Tire Pressure

[Traction]

If you are OCD enough, you would need to adjust your tire pressure several times a day. Just keep it in a reasonable range for the conditions is all that's needed. In town, low for bumps, and highway/high loads then maybe go higher. It all is about common sense, which is lacking too many times. Look at the load/inflation tables.

 

[Lubener]

Originally Posted by das_peikko
I was told today from a reliable source that you should set your cold tire pressure 4 psi below the max pressure printed on the tire. The owners manual recommendation or any sticker specifications on the car pertain to the original tires that came on the car from the factory and no longer apply. With new replacement tires, go by what the tire manufacturer says. That's what I was told today.

Merkava at it again.

 

[CapriRacer]

Originally Posted by HangFire
…… Some Vehicle owner's manuals defer to the tire manufacturer. …….


I'm going to challenge you to produce any owner's manual that says that.

Why? Because I have sat in many meetings with other tire manufacturer's representatives and every time, we all deferred to the vehicle manufacturer for inflation pressure specification.

And for reference, I'm talking passenger cars and light trucks - ones where there is a vehicle tire placard as required by the government. Other types of vehicles (over-the-road trucks, mining equipment, etc) are handled differently.

 

[Wolf359]

Originally Posted by CapriRacer
Originally Posted by HangFire
…… Some Vehicle owner's manuals defer to the tire manufacturer. …….


I'm going to challenge you to produce any owner's manual that says that.

Why? Because I have sat in many meetings with other tire manufacturer's representatives and every time, we all deferred to the vehicle manufacturer for inflation pressure specification.

And for reference, I'm talking passenger cars and light trucks - ones where there is a vehicle tire placard as required by the government. Other types of vehicles (over-the-road trucks, mining equipment, etc) are handled differently.


That's a good challenge. Never heard of any car that didn't have a recommended tire pressure on the driver's side door. At least not one made in the last 10-20 years. Maybe when they didn't have tire standards when cars were first made.

 

[zeng]

Originally Posted by CapriRacer
Originally Posted by HangFire
…… Some Vehicle owner's manuals defer to the tire manufacturer. …….


I'm going to challenge you to produce any owner's manual that says that.

Why? Because I have sat in many meetings with other tire manufacturer's representatives and every time, we all deferred to the vehicle manufacturer for inflation pressure specification.

And for reference, I'm talking passenger cars and light trucks - ones where there is a vehicle tire placard as required by the government. Other types of vehicles (over-the-road trucks, mining equipment, etc) are handled differently.

...... only to the extent of selecting psi (of selected tire size) on a particular vehicle make , say selecting 30 psi on 1xx/6xR1x 88H tires.
However, provision of guidelines/standards must come from tire manufacturers, not vehicle OEM's.
I would be horrified if the competent(?) tire manufacturer representatives are NOT aware ,and hence NOT knowledgeabe of tire industry standards/guidelines.
Hence, I would challenge your position.

HangFire's contention on deferment is valid.

 

[JohnnyJohnson]

As long as you stay in the rated range of your tire you will be just fine. My Hankook's are rated for 51 PSI. I inflate them to 40 that sure isn't going to hurt them.

 

[RDY4WAR]

This also depends on the tire used as well, assuming differences in the construction of different brands of radial tires.

Speaking from my experience in the drag racing world. There's a brand (call it Brand "A") of radial-slick tire that you avoid if you need to put a lot of power to the ground down track. (usually the case with turbos and centri-superchargers) This particular brand of tire seems to have less structural integrity or just enough to be called a radial tire. It wants to "stand up" a good bit once you get above about 100 mph which is about 2 seconds into the run and about where the big turbo cars would start pouring all the boost to the engine it can make. As the tire stands up, that contact patch narrows and it looses traction. The car will launch good, get about 200 ft out and light the tires up.

Another brand (B) that is a competitor seems to be more structurally sound. However, it also means the tire doesn't "squat" as well on the launch, meaning you can't throw as much power to the ground off the starting line without smoking the tires. However, they maintain their contact patch the entire way down the track allowing you pour more power to them down track.

