Time to go home so I leave you all with a question. Do you run your tires at the maximum pressure labeled on the side of the tire when pulling a full load or at the pressure the vehicle manufacturer recomends? I have a older Ford F350. Ford recomends 50 PSI per the label on the door jam but my tires say 65 PSI max on the sidewall. What are your all's thaughts?
Posted 2005-07-07 2:58 PM (#27749 - in reply to #27747) Subject: RE: TIRE PRESSURE
Elite Veteran
Posts: 1160 Location: Denver Colorado
The owners manual will tell you to go with Ford's # in the door. That's the chain of command, Ford is the tire companies customer and you are Ford's customer. So Ford is the one that spec'd the tire for their application. Personally in the summer heat I go higher on psi when loaded.
Posted 2005-07-07 3:09 PM (#27751 - in reply to #27747) Subject: RE: TIRE PRESSURE
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Posts: 2689
Originally written by FordLvr on 2005-07-07 2:49 PM
Time to go home so I leave you all with a question. Do you run your tires at the maximum pressure labeled on the side of the tire when pulling a full load or at the pressure the vehicle manufacturer recomends? I have a older Ford F350. Ford recomends 50 PSI per the label on the door jam but my tires say 65 PSI max on the sidewall. What are your all's thaughts?
Please see the recent thread on exactly this topic.
Basically the vehicle manufacturer's recommendation should be followed.
The exception is if/when they make bad decisions and recommend underinflation for reasons of "ride quality" resulting in tire failure, vehicle roll-over, etc.
Posted 2005-07-08 6:11 AM (#27767 - in reply to #27747) Subject: RE: TIRE PRESSURE
Member
Posts: 30 Location: Summerville, SC
Thank you for your input. I usually lower tire pressure frm 65 to 50 - 55 for general around town driving as Ford recommends but when I am pulling fully loaded GN and truck full of people/show equip/etc.. I normally bump pressure up to tire rating of 65. Just thought Id check what you all thaught.
Posted 2005-07-08 6:37 AM (#27768 - in reply to #27747) Subject: RE: TIRE PRESSURE
Veteran
Posts: 225 Location: Kansas City
Poster stated an older 350 truck. What do you do when you change tires from the orginal? Time & technology may change what is in the owner's manual or on the door. In my experience, auto mfgs go to great measures to note that all tire warranty work is the responsibility of the tire company and not the vehicle mfg. There have always been seperate warranty books that came with my vehicle.
I personally choose to go with the max pressure stated on the tire. That is what the company that makes the tire states - they should know the safety limits and constraints.
Posted 2005-07-08 7:18 AM (#27769 - in reply to #27768) Subject: RE: TIRE PRESSURE
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Posts: 2689
Originally written by barry on 2005-07-08 6:37 AM
Poster stated an older 350 truck. What do you do when you change tires from the orginal? Time & technology may change what is in the owner's manual or on the door. In my experience, auto mfgs go to great measures to note that all tire warranty work is the responsibility of the tire company and not the vehicle mfg. There have always been seperate warranty books that came with my vehicle.
I personally choose to go with the max pressure stated on the tire. That is what the company that makes the tire states - they should know the safety limits and constraints.
a) Do NOT change tire sizes from original. Contrary to popular myth, wider tires are generally less safe than original equipment spec.
b) Changes to door pillar sticker pressures over time represent changes to the vehicle more than changes to tires - air is still air, though not as clean as it once was. It makes no sense to change the pressures on, say an '86 3/4 ton truck to what is specified on the door pillar of an '06 3/4 ton truck. Physics is physics, "PRESSURE" is measured in force per unit area, e.g. pounds per square inch. One of the goals of proper suspension design is to select a wheel and tire size that will adequately support the load with a suitable (size AND shape) contact patch on the road. Deriving a suitable inflation pressure is part of this design and is clearly the responsibility of the vehicle designer/manufacturer. Clearly this must be WITHIN the application specs set forth by the tire manufacturer, preferably not at the limit of those specs.
c) Blame shift is just part of the industry's way of doing things, it used to apply to wiper blades.
d) Yes, tire manufacturers spec MAXIMUM load ratings. They probably "consult" with vehicle manufacturers, but are in no way responsible for the application of their product on any particular vehicle.
e) You only need to run your tires at max pressure if/when you are carrying max load. There are plenty enough good reasons to not run at max load.
