Tyre/Tire Pressures. What do you run? (MERGED)

[Rally]

Interesting. In all my off roading, I’ve only gone down to a nominal 25 psi. Maybe by accident a couple may have gone down to 22. It’s good to know there’s a lot of elbow room left if my diff and tyre combination are not equal to the task at 25.

 

[MiddleAgeSubie]

Tyre pressure is critical to offroad performance.

By P-metric, do you mean normal passenger tyres? Use the table listed before.

Like I said, don't complicate it. Stick to the table listed & you will be fine in 99% of situations. If you're on a loose or slippery surface & are spinning tyres & want more grip, just drop 4psi & feel the difference

For me that table is off and unnecessarily complicated. It seems to apply to LT-D/E tires and/or MT tires.

There never was a need to air down under 20 on the Outback, except for sand, cement, cereal, whatever.

I don't know about Australia, but in the US the whole "must air down" idea comes from the use of MT tires on Wranglers. Since they are unbearable at anything close to street pressures, they must be aired down.

When it comes to traction, it also relates to Wranglers and trucks but now we are talking about the US sport of rock crawling. Then we are talking beadlocks and single digit psi. Even dramatic looking regular difficult trails don't require anything under 20 on modern vehicles (lockers, traction control systems, etc).

P-metric tires, whether street or all-terrain, should not be aired down unnecessarily because they have thinner sidewalls. Sure, the better designs, like the one I use, have very robust shoulder protectors that double the rubber in that area. But if you air down enough for a big bulge, then the unprotected part of the sidewall becomes exposed.

Interesting. In all my off roading, I’ve only gone down to a nominal 25 psi. Maybe by accident a couple may have gone down to 22. It’s good to know there’s a lot of elbow room left if my diff and tyre combination are not equal to the task at 25.

This is a GOOD PART of the reason why you have been so happy with your performance street tires (plus performance tires have stiff sidewalls). Air them down and see if they last you one rocky trail.

That said, @NachaLuva is also right that tires TOO aired up can be punctured through the tread.

That's why 3-ply sidewalls are best for truly harsh terrain like the one right where I live but that means LT-D/E tires and dealing with the issues those bring on the table when used on a DD.

 

[Rally]

I drop to 25 once I hit gravel, even if it’s a smooth road. The car is quite skittish at 40. I don’t drop it below 25 when I go into low range. However, with the LT tyres I don’t know, I haven’t even driven on a gravel road yet, let alone low range. I’ve always been one to go by the feel of the car. I think I’ll drop to about 30 and see how it feels, bearing in mind speed and load

 

[NachaLuva]

Perhaps to run those thick sidewalls of the LT you need more pressure. I don’t know.

Yeah, it's actually the opposite. As I said, LT tyres have a thicker sidewall so need to be aired down more to achieve the same bagging.

Keep in mind that when a tyre bags out, it's not the extra width (marginal) of the contact patch that matters, it's the extra length

Interesting. In all my off roading, I’ve only gone down to a nominal 25 psi. Maybe by accident a couple may have gone down to 22. It’s good to know there’s a lot of elbow room left if my diff and tyre combination are not equal to the task at 25.

25 or 22psi has only slightly extra grip than highway pressure. Mind you, that's for ATs with proper offroad tread & grip. Probably won't make any difference with RE003s lol
[MENTION=13125]MiddleAgeSubie[/MENTION] airing down is only mildly to do with comfort. It's 90% about grip. I know Jeeps are a big deal in the US but here they're not very common offroad. Too unreliable!

ALL tyres should be aired down to suit the terrain. This is rule #1 of offroading. Forget every single other thing you've ever learnt about driving offroad. Airing down is the single most important thing to do, bar none.

It makes me angry when I see 4wd boofheads ripping up tracks on highway pressures. That's what it does...not airing down or not airing down enough dramatically reduces grip, so the tyres spin much more easily, which damages tracks. I really hate seeing people do this. This is a big reason why so many tracks get closed permanently because they just keep being damaged

 

[MiddleAgeSubie]

@MiddleAgeSubie airing down is only mildly to do with comfort. It's 90% about grip. I know Jeeps are a big deal in the US but here they're not very common offroad. Too unreliable!

