Advice for trailer tire pressure

[canamjhb]

Another thread about purchasing a trailer to transport a Spyder has prompted me to ask about pressure for trailer tires. EVERY dealer and EVERY tire manufacturer says to ALWAYS pressure up to the maximum stated on the tire in order to maintain maximum load capacities. But I have a fixed load at about 50% of my tire's capacity. So the tires are matched for the load capacity of the trailer and NOT to what my fixed load really is. Here are the specifics. I have a 6X10 aluminum trailer that weighs 550#s. My fixed load is 1,200#s so total load is 1,750#s My tires are ST205/75R15s with a load range C maximum load of 1,820 each at 50psi or 3,640 total which matches my 3,500# axle nicely. I have been maintaining 50psi so far. But my tires look like they are running on their tippy toes. They do not have that usual radial bulge at the contact point. When hitting bumps the trailer seems to have a jarring reaction as if the tires are not absorbing any of the action.

Since I am running a very light load for the tires and axle I am inclined to reduce tire pressure to the 35 to 40 psi range. I know trailer tires do not undergo the stresses that vehicle tires encounter, so I'm inclined to shoot for a pressure that increases 2psi from cold to traveling temperature. Or do I always stay with what THEY tell me and keep them at maximum ALWAYS? Thanks..... Jim

 

[Peter Aawen]

Pneumatic tires need enough air inside them to carry the loads you put on them, so yeah, the dealers are right to say "ALWAYS pressure up to the maximum stated on the tire in order to maintain maximum load capacities" -
BUT they have missed out on finishing that statement by including the next VERY IMPORTANT 'end of the warning', which should be -
"THIS ONLY APPLIES WHEN YOU NEED TO CARRY THE MAXIMUM LOAD!" :gaah:

So, if you AREN'T carrying the tire's Maximum Load, then you'll be doing yourself, your tow vehicle AND your trailer, it's load, and your trailer tires a MASSIVE DISSERVICE by running your trailer tires at their Maximum pressures when the load imposed upon them doesn't warrant pressures that high! :banghead:

Look at the Max load/Max pressure info on the sidewalls, that says MAXIMUM Load at MAXIMUM PRESSURE - not OPERATIONAL PRESSURE for ANY load! :bdh:

Just like running Auto Tires under a lightweight Spyder, if you are only carrying a small portion of the tire's Maximum load, you only need a proportional amount of air pressure in the tires to do the job properly and in a way to get the best from those tires and to let them give you their best!! :lecturef_smilie: Bloody Tire techs & trailer dealers etc should know better than to propogate that BS about Max pressure all the time, it's crap, it's not what the tire manufacturers say, it's not what all the authoritive tire documentation in your country or mine (or anyone else's) says, and it WILL be 'less than ideal/optimal' for all those things previously mentioned - but I guess it will also probably mean that those techs/dealers peddling this crap either have No bloody Idea or maybe they might get to take more of your hard earned $$ sooner rather than later... IF you don't have a prang & maybe destroy the whole trailer, load, and tow vehicle, and maybe even more beforehand!! :yikes:

There are meant to be load/pressure tables available for every tire made that shows what pressures you should run in them for a given load, but some places/people/dealers don't make it easy for you to access that info/don't ever pay attention to it (maybe because that'd mean your tires will work better & last longer, so they make less money off you?!? :dontknow so you might need to search a bit to track that info down; or if you know your trailer load/weight & can access the Max load/Max pressure info on the tire sidewalls (or anywhere else ) you can maybe do the calcs for yourself - BUT, how can I say this in a way that will be recognised & still stress how bloody important it is for pneumatic tires.... hmmm, let's see...

UNLESS YOU ARE CARRYING THE INDICATED MAX LOAD ON THOSE TIRES, YOU SHOULD NOT BE RUNNING THE INDICATED MAX PRESSURE!! :lecturef_smilie:

Ps: the 'rule of thumb' for pressure increase in your tires is to aim for a FOUR (4) psi increase after an hour's operation - yep, that's 4 psi, not just 2! Anything much less than a 4 psi increase, your starting pressure was too HIGH & you are compromising ride, handling, traction, tire life, puncture resistance et al; anything much more than a 4 psi increase, your starting pressure was too LOW & you are compromising ride, handling, traction, tire life, puncture resistance et al! :shocked: . But still, even a 2 psi increase is quids ahead of running your tires at their Max pressure ALL the time when your load doesn't warrant that much pressure! :thumbup:

 

[Snoking1127]

Here is the inflation table:

ST205/75R15
Single Tire
1220 lbs @25PSI
1360 lbs @30PSI
1480 lbs (B) @35PSI
1610 lbs @40PSI
1720 lbs @45PSI
1820 lbs (C) @50PSI
1940 lbs @55PSI
2040 lbs @60PSI
2150 lbs (D) @65PSI

 

[canamjhb]

Thank you Peter and Chris. I did look at that pressure table but my load is much lower than the lowest listed. I'm hesitant to run lower than 25psi. My tires are carrying only 875#s of load each. I think I will drop down to 35#s and measure my increase from that point and adjust up or down as needed. My initial thought of a 2psi increase was based upon trailer tires not having as much stress as car (or bike) tires. They just roll along and don't provide traction or braking. But, Peter, I will defer to your expertise. Just in case you didn't notice, my question was asked in hopes you would respond. I think this is information many here can use. Thanks..... Jim

 

[Peter Aawen]

Thank you Peter and Chris. I did look at that pressure table but my load is much lower than the lowest listed. I'm hesitant to run lower than 25psi. My tires are carrying only 875#s of load each. I think I will drop down to 35#s and measure my increase from that point and adjust up or down as needed. My initial thought of a 2psi increase was based upon trailer tires not having as much stress as car (or bike) tires. They just roll along and don't provide traction or braking. But, Peter, I will defer to your expertise. Just in case you didn't notice, my question was asked in hopes you would respond. I think this is information many here can use. Thanks..... Jim

Sounds like a plan to me! :thumbup: