Proper trailer tire inflation

[erikjohnnelson]

This may seem like a stupid question, but I have learned the hard way that what is on the sidewall is not always what you should run for inflation. Case in point, my wife's sedan. The sidewall on the tire says 55 PSI. Pop open the fuel door and the sticker suggests 37 PSI<br /><br />I just bought a 94 18' runabout. The trailer has 15 inch tires. Sidewall says 50 PSI. They are currently at 40. 50 seems high to me, but I'd like some input as I really don't want to deal with a blowout.<br /><br />Suggestions?

 

[pwiseman]

Re: Proper trailer tire inflation

I trust what is says on the tire more than the gas cover. If you are too low on pressure, you can have a blowout as well.

 

[BoatBuoy]

Re: Proper trailer tire inflation

My trailer tires say 90 psi. Talk about raising your pucker factor filling those.

 

[baja power]

Re: Proper trailer tire inflation

Originally posted by erikjohnnelson:<br /> The sidewall on the tire says 55 PSI. Pop open the fuel door and the sticker suggests 37 PSI

are they the same tires that came on it when new? mabye the stock tires that came on it required 37 and it had new tires put on it that require 50?

 

[Lakebiker1st]

Re: Proper trailer tire inflation

If the boat trailer tires say 50#, put 50# in them. I had to replace a set of tires with less than 2,000 miles on them because of low air pressure. I had two different tire men tell me the same thing after both them looked at the old tires, "low air pressure". Now, I keep em at 50#, close to 2,000 miles on them and you cannot tell them from new.

 

[amirm]

Re: Proper trailer tire inflation

I am with Ron. My new EZ Loader trailer has tires with 65 psi marked on it. The EZ Loader manual says to fill them to 65 psi as does the goodyear web site.<br /><br />And yes, I was also surprised to see that you are supposed to fill them to capacity. This is very different than car tires which are rarely if ever filled to maximum PSI.<br /><br />Amir

 

[NateCCIE]

Re: Proper trailer tire inflation

The weight carrying capacity changes with inflation.<br /><br />On a car, if the car weighs X, and the tires only need 35 psi to carry X, then inflating to more than 35 psi just makes the ride worse, and reduces traction.<br /><br />Inflating less than the needed PSI to carry the weight is underinflating.<br /><br />Now, on a trailer, most people recomend running the max pressure on the sidewall of the tire, because most trailers are designed with tires at the maxed at their weight carrying capacity.

 

[Silvertip]

Re: Proper trailer tire inflation

Read what the trailer and auto sidewall says. Trailer tires generally read "inflate to xx PSI". That pressure is required to carry the maximum rated load. Now read what your auto decal says and it should be confirmed in the owners manual as well. It generally indicates a recommended inflation pressure for standard as well as heavy load. The sidewall on an auto tire reads "xxxx maximum load at xx inflation pressure". These are two distinctly different specifications for two distinctly different reasons. Auto tire pressure is dictated for ride and handling with a given load which is rarely at the maximum tire inflation pressure. Trailer tires are simply rated for the maximum load and should always be inflated as instructed on the sidewall. Therefore, the instruction INFLATE TO means do it. For cars, it means adhere to the label, not the sidewall.

 

[bigbad4cyl]

Re: Proper trailer tire inflation

tire presure listed on tire indicates....how much presure is needed when that tire is at maximum load capacity to maintain the sidewall and tires correct shape therefor letting its design factors work correctly.