The cars that want to throw a lot of power to the ground right off the starting line, such as nitrous powered and naturally aspirated cars, like brand A. The turbocharged and blower cars want brand B so they can let the forced induction sing on the top end of the track and run the nitrous cars down.

I'm not sure if the same thing happens with DOT radials, whether one brand is more structurally sound and won't "ride the center" of the tire as bad with speed vs another brand.

 

[Quattro Pete]

Originally Posted by zeng
Originally Posted by CapriRacer
Originally Posted by HangFire
…… Some Vehicle owner's manuals defer to the tire manufacturer. …….


I'm going to challenge you to produce any owner's manual that says that.

Why? Because I have sat in many meetings with other tire manufacturer's representatives and every time, we all deferred to the vehicle manufacturer for inflation pressure specification.

And for reference, I'm talking passenger cars and light trucks - ones where there is a vehicle tire placard as required by the government. Other types of vehicles (over-the-road trucks, mining equipment, etc) are handled differently.

...... only to the extent of selecting psi (of selected tire size) on a particular vehicle make , say selecting 30 psi on 1xx/6xR1x 88H tires.
However, provision of guidelines/standards must come from tire manufacturers, not vehicle OEM's.
I would be horrified if the competent(?) tire manufacturer representatives are NOT aware ,and hence NOT knowledgeabe of tire industry standards/guidelines.
Hence, I would challenge your position.

HangFire's contention on deferment is valid.

Tire manufacturer has no idea what vehicle the customer is going to mount their tire on, so how can they recommend anything?

 

[RDY4WAR]

Originally Posted by Quattro Pete

Tire manufacturer has no idea what vehicle the customer is going to mount their tire on, so how can they recommend anything?



Case in point, I'm running 165/80r15 tires on the front of a Camaro drag car. It's at least 1,000 lbs heavier than any car meant for that size of tire, and they are aired up to the absolute max. (44 psi) This car doesn't have to turn though.

 

[zeng]

Originally Posted by Quattro Pete
Originally Posted by zeng
Originally Posted by CapriRacer
Originally Posted by HangFire
…… Some Vehicle owner's manuals defer to the tire manufacturer. …….


I'm going to challenge you to produce any owner's manual that says that.

Why? Because I have sat in many meetings with other tire manufacturer's representatives and every time, we all deferred to the vehicle manufacturer for inflation pressure specification.

And for reference, I'm talking passenger cars and light trucks - ones where there is a vehicle tire placard as required by the government. Other types of vehicles (over-the-road trucks, mining equipment, etc) are handled differently.

...... only to the extent of selecting psi (of selected tire size) on a particular vehicle make , say selecting 30 psi on 1xx/6xR1x 88H tires.
However, provision of guidelines/standards must come from tire manufacturers, not vehicle OEM's.
I would be horrified if the competent(?) tire manufacturer representatives are NOT aware ,and hence NOT knowledgeabe of tire industry standards/guidelines.
Hence, I would challenge your position.

HangFire's contention on deferment is valid.

Tire manufacturer has no idea what vehicle the customer is going to mount their tire on, so how can they recommend anything?


a)OEM first select desired tire size, say 185/70R14, then goes to 2 manufacturers for offers and advice ,
b)Manufacturer M offers said size at Load Index 88, whilst Manufacturer G offers load index of whatever,
c)Then OEM select Manufacturer M for whatever reasons .
d)Then tire manufacturer M provides table of range of loads per tire and respective recommended psi to OEM, like say 470 kg(2.0 bar); 485 kg (2.1 bar) .......up to 560 kg (2.5 bar) ;
e)Base on design load calculations, OEM selects 2.1 bar (31 psi) for front tires, and 2.4 bar (35 psi) for rear tires.
Alternatively OEM may choose to select 2.4 bar (35 psi) on all tires front and rear , whilst complying with guidelines/standards from tire manufacturer/Standards organisation.
f)When car owners swapped new tires in later years with LI say, 80 ...... then all above psi readings basing on LI of 88 from OEM are no longer valid, thence another table of load range at respective psi for Load Index 80 must be made available to owner/tire shop or whoever so as to select the proper psi whislt complying with Standards organisation requirements.

