Tyre Air Pressure.

[phutoie2]

One for the tyre experts here. Just put some new Nexen tyres on the pickup and forgot to ask about air pressures at the tyre shop. On the side wall its has the max load at 44 PSI, my gauge has gone missing so cannot check at the moment.

What air pressure would be suitable for normal driving etc?, do not carry any heavy loads. I was thinking about 34-36 PSI.

Tyre size is 245/45/R17.

[PattayaParent]

You've opened up a can of worms here if previous posts on this topic are anything to go by.

I'll sit back and watch the fun.

[ripstanley]

Have a read of this link http://en.wikipedia.org/wiki/Tire_code#Load_index

[Semper]

You've opened up a can of worms here if previous posts on this topic are anything to go by.

I'll sit back and watch the fun.

I'll join you.

[TommoPhysicist]

I would go much higher, 52PSI in my truck.

[thailoht]

The recommended and optimal tyre pressure for every vehicle (with OEM/mfg tyres) is listed on a plate that is usually stamped on the driver's side, lower inside door pillar.

[Spoonman]

Those tyres I would run at 32 front and 34 rear.

[Jitar]

Tyre experts are a bit like economists, it is rare to find two that agree.

The load index of your new tyres should be close to that of the old, so the OEM recommended pressure should still be close. For light loads, mid 30's is also a good guess IMO although (as pointed out above), I recall another lengthy Thaivisa thread with many alternatives.

Experiment a little and find a compromise you are happy with between low 30's (better ride) and mid to high 30's (good for tyre life, fuel economy, steering response and sidewall damage resistance).

[transam]

I would go much higher, 52PSI in my truck.

[Crossy]

Oh dear, here we go again.

Do NOT exceed the maximum pressure stated on the side-wall. Start off with the pressures recommended for your vehicle (look on the door pillar drivers side or in the handbook), a few pounds either way can do no serious harm if you find it improves handling or ride.

[transam]

Oh dear, here we go again.

Do NOT exceed the maximum pressure stated on the side-wall. Start off with the pressures recommended for your vehicle (look on the door pillar drivers side or in the handbook), a few pounds either way can do no serious harm if you find it improves handling or ride.

Weeeeeeeeeeeeellllllll, few pounds under is dangerous, mega pounds over is dangerous, but yes we have been here before and tyre pressure topics shut down. But PM's are allowed to make your worry a little less worrying.

[phutoie2]

Those tyres I would run at 32 front and 34 rear.

Yep, I was thinking about the same, could not find much on Nexens website. Should have mentioned slightly smaller tyre on the front, 235/45/17 on a 8" wheel, the 245/45/17's are on 9" 's.

Spoonman - suspension all sorted now, lower than a cobra's belly, Saving up for some Nitto pipes next!.

[Kwasaki]

This is exerts and savings from posts that have been edited in places but with some additional info included, most of which was previously posted by MRO who is a valid source of info.

A bit to digest but easy to work out common sense is usually the rule of the day.

So in order to know what the proper pressures should be, we need to know:

1. The car manufacturers' recommended pressures for the OEM tyres.

2. The Load rating of the OEM tyres (e.g. 112V, 111H, 109S etc)

3. The Load rating of the new tyres..

If your changing to different profile tyres.

The correct rule is: Adjust the OEM recommended PSI pressures by subtracting or adding the load rating of the new tyre from the load rating of OEM new tyre.

Examples:

If the OEM tyre is 109S and the new tyre is 112V, and the OEM pressure is 29PSI:

109 minus 112 = minus 3

29PSI minus 3 = 26 PSI

If the OEM tire is 112H and the new tyre is 111R, and the OEM pressure is 32PSI:

112 minus 111 = +1

32PSI + 1 = 33 PSI.

So obviously important to know what the OEM load of your vehicles OEM tyre.

If you didn't swap your spare tyre, you should be able to look at it to determine the OEM load rating that corresponds to the vehicle manufacturers recommended pressures.

If your new load index works out at a full 6 points lower than OEM tyres, I would be very concerned that you've got an unsafe fitment (it sounds like you have a passenger car tyre

on an SUV or pickup). Be careful out there when buying tyres.

With the cold pressure recommendations given, it’s a good idea when have to drive to a garage to get air, when using a gauge you have already put heat into the tyre so nock off 2 psi and / or check in the morning.

Have a look on this site at the table here to see how the load index corresponds to the weight rating of the tyre :- http://en.wikipedia....code#Load_index

IMO This site is good info although most of it supports OEM.

6 points lower load index means between 150-210KG less weight capability per tyre, so 600-840KG less vehicle weight safely supported.

Normally no need go down on load index, you'd either keep it the same or perhaps go up. I'm never going to hit the maximum GVM of the car, so I normally try to keep it in the -1 to +3 range, if you're perhaps going to have a full load on board, use a 0 to +3 range when buying tyres.

If above +3, the tyre is so far out of original spec that pressures would have to be dangerously low to maintain any ride quality, I would not necessarily agree but with high speed yes !!.

Phew !!

Edited July 18, 2012 by Kwasaki

[transam]

This is exerts and savings from posts that have been edited in places but with some additional info included, most of which was previously posted by MRO who is a valid source of info.