 

[cp]

Re: Proper trailer tire inflation

Not meaning to start a war of words or anything, just want to point out that the Goodyear website lists load/inflation information that gives tire load limits at various inflation pressures for ST tires. See the below link:<br /><br />ST Tire Load vs.Inflation<br /><br />This would seem to indicate that trailer tires need not always be inflated to maximum rated, as long as the load and inflation pressure match, i.e. the tire is inflated enough to safely carry the load placed on it.<br /><br />The local trailer tire guy says to always inflate to the rated max pressure cold, but that leaves no margin for unexpected pressure increases. Trailer tire design allows for an increase in pressure above max rated resulting from normal tire heating, but what about abnormal heating like when a brake drags or a bearing starts to go? Seems prudent to inflate only enough to safely carry any expected load and leave the rest as a safety/comfort margin. Besides a softer ride from tires not fully inflated, there'll be some added margin in the event of unexpected heating and pressure increase. It could be the difference between a dragging brake causing a blowout or just finding and fixing a dragging brake when you get home.<br /><br />As an example, if you're trailering 2100# on a single axle with ST175/80R13B tires the Goodyear info shows that you'd better inflate to max 35 psi to carry that load. But if you had ST175/80R13C tires you could still carry that 2100# load at 35 psi instead of the max 50 psi. Prob'ly be good to go to 40 psi, but you see that'd still leave 10 psi 'cushion' against any blowout from the tire overheating and pressure increasing due to a dragging brake.<br /><br />If you're max'd out on your trailer tire load rating, then inflate to max psi. If you're not maxed out on load, you don't have to max out psi. Just my 2¢...

 

[Silvertip]

Re: Proper trailer tire inflation

PC -- Next time you follow a trailer take note sidewall flexing. Under inflated trailer tires exhibit a tremendous amount of sidewall flex which also makes the trailer more prone to sway and makes it tow harder. Flexing creates heat even if under inflation leaves the tire load capacity within the weight the trailer is carrying at the time. You are suggesting its ok to under inflating trailer tires and are possibly misinterpreting what GoodYear is saying. As for a "local tire guy" giving you advice, read what some of the other posters in this thread have said about their "local tire guys". I again suggest you read what the trailer tire sidewall says. It says "Inflate to xx pounds". That leaves little to interpretation. As for unexpected heat rise, underinflating a tire to compensate for "what might happen" is rediculous. That logic would seem to indicate one should bandage ones finger just in case you cut yourself. A properly inflated trailer tire runs cooler than one that is underflated and makes for safer towing. Bearing and brake problems are due to lack of maintenance and if you are tuned to what's going on behind you, you will notice a trailer brake or bearing problem long before it causes a tire problem. Every instance of a severe bearing failure I've seen has caused a spindle separation resulting in loss of the wheel and but the tire has been intact. Tire failure is almost always due to wear, underinflation, overloading, alignment, manufacturing flaw, or age.

 

[ALAG3]

Re: Proper trailer tire inflation

low air pressure is bad...I agree that if they say 50, run 50.....

 

[craze1cars]

Re: Proper trailer tire inflation

Just for the fun of people who run nothing but 30 to 40 psi tires on their passenger car tires...the door labels on most 3/4 ton pickups specify 80 psi for their rear tires (assuming a full load), and tires on semi trucks frequently call for 105 to 110 psi.<br /><br />As for your initial question, you should absolutely be running 50 psi in both of your trailer tires.

 

[fondafj]

Re: Proper trailer tire inflation

Well, assuming the trailer is correctly sized for the boat, I have found in EVERY case that the OEM tires are barely sized to carry the load, or GVW of the trailer. It is a $$$$$ thing with the trailer manufacturers. Hence, the inflate to max PSI on the sidewall rule of thumb. The only exception is if the consumer has replaced the tires and moved up one or two load ranges. Heat is the tire killer and is generated by internal belt friction. Higher pressures reduce that friction.

 

[QC]

Re: Proper trailer tire inflation

UIS and The Crazy One,<br /><br />First, both of you guys have consistently been the best source of info regarding on-highway stuff. So please understand that I respect your positions . . . a lot!! But . . .<br /><br />Why would you guys recommend ignoring what appears to me to be a very legitimate and helpful chart from Goodyear? I agree that the best failsafe method is to inflate to max, but if the user takes the time to really follow manufacturers advice, shouldn't they?<br /><br />I truly want to understand your postions, I am not disputing them, just confused about why the manufacturers ideas are invalid . . . If the answer is again that it is just a more failsafe approach, then I understand. But I don't think you guys mean to infer that the manufacturer's advice is bogus, right?

