Bluedog225
Observer
I believe you need to keep trailer tires well inflated to decrease sidewall flexing and sway.
Trailer Tire Pressure
- Thread starter squinko
- Start date
grogie
Like to Camp
I've read that, but it's seems to be talking about typically trailer tires on RVs that are narrow, and heavy trailers. Too much pressure on my tires and I think it would cause the trailer to bounce.
I towed last fall about 1200 miles at 20 psi and had no sway (tires are fairly wide... I assume that helps on it's own?).
Robert Bills
Explorer
I think you are encountering the dilemma caused by matching trailer tires to a much heavier tow rig rather than to the trailer weight. BTDT.
The advantages are that you only need one spare for both tow rig and trailer, and of course aesthetics. The disadvantage is that you end up with too much tire for the weight of the trailer and are forced to run the trailer tires at extremely low air pressures in order to reduce bounce and get an even wear pattern with resulting handling issues and sidewalls that build up heat by flexing too much.
My suggestion is that you do the "chalk test" with a loaded trailer to determine the tire pressure necessary for even wear, and as long as the result is somewhere above 18-20 psi that you try it for awhile to determine whether the sidewalls flex too much on the highway at that pressure (exhibited by handling issues or heat build up). If not, you're good to go. However, if you have to run the tires on the highway at dangerously low pressures then your choice is: (1) put in more air and rotate to the tow rig often to even out the wear, or (2) get smaller and lighter tires for the trailer.
Personally, I gave up matching tow rig and trailer tires when the threshold size for "big" tires evolved above 31" in diameter. It wasn't worth the trade offs just for looks or to eliminate a second spare. Besides, I decided to restore my Bantam trailer and the original fenders couldn't handle a tire larger than 31" in diameter without fitment issues. My CJ-7 was running 35's at the time and there was no way to match those.
This is my current set up:
The advantages are that you only need one spare for both tow rig and trailer, and of course aesthetics. The disadvantage is that you end up with too much tire for the weight of the trailer and are forced to run the trailer tires at extremely low air pressures in order to reduce bounce and get an even wear pattern with resulting handling issues and sidewalls that build up heat by flexing too much.
My suggestion is that you do the "chalk test" with a loaded trailer to determine the tire pressure necessary for even wear, and as long as the result is somewhere above 18-20 psi that you try it for awhile to determine whether the sidewalls flex too much on the highway at that pressure (exhibited by handling issues or heat build up). If not, you're good to go. However, if you have to run the tires on the highway at dangerously low pressures then your choice is: (1) put in more air and rotate to the tow rig often to even out the wear, or (2) get smaller and lighter tires for the trailer.
Personally, I gave up matching tow rig and trailer tires when the threshold size for "big" tires evolved above 31" in diameter. It wasn't worth the trade offs just for looks or to eliminate a second spare. Besides, I decided to restore my Bantam trailer and the original fenders couldn't handle a tire larger than 31" in diameter without fitment issues. My CJ-7 was running 35's at the time and there was no way to match those.
This is my current set up:
Whats the big deal about the trailer bouncing? Who cares? So long as you're not using a shopping mall ball hitch or screaming around corners at 50mph.
Airing down trailer tires, unless I am missing something, seems silly since there is no need for (motive/braking) traction other than lateral stability (which decreases with lower pressures anyway). Do you want maximum tread on the ground? Maybe, but I dont see where it matters, again, not looking to achieve 1.0g lateral acceleration capability.
What I definitely want out of a trailer tire is low rolling resistance to reduce mechanical stress on the tow vehicle, more important on off-road segments. And also proper load capability so I dont wind up on the side of the road with all those cheap junk home depot trailers with shredded tires. Both of these requirements seem to indicate higher pressures, not lower. If there is a suspension problem then appropriate suspension tuning should be done, but damaging tires or tow vehicle isnt the recommended choice.
The main point of using a trailer is to take some load off the vehicle drivetrain/suspension. Tongue weight and pulling load remain the prime concerns. Keep tongue weight as low as possible* (considering stability), and rolling resistance as low as possible.
* - note that the oft used "rule of thumb" of 10% of total weight is a WAG and not supported by data (at least that I have ever found). Sufficient weight to keep the tongue from lifting the rear of the tow vehicle under expected road conditions seems to work.
Airing down trailer tires, unless I am missing something, seems silly since there is no need for (motive/braking) traction other than lateral stability (which decreases with lower pressures anyway). Do you want maximum tread on the ground? Maybe, but I dont see where it matters, again, not looking to achieve 1.0g lateral acceleration capability.
What I definitely want out of a trailer tire is low rolling resistance to reduce mechanical stress on the tow vehicle, more important on off-road segments. And also proper load capability so I dont wind up on the side of the road with all those cheap junk home depot trailers with shredded tires. Both of these requirements seem to indicate higher pressures, not lower. If there is a suspension problem then appropriate suspension tuning should be done, but damaging tires or tow vehicle isnt the recommended choice.