Posted 2005-07-08 7:24 AM (#27770 - in reply to #27768) Subject: RE: TIRE PRESSURE
Member
Posts: 30 Location: Summerville, SC
barry, you have a good point. Tire technology has changed a lot since the early 90's. I do know that the tires say max load (xxxx) at 65 psi. To me this means just what it says (max). If Im driving around an empty truck, then I think Im safe lowering the pressure to Ford specs of 50-55 and getting a little better ride quality. Under big load, I bump up to max of 65 to make sure I dont overload tire. I think as long as you dont go to extreme one way or the other your probably safe. Similiar to speed limits. 50 - 60 mph in a 55mph zone and you most likely wont get a ticket. Any slower or faster and your gonna have to pay someday. Thanks for everyones great input
Posted 2005-07-08 8:13 AM (#27771 - in reply to #27768) Subject: RE: TIRE PRESSURE
Expert
Posts: 1416 Location: sc
Originally written by barry on 2005-07-08 7:37 AM
Poster stated an older 350 truck. What do you do when you change tires from the orginal? Time & technology may change what is in the owner's manual or on the door. In my experience, auto mfgs go to great measures to note that all tire warranty work is the responsibility of the tire company and not the vehicle mfg. There have always been seperate warranty books that came with my vehicle. I personally choose to go with the max pressure stated on the tire. That is what the company that makes the tire states - they should know the safety limits and constraints.
what do you do, you ask? well the safest thing to do is call the tire manuf. there are size/inflation charts avaliable for tires, they will take the tire size you are using and then divide the GVWR of the truck(or car, etc) by 3 and then look it up on the chart. run the max if you want, maybe you wont wear out the center of the tire, maybe you will. i personally would rather make a phone call than to chance wearing out my tires prematurely, theyre to damn expensive.
Posted 2005-07-08 2:07 PM (#27794 - in reply to #27769) Subject: RE: TIRE PRESSURE
Veteran
Posts: 225 Location: Kansas City
Originally written by Reg on 2005-07-08 7:18 AM
b) Changes to door pillar sticker pressures over time represent changes to the vehicle more than changes to tires - air is still air, though not as clean as it once was. It makes no sense to change the pressures on, say an '86 3/4 ton truck to what is specified on the door pillar of an '06 3/4 ton truck. . .
I agree somewhat, however what was written for a piece of equipment in 1986 may have little to do "new" replacement equipment purchased today. Spec do change. I sell and use synthetic oil in my truck. Run 15,000+ mile oil changes pulling a trailer. Those specs were unheard of 20 years ago yet they work today - even on vehicles made back then. Tires mfg way back 5 years ago may not be made to the specification of today given all we know about roll-overs, tire failure, etc. So it is wise to check around, do as Chadsalt said and go to the tire mfg, or yes, check the door post of an '06 and see how that relates to new tire technology.
Posted 2005-07-11 12:16 PM (#27897 - in reply to #27794) Subject: RE: TIRE PRESSURE
Expert
Posts: 1391 Location: North of Detroit, MI
Next part of the equation.... doesn't the pressure increase as the tire heats up? as in... "COLD" pressure ratings?
So - if the MAXIMUM, as stated on the sidewall of the tire says "65 psi"... wouldn't you want the cold pressure to be somewhat under that when COLD so that you don't exceed the 65 psi, when the tires heat up? I understand that UNDER-INFLATION is more dangerous than over-inflation.
So far as "NOT changing from the originals"...as someone said... that's a very stupid thing to say. My F150 came with passenger-type tires - even though it came with the manufacturer-installed tow package. Are you saying that I should NOT upgrade my tires to a more suitable truck tire since I haul a GN trailer? If I DO upgrade, what tire pressure should I go with then? what's stated on the doorjamb or what the tire mfg.recommends?
Also - when I read the data plate on my trailer - it states what the maximum load is for each axle with the tires at a certain pressure which is 55 psi, compared to 65 psi which is the max cold rated pressure stamped on the side of the tire.
Posted 2005-07-11 12:25 PM (#27899 - in reply to #27897) Subject: RE: TIRE PRESSURE
Extreme Veteran
Posts: 366 Location: Albany, Oregon
Originally written by gabz on 2005-07-11 12:16 PM
Next part of the equation.... doesn't the pressure increase as the tire heats up? as in... "COLD" pressure ratings?
So - if the MAXIMUM, as stated on the sidewall of the tire says "65 psi"... wouldn't you want the cold pressure to be somewhat under that when COLD so that you don't exceed the 65 psi, when the tires heat up? I understand that UNDER-INFLATION is more dangerous than over-inflation.