A bit to digest but easy to work out common sense is usually the rule of the day.

So in order to know what the proper pressures should be, we need to know:

1. The car manufacturers' recommended pressures for the OEM tyres.

2. The Load rating of the OEM tyres (e.g. 112V, 111H, 109S etc)

3. The Load rating of the new tyres..

If your changing to different profile tyres.

The correct rule is: Adjust the OEM recommended PSI pressures by subtracting or adding the load rating of the new tyre from the load rating of OEM new tyre.

Examples:

If the OEM tyre is 109S and the new tyre is 112V, and the OEM pressure is 29PSI:

109 minus 112 = minus 3

29PSI minus 3 = 26 PSI

If the OEM tire is 112H and the new tyre is 111R, and the OEM pressure is 32PSI:

112 minus 111 = +1

32PSI + 1 = 33 PSI.

So obviously important to know what the OEM load of your vehicles OEM tyre.

If you didn't swap your spare tyre, you should be able to look at it to determine the OEM load rating that corresponds to the vehicle manufacturers recommended pressures.

If your new load index works out at a full 6 points lower than OEM tyres, I would be very concerned that you've got an unsafe fitment (it sounds like you have a passenger car tyre

on an SUV or pickup). Be careful out there when buying tyres.

With the cold pressure recommendations given, it’s a good idea when have to drive to a garage to get air, when using a gauge you have already put heat into the tyre so nock off 2 psi and / or check in the morning.

Have a look on this site at the table here to see how the load index corresponds to the weight rating of the tyre :- http://en.wikipedia....code#Load_index

IMO This site is good info although most of it supports OEM.

6 points lower load index means between 150-210KG less weight capability per tyre, so 600-840KG less vehicle weight safely supported.

Normally no need go down on load index, you'd either keep it the same or perhaps go up. I'm never going to hit the maximum GVM of the car, so I normally try to keep it in the -1 to +3 range, if you're perhaps going to have a full load on board, use a 0 to +3 range when buying tyres.

If above +3, the tyre is so far out of original spec that pressures would have to be dangerously low to maintain any ride quality, I would not necessarily agree but with high speed yes !!.

Phew !!

I'm going for a lye down now.

[Kwasaki]

Phew !!

I'm going for a lye down now.

Yeah I am full of good shit sometimes.

[BangkokMatt]

is tyre pressure that important. I had a Isuzu Grand Adventure for 7 years. Ran the tyres at 33. Never a problem. I now have a PJS and run all 4 tyres at 35. Still no problems. I think I drive at sensible speeds (140 max, mostly 100 -120) so maybe it is not an issue. Experts - am I being unsafe?

Speeds are highway driving btw

Edited July 18, 2012 by BangkokMatt

[BSJ]

I go maximum pressure on the Bridgestone tyre scale all the time. On a run to Bangers the pressure probably increases 10 psi with the heat build-up. Running more than recommended is nuts!!!

[transam]

is tyre pressure that important. I had a Isuzu Grand Adventure for 7 years. Ran the tyres at 33. Never a problem. I now have a PJS and run all 4 tyres at 35. Still no problems. I think I drive at sensible speeds (140 max, mostly 100 -120) so maybe it is not an issue. Experts - am I being unsafe?

Speeds are highway driving btw

Open the drivers door and a sticker on the door post will reveal all. Manufactures test their new vehicles to the extreme to provide a safe pressure for it. These are ''cold'' pressures, which means check before going on long run or tear- assing around . Tyre pressures rise as the tyre gets warm via driving.

[how241]

The recommended and optimal tyre pressure for every vehicle (with OEM/mfg tyres) is listed on a plate that is usually stamped on the driver's side, lower inside door pillar.

Yes, good info. Usually about 35 psi is OK---don't forget check when the tires are cold, before you drive anywhere in the morning or add a few extra pounds if their hot.

[transam]

The recommended and optimal tyre pressure for every vehicle (with OEM/mfg tyres) is listed on a plate that is usually stamped on the driver's side, lower inside door pillar.

Yes, good info. Usually about 35 psi is OK---don't forget check when the tires are cold, before you drive anywhere in the morning or add a few extra pounds if their hot.

Noooo, reduce if they are hot.

BUT, never check when ''hot''.

Edited July 22, 2012 by transam

[stevenl]

The recommended and optimal tyre pressure for every vehicle (with OEM/mfg tyres) is listed on a plate that is usually stamped on the driver's side, lower inside door pillar.

Yes, good info. Usually about 35 psi is OK---don't forget check when the tires are cold, before you drive anywhere in the morning or add a few extra pounds if their hot.

Noooo, reduce if they are hot.

BUT, never check when ''hot''.

35 PSI, but when the tire gets hot the pressure increases, to let's say 38. So when I test the pressure I should reduce it yousay? So when it cools down it will say 32 minus what I let out?

Does not make any sense, it really should be as was written: add a few extra pounds if they're hot.

[transam]

The recommended and optimal tyre pressure for every vehicle (with OEM/mfg tyres) is listed on a plate that is usually stamped on the driver's side, lower inside door pillar.

