: Your now on aftermarket rims with bigger & wider tires !!!!!!

 

 

Simple : DO NOT pump the tire until TOO under & over on tire pressure .

 

U Don't wanna explode ur tire while driving down the highway on a sunny day.

 

 

 

 

 

 

Extra info advance

Pressure=weight/area

Over much air = less contact area

Under much air = more contact area

 

Low profile = Less flex,more accurate cornering

High profile = More flex,comfortable

 

Find a sweet spot in between.

Edited November 16, 2011 by Teddy123

[Good-Carbuyer]

Can check with AD? or use tyre sidewall maximum inflation presure X 0.8 for front and X 0.75 for rear (assume to be front wheel drive) If rear wheel drive reverse it. Observe what Teddy123 shown with those photos after about 5000km and adjust inflation pressure if needed.

Edited November 16, 2011 by Good-Carbuyer

[Grix17]

In general, we increase the pressure if upsizing with standard load tyres.

If upsizing to extra load, usually no need to change the stock pressure.

[Beregond]

same size of tyres dun mean same pressure for every car.

 

generaly speaking, lightly car will need lesser pressure,

 

like a lotus 225.45.17 rear pressure is at 26 psi i think. because the car is too light.

 

most ppl like to over pump to get the feel good feeling or feedback from car, and to lower FC.

 

(over inflat tyre mean your steering should feel lighter, COS LESSER CONTACT WITH ROAD, and pick off will more feel less slugglish)

 

but pls bear in mind , when brakeing, the design of the tyres is suppose to go lower. in order to obtain more contact point with the road , and stop the car.

 

and if your car is too light , and your pressure is too high, u will have problem stoping when ebraking.

 

for a normal jap car, like 1/6 - 1.8 civic that upgrade to 215.45.17, i wont pump more then 36 for front, and 34 for rear,

 

but every driver got his own taste. just take note if u feel your steering is very light, u better check your pressure,

 

'underinflat, at most u waste fc and burn more tyres. overinflat will cause u accident.'

[Joelwong]

alot of tire shop uncle just recommend a generic 220 or