Is the limit of putting air out of your tire relative to your wheel and tire combo?

[keith_refused]

Hello EXPO world,

New member. I'm not sure if this has been discuss elsewhere but I couldn't find any info after doing a few searches.

Does anyone know if there is a relation with the wheel and tire combo with the limitations of how low in terms of PSI can you go when you air down? I currently have a 16x7 ET11 alloy wheel paired with 255/85/16 BFG MT. I am currently considering the new expanded steel wheel from Nakatanenga at 16x8 ET0. The seller says the narrowest the wheels can take is 245/70/16.

Here's the link:

Nakatanenga ANR CLASSIC steel rim 8x16"

ANR-Classic - the rim for the Defender. 8x16-Inch steel in such an classical look, that this rim could be easily termed as the earliest form of the Defender rim. But looks are not everything - the max load of 1160 also impresses. The...

www.nakatanenga.de

With my current alloy 16x7, I could air down to 16-18 psi and rock crawl in semi hard and technical terrain. But nothing extreme that i find the need for beadlocks. And that's probably also the limit of my skills. If i change my wheel to 16x8 and retain my tires which is only 2 years old (i like skinny tires), will the limit of the my air down be lower, like 20 psi before separating the rim from the tire?

In my head, BFGs are know to contour around rocks which could also lead to tearing off the rim when stretching the tire around a rock and easily reach the edge of the rim.

Am I over analysing it? Does my question makes sense?

- Keith

 

[calicamper]

Your over thinking it and missing some big factors. Rig weight and driving skill. Basically at a certain point you hit the point of no return which will be different based on weight and driving skill. Also vehicle wheel base length can play a role in how much weight can get transferred to a single wheel in a given trail situation again lots of factors that are changeable that your not thinking about and your over thinking the basic known/fixed data points.

 

[Peter_n_Margaret]

A safe air pressure is closely related to load and speed for a particular tyre. Exceeding the speed at a particular loading or going too low in pressure for a particular speed results in the tyre generating heat (due to tread and sidewall flex) faster than it can dissipate it and the tyre heats up. That can very quickly result in permanent tyre damage (although it may not be immediately apparent).
At walking speed you can safely reduce pressures to a point where it falls off the rim without significant risk of damage.
I don't know, but I imagine that an alloy rim may have only a miniscule beneficial effect.
Cheers,
Peter
OKA196 motorhome

 

[keith_refused]

Forgot to mention that my truck is almost always light. No roof rack, basic camping gear with 2 passengers. I've a defender 90, so it's short. Heaviest thing a have on the truck is a winch and a tubular bumper.

 

[keith_refused]

A safe air pressure is closely related to load and speed for a particular tyre. Exceeding the speed at a particular loading or going too low in pressure for a particular speed results in the tyre generating heat (due to tread and sidewall flex) faster than it can dissipate it and the tyre heats up. That can very quickly result in permanent tyre damage (although it may not be immediately apparent).
At walking speed you can safely reduce pressures to a point where it falls off the rim without significant risk of damage.
I don't know, but I imagine that an alloy rim may have only a miniscule beneficial effect.
Cheers,
Peter
OKA196 motorhome

For relatively fast offroad driving in our ash covered playground around the volcano, we air down to 20 psi. For some technical slow terrain through the jungle, we air down to 16 psi. So we drop down relative to the terrain.

 

[gatorgrizz27]

I like the simple looks of those, I hadn’t seen them before.

I don’t see the size making a big difference, anything over 15 psi generally considered pretty safe unless you’re bashing through rocks at speed, or running a wheel that’s as wide as the tire. One thing that may make a difference is that factory Land Rover alloys have a significantly larger safety bead than most other wheels, which helps hold the tire on at lower pressures. I, not sure if those wheels carry that design characteristic over or not.

 

[rlynch356]

for technical terrain I use 12-16psi normally, for sharp rocks a bit more (20 psi ash), for dirt roads it depends on the corrugations and the speed to the sweet spot.
I use normal wolfs on a D90 NAS, my friends use the ANR wheels that those are copied from. Your fine
Below 10 psi I have had a tire break the bead though.

An interesting tidbit is that the tire Cups at pressures below apex ~15psi depending on the tire, that can Help or it can hurt traction depending on what your trying to grip and the tire.

 

[Robert Bills]

. . . If i change my wheel to 16x8 and retain my tires which is only 2 years old (i like skinny tires), will the limit of the my air down be lower, like 20 psi before separating the rim from the tire. . . ?

Your current tires are 33.1" in diameter with a 10" section width. BFG specifies an acceptable rim width of 6.5-8".

Your current wheels are 7" wide; your new wheels will be 8" wide. Both are within manufacturer's specifications and you will probably not notice any measurable performance difference between wheel widths at various air pressures.

Currently, you should be able to air down to 10-12 psi without risk of "popping" a tire bead unless you do something quite foolish. [Actually lower, but I don't want to encourage you to find that limit unless you really want to.] Increasing the wheel width by 1" might move the "zero risk" point a small amount, perhaps as much as 1 psi, but since you currently air down to 16 psi at the lowest the change in wheel width will be a non issue for you.

 

[keith_refused]

I never knew that you could go down as low as 12 psi with no beadlocks as 16 seems already beyond my comfort zone. Don't wanna my tire tearing off the rim at an uneven surface.

Thanks for your input Robert BIlls, rlynch365, gatorgrizz27.

 

[keith_refused]

for technical terrain I use 12-16psi normally, for sharp rocks a bit more (20 psi ash), for dirt roads it depends on the corrugations and the speed to the sweet spot.
I use normal wolfs on a D90 NAS, my friends use the ANR wheels that those are copied from. Your fine
Below 10 psi I have had a tire break the bead though.

An interesting tidbit is that the tire Cups at pressures below apex ~15psi depending on the tire, that can Help or it can hurt traction depending on what your trying to grip and the tire.

What tire size do you have on your wolf? And what does your friend have in his ANR?