So far as "NOT changing from the originals"...as someone said... that's a very stupid thing to say. My F150 came with passenger-type tires - even though it came with the manufacturer-installed tow package. Are you saying that I should NOT upgrade my tires to a more suitable truck tire since I haul a GN trailer? If I DO upgrade, what tire pressure should I go with then? what's stated on the doorjamb or what the tire mfg.recommends?
Also - when I read the data plate on my trailer - it states what the maximum load is for each axle with the tires at a certain pressure. That is 55 psi, compared to 65 psi which is the max cold rated pressure stamped on the side of the trailer.
Posted 2005-07-11 1:00 PM (#27905 - in reply to #27897) Subject: RE: TIRE PRESSURE
Expert
Posts: 2828 Location: Southern New Mexico
65 psi which is the max cold rated pressure stamped on the side of the tire.
If it says cold pressure, then they want you to check the pressure when the tire is cold. They have already made the adjustments for the "hot" pressure.
Posted 2005-07-11 1:35 PM (#27909 - in reply to #27747) Subject: RE: TIRE PRESSURE
Member
Posts: 6
Location: Outside Dallas, Texas
Mr Truck, I'm not sure why you go to a higher pressure in the summer. If nothing else you could come off the pressure just a touch since you know the roadway is hotter and the pressure in the tire will climb more than in the winter. It's my opinion that even though I'm currently on my 4th set of tires on my pickup I still set the pressures based on the jamb. Whether or not the sidewall technology evolved in the tire or not is irrelevant when it comes to what the pressure needs to be for my particular vehicle. The pressure Ford recommends still needs to be used since nothing else about the truck has changed. If the tires I buy this year are better than the tires that came on it originally 7 years ago, great. Theres still no reason to jack with your pressures. Like others have mentioned I'll drop my pressures all around maybe a couple pounds for unloaded driving, but as soon as I hang a GN on the back I'll raise them back up to the door jamb levels.
Posted 2005-07-11 2:15 PM (#27912 - in reply to #27897) Subject: RE: TIRE PRESSURE
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Posts: 2689
Originally written by gabz on 2005-07-11 12:16 PM
Next part of the equation.... doesn't the pressure increase as the tire heats up? as in... "COLD" pressure ratings?
So - if the MAXIMUM, as stated on the sidewall of the tire says "65 psi"... wouldn't you want the cold pressure to be somewhat under that when COLD so that you don't exceed the 65 psi, when the tires heat up? I understand that UNDER-INFLATION is more dangerous than over-inflation.
So far as "NOT changing from the originals"...as someone said... that's a very stupid thing to say. My F150 came with passenger-type tires - even though it came with the manufacturer-installed tow package. Are you saying that I should NOT upgrade my tires to a more suitable truck tire since I haul a GN trailer? If I DO upgrade, what tire pressure should I go with then? what's stated on the doorjamb or what the tire mfg.recommends?
Also - when I read the data plate on my trailer - it states what the maximum load is for each axle with the tires at a certain pressure which is 55 psi, compared to 65 psi which is the max cold rated pressure stamped on the side of the tire.
Re COLD pressure: A reference standard is needed, they chose COLD, easier than having to chose between warm, hot, very hot, how hot, etc. COLD is usually defined as not having been driven for more than 1 mile in the last 3 hours (and probably not sat on hot blacktop in blazing sun either).
If they're inflated to the proper pressure for the load they're carrying they shouldn't heat up much anyway.
Re a very stupid things to say: I thought I had said to not change from what the vehicle manufacturer had spec'd - at least that is what I had MEANT to say. Sure if your truck came with "passenger" tires you should upgrade to LTs, but the number of things that change when you change tire WIDTH are too complex (for MOST of us) to fully understand or adjust for with pressure. I havn't looked lately, but I think my door jamb label has pressures for lightly loaded and for fully loaded. See other forums for stories of people putting 285 and 305mm tires on trucks that were spec'd for 245s, they're SO SURPRISED that the truck "walks" kinda sideways.
I really don't know what pressure to use for even a 20 mm increase in tire width. I don't think "the same" is correct, since that would shorten the contact patch. Higher or lower ? I think you face potential problems either way.
RE axle rating vs tire rating: They're different.
Go with the lower one. In your particular case the two different ratings are telling you that your axles will reach overload before your tires will. You can view this positively as your tires have more margin than your axles. They've already done the table look-up for you and they're telling you to go with 55 psi when your AXLES are loaded to their max.
Inflate your tires to what they ARE carrying, not to what they COULD carry in a different application - or on a different vehicle.