Edit:Selecting recommended psi in part (e) could be done by tire manufacturer M, after obtaining designed loads (front and rear) from OEM.

 

[CapriRacer]

First, the software in this only allows 3 embedded quotes, so I truncated all but the last one.


Originally Posted by zeng
a)OEM first select desired tire size, say 185/70R14, then goes to 2 manufacturers for offers and advice ,
b)Manufacturer M offers said size at Load Index 88, whilst Manufacturer G offers load index of whatever,
c)Then OEM select Manufacturer M for whatever reasons .
d)Then tire manufacturer M provides table of range of loads per tire and respective recommended psi to OEM, like say 470 kg(2.0 bar); 485 kg (2.1 bar) .......up to 560 kg (2.5 bar) ;
e)Base on design load calculations, OEM selects 2.1 bar (31 psi) for front tires, and 2.4 bar (35 psi) for rear tires.
Alternatively OEM may choose to select 2.4 bar (35 psi) on all tires front and rear , whilst complying with guidelines/standards from tire manufacturer/Standards organisation.
f)When car owners swapped new tires in later years with LI say, 80 ...... then all above psi readings basing on LI of 88 from OEM are no longer valid, thence another table of load range at respective psi for Load Index 80 must be made available to owner/tire shop or whoever so as to select the proper psi whislt complying with Standards organisation requirements.

Edit:Selecting recommended psi in part (e) could be done by tire manufacturer M, after obtaining designed loads (front and rear) from OEM.


Well, that's not how Ford did it when I called on them. They issued a one page document with the tire size, the inflation pressure specification, and a list of tests that the tire had tp pass.

Further - let's take step a) I was never asked to offer advice or have someone within the company offer advice - and I would have been the guy that request would have gone through. And I am not aware that anyone else was ever asked. Sure, there may have been some discussion while the vehicle was been conceptualized, but ALL the decisions were up to the vehicle designers.

And in step b, the Load Indices are set by the Tire Standardizing Organizations, not the tire manufacturers. Yes, there is a slight difference between standardizing organization - and the operative word here is SLIGHT - and, yes, the tire manufacturer doesn't have to follow those standards, but those load table published by the Tire Standardizing Organization are published so that both the vehicle manufacturers and the tire manufacturers are working off the same document. I know of no vehicle manufacturer that doesn't use one of those published tables - and if it isn't obvious, they state which one they are using when they talk to the tire manufacturers about supplying tires.

So the load tables come from the Tire Standardizing Organization. Those tables are based on a set of formulae that is the same for every tire size published by that organization. In the case of a new size, the standardizing organization is requested by one the member tire manufacturers to publish a new size within the existing formula guidelines. All the member tire manufacturers have to agree BEFORE the load table is published - and it is published by the standardizing organization. not the tire manufacturer. If you see a load table published by a tire manufacturer, it's IDENTICAL to the one published by the Tire Standardizing Organization.

Besides, HangFire said the owners manual sometimes defers to the tire manufacturer - and THAT was what I was objecting to.

 

[Traction]

Anyone out there besides me, ever notice almost every car GM has produced for many years ALL ran 30 psi cold. That's because they engineered the exact tire size the vehicle would need for it's size/weight/performance, and run at a comfortable 30 psi. Which raises naturally to around 35 psi as they heat up at higher speeds/temps. Perfect cold pressure for C4/C5/C6/C7 Corvettes, which all specified 30 psi cold, which changes almost every morning. You need to anticipate temperatures for best settings, with the current weather averages.

 

[HangFire]

Originally Posted by CapriRacer
Besides, HangFire said the owners manual sometimes defers to the tire manufacturer - and THAT was what I was objecting to.

Yeah, I was relying on my own hazy memory. Maybe something from the bias play to radial transition days. I stand by the rest of what I said.