The main point of using a trailer is to take some load off the vehicle drivetrain/suspension. Tongue weight and pulling load remain the prime concerns. Keep tongue weight as low as possible* (considering stability), and rolling resistance as low as possible.
* - note that the oft used "rule of thumb" of 10% of total weight is a WAG and not supported by data (at least that I have ever found). Sufficient weight to keep the tongue from lifting the rear of the tow vehicle under expected road conditions seems to work.
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grogie
Like to Camp
So I pulled the trailer 600 miles today on the highway at mostly 70 to 75 mph. The trailer's tires are at 20 psi. I mostly don't know the trailer is back there other then that it takes a little more gas to get to speed, and it's dropped the mpg by 1 mpg or so. (My Jeep TJ has it's own issues at that speed.)
My trailer's suspension (with leaf springs and shocks) seems to do a very nice job on the highway, as boy I-70 through Illinois and Missouri is rough in places and the trailer does jerk some at those speeds on the beat to hell sections of the road. No, bouncing is not a big deal but with a custom built expo trailer, there are few guides to all of the aspects of using one. I've read threads about towing on RV forums, and they're all talking about big trailers with skinny Chinese made tires. I don't expect to have problems with the MTRs I'm running, but easy of travel and safety is always a consideration.
My trailer's suspension (with leaf springs and shocks) seems to do a very nice job on the highway, as boy I-70 through Illinois and Missouri is rough in places and the trailer does jerk some at those speeds on the beat to hell sections of the road. No, bouncing is not a big deal but with a custom built expo trailer, there are few guides to all of the aspects of using one. I've read threads about towing on RV forums, and they're all talking about big trailers with skinny Chinese made tires. I don't expect to have problems with the MTRs I'm running, but easy of travel and safety is always a consideration.
I agree with this statement, as long as you're talking about hwy driving. On the dirt, I air down in order to increase comfort and ease wear and tear on my equipment. My standard is 9 PSI for my tow rig. My trailer can run fine (same tires as tow rig) with 3 PSI.
grogie
Like to Camp
So I ended up driving 4200 miles over 15 days. I left the trailer's tire pressure at 20 psi for the entire trip. I think my concern was due to towing with a two-door Jeep. But absolutely no problems. The trailer towed great on and off-road. In fact I towed it up the mesa on Gemini Bridges trail outside of Moab. Utah had had a lot of rain that made a mess of the dirt roads and trails, and the trailer did get following along. This particular trail was a bit of a rough climb in places.
Video of the trail condition:
http://www.youtube.com/watch?v=dibHX-ApwYM
Video of the trail condition:
http://www.youtube.com/watch?v=dibHX-ApwYM
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JasonRedwood
Explorer
Thanks for the update on this. I just switched out the hubs on my little popup trailer to match the 4Runner wheels and tires. When I took it for a test drive I noticed a good amount of hop. I'll have to lower the psi down near 20 to see what kind of difference it makes.
Best,
Jason
Best,
Jason
Bringing this thread back. I have a small off-road trailer (750lbs unloaded, 1300lbs loaded. I have a Timbren Axle-less suspension that is 2200lb rated. I currently have Nitto Terra Grappler tires (285/65/18 ... 33" measured once installed). I was running them at 30psi for a little while and was noticing the trailer bouncing everywhere, rocking side to side and waggling. Took it to a trailer specialist. They said everything was fine from an alignment and balance standpoint. They said my pressures were WAY too low and that was causing the tires to flex. They inflated them to 65psi (sidewall rated for 80). Low and behold the trailer tracks true now and doesn't bounce, wander or waggle. I don't even know why that would be. They said that trailer tires are designed with stiffer sidewalls that resist lateral flex and "regular" tires (even E rated off-road tires) can flex laterally more. They told me to run them as high as 70 when on the road. On trails, they said it would be fine to lower them down to 25 since there isn't a lot of speed involved.
Pic was before I added the rooftop tent, awning and tongue box with battery system
Pic was before I added the rooftop tent, awning and tongue box with battery system
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JasonRedwood
Explorer
Yup. I did a chalk line across them when they were 30psi and the chalk would wear off the middle quick leaving the outer and inner tread with chalk on them. At 65psi, the chalk wears off evenly across the entire tread. Not even sure why that is happening. Almost seems counter-intuitive. If I ran 65psi on the KO2 on my LX470 (aside from losing teeth from the harshness) the tires would wear out in the middle. Too low on the psi and the edges would wear. I had assumed that going so high on the tires on the trailer would result in a huge arc across the tread. But, it didn't. The behavior of the tires on the trailer seem to be completely opposite of what I would expect on the LX.
JasonRedwood
Explorer
OK I gota try that. Noticed that I have an arc on my 33's cooper AT3's, on my last trip. Lots of bounce too. Ill experiment this week before our next venture. thanks