Trailer tire pressure question

[Jeremy Soule]

Trailer tire pressure question.
I have an open trailer with no suspension, that is solid axle welded to the frame. I just purchased a new set of Heartland ST205 70 5R 15 trailer tires from Discount Tire. The max rating is 2150 pounds, max tire pressure 65 PSI. I aproximate the trailer at 900 pounds or less the Zink formula ford at 1100, so approx 1000 pound load per tire on the trailer.

I usually don't go above 65MPH, what do you think is a good tire pressure to run in this situation?
Thanks for your feedback. J

[Purple Frog]

Between 50 and 60 psi. You are not going to stress those tires with your load.

For grins, if you run down the highway for a long distance in the summer. Check them to see if they grow over 65. I doubt it.

I wouldn't wander much below 45 psi. Even though you mike be tempted to get a softer ride for the Vee.

I pull a single axle trailer everyday for work with that size tire. Based on your comment, I drive faster with it.

[Swift17]

....

[TimH]

....

Bummer. I was going to comment about how well he had it strapped down.

Will we be seeing you in another FF Jeremy? Something a little more svelt?

[Jeremy Soule]

Thanks for flipping the photo, how did you do that magic?
Tim, Yens has found a buyer I don't want this wonderful machine sitting any longer. My run the FST in the near future.
thanks will start out at 50 psi see how it goes...... J

[Hardingfv32]

Google the Pressure Inflation Chart. The one I found says that 25 psi is good for 1220 lb per tire.

Brian

[problemchild]

I know car tires are different than trailer tires ...... but when I had solid axle trailers with formula cars on board, I would look for oversized street car tires and run at 12-15 psi. I think you want to be at the very soft end of the range the tires are rated for.

[dsmithwc04]

I thought trailer tires were always supposed to be aired up to their maximum tire pressures (cold) no matter the load?

https://www.etrailer.com/question-139225.html

[Mike B]

I thought trailer tires were always supposed to be aired up to their maximum tire pressures (cold) no matter the load?

https://www.etrailer.com/question-139225.html

The correct answer to Jeremy's question.

[problemchild]

The correct answer to Jeremy's question.

That clearly would depend on whether you want to follow some liability based safety standard based on sprung trailers, or whether you want to give your race car a nice soft ride on your unsprung trailer. Clearly we will have to agree to disagree.

[DaveW]

I thought trailer tires were always supposed to be aired up to their maximum tire pressures (cold) no matter the load?

https://www.etrailer.com/question-139225.html

The correct answer to Jeremy's question.

Related thread: http://www.apexspeed.com/forums/show...=trailer+tires

[dsmithwc04]

That clearly would depend on whether you want to follow some liability based safety standard based on sprung trailers, or whether you want to give your race car a nice soft ride on your unsprung trailer. Clearly we will have to agree to disagree.

Yeah, I can definitely see trying to soften the vibration and bumps to a race car but aren't FV's frames pretty darn stout and the suspension softly sprung? I can see trying to take it easy on an FC but I would think if the FV is strapped down by the wheel/hub that the suspension should be able to do it's job rather well? Perhaps leave the pressure high and then place some used tires under the frame and then strap the car down on top of them. That might give a little bit of relief from the harsh ride.

[Mike B]

That clearly would depend on whether you want to follow some liability based safety standard based on sprung trailers, or whether you want to give your race car a nice soft ride on your unsprung trailer.

Or you want to allow the side walls to flex more than intended, overheat, and blow out. BTDT. I know we're all a lot smarter than the engineers that designed the tire but I'll go with their suggested pressure.

Clearly we will have to agree to disagree.

I agree!

[problemchild]

Yeah, I can definitely see trying to soften the vibration and bumps to a race car but aren't FV's frames pretty darn stout and the suspension softly sprung? I can see trying to take it easy on an FC but I would think if the FV is strapped down by the wheel/hub that the suspension should be able to do it's job rather well? Perhaps leave the pressure high and then place some used tires under the frame and then strap the car down on top of them. That might give a little bit of relief from the harsh ride.