 

[zeng]

Originally Posted by CapriRacer
First, the software in this only allows 3 embedded quotes, so I truncated all but the last one.


Originally Posted by zeng
a)OEM first select desired tire size, say 185/70R14, then goes to 2 manufacturers for offers and advice ,
b)Manufacturer M offers said size at Load Index 88, whilst Manufacturer G offers load index of whatever,
c)Then OEM select Manufacturer M for whatever reasons .
d)Then tire manufacturer M provides table of range of loads per tire and respective recommended psi to OEM, like say 470 kg(2.0 bar); 485 kg (2.1 bar) .......up to 560 kg (2.5 bar) ;
e)Base on design load calculations, OEM selects 2.1 bar (31 psi) for front tires, and 2.4 bar (35 psi) for rear tires.
Alternatively OEM may choose to select 2.4 bar (35 psi) on all tires front and rear , whilst complying with guidelines/standards from tire manufacturer/Standards organisation.
f)When car owners swapped new tires in later years with LI say, 80 ...... then all above psi readings basing on LI of 88 from OEM are no longer valid, thence another table of load range at respective psi for Load Index 80 must be made available to owner/tire shop or whoever so as to select the proper psi whislt complying with Standards organisation requirements.

Edit:Selecting recommended psi in part (e) could be done by tire manufacturer M, after obtaining designed loads (front and rear) from OEM.


Well, that's not how Ford did it when I called on them. They issued a one page document with the tire size, the inflation pressure specification, and a list of tests that the tire had tp pass.

Further - let's take step a) I was never asked to offer advice or have someone within the company offer advice - and I would have been the guy that request would have gone through. And I am not aware that anyone else was ever asked. Sure, there may have been some discussion while the vehicle was been conceptualized, but ALL the decisions were up to the vehicle designers.


Ford must have first obtained product Load Index ( from respective tire tenderers/suppliers/manufacturers) on a particular Ford-specified tire size AND ........
Ford must be referencing or in possession of (appropriate) Load Index table of load ranges issued by respective Standards Organisation (wherein a Load Index is determined/selected by tire manufacturers) as basis or foundation upon which Ford prepares tender specifications for procurements in the context of tire pressure.

It is the Load Index of 'specific' tire product size given by the tire manufacturers AND the Load Index table issued by Standards Organisation that are made available to vehicle OEM's , that forms the very basis of Ford to determine/select the recommended tire pressure (in psi or bar) at designed/calculated loads on tires .........
hence my position on vehicle OEM's deferring to tire manufacturers and/or Standards Organisation in question in the process of determining recommended tire pressures.

Quote
And in step b, the Load Indices are set by the Tire Standardizing Organizations, not the tire manufacturers. Yes, there is a slight difference between standardizing organization - and the operative word here is SLIGHT - and, yes, the tire manufacturer doesn't have to follow those standards, but those load table published by the Tire Standardizing Organization are published so that both the vehicle manufacturers and the tire manufacturers are working off the same document. I know of no vehicle manufacturer that doesn't use one of those published tables - and if it isn't obvious, they state which one they are using when they talk to the tire manufacturers about supplying tires.

So the load tables come from the Tire Standardizing Organization. Those tables are based on a set of formulae that is the same for every tire size published by that organization. In the case of a new size, the standardizing organization is requested by one the member tire manufacturers to publish a new size within the existing formula guidelines. All the member tire manufacturers have to agree BEFORE the load table is published - and it is published by the standardizing organization. not the tire manufacturer. If you see a load table published by a tire manufacturer, it's IDENTICAL to the one published by the Tire Standardizing Organization.


Yes, absolutely.
AND .... tire manufacturers determine Load Index of tires (of a particular size) in question, as part of their product ranges/specifications on offer .
OEM's do NOT determine Load Index table of load ranges.
Vehicle OEM's can't procure tires where it's selected Load Index (of a particular tire size) are not being offered by all/most tenderers, if you know what I mean.