Sand Driving Tyre Pressures

[TheTree]

Hi

I am doing a Sand Driver training course with the RR Club of NSW this Sat on Stockton Beach and have been thinking about tyre pressures.

My question is given the 10PSI difference between front and back on a P38, should I maintain the difference when i deflate?

EG: If I go to 15PSI in the front should I go to 25PSI in the back or is it OK to drop the back pressures to 15PSI as well?

Note to Hoges; I will keep an eye out for the Polo ponies mate :angel:

Steve

[benji]

Ive always gone 16psi front and back if im lightly loaded, and 18 if im loaded. 26 would be way to high.

[TheTree]

benji,

That's what I was thinking as well, it actually pretty unusual in my experience for the back to be 10PSI more than the front, but I guess in low speed sand driving, it makes no difference whereas on the road, heat buildup etc is an issue

Thanks
Steve

[DiscoWeb]

Hi

I am doing a Sand Driver training course with the RR Club of NSW this Sat on Stockton Beach and have been thinking about tyre pressures.

My question is given the 10PSI difference between front and back on a P38, should I maintain the difference when i deflate?

EG: If I go to 15PSI in the front should I go to 25PSI in the back or is it OK to drop the back pressures to 15PSI as well?

Note to Hoges; I will keep an eye out for the Polo ponies mate :angel:

Steve

Steve,

Wait until Saturday :) and we will tell you all you need to know, or at least give you some guidance. !!!

George

[PhilipA]

I know I will be dropping mine to 16PSI.
It will be interesting to me how my 2002 D2 TD5 auto without CDL will go at Stockton although the sand will be so wet you could probably leave street pressures! LOL
My RRC with the "dreaded" VC had no problem last time I was there , while a RRS had all sorts of trouble until he switched off DSC, and the bloke was a VERY experienced sand driver.
Regards Philip A

[Slunnie]

On Stockton, with the 16" P38 rims I would go straight to 16psi. I doubt you will need to go lower, but those rims are the best in the business for holding onto tyres if you do need to go lower.

[PhilipA]

Unfortunately I also have 18s on my D2, and they are Chinese junk, but I have 2 sets of 16s under the house waiting for tyres which I cannot currently afford.
Regards Philip A

[Keithy P38]

Yeah 16psi all round and you'll be lapping stocko like a pro.

[TheTree]

Steve,

Wait until Saturday :) and we will tell you all you need to know, or at least give you some guidance. !!!

George

George,

I am sure you will :cool:

Steve

[TheTree]

Thanks everyone for all the answers :D

I am sure the P38 on Stockton is going to be a little different from driving my Series One through the Flinders Ranges and across the desert to Lake Eyre... but then that was longer ago than I can remember :eek:

Steve

[benji]

Empty the p38s are 150kg heavier in the front anyway. We were down at 8 and 10 psi a few years ago, just dont turn quickly... its completely bonkers where it went though.

[TheTree]

Empty the p38s are 150kg heavier in the front anyway.

This why I find it a little odd that the rears have 10PSI more than the front.. by hey I guess it's just a little bit of Land Rover magic :p

Steve

[Keithy P38]

It's all about handling - lower pressures in the front mean when you accelerate out of a corner or off a round about, the front end takes the drive and pulls the Rangie around. The preload on the viscous coupling is what it's all about!

Sadly though, outer tyre wear is a result.

My road pressures on an average day are 35/38 f/r and once aired down with a load ill measure the footprint to gauge how low I need to go. Generally around the 20/22 f/r split. At those pressures I gain 3.5" of footprint on each corner.

[TheTree]

My road pressures on an average day are 35/38 f/r

My owners manual and compliance plat specify 28/38 f/r for my MY99 beast

Steve

[intheozone]

Interesting reading this as I always put all my tyres down equally about 16 on sand 18-20 on mud gravel and pump them up to 43psi on the black top. I am running 255/70r16 KM2 tyres. I'm probably doing it wrong not that it seems to stop me.

[Keithy P38]

Yeah Steve, mine says 28/38 as well, I choose to run different pressures for two reasons:

- stops the tramlining on well driven roads
- stops the outside edge wear on the tyres

As you are inthezone, I'm on 255/70 km2's also.

[OffTrack]

My owners manual and compliance plat specify 28/38 f/r for my MY99 beast

Steve

The placard pressures for the rear tyres are set for a specific loading, not sure what it will be on the P38a but for the D2 it's five passengers plus luggage. It's a compromise value that ensures the average owner doesn't need to adjust pressures in normal day to day usage. For a lightly loaded vehicle the placard pressure for the rears will be too high.

cheers
Paul

[benji]

Lr also say 38 for all loads. You certainly wouldnt put 500kg in the back at 28. Though 28 gives a nice ride.

The last of the classics said to increase pressures 3psi for gvm loads or sustained speeds over 160.

I usually run 30/32.

[TheTree]

Hi

I seem to remember every vehicle i have owned had had something similar to "increase rear pressures by x psi for full loading or sustained high speeds" x is usually 4PSI

I will give some serious thought to reducing the pressure in my rears!

Steve

[p38oncoils]

Interesting reading this as I always put all my tyres down equally about 16 on sand 18-20 on mud gravel and pump them up to 43psi on the black top. I am running 255/70r16 KM2 tyres. I'm probably doing it wrong not that it seems to stop me.

I'm running 285/75/16 Maxxis Bighorn mud tyres and run 40 psi front and back for driving on road and 14 - 16 psi for off road driving. On the picture below I've got the tyres pumped to 16 psi.

http://www.aulro.com/afvb/members/p38oncoils-albums-p38oncoils-picture4375-dscn6173.jpg

[bushrover]

I like these tyre pressure threads...............all the variations confirm an exact pressure is not necessarily something to obsess over so long as the pressure is within a range that is safe for the speed, load, distance travelled. Temperature is the biggest concern, if you can maintain a constant and correct belt temperature for the tyre you are using you have the correct pressure for the speed, load and distance.

Pressures for sand, mud, rocks should be the highest you can use to achieve traction and the lower you go the slower you go, or you can reduce weight, which is not usually practical.

I use (used to use, it just spat the dummy so the tyre dogs are back on)a rather expensive tyre pressure/temperature monitoring system and run 26 front and 28 rear (defender unloaded and Cooper ST maxx ) with a 2-3 psi increase at running temperature. Add a bit of weight and I might have to go to mid thirties or higher to maintain correct temperature. Most tyres are way, way over inflated for road use.

Rick

[PaulP38a]

Most tyres are way, way over inflated for road use.


Why do you say that Rick? I am not trying to be a smart-ass just interested in your views on this.
At a defensive driving course I did almost 20 years ago they taught us that running on-road tyres at 35-40psi was better for several reasons:
- flatter contact of tyre to road surface
- better dispersion of water
- more even tyre wear
Maybe that was the case 20 years ago and is not any more due to changes/improvements in tyre design?

I appreciate that high-20's gives a more comfortable ride than high 30's on the road.

For my off-road jaunts, I rarely drop much below 20psi on 255/85R16 BFG KM2's (or previous Maxxis Bighorn 255/85R16) and have never had any real problems. I have been afraid to drop to sub 10psi in case I pop a bead on my 16" rims. Heartened to hear the 16" P38 rims are rated well in terms of non-bead-popping :)

Cheers, Paul.

[bushrover]

Why do you say that Rick? I am not trying to be a smart-ass just interested in your views on this.
At a defensive driving course I did almost 20 years ago they taught us that running on-road tyres at 35-40psi was better for several reasons:
- flatter contact of tyre to road surface less road grip and can be dangerous if overinflated for conditions.
- better dispersion of water as above, less road grip at high pressure, slow down to allow the tyre to disperse water. It is the tread pattern that disperses water, slow to a speed to let the tyre work.
- more even tyre wear and much greater potential to do tyre damage. At the correct pressure for the weight and speed a tyre will wear evenly. Over inflation causes crown wear and centralised heat buildup at the crown.
Maybe that was the case 20 years ago and is not any more due to changes/improvements in tyre design?