I posted a link to a tire manufacturer's website in a previous topic about this. There are tables of recommended pressures for a given load for each tire size. What is molded into the sidewall is basically the upper limit from that table.
Tires that are overinflated FOR THE APPLICATION THEY'RE IN are likely to be skippy, especially on rough surfaces. They will also wear prematurely in the center.
Only slightly related: You probably won't find (m)any nose wheels on light aircraft inflated to ANYWHERE NEAR their max pressure at max rated load.
Say "SKIPPY " !!!
Oh sure, they don't have time to heat up before the plane stops.
It doesn't stop straight and might not even stay on the runway if there is little/no steering... )-:
Posted 2005-07-12 2:52 AM (#27942 - in reply to #27747) Subject: RE: TIRE PRESSURE
Elite Veteran
Posts: 1160 Location: Denver Colorado
I haven't scientifically tested my over inflated theory. I have seen the data on the Ford Explorer/Firestone tire separation recall and under inflated tires where a big part of the problem. Yes over inflated trailer tires do wear more in the middle and ride a little rougher. But I think we are getting carried away on the increased tire temperature with overinflatation. I've never had a tire blow out from over inflation but have from under inflation. Tires don't continue to rise in temperature in tires properly inflated or over inflated. But tires can continue to increase in temperature in under inflated tires. I use an external laser thermometer to test Centramatic automatic tire balancers and balanced tire can lower your tire temperature by 10%. But when I measure tire temperatures, I don't see them go up all day. It's neat on the new vehicles to watch the tire inflation lbs on the digital display and see the tires raise 5 lbs from morning to afternoon.
These external laser thermometers are only $100 at Harbor freight and you can measure your brake temperature, radiator temperature, barb-a-que or just about anything. I first saw these coming down Pikes Peak, (14,000 ft) with a Quadrasteer and Logan 3 horse where the park rangers measure your brake temp. 1/2 way down the mountain. Good place to practice engine braking. Tomorrow I'll be reviewing a LQ behind Monroe's C4500 with an exhaust brake. I'll be testing (Jake brake wanna be) in the high country on the way to Steamboat Springs to ride horses and cool off at 12,000 FT. Work, work, work.
Posted 2005-07-12 6:21 AM (#27944 - in reply to #27747) Subject: RE: TIRE PRESSURE
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Posts: 2689
Temperature rise in tires is primarily due to sidewall flexing. The lower the pressure the more flexing, as each part of the tire goes from loaded (at the bottom) to unloaded (top 3/4 or so) and back again to loaded. Tires "absorb more energy" the more they flex, you can certainly feel the increased drag when a tire gets REALLY LOW on pressure.
I think this is second order, it may even be insignificant, but a lower pressure also means the air in the tire that is less dense and therefore less able to conduct heat away to the rim and drum/hub.
RE inflating to a bit over pressure: It can be a good thing if you have a slow leak or if you don't have a decent tire guage you can use at home BEFORE driving to the gas station and have to allow for the few degrees of rise to get there. Good guages are cheap and a big advantage of having your own is that you always use the same one, so you know if you have a slow leak vs suspecting that the gas station guages are just all different.
RE Pikes Peak and brake/tire temperatures: The last time I was there they seemed to be pulling people out based on how they were driving (-:
This was a while ago, when they used the "manual" thermal detection devices, i.e. hands ON tires, hands NEAR brakes. I doubt that they are using laser thermal senser tools from Horrible Fright, the walmart of mail order tools, more likely a "fer real" industrial version (-:
Posted 2005-07-12 6:52 AM (#27945 - in reply to #27944) Subject: RE: TIRE PRESSURE
Veteran
Posts: 225 Location: Kansas City
Originally written by Reg on 2005-07-12 6:21 AM
. . . I doubt that they are using laser thermal senser tools from Horrible Fright, the walmart of mail order tools, more likely a "fer real" industrial version (-:
There is no secret technology on these laser sensors. Everyone makes them. I would hope that the gov. park rangers are using the $70-100 versions rather than some $10 million version the military probably buys. Maybe the cheap ones are off 10 degrees - so what? Harbor Freight does have its place in the world. I too use them on my brakes, transmission, rear end, trailer brakes, etc. when I am towing. It is a very easy way to walk around your vehicle and check on mechanical performance before a problem pops up. For example, if you have a magnet start dragging on your trailer brakes or one break set too tight you will notice a heat difference between the other 3 wheels.
TIRE PRESSURE
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