ALL tyres should be aired down to suit the terrain. This is rule #1 of offroading. Forget every single other thing you've ever learnt about driving offroad. Airing down is the single most important thing to do, bar none.

It makes me angry when I see 4wd boofheads ripping up tracks on highway pressures. That's what it does...not airing down or not airing down enough dramatically reduces grip, so the tyres spin much more easily, which damages tracks. I really hate seeing people do this. This is a big reason why so many tracks get closed permanently because they just keep being damaged

LOL, Wranglers are 90% of what you see offroad in the US. Often it feels like 100%.

And, yes, airing down is 90% about comfort in the US. Mind you that most of the Wranglers you see nowadays are Rubicons and they have traction to sell. I also have traction to sell since moving to this particular 4R model.

You are right about the spinning wheels issue. That's why I brought lockers and traction control systems in the picture. If you spin, you should air down, but a specialized vehicle does not spin easily when properly used just because it is at street pressures until it encounters very soft terrain.

But, yeah, one needs to use those traction control systems and the locker(s).

 

[Rally]

I get what you are saying about needing to air LT tyres down more for bagging out. I’m looking at it from the other side. Does doing that create extra stress on the tyre more than a non LT tyre from a fatigue point of view? I don’t know, maybe it’s worth getting in contact with Bridgestone again.

Airing down on road tyres should have the same or similar affect as AT tyres. Bear in mind both types of tyres can have thin or thick sidewalls, albeit not as thick as LT versions of the AT tyre. That I have done so well at such relatively high pressures shows that a road tyre does perform well in this environment from a grip perspective. MAS though feels that those same relatively high pressures save the thicker walled road tyre from sidewall failure. In which case, the same concern about going to low on the even thicker walled LT tyre must then arise. I don’t know, lots of theories, no actual proof. I’m not knocking the theories, as they seem worthy theories.

I agree about airing down being important. No doubt about that. I don’t want to go so far as to say it is a clear number 1 though. My experience in both general driving, motorsport and off roading has been driver training has achieved best results. I posted previously of the results I have achieved in motorsport and off roading instructing people to substantially improve either their times or getting to where they wish to go. With off roading, they would go further on highway pressures following instruction than they could prior to instruction on lower pressures. Best to have both of course.

None of us are happy about people destroying tracks, forcing their closure. I think this happens also due to idiots in mud puddles deliberately churning up the mud, as well as trying too long to climb a hill because their determination to do so exceeds the car’s or drivers ability to do so. For that we can blame the driver, the diffs or electronics and tyre pressures. We need to think of others who come after us.

 

[scalman]

about airing down
5psi vs 30psi . night and day difference

30psi

5psi

works even for those who maybe dont have any mud or soft ground

 

[Beachworm]

I was under the impression that tyre sidewall failure, excluding impacts and punctures, was due to excessive heat build up generated as the sidewall flexes.
On tarmac there is a combination of vertical and lateral stress on the tyre sidewall (which is why when driving in a mororkhana, high tyre pressures are required) and a high frequency of tyre distortion due to speed and irregularities in the road surface whereas in off-roading, loading is much more likely to be vertical due to low speeds and absence of hard cornering. Frequency of tyre distortion is also greatly reduced due to the nature of the road surface and low speeds. This, of course, excludes driving on typical Australian outback roads where corrugations increase the frequency dramatically.
Therefore, in slow off-roading, tyre sidewall failure due to excessive heat build up is not really an issue. Damage/cuts from sharp rocks, exposed roots and pinching remains the number one cause of AT tyre failure in these conditions.

 

[NachaLuva]

LOL, Wranglers are 90% of what you see offroad in the US. Often it feels like 100%.

It's funny seeing how Toyotas get idolized in the US offroad scene, I guess because they're so capable but not many of them. Yet from what I've seen, there are very few Patrols if any. Patrols & Landcruisers make up the bulk of the offroading scene here, along with Rangers & other utes

airing down anyt tires on any surface is better then locker. for open diff acting older subarus that should be specially good difference like night and day

Yep. A rear locker, locking centre diff, LSDs, etc are no good if all 4 wheels are spinning with no grip. We seen the videos like that....