A lot of people are not understanding the dynamics of the unsprung trailer. I used various light unsprung trailers for 30 years with small formula cars on them, usually towing at 10-15mph above the posted speed limit. With the proper pressures, I believe the race car is not being abused any more than on a sprung trailer, and less than on the track.The little trailer allows towing with small vehicles, and provides major logistics and storage benefits.

All you need to do is tow the trailer somewhere minus the race car, and you will understand why 60psi in the tires will be brutallly abusive to the race car. The tires will be in the air 90% of the time. Drop the pressures to 10psi and ihe same trailer will tow like a dream. You will want more pressure once you put the race car on, but it sure won't be 60 psi.

[DaveW]

That clearly would depend on whether you want to follow some liability based safety standard based on sprung trailers, or whether you want to give your race car a nice soft ride on your unsprung trailer. Clearly we will have to agree to disagree.

A lot of people are not understanding the dynamics of the unsprung trailer. I used various light unsprung trailers for 30 years with small formula cars on them, usually towing at 10-15mph above the posted speed limit. With the proper pressures, I believe the race car is not being abused any more than on a sprung trailer, and less than on the track.The little trailer allows towing with small vehicles, and provides major logistics and storage benefits.

All you need to do is tow the trailer somewhere minus the race car, and you will understand why 60psi in the tires will be brutally abusive to the race car. The tires will be in the air 90% of the time. Drop the pressures to 10psi and the same trailer will tow like a dream. You will want more pressure once you put the race car on, but it sure won't be 60 psi.

IMO, Greg has it exactly right. To a much smaller degree, I do the same on my enclosed trailer using LT tires. You just have to use some common sense regarding tire capacity at a given pressure, etc., when you do this.

[R. Pare]

Or you want to allow the side walls to flex more than intended, overheat, and blow out. BTDT. I know we're all a lot smarter than the engineers that designed the tire but I'll go with their suggested pressure.

"Suggested pressure" is for when the tire is loaded to its maximum rating as a means of keeping the sidewall and tread flex to the desired level. At loads below the maximum rated, the pressure can be decreased and still keep the flexing at the desired level.

[Daryl DeArman]

I'd start with 30psi, keeping psi to load proportional to engineers' specs and lower it from there after towing a handful of miles at speed and evaluate.

Check the heat in the sidewalls and evaluate how it tows.

Higher PSI is going to tow with less drag but beat the crap out of the trailer if taken to extreme. No springs and 1000# payload can't be good for the welds and steel if the trailer is bouncing down the road.

Too low and you risk overheating the sidewalls.

[Hardingfv32]

Doesn't the Pressure Inflation Chart for a given tire provided by the manufacture pretty much tell you what the engineers think is best for any given load?

For light weight loads I would use passenger tires for a softer ride. A 2 ply sidewall tire is ideal. Most trailer tires have 2 to 4 more sidewall plies than a passenger tire making then stiffer for a given pressure/load.

Brian

[Jim Edmonds]

All of this is subjective without data. Buy a set of tire pressure/temperature valve stems and associated in car readout from TireRack.

Start with perhaps 50PSI. On each trip graph temperature rise over time while recording ambient temperature. Lower the pressure 10PSI for each trip until you see an "interesting" temperature rise over time. Then add 10 or 15 PSI back to the tires.

Ambient temperatures 60 degrees F and below don't count. You can get a good start on the data after 30 trips. 8^)

If you do this in Arizona replace the trailer tires after noticing the "interesting" temperature rise.

Humor, but a little truth in it.

Does anyone have another suggestion to get data? Correlate trailer tire pressure with your shock movement sensors in the car?

Jim

[EYERACE]

But it is science and physics............which are arguably the same thing.

First of all..........I like the tires you selected..........I think. I'm not sure exactly how well and long mine will hold up as I only started using that brand last year. My intent was I think this brand tire can tow at about 75 mph all day at a starting pressure of 50 cold.............18 foot tall and wide box trailer with stuff and an FC inside.

You're towing a lot less weight than I am so a tiny bit less pressure is maybe all I'd attempt in an effort to get the sidewall to absorb a few bumps......but the face of the tire is still going to deflect as it comes around to hit the ground........so 43 and no less.