Yes, good info. Usually about 35 psi is OK---don't forget check when the tires are cold, before you drive anywhere in the morning or add a few extra pounds if their hot.

Noooo, reduce if they are hot.

BUT, never check when ''hot''.

35 PSI, but when the tire gets hot the pressure increases, to let's say 38. So when I test the pressure I should reduce it yousay? So when it cools down it will say 32 minus what I let out?

Does not make any sense, it really should be as was written: add a few extra pounds if they're hot.

I replied to a post to show/state that tyre pressure increases when hot so if you check when hot you decrease pressure BUT you never check when hot.

[stevenl]

Yes, good info. Usually about 35 psi is OK---don't forget check when the tires are cold, before you drive anywhere in the morning or add a few extra pounds if their hot.

Noooo, reduce if they are hot.

BUT, never check when ''hot''.

35 PSI, but when the tire gets hot the pressure increases, to let's say 38. So when I test the pressure I should reduce it yousay? So when it cools down it will say 32 minus what I let out?

Does not make any sense, it really should be as was written: add a few extra pounds if they're hot.

I replied to a post to show/state that tyre pressure increases when hot so if you check when hot you decrease pressure BUT you never check when hot.

Yes, and I answered to that saying what you're writing is not true, you do not decrease.

[transam]

CHRIST it's difficult sometimes, I am trying to clarifying a perhaps misunderstanding to the readers regarding how241's post.

So lets start again. Get out of bed, have your breakfast, THEN, check your tyre pressures. Adjust to the stated figures on the sticker on the door pillar.

Do not check when the motor has been run as the tyre pressure will have increased via heat. It will decrease when tyre heat disipates/cools down.

OK now.

[stevenl]

CHRIST it's difficult sometimes, I am trying to clarifying a perhaps misunderstanding to the readers regarding how241's post.

So lets start again. Get out of bed, have your breakfast, THEN, check your tyre pressures. Adjust to the stated figures on the sticker on the door pillar.

Do not check when the motor has been run as the tyre pressure will have increased via heat. It will decrease when tyre heat disipates/cools down.

OK now.

Yes, that is correct.

It's ok to admit to a mistake BTW.

Edited July 22, 2012 by stevenl

[Spoonman]

is tyre pressure that important. I had a Isuzu Grand Adventure for 7 years. Ran the tyres at 33. Never a problem. I now have a PJS and run all 4 tyres at 35. Still no problems. I think I drive at sensible speeds (140 max, mostly 100 -120) so maybe it is not an issue. Experts - am I being unsafe?

Speeds are highway driving btw

Open the drivers door and a sticker on the door post will reveal all. Manufactures test their new vehicles to the extreme to provide a safe pressure for it. These are ''cold'' pressures, which means check before going on long run or tear- assing around . Tyre pressures rise as the tyre gets warm via driving.

The tyres (size) fitted to my vehicle are not dictated on the vehicle placard. what should I run them at ?

[transam]

is tyre pressure that important. I had a Isuzu Grand Adventure for 7 years. Ran the tyres at 33. Never a problem. I now have a PJS and run all 4 tyres at 35. Still no problems. I think I drive at sensible speeds (140 max, mostly 100 -120) so maybe it is not an issue. Experts - am I being unsafe?

Speeds are highway driving btw

Open the drivers door and a sticker on the door post will reveal all. Manufactures test their new vehicles to the extreme to provide a safe pressure for it. These are ''cold'' pressures, which means check before going on long run or tear- assing around . Tyre pressures rise as the tyre gets warm via driving.

The tyres (size) fitted to my vehicle are not dictated on the vehicle placard. what should I run them at ?

Ask the manufacturer . Easy stuff for an ex racer like yourself. We have all done it eh.

[phutoie2]

Instruction manual!, that's funny, well maybe along the lines of "max inflation 44 PSI".

Spoon - try not to wind the Trans up, you know after his daily allowance of Chang his job is to regurgitate <deleted> he has put on here 4 years or so back.

[transam]

Instruction manual!, that's funny, well maybe along the lines of "max inflation 44 PSI".

Spoon - try not to wind the Trans up, you know after his daily allowance of Chang his job is to regurgitate <deleted> he has put on here 4 years or so back.

Ooooooooooooooooooooooooooooooh, you are awful, but l like you.

[Spoonman]

is tyre pressure that important. I had a Isuzu Grand Adventure for 7 years. Ran the tyres at 33. Never a problem. I now have a PJS and run all 4 tyres at 35. Still no problems. I think I drive at sensible speeds (140 max, mostly 100 -120) so maybe it is not an issue. Experts - am I being unsafe?

Speeds are highway driving btw

Open the drivers door and a sticker on the door post will reveal all. Manufactures test their new vehicles to the extreme to provide a safe pressure for it. These are ''cold'' pressures, which means check before going on long run or tear- assing around . Tyre pressures rise as the tyre gets warm via driving.

The tyres (size) fitted to my vehicle are not dictated on the vehicle placard. what should I run them at ?

Ask the manufacturer . Easy stuff for an ex racer like yourself. We have all done it eh.

Have you got Falken's number handy ?