Tire pressures vs conditions (and towing)

mzeee

New member
I have a Volvo XC90, running Yokohama Geolandar G015 tires. Can someone suggest tire pressures to run on:

Forest service roads with speeds under 40mph?
Rougher roads with some bigger rocks?
Sand / mud / really tricky stuff?

How to adjust the above if I'm towing a 3.5K to 4K pound offroad trailer? This is where I really am not sure what to do!

On the road I plan to stick to the 38F / 38R recommended, perhaps bumping up the rear a couple PSI when towing.

I appreciate any advice!

Edit for clarity: I am running the Euro-Metric version of the tires.
 

4000lbsOfGoat

Well-known member
I can't say anything specifically about your Volvo or your tires, but I encounter the same scenarios. So, for what it's worth...

I run a Tacoma with E-rated BFG KO2s. The rated tire pressure for the truck (stock) is 30psi. The max pressure for the tires is 80psi. I pull a 3k pound trailer all over creation - Interstates, ATV trails, and everything in between.

For regular road driving with the trailer I run 35 psi up front, 47-49 psi in the rear and 35 psi on the trailer. So I'm running quite a bit above "factory spec" when I'm running loaded at high speed.

That setup will also work for most dirt road driving but if the road gets too rocky I'll drop the front tires and trailer tires down to 25-30 and the rear down closer to 40. I never go below 40 in the rear with the trailer attached.

All of these numbers can vary a little bit between summer and winter.

When I'm unhooked and ready to run around the woods, I'll take everything down to 20-25. I've never gone below 20 since that has always done it for me.

I arrived at these numbers after a lot of driving around and seeing what felt right. You'll need to do some experimenting of your own to get your rig dialed in. If the rear tires are bulging under the trailer weight then they need more air (up to the maximum rating) for long distance road driving.

Cheers!
 

mzeee

New member
I can't say anything specifically about your Volvo or your tires, but I encounter the same scenarios. So, for what it's worth...

I run a Tacoma with E-rated BFG KO2s. The rated tire pressure for the truck (stock) is 30psi. The max pressure for the tires is 80psi. I pull a 3k pound trailer all over creation - Interstates, ATV trails, and everything in between.

For regular road driving with the trailer I run 35 psi up front, 47-49 psi in the rear and 35 psi on the trailer. So I'm running quite a bit above "factory spec" when I'm running loaded at high speed.

That setup will also work for most dirt road driving but if the road gets too rocky I'll drop the front tires and trailer tires down to 25-30 and the rear down closer to 40. I never go below 40 in the rear with the trailer attached.

All of these numbers can vary a little bit between summer and winter.

When I'm unhooked and ready to run around the woods, I'll take everything down to 20-25. I've never gone below 20 since that has always done it for me.

I arrived at these numbers after a lot of driving around and seeing what felt right. You'll need to do some experimenting of your own to get your rig dialed in. If the rear tires are bulging under the trailer weight then they need more air (up to the maximum rating) for long distance road driving.

Cheers!
Thanks for the reply. I'm really surprised you go so high on the rear tire pressure with the trailer attached. Your pressure is 60% higher on the rear tires for trailer vs no-trailer. And yet, your rear axle load doesn't increase anything near that much (figure your tongue weight is 400 to 500 pounds).

It seems to me that if you go to 20 psi without a trailer, you really could safely go 25 to 30 with a trailer? Is my logic here flawed somehow?
 

alanymarce

Well-known member
Just an opinion, and I have to say that the standard pressures seem a little high to me, however:

- Forest service roads with speeds under 40mph? I'd go with 35F/35R.
- Rougher roads with some bigger rocks? I'd go with 35F/35R and drive to avoipd hitting the big rocks. If this category is getting into "rock-crawling" country then I might drop to 30F/30R
- Sand / mud / really tricky stuff? Depends - for sand I'd start with 25 and drop as far as 18 if the sand is deep and soft; for mud I'd stay with 35F/35R and if the tyres can;t handle it switch to MT (if these conditions are going to be routine); for "rock-crawling" I'd drop pressures to 25 and less if necessary.

Then I'd adjust the above based on experience.
 

mzeee

New member
Just an opinion, and I have to say that the standard pressures seem a little high to me, however:

- Forest service roads with speeds under 40mph? I'd go with 35F/35R.
- Rougher roads with some bigger rocks? I'd go with 35F/35R and drive to avoipd hitting the big rocks. If this category is getting into "rock-crawling" country then I might drop to 30F/30R
- Sand / mud / really tricky stuff? Depends - for sand I'd start with 25 and drop as far as 18 if the sand is deep and soft; for mud I'd stay with 35F/35R and if the tyres can;t handle it switch to MT (if these conditions are going to be routine); for "rock-crawling" I'd drop pressures to 25 and less if necessary.

Then I'd adjust the above based on experience.
Do you tow a trailer? Is that what these pressures are referring to?
 

4000lbsOfGoat

Well-known member
Thanks for the reply. I'm really surprised you go so high on the rear tire pressure with the trailer attached. Your pressure is 60% higher on the rear tires for trailer vs no-trailer. And yet, your rear axle load doesn't increase anything near that much (figure your tongue weight is 400 to 500 pounds).

It seems to me that if you go to 20 psi without a trailer, you really could safely go 25 to 30 with a trailer? Is my logic here flawed somehow?
Yes, at low speeds on rough roads I can, and very occasionally do, go down to 30 or so even with the trailer but that is way too spongy for high speed highway driving. The truck just doesn't feel planted at speed with rear pressure below 45. Below that the tires will also start to bulge too much - i.e. build up too much heat at speed.

My rig runs heavy so I have to make adjustments for that.

It takes some fiddling to figure out exactly what feels safe for your rig. Guess you'll just have to get out there exploring!
 

alanymarce

Well-known member
Do you tow a trailer? Is that what these pressures are referring to?
I apologise - I wasn't clear. These are all pressures for the vehicle alone. We don't tow a trailer, for a variety of reasons, principally that we have no need for one and have no wish to add stress to our vehicle and increase fuel consumption. Having said this, if your trailer is properly balanced (fore/aft) then there should be little increased load on the vehicle tyres so the rear pressures don't need to carry more load. As far as the trailer tyres are concerned, I have to say that I'm no expert however I'd drop the trailer tyre pressures in the same ratio as the vehicle tyres for the conditions.
 

billiebob

Well-known member
Towing or not, highway, forestry road, logging spur I run 26psi all around.
Soft sand I try to avoid, pick the route across the beach which appears hard packed.
If I ever air down it would only be for sand when there was no other choice but I'd have a rescue plan figured out first.

I run a TJR, 4200# and tow a 1500# SquareDrop trailer. Both on skinny 7.50R16 Yokohamas.

DSCN2815.jpeg

and I carry tire chains year round..... way better than airing down..... even better than a winch

IMG_0577.jpeg

Second set of Yokohama 742S tires, at 26psi
I got even wear on the first set and at 100K kms, 60K miles they still have a summer or two of tread left

I ran 33" KO2s and 255/80R16 KM2s before and they were bald at 75K kms, 47K miles.
My daily driver and work truck, it sees 1000 kms, 600 miles a week. Mostly highway towing my tools trailer.

IMG_0442.jpeg
 
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XCvagn

New member
I have a Volvo XC90, running Yokohama Geolandar G015 tires. Can someone suggest tire pressures to run on:

Forest service roads with speeds under 40mph?
Rougher roads with some bigger rocks?
Sand / mud / really tricky stuff?

How to adjust the above if I'm towing a 3.5K to 4K pound offroad trailer? This is where I really am not sure what to do!

On the road I plan to stick to the 38F / 38R recommended, perhaps bumping up the rear a couple PSI when towing.

I appreciate any advice!

Edit for clarity: I am running the Euro-Metric version of the tires.
Which size G015 did you go with? How are they handling/performing on-road and off-road? I've been looking at options for when stock street Pirelli Scorpions are done.

As for pressures, I've gone as low as 32 on our 2017 XC90 although it's been on the Pirelli so I've hesitated going lower to avoid exposing too much of the sidewall and given the relative low profile of 275/45 series on 20" wheels. If I had proper AT tires I'd likely venture with pressures below 30 if conditions required it like I've done on occasions with our 2010 XC90. FYI T8s have a higher recommended pressure of 42PSI front and rear which is what I run on the road. It’s not just for their added weight vs T6 but I’m sure to also lower rolling resistance.

Usually on forest service roads 36PSI is enough to take the edge off. Given the higher baseline that's more like 30-33 on yours which is more comparable to our 2010 XC90 weight wise I think. Even on the rougher roads and at that pressure the ride comfort has been very good and I typically travel in suspension setting of Hybrid on most service roads - I believe it’s equivalent to Comfort on yours. Am I recalling correctly you have air suspension? When it gets rough and I need constant AWD and finer pedal control and/or I need the added clearance I'll go to Off-Road drive mode. Although we're not on AT tires on the T8 (yet) we've not experienced traction issues with these pressures even climbing over big rocks.

Fully loaded this summer with our R-Pod I still dropped down to 36PSI depending on terrain and distance. For the R-Pod over smallish rocks like in the 4th pic below we slowly towed the R-Pod up that BLM trail it was the only time I had dropped pressure on the R-Pod to 50PSI from 65. It’s running on LT rated Nokian Rotiiva AT which I was pleasantly surprised at how compliant they are even though they are 10ply. It was a smoother ride at 50PSI than on the old cheap 6ply Mudstar it came with for which Forest River recommended 50psi pressure. We had started the trip with the Mudstar AT and early on dumped them for the Rotiiva (the original tires were wearing badly and made me uncomfortable 2k mi into our adventure - we got just over 13k mi out them). For road/highway I bumped up to 65psi to take the squish out of them. Their max weight rating is based at 80psi. It goes to show that pressures depend on tires as much as vehicle and sometimes you do have to experiment. The recommended pressure is a good starting point and then adjust within rated parameters - great when known. What’s cool is Nokian publishes their weight ratings by pressure - load rating drops with pressure. The R-Pod was packed out to about 4100lbs for our summer adventure.

When the going got more rocky and jagged, at 32psi on our T8 (without R-Pod) was enough to smooth out the ride and baby the Pirelli in conditions beyond their natural habitat. We saw sand, mud, clay, badly rutted terrain, large rocks, and sadly not a lot of snow.

Our complete summer adventure this year was just over 7k mi and 2 months. We enjoyed exploring state parks, national parks, NF, BLM, and everything in between. Even some state parks had overland trails which were great.



As for lower pressures and towing - when we went to YK and NT with our 2010 XC90 and had a T@B I dropped the General Grabber AT2 we had on our 2010 XC down to 30psi. Even when on we hit the Dempster Highway and we traveled at 50-60mph on it the lower pressure was not only a huge improvement for comfort and and wear, handling was great and we had no issues. It was a good thing too as on that leg we came across a couple of other travelers that had experienced flats and tire failures (those were traveling fully inflated on their trucks while hauling trailers or had truck campers). It seemed many of those failures were when they went over slate rock portions of the Dempster. One family had a flat and a failure fortunately at two different times and had managed to get a replacement tire at Ft. McPherson. For that trip we carried two full size spares and the stock donut. Thankfully we didn’t need them but we did use the Jerry cans a number of times.

On the 2010 XC90 with Grabber AT2 I've gone as low as 18psi (deep snow on forest service roads) and 25psi for soft sand although I was not towing when I went that low on them. Weight wise and pressure wise it's more comparable to your XC90 than our T8. Volvo recommends 36 to 39 on that one based on load.

On this outing chains ended up being a must to eliminate the pucker factor on the descent when the snow turned to ice. If I recall on that trip we lowered to 30 I think - I was trying to balance between traction and clearance. I probably could have gone lower.
 
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mzeee

New member
Which size G015 did you go with? How are they handling/performing on-road and off-road? I've been looking at options for when stock street Pirelli Scorpions are done.
Went with 235/60R-18 for the G015s. They are fine on-road, though definitely more sidewall flex than the previous tires and all the ones I'm used to. I'm not a very good resource for comparisons. These are the first AT tires I've ever owned, so I can only compare to various other all-season, summer, and winter performance tires. I read a lot of reviews though, and they were rated highly by many.

No air suspension. Regretting that decision now, as I'm getting a fair bit of rear sag when towing. I think the air suspension would help a lot with that?

Thanks for all the input on pressures. Your numbers are similar to what I'm thinking, though I'm leaning towards staying a few psi higher when towing to compensate for trailer effect. Also, I have a bit of fear that one day I'll forget to air up before going to 60 mph+ on the highway.

Awesome trips and pics! I'm a bit jealous!
 

XCvagn

New member
Airing down trailer tires for mud or sand makes no sense to me.

Really only the propulsion wheels right?
To soften the ride and minimize damage to contents over rough and/or rocky trails, definitely a good idea. Especially with how firm they are for highway use. It was a lesson we learned from traveling the Dempster Highway and other rough roads and trails on our YK/NT trip a few years ago. The big failure ended up we totally destroyed the converter which we hadn't realized and then led to a failed battery. The converter was brand new for the trip and I thought it'd be a warranty item for when we returned home and that's when we learned all of the internal components were essentially pulverized. Softer trails I didn't air down the R-Pod as we were going slowly enough on them but airing down can still go a long way with improving absorption of uneven surfaces and flotation if the going gets really soggy. Through CO and WY this summer we came across state and county "roads" that definitely would have allowed us to tread more lightly if we'd aired it down but they caught us off guard and went on for miles in convoys so we didn't get a chance to pull off to adjust. Still slow speed helped compensate. On it did wanted to protect fridge, oven/micro, tempered plates to prevent chipping, and other cargo and components we had for the trip.

I could also feel it on how it reduced the harshness transferred through the hitch. On this trip we enjoyed it with nothing coming apart or breaking along the journey.
 
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XCvagn

New member
Went with 235/60R-18 for the G015s. They are fine on-road, though definitely more sidewall flex than the previous tires and all the ones I'm used to. I'm not a very good resource for comparisons. These are the first AT tires I've ever owned, so I can only compare to various other all-season, summer, and winter performance tires. I read a lot of reviews though, and they were rated highly by many.

No air suspension. Regretting that decision now, as I'm getting a fair bit of rear sag when towing. I think the air suspension would help a lot with that?

Thanks for all the input on pressures. Your numbers are similar to what I'm thinking, though I'm leaning towards staying a few psi higher when towing to compensate for trailer effect. Also, I have a bit of fear that one day I'll forget to air up before going to 60 mph+ on the highway.

Awesome trips and pics! I'm a bit jealous!
Lucky! I wish I'd taken more time to find 19s for mine. I'm not sure if 18s would have worked given R-Design T8 has the largest rotors of the XC90s. There are definitely more choices in 19 and especially 18s.

Bummer about the sag - I wonder if you could alleviate some by reducing load in the rear of your XC90 and moving it more to the trailer or perhaps even roof to distribute it more. We've been fortunate that with our 2010 XC90 being an R-Design it came with Nivomat rear shocks which are mechanically self leveling. It's definitely turned into a super cool perk of having gone R-Design (I recall every time I drove a non R-Design of the old XC90s I'd always feel underwhelmed). Volvo has always done a good job with them only with new XC90 it's more styling and less differentiation. Still I do prefer the R-Design on our T8 as the extra perk there was the paddle shifters and seats. I finally learned to paddle shift on our summer trip with all of the massive elevation changes we drove through going to over 11,400ft and as most things that go up... What I found elusive about using paddle shifters, just shifting in general in the T8 is that it's so silent most of the time and the engine braking light compared to our 2010. The long trip made it possible to spend time on it and once I got tuned in to it it was even more fun of a drive.

On the Air Suspension - yes it's great at keeping the ride level but initially it also took some getting used to as it felt a little floaty relative to mechanical suspension when towing. I solved that by using Power suspension setting in Individual mode (Dynamic on T6) to firm it up and coincidentally lowers it to the lowest drive setting. Ride height with R-Pod in that setting is still good although Constant AWD would be a better. I use Individual so I can also adjust drivetrain settings as needed based on conditions.
 
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