Even though the guys at the store look at me cross-eyed when I say it.........I tell 'em to balance my trailer tires. The less vibration the better I figure it. Whatever, it doesn't hurt anything and I believe it helps something............probably not my sobriety.

[mark defer]

Always use trailer tires on a trailer. They are specifically designed and constructed for trailer use.
Always inflate to the max pressure. They will run cooler and you'll have a bigger margin of error. You'd be shocked how many people underestimate the weight of the trailer, the cargo, the tools, etc, etc.
We are constantly replacing trailer tires with higher load ratings because they are being overloaded.
And remember, under-inflation and overloading is the same thing.
And yes, always balance your trailer tires as well. It helps keep the cupping at a minimum.
End of story.

Mark Defer
Defer Tire

[Jeremy Soule]

Thanks all who replied. I've read all the replies also the linked thread and been mulling over how to respond....

Basically the idea was to reduce tire pressure to reduce wheel hop and keep tires on the ground, i'm not too worried about the car, if it can't take the trailer ride there I don't suppose it should be on the track..... But I don't like blowouts and I understand that to low of a pressure leads to too much sidewall flex which builds heat and is harsh on the sidewall possibly leading to tread separation.

On the day in question I set the pressure to 60 PSI five below Max recommended, it's a very smooth road from, Tucson to Phoenix 100 miles mostly fresh pavement, it was an overcast day, 95 deg. relatively cool for southern Arizona in July, I had mis-placed my thermometer but stopped twice each way to hand feel the tire temperatures, (also really good way to check wheel bearings...). The trailer towed nice, tires weren't warming up much if at all, kept it under 75 and I haven't gone on any highway trips since.

I agree with Greg Rice and I am very much in praise of small open trailers which is mostly all I've ever used, easy to store, easy to hook up and a great way to promote our sport. I always get people coming over to chat when I stop to fill up. sometimes if I have time I let kids sit in the car; parents take pictures ofcoarse. Folks see me doing this with a mid-size pickup with a couple of toolboxes a couple of spare tires, a jack in the back, a race car and small trailer and think hey this guys having fun and this is do-able. Ha
On the flipside I do think it's a little irresponsible not having brakes on the trailer. essentially everything I own is tied up in this little package and I should have all the stopping power that technology can supply. J

[captain_pants]

For reference; I recently towed my enclosed 16x7 Thule aluminum trailer completely empty for a short highway drive with 60 psi in the tires. It bounced down the road at much over 55 mph. I could see the tire sidewalls deflecting in-time with the bounce in the mirror. This is a torsion-beam suspension, but the tires weren't moving up and down very much in the fenders.

In hindsight, I should have lowered the tire pressure like was discussed in this thread! I just drove at 55 instead for this short trip on a 60 mph road.

[DanW]

....On the flipside I do think it's a little irresponsible not having brakes on the trailer. essentially everything I own is tied up in this little package and I should have all the stopping power that technology can supply. J

You can buy a trailer brake kit on fleabay for about $200. R&L carriage is the seller I think.

[captain_pants]

For reference; I recently towed my enclosed 16x7 Thule aluminum trailer completely empty for a short highway drive with 60 psi in the tires. It bounced down the road at much over 55 mph. I could see the tire sidewalls deflecting in-time with the bounce in the mirror. This is a torsion-beam suspension, but the tires weren't moving up and down very much in the fenders.

In hindsight, I should have lowered the tire pressure like was discussed in this thread! I just drove at 55 instead for this short trip on a 60 mph road.

An error in the above, my tires are listed as having a 50 psi max, and that's what I ran.

I tried towing my empty trailer on another short trip. This time I dropped the tires to 40 psi. The bouncing was even worse! It bounced anywhere between 50 mph and 70 mph. I'll just plan to go slow when empty.

[R. Pare]

You hit a harmonic with that lower pressure. It might go away with even lower pressure. Been there, done that.

[DaveW]

You can buy a trailer brake kit on fleabay for about $200. R&L carriage is the seller I think.

I bought a complete Dexter 2-axle 10x2.25 trailer brake kit incl. all brake parts, drums, wiring & break-away parts (used it to replace all the brake stuff on my 1989 Wells Cargo) for $421 from trailerparts.com. It arrived quickly and was everything I needed.

[Steve Demeter]

Dave,

good advice.

Have had one heck of a time finding brake parts locally the past few years. All the RV places used to carry them. Not so much anymore for cargo trailers anymore.

[ewcmr2]

Always use trailer tires on a trailer. They are specifically designed and constructed for trailer use.

Highly disagree.
Tire shops always pull the trailer tires are designed for trailers but can never give the what/why they are better for trailers.
My 2001 triple axle GN came with Marathons, they didn't last. Tried most all the other trailer tire options, none held together reliably. Trailer tire sidewalls are wafer thin, thinner than passenger tire sidewalls. Maybe there're good for a smooth ride but they don't hold up well to mileage/heat/speed. After 12 years of carrying multiple spares and changing tires on the side of the road I had enough.
In the spring of 2013 I put Bridgestone Duravis r250 LT tires on he trailer. Five years with zero tire issues, barely even have to check air pressure! I'm never buying a trailer tire again.

[xmazdatracy]

Trailer tires and many other trailer items have very very low quality control. ST tires have different banding allowing the trailer to be turned in a tight spot without hurting other components of your suspension to mention just one of the reasons of the ST tire construction. Putting LT tires on a trailer is a common move. You get a better tire with the tighter quality control scrutiny. However other (more expensive) items will now fail first.
If your "tire guy" cant explain why ST tires are recommended for trailers then perhaps you need a new "tire guy". Look harder. Maxxis makes a tire with a bit more quality control as all of their tires are shipped to them from china before they go off to shops. And I believe there is now a USA made ST tire option, but with little feedback on them so far.

[DaveW]

Trailer tires and many other trailer items have very very low quality control. ST tires have different banding allowing the trailer to be turned in a tight spot without hurting other components of your suspension to mention just one of the reasons of the ST tire construction. Putting LT tires on a trailer is a common move. You get a better tire with the tighter quality control scrutiny. However other (more expensive) items will now fail first.
If your "tire guy" cant explain why ST tires are recommended for trailers then perhaps you need a new "tire guy". Look harder. Maxxis makes a tire with a bit more quality control as all of their tires are shipped to them from china before they go off to shops. And I believe there is now a USA made ST tire option, but with little feedback on them so far.

I've been recommending LT tires for many years. In add'n to what you said, LT tires ride better and have higher speed ratings due to circumferential belt-edge reinforcement which prevents almost all tread separations (actually BLB seps - belt leaving belt).

BTW, I've never had an issue with tight turns - they just abrade the tread edges faster. Never harmed any of the suspension (actually, I don't see how trailer tires could help this, unless the trailer tires have a much lower coefficient of friction, which would not be good for safety).

[jaltaman]

Interesting thread.

I've towed about 90,000 miles in the last 13 years. I'm fortunate in that I have had only one flat in that time

My current trailer is a 2015 24' Haulmark Edge that I purchased new in 2014. It came with the Goodyear Marathon tires. I've towed it over 35,000 miles now and the Marathons have been flawless. I always run them at the max pressure (65 PSI cold) and rarely tow above 72 mph.

Never had an issue with bouncing, because the trailer is 4550 lbs empty (8000 lbs loaded). I load the trailer so that the tongue is not overloaded and always tow with an equal-i-zer weight distribution hitch (even when empty).

Not sure why I have been so fortunate with these tires, but I guess this just shows that YMMV.

[Charles Warner]

A slight bit of thread creep . . . .

What bothers me is the concept that a FV is somehow less deserving than a FC of proper treatment. I don't know how anyone can formulate that one race car is stronger or less likely to be harmed than another. Treat them all the same. Regardless of the trailer and car, IMO always tie down by the tires/wheels and let the race car suspension do its job. Tying down by the lower a-arms is probably the worst case, putting a myriad of stresses through several critical points - such as the rod ends.