I appreciate that high-20's gives a more comfortable ride than high 30's on the road. I am not interested in comfort. Just tyre life and road grip.

For my off-road jaunts, I rarely drop much below 20psi on 255/85R16 BFG KM2's (or previous Maxxis Bighorn 255/85R16) and have never had any real problems. I have been afraid to drop to sub 10psi in case I pop a bead on my 16" rims. Heartened to hear the 16" P38 rims are rated well in terms of non-bead-popping :) I have dropped to 6psi to get out of trouble and re-inflated immediately after. Low low pressure equals low low speed. At 10psi you should be able to idle out of most situations in sand. Big revs digs holes and spits tyres, but looks impressive.

Cheers, Paul. I am no tyre expert, but in my last role my tyre and tyre management budget was around $15M so management was very interested in extending tyre life. Tyres pressures on the side wall are usually at maximum rated load and rated speed for that tyre type. For any particular trip, pressures should be adjusted to suit the changing travelling conditions. If you are on bitumen, I think the biggest advantage of increased pressures is fuel economy and less rolling resistance, but correct pressure is best and that is not the same as your mate in his vehicle or anyone's recommendation from their vehicle. Different tyres, different driving styles, different weight, different speed, distance to be travelled, road surface conditions all determine tyre pressure required. Pressures should be the lowest possible to be safe for the conditions. However, we all compromise.

Rick

[benji]

We were worried about popping a bead too, and pumped them back to 20ish as soon as we were through. The back rim was about 2 inches off the ground.

Ive always thought in a passenger constructed tire you can get away with lower pressures, but on an lt carcass you dont want much flex in it at all. Weve run 65 in the rear whilst towing and they were a lot cooler than at 40 which ive always thought had a direct bearing on tread life too - but who knows.

[RoverMac]

Ive always gone 16psi front and back if im lightly loaded, and 18 if im loaded. 26 would be way to high.

Agreed , that's what's I have used with 32 and 33" tyres on 16 inch factory rims

Never popped a bead , but I have had grit and sand become trapped between the rim and the tyre causing a slow leak
The pre set / adjustable tyre deflation valves can make life easier , recommend Staun Brand , and "no loss"valve caps

[mtb_gary]

Agreed , that's what's I have used with 32 and 33" tyres on 16 inch factory rims

Never popped a bead , but I have had grit and sand become trapped between the rim and the tyre causing a slow leak
The pre set / adjustable tyre deflation valves can make life easier , recommend Staunch Brand , and "no loss"valve caps

I also use the staunch presets, 16 up front and 18 in the rears on the 265/75/16's on the standard RR 16" rims.

Gary

[TheTree]

HI

I started out with 16 all round but dropped it to 14 all round to help get out of a pretty gnarly spot.

Steve

[PhilipA]

And you did well my son.
Showed those D3-4s how to do it.
Pity about the back bumper on your race down the dune to get to the climb out. But who needs plastic anyway.
And we now know how good Evoques are in sand .NOT!!
Regards Philip A

[TheTree]

And you did well my son.
Showed those D3-4s how to do it.
Pity about the back bumper on your race down the dune to get to the climb out. But who needs plastic anyway.
And we now know how good Evoques are in sand .NOT!!
Regards Philip A

Hi Phillip

I think the main advantage the P38 had over the Disco was sheer brute force, the situation required momentum and the 4.6 V8 was able to accelerate faster than the diesel Disco so I hit the slope at a higher initial speed.

Yeah the plastic fantastic bits are in my sights now, time for the Bauhaus approach :cool:

Steve