Tyre Pressures

Submitted: Saturday, Jan 31, 2009 at 20:23
ThreadID: 65579 Views:2806 Replies:7 FollowUps:10
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Greetings one and all, i have just recently invested in a new set of Bridgestone 694 AT 265,70,16 and thinking ahead to our travels I was wondering if anyone had any experience on sand driving with them and any ideas on the correct pressures, any help would be greatly appreciated,
Cheers,
Chris
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Reply By: troopyman - Saturday, Jan 31, 2009 at 20:45

Saturday, Jan 31, 2009 at 20:45
Type in "4 psi rule"
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Follow Up By: Crackles - Saturday, Jan 31, 2009 at 22:59

Saturday, Jan 31, 2009 at 22:59
Does the 4 psi rule even apply when driving on sand?
Cheers Craig..............
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Follow Up By: troopyman - Sunday, Feb 01, 2009 at 10:48

Sunday, Feb 01, 2009 at 10:48
Yes .
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Follow Up By: Crackles - Sunday, Feb 01, 2009 at 10:54

Sunday, Feb 01, 2009 at 10:54
How does it work? If you get bogged in sand let another 4 psi out? :-)
Cheers Craig............
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Reply By: Peter_n_Margaret - Saturday, Jan 31, 2009 at 21:31

Saturday, Jan 31, 2009 at 21:31
1. Get pressure / load / speed charts in wrting from Bridgestone Tyres (not the dealer, not your 'mate', .......)
2. Follow them VERY carefully.
3. Be VERY careful of ANY other advise.

Cheers,
Peter
OKA196 Motorhome
AnswerID: 346953

Reply By: Crackles - Saturday, Jan 31, 2009 at 22:57

Saturday, Jan 31, 2009 at 22:57
Chris I find it depends a bit on what type of vehicle, the load being carried & how soft the sand is but in general most start at 18 to 20 psi dropping to 15 in hard going.
Cheers Craig...............
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Follow Up By: Member - Bucky, the "Mexican"- Sunday, Feb 01, 2009 at 06:30

Sunday, Feb 01, 2009 at 06:30
Crackles

Your call is spot on !

Cheers
Bucky


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Reply By: GerryP - Saturday, Jan 31, 2009 at 23:38

Saturday, Jan 31, 2009 at 23:38
Hi Chris,

The advice above (except for Crackles) is OK for general running, but I think what you're after is pressures on sand...

It does depend on the condition of the sand and also your vehicle, but generally I would start around the low 20's. As Crackles says, if the going gets tougher, drop them down a bit more. I have had to go all the way down to around 12 for some dunes, but be careful not to corner too hard as you could pop the seal on a tyre.

The secret is to let it down sufficiently so the tyre bags out and lengthens the contact surface on the sand. Also need to be more aware of possible sidewall damage or staking as they will be more exposed.

Cheers
Gerry
AnswerID: 346969

Follow Up By: Member - Warfer (VIC) - Sunday, Feb 01, 2009 at 02:08

Sunday, Feb 01, 2009 at 02:08
*The advice above (except for Crackles) is OK for general running, but I think what you're after is pressures on sand...**

It does depend on the condition of the sand and also your vehicle, but generally I would start around the low 20's. As Crackles says, if the going gets tougher, drop them down a bit more*


A bit contradictory isn't it Gerry,one minute your saying dont listen to crackles and then advise he does...I dont see anything wrong with his advice,Whats a couple of psi between friends...I know every situation is diff but you've basically come up with the same answer.


Cheers
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Follow Up By: Bonz (Vic) - Thoughtfully- Sunday, Feb 01, 2009 at 07:31

Sunday, Feb 01, 2009 at 07:31
For sand I would always start at 18psi at the base point. I think Crackles is spot on
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Follow Up By: GerryP - Sunday, Feb 01, 2009 at 12:01

Sunday, Feb 01, 2009 at 12:01
Hi Mr Warfer,

Sorry mate, but I probably didn't explain clearly enough. What I meant was that except for Crackles, the other replies all related to highway driving. I was actually acknowledging that Crackles was the only one to mention sand driving, which is why I agreed with him in the latter paragraph.

Sorry if I upset anyone, especially Crackles...

Cheers
Gerry
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Follow Up By: Bonz (Vic) - Thoughtfully- Sunday, Feb 01, 2009 at 14:02

Sunday, Feb 01, 2009 at 14:02
fine post Gerry well done
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Reply By: glids - Sunday, Feb 01, 2009 at 09:13

Sunday, Feb 01, 2009 at 09:13
Hi Chris,

The advice from others regards pressures for sand driving is pretty much spot-on, just be careful at really low pressures that you don't accellerate hard or corner hard as the lower pressure means reduced grip of the tyre on the rim.

You may be interested in the following...

I'm running Pirelli Scorpion LT AT's at the moment but have bought a set of Bridgestone 694 AT's for replacements soon - letting them age a bit. I sent an email to Bridgestone requesting recommendations regards tyre pressure for normal driving, highway driving and towing.

Alan Watts from Bridgestone rang me back and we had a chat about pressures etc. He has done a lot of testing regards the pressure increase from cold tyres to hot after driving, and reckons it is a lot of bunk!

The theory was that the tyre pressure will increase with temperature rise - ie driving - and if more than 4-5 psi then the tyre is getting too hot and is therefore underinflated. There is a basis of fact here (pressure WILL rise as the tyre gets hot) but how can an increase in pressure be a RELIABLE measure when there are so many other variables - mainly, cold day/cold road vs hot day and blistering hot bitumen.

Alan's recommendation was start at 35psi (for the 694's) and see how the tyres wear. If wearing in centre, pressure is too high.

I rotate my tyres at 5000k intervals and measure tyre wear. The Pirelli's were too high at 39psi, and I have dropped to 37 psi.

cheers,
glids
AnswerID: 346992

Follow Up By: trainslux - Sunday, Feb 01, 2009 at 09:35

Sunday, Feb 01, 2009 at 09:35
Dont forget that when setting the tyres cold pressure, say at 34psi on a 20 deg day.
When the day heats up to 40, the tyres will increase 4psi without even rolling.
I found that with the recent warm weather, 44, 46, 44, 43 deg days, it didnt matter if the tyