Tire pressure

[qcdavid]

On my trip to James Bay, I'll be taking the North Road which is 400kms of gravel (with good sized rocks thrown in from what I hear). I am planning to air down to save the tires and suspension and was wondering if I should also air down the tires on my trailer. It would seem logical to do so but just wanted to know your thoughts.

The trailer is a small 4x6 with 14 inch trailer wheels running 6 ply trailer tires at 50psi. I figure the trailer will weigh 1000 to 1500 lbs gross once loaded up.

On my Jeep I run 40psi normally and am planning to air down to 20psi. For the trailer, it runs at 50psi and was thinking bringing it down to 30. Thoughts?

[TheOtherSide]

I have run my Jeep on 33's and now the Suburban on 35's on 15-18psi for the trail. Still holds it's shape when rolling to keep clearance under the diffs or suspension, but folds and flexes perfectly.

Aired down pic... you can see the minimal flatness from the tires:
http://pics.overlandcanada.com/tripreports/201010hale/011.jpg

And same pressure flexing nicely over an obstacle...
http://pics.overlandcanada.com/tripreports/201010hale/035.jpg

Same pressure again... hanging onto it's shape with only partial tread contact on a rock:
http://pics.overlandcanada.com/tripreports/201010hale/036.jpg

Anyhow... hope that helps. No need for a high pressure at all.... run them all at 15-20psi... especially if you don't have a tougher tire. No need for the trailer to be at 30psi.

:canadian:

[Squiggy]

if you have air available I would just suggest playing with it to find what is right for the situation. I have run my Toyota's with 0 in the back, 35" bias claw, 5 in the front. now on radials 8-10 psi is good on trails when not loaded.

Just play and figure it out.

Brad

[Gaidheal]

On my trip to James Bay, I'll be taking the North Road which is 400kms of gravel (with good sized rocks thrown in from what I hear). I am planning to air down to save the tires

Are you saying you want to air down the tires to drive on a road... to save the tires?

If you air down and drive faster than a crawl you will actually be hurting the tires as the flexing that airing down allows for will generate sidewall heat the tires were not designed for.

Maybe I missed your intention on speed?

:cheers:

[The Adam Blaster]

I saw this thread and asked my boss about his opinion - he's been in the tire business about 15 years now.
Depending on the speed, he said maybe air them down 5-8 below normal, or even a touch more just for a comfort factor. If you lower them much more than that and are driving a bit quicker ~ up to 80 km/h would be my assumption, you're risking the heat issue as Gaidheal mentioned, also you're probably going to get more chunking out of your lugs.

If you're running really slow and more technical trails, neither of these occurrences is an issue, but I'm guessing you don't want to drive that whole 400 km stretch in 1st gear? :D

[qcdavid]

Yes, I will be airing down to drive on a gravel road. The speed we'll probably be traveling at will be 70-80km/h.

I've heard second hand from someone who did some similar gravel roads (actually when I say gravel, I mean gravel with some large rocks) and blew out a pickup tire and trailer tire in one shot. They hadn't aired down. I also saw a couple of video articles on Youtube indicating you should air down if traveling over rocky roads in order to prevent damaging the tire. The idea is that at full pressure, when going over a rock, all the weight carried by the tire is concentrated in one spot. By airing down, the tire can deform around the rock reducing risk of damage. It also helps save some of the shock absorbed by the suspension.

There was an article in the Overland Journal (summer 2008) where a couple in their Land Rover did the same road (400kms more or less). In the article they mentioned they had aired down to 20-25psi which is why I figured 20psi would be a good place to start. My assumption is that the same would hold for the trailer. At full pressure, the trailer's probably going to bounce around.

I'm going to see if I can find a gravel road close by to test out different pressures but was hoping someone on the forum had done something similar.

[frankspinz]

...I'm going to see if I can find a gravel road close by to test out different pressures but was hoping someone on the forum had done something similar.

Any city street or country road will do ... with all the potholes we have this time of year !!!

Seriously, you don't want to air down too much, it will increase the tire temperature... and risk damaging it - or a blowout ...

So it's a delicate balance, especially at those speeds !

[qcdavid]

Yeah good point Frankspinz, I'll just take a quick trip to Montreal :D

You know, I break my head researching these type of things, I want to avoid tire damage but need to make sure I don't air down too much or I'll end up damaging the tires anyways... and then you get passed some guy in a crappy car going 120km/h on the highway with winter tires in July with one half flat!
:confused:

I appreciate the advice guys. I think I'll start less aggressive and go 25-30psi and see how that goes.

[Spectyr]

All the articles I have read in Australian 4x4 magazines recommend only airing down to about a minimum of 20 psi. unless in an extreme situation such as deep soft sand. I will try and dig up some references when I am back home.

The Aussies know there stuff when it comes to long distance gravel road travel. They aren't too big on extreme rock crawling and all that.

[qcdavid]

Yeah, articles from Australia is where I found most articles relating to driving on gravel roads.

Two things seem to be constant in these articles: keep your speed down, and don't use max pressure. In terms of pressure, they seem to indicate to air down 5-7psi (Adam Blaster, looks like your boss knows what he's talking about!). I came across a couple articles indicating that you should air down to the vehicle's recommended pressure (because most run higher pressures on the road).

My gut feeling is that the 40psi I'm running on the road will be too high for the gravel road. The Jeep recommended tire pressure is 35 or 33 (I'll have to check the door sticker) so perhaps running at around 33psi would be a good way to go.

[Spectyr]

I run about 30-35 psi on the road with my 33" tires. I find this is a good compromise between noise and ride quality. On a normal gravel road, I might air down to about 20 psi, maybe 18 psi if the road is really bad.

[The Adam Blaster]

David, when you're doing your trial runs on local gravel roads, make sure to have approx. the same amount of weight/gear/whatever in the back of the vehicle so it will be as close to the total weight as it will be on your trip.
Without testing it like this, you'll probably be wasting your time as the ride characteristics will be totally different with the added weight vs. a mostly empty vehicle.
Also something to consider - the lower the pressure in your tires, the less weight they can safely carry at speed. So, if your rig is going to be heavily laden you really shouldn't drop the psi that much.

[qcdavid]

Good point Adam... If the weather's nice, I'm going to see if I can go look for a gravel road and tag the trailer along and give it test run.

[qcdavid]

The weather was nice this past weekend so I hooked up the trailer, put on the roof rack and awning, loaded up my tool chest, compressor, cooler, etc, and headed out for a test run.

Turns out it wasn't as easy finding a gravel road as I thought. The one I was going to try indicated there was no exit. I figured I was out of luck and headed to my in-laws to setup camp. On the way home, I took a little gravel road I knew of, too short to be of any use in terms of testing tire pressure, but fun just the same. As it turns out, it led to another gravel road. I only ended up doing about 5 kms or so on gravel before I was back on pavement but I did gather a few bits of info:

1. Ride was smooth without changing tire pressure so unless the gravel roads up north are really bad, I probably won't change the pressure.

2. 70km/h was a good speed. Any faster and the Jeep moved around too much.

3. Dust! When it's dry, a gravel road creates a lot of dust. Even after the short ride I did, dust was everywhere and had worked it's way into the trailer through whatever little hole it could find. Everything will need to be in containers.

4. Chewed up paint on the trailer. Even with the Range Rover style mudflaps that reach way down, I could hear the gravel flying off the trailer fenders. When I got home and washed the dust off, the front of the trailer fenders were all speckled with chips in the paint. I figure after 400km of gravel, they'll pretty much be sand blasted! :rant:

Was a pretty good weekend until the check engine light came on half-way home.:mad2: Oh, better now than when we're in the middle of nowhere. Managed to limp home though, so not a total disaster...

[The Adam Blaster]

Sounds like at the minimum, you learned some helpful info about the trailer, and how much damage the gravel can cause.
Are you thinking about putting up any screening or anything to deflect the gravel from hitting the trailer straight on?
I'm having a trailer built by a buddy of mine and I have heard of guys getting punctures in their metal jerry cans from flying gravel, so I've been thinking about placement and protection.

[frankspinz]

...3. Dust! When it's dry, a gravel road creates a lot of dust. ...
4. Chewed up paint on the trailer...

I drove close to 1000kms on dirt/gravel roads last summer and learned the same lessons. The in-cabin air filter (if you have one) is a must. Closed windows with AC on, is a charm - if you are following - you can't pass anyways because visibility is Zero !

And yes the gravel will sandblast or pierce through metal in a matter of a few hours ...

[qcdavid]

Hmmm, good point about cabin air filter. I'll have to check into if I have one and if not whether I can put one in.

The trailer and Jeep have pretty much the same track width so it's basically just the fenders taking a beating. The front of the trailer had nothing. I was thinking about making some rubber "chaps" for the fenders. I haven't delved into the details yet but either strips of rubber mat the width and length of the fenders that I can hook onto the fenders (should look nice and ugly;) ) or create some deflectors with strips of rubber mat and magnetic tape that I can just slap on to the front of the fenders when I need.

[The Adam Blaster]

I'm sure you could buy some magnetic "mats" and just cut them to shape.
Maybe check with a sign shop that makes magnetic vehicle signs, they might sell you a chunk from the end of a roll. Maybe you could ask for neon green or something? :D

[qcdavid]

I had just about abandoned the thought of having to air down after the several trips I did this summer. I did quite a bit of gravel and back roads this summer and didn't air down once. But...

This past long weekend, my wife and I headed out to PEI. The weather was absolutely wonderful so we opted to go explore parts of the island we hadn't seen in a while and visit some of the less known beaches and coves. The plan was to drive the back roads along the coast and take every little road that seemed to head to the shore. Some of the back roads were a patch work of asphalt, a product of many years of patching up the cracks and pot holes. The dirt roads we came across were rough considering the wet weather they've had this year. After several several back roads and dirt paths to the shore, we were getting jostled pretty good in the Jeep. It got to the point where I was dreading taking the next small road.

Then I got the idea to air down. The pressure I typically run is 40psi which is great for highway driving but not so great for rough roads. During one of our stops I aired down the tires to 32psi. What a difference! With the lower pressure, the ride was much smoother and we definitely bounced around less. I kept the pressure at 32psi for the rest of our stay, only airing back up when it was time to head back onto the Trans Canada for our 13 hour drive home.

I'm glad I had the chance to try this out and gain some experience. This will definitely come in handy for James Bay take 2!

[Gaidheal]

Too bad I didn't know you were here on PEI - would have been nice to meet up with someone else from OLC.

Glad you liked the Island... we don't have a lot of places to 'wheel, but we make the best of it.

My yard is modest (3.5 acres) but always available for *FREE* to overlanders who don't mind getting what they pay for. LOL

:)

Jamie

[qcdavid]

Thanks for the offer Jamie. While driving around I did keep my eye open for a Jeep Wrangler with no doors and the windshield folded down:D

I'm not much into hardcore wheeling but do love dirt roads and those are easy to find on PEI! Our jaunt to the Island was pretty much a last minute thing without too much preparation. We love it there and go on a regular basis so when we were trying to decide where to go for our wedding anniversary, PEI came up and that was that. As a bonus, it looks like we picked the perfect weekend as the weather was amazing! (though it looks like you guys got hammered mid-week)

We'll likely be heading back next summer for family vacation so maybe we could hook up then. Till then I'll keep the red mud on the Jeep as long as I can;)

[Gaidheal]

Thanks for the offer Jamie. While driving around I did keep my eye open for a Jeep Wrangler with no doors and the windshield folded down:D

I'm not much into hardcore wheeling but do love dirt roads and those are easy to find on PEI! Our jaunt to the Island was pretty much a last minute thing without too much preparation. We love it there and go on a regular basis so when we were trying to decide where to go for our wedding anniversary, PEI came up and that was that. As a bonus, it looks like we picked the perfect weekend as the weather was amazing! (though it looks like you guys got hammered mid-week)

We'll likely be heading back next summer for family vacation so maybe we could hook up then. Till then I'll keep the red mud on the Jeep as long as I can;)

haha - Good thing I'm not into hard core wheeling either as there is basically none here. LOL

Sounds like you were here for ALL of our good weather this year. It feels like it has been raining since the snow stopped. And will continue until the snow starts again.

:cheers:

[R_Lefebvre]

I missed this the first time around.

My truck is about 6500lbs, and I'm running 245/75/16 LT Load E tires. These specs are MANDATORY for any discussion about this topic.

I typically run about 45psi on the street. But soon as I go on gravel, I drop it to 35psi. 30psi if it's rough gravel. 25psi on a trail, and the lowest I've gone is 20psi on a really bad trail. That's about as low as I can go without risking a sidewall puncture.

It does make a huge difference.

[ssrig55]

I am around 10,000lb's on 285/70 19.5's, they are rated for 6,000+ lb,s and dont carry close to that so as soon as I hit a dirt road they go down to 32PSI front 38PSI rear, usually operate in the upper fifties on the road, like many have said already, you have to try out several PSI's to see what works for you, so many variables to consider, weight for me is the biggest. But airing down is absolutely necessary for me, I dont ever question it. My boat trailer gets the same treatment when going on FSR's for more than 20km's, depending on how much stuff Im dragging around in it they go down to 15PSI.
A decent compressor is mandatory, I hate waiting for a tire to fill!

[morerpmfred]

My xj weighs in at 4000 pds with full tank of gas and all trail recovery gear and tools and me sitting in the drivers seat. Tires are 33r12.5x15. During tire breakin period first 5000 klics 20 psi in front and 18 in rear on the highway. after that 25 in the front and 22 in back. If I know i,m doing a lot of gravel roads then 20 in front and 18 in back. trail pressures are 12 front and 10 in back. Extreme rocks etc , will go lower yet. Air pump is from titan winch.

[Jeremy]

I'm at 5800lbs unloaded I have been playing with pressures in my 315/75R16 GY Duratrac for the last few trips. From 15psi to 25psi on the FSR's and trails. I found the sweet spot on Monday at 20psi front and rear unloaded. At 15psi I felt like I maybe lower than needed for the terrain I was covering. 25psi felt a bit harsh my street pressure of 40psi felt like a filling was going to fall out.

The York aired up all the tires in 5min including digging the air line out of the back and putting it away again. About 35sec from 20 psi to 40psi at idle. Would be faster if I had a high idle.....love this OBA setup. :party:

[ssrig55]

I'm at 5800lbs unloaded I have been playing with pressures in my 315/75R16 GY Duratrac for the last few trips. From 15psi to 25psi on the FSR's and trails. I found the sweet spot on Monday at 20psi front and rear unloaded. At 15psi I felt like I maybe lower than needed for the terrain I was covering. 25psi felt a bit harsh my street pressure of 40psi felt like a filling was going to fall out.

The York aired up all the tires in 5min including digging the air line out of the back and putting it away again. About 35sec from 20 psi to 40psi at idle. Would be faster if I had a high idle.....love this OBA setup. :party:

That is exactly what I wanted to do! makes allot of sense, for now I am using a viair system, works OK but would like way faster.

[Jeremy]

That is exactly what I wanted to do! makes allot of sense, for now I am using a viair system, works OK but would like way faster.

Yeah its the same thing I did with the 4runner, works well. Needs to be done for every different surface though. The 4runner was perfect at 10psi on snow and sand 15psi everywhere else.

The Viair systems I have used and seen used seem to work really well. I'm impressed how quiet they are compared to the ARB's. Only way you get fast air fills is with a York or Co2.

[qcdavid]

I missed this the first time around.

My truck is about 6500lbs, and I'm running 245/75/16 LT Load E tires. These specs are MANDATORY for any discussion about this topic.



That the size and type of tire I run as well.

[qcdavid]

For now I've got a Bionaire dual cylinder compressor which is decent for what I use it for. However, on PEI, you're never far from anywhere so I just hit the first gas station and used their pump instead of pulling mine out :D

[Gaidheal]

I drive a JK Unlimited with a winch, rack, tools, stuff, and more stuff. No idea what the rig's weight is before I throw on the RTT, awning, pack with gear, dog, etc. Heavy.

My tires are 315/77-17s (basically 35x12.5) that weigh 60 pounds each (x5)

I run ~28-30 pounds, and don't bother airing down for much, as we have nothing here on PEI that requires it. In deep snow (like door-sill deep and deeper) I'll drop down to 10-12 and go where ever I wish. :)