Therefore, in slow off-roading, tyre sidewall failure due to excessive heat build up is not really an issue. Damage/cuts from sharp rocks, exposed roots and pinching remains the number one cause of AT tyre failure in these conditions.

Yep. Pinching shouldn't really be a problem with our little Subies if you're running tyres with a decent sidewall. With 17" & esp 18" it would be more of a problem, along with reduced grip

 

[ABFoz]

ALL tyres should be aired down to suit the terrain. This is rule #1 of offroading. Forget every single other thing you've ever learnt about driving offroad. Airing down is the single most important thing to do, bar none.

It makes me angry when I see 4wd boofheads ripping up tracks on highway pressures. That's what it does...not airing down or not airing down enough dramatically reduces grip, so the tyres spin much more easily, which damages tracks. I really hate seeing people do this. This is a big reason why so many tracks get closed permanently because they just keep being damaged

Our track closures here in many North Island forests are due to those 4wders that rip the tracks up with their highway pressures. I would see them attack the old forest trails with their lifted vehicles and did not even air down. When confronted by the forester (the human not the car) about lowering the pressures to prevent wheel spin, they just replied, "We will just air down if we get stuck." At that point in time, they were already spinning their wheels into oblivion. 2 weeks after, the trail was closed. It's a shame because some of them are just 15 to 20 mins away from me.

 

[MiddleAgeSubie]

It's funny seeing how Toyotas get idolized in the US offroad scene, I guess because they're so capable but not many of them. Yet from what I've seen, there are very few Patrols if any. Patrols & Landcruisers make up the bulk of the offroading scene here, along with Rangers & other utes

Again, remember that Toyotas are bought for Instragram and the local mall. They are "too nice" to be beaten offroad until old. On trail, you have Wranglers, including brand new, old trucks and SUVs of all types, including Toyotas, and a VERY RARE new non-Wrangler. It is a completely different offroading landscape.

There are like one dozen people on the 4Runner forum that really use their vehicles A LOT, maybe a dozen and a half.

 

[Rally]

Therefore, in slow off-roading, tyre sidewall failure due to excessive heat build up is not really an issue. Damage/cuts from sharp rocks, exposed roots and pinching remains the number one cause of AT tyre failure in these conditions.

Well said

 

[Ben Up North]

Again, remember that Toyotas are bought for Instragram and the local mall.

Really? They're pretty much the workhorse of the outback in OZ. Not so much any more, with other brands becoming popular but most landowners run Landcruisers from what I see.

 

[NachaLuva]

[MENTION=15721]scalman[/MENTION] brilliant videos to show just how effective airing down is!
[MENTION=114]Kevin[/MENTION] could we move this to the tyre pressure thread? This is a perfect example of what it's all about

 

[Kevin]

[MENTION=15721]scalman[/MENTION] brilliant videos to show just how effective airing down is!

[MENTION=114]Kevin[/MENTION] could we move this to the tyre pressure thread? This is a perfect example of what it's all about

Done ;-)

 

[MiddleAgeSubie]

Really? They're pretty much the workhorse of the outback in OZ. Not so much any more, with other brands becoming popular but most landowners run Landcruisers from what I see.

Well, no, but yes. Meaning that there are a lot more people who use them offroad than Subarus but that these are a just a fraction of those who buy them. The only vehicle that is offroaded by a big % of its owners is the Wrangler. I mean, Wranglers absolutely dominate the trails when it comes to street-legal vehicles: everything from CJs to JLs.

 

[Kevin]

MAS & Ben I split your above posts into the correct threads.

 

[Ben Up North]

MAS & Ben I split your above posts into the correct threads.

You sure about that?

 

[Kevin]

The way threads are being taken off topic lately who knows! :iconwink:

 

[Ben Up North]

I'm working on staying on topic. kinda hard though when the last forum I was really involved with was dedicated to being off topic.

I think I'm improving.

Oh.. hang on.. what was the topic?

Ahh! I'm beginning to think I'm running my tyre pressures too high. currently about 42 psi on the road because that's what Bridgestone put them on the car at.
Thinking of dropping to 38 so it's a bit more forgiving.

Thoughts anyone?