 

[tommays]

Re: Proper trailer tire inflation

quiet<br /><br />i printed the chart and read it it seems geared more towards an OEM builder than and end user<br /><br />i cant see most people being able to do the more complex setups in the chart<br /><br />i feel you should go for the max because of sidewall flex <br /><br />i have had light trucks that when useing some brands of tires at the recomend pressure were hard to control due to tire induced sway<br /><br />the only cure was to run at a higher pressure within the limits on the tire<br /><br />tommays

 

[QC]

Re: Proper trailer tire inflation

tommays,<br /><br />Makes sense, but I still think more info is good if you can follow it. I had the same tires on my last setup which probaly ran at 3500 lbs as I do now which probably runs at 5500 lbs. Anyway, I always felt it was a little silly to run 50 PSI when the load was low enough for a single axle yet I had it distributed over 4 tires. I ran that combo at about 40 PSI. The heavier load I am running at 50, but that Goodyear chart suggests 35 for my newer load!! There is some benefit to cushioning the hull etc. when you can, right?

 

[tommays]

Re: Proper trailer tire inflation

quiet <br /><br />my biggest concern is starting a sway that cant be stoped other that buy the grace of god<br /><br />the best way i have seen to do this is run at at the highest recomended pressure<br /><br />i have never see a boat damaged that was correctly supported buy the trailer<br /><br /> only when the support system does not meet the boat builders requirments<br /><br /><br />tommays

 

[craze1cars]

Re: Proper trailer tire inflation

Originally posted by Quietcat:<br /> <br />Why would you guys recommend ignoring what appears to me to be a very legitimate and helpful chart from Goodyear? I agree that the best failsafe method is to inflate to max, but if the user takes the time to really follow manufacturers advice, shouldn't they?<br /><br />...But I don't think you guys mean to infer that the manufacturer's advice is bogus, right?

Nope, not saying ignore it or that they're bogus. But their chart says "Load LIMITS at various tire inflation pressures." It doesn't say "recommended inflation for various load limits." I interpret these as two distinctly different things. If it said the latter, I'd likely recommend following the chart...but frankly I don't think you're utilizing the info on those charts properly.<br /><br />Cars have "recommended" inflation levels that provide the best combination of fuel economy, handling, comfort, tire wear, and safety.<br /><br />Here's how I interpret that chart...If someone has taken the time to weigh the exact load on each individual tire of their rig, and you want to go with the minimum pressure to just have the minimum amount of load carrying capacity on a tire, then you can safely squeek by if you utilize the minimum pressure they have stated on the chart. <br /><br />Most people don't go through all that trouble, and even if I did, I'd prefer the margin of safety of a larger load limit on each tire, and the stiffer sidewalls to help prevent sway of the maximum pressure printed on the sidewall. I've never heard of a boat hull being damaged by trailer tires being inflated to their max, so I really don't think hull cushioning is a factor.<br /><br />I agree with a previous poster here that the Goodyear chart is likely intended for vehicle manufacturers (like RV or trailer mfrs, for instance), who are writing owners manuals for their owners so they can instruct their owners on a specific tire pressure that gives the best combination of handling characteristics while still safely carrying the weight of their RV. <br /><br />And most importantly, I've bought a lot of trailers brand new over the years, AND believe it or not I've read my boat and snowmobile trailer owner's manuals. The owners manuals on all of my trailers have always stated to run the max pressure printed on the tire sidewall.<br /><br />So that's where I'm coming from...hope that explains my funky brain a bit...

 

[Silvertip]

Re: Proper trailer tire inflation

And I agree with Craze1cars. Nowhere in that chart does it say "recommended". That chart merely says, if you have a ST185R13 and you have 15 pounds of air in it, you better have 740 or less pounds of weight on that tire. I might add that the max GVW (vehicle plus load) for a car is specified at the "recommended" tire pressure, not the maximum allowable for the tire. As for cushioning the hull, that's what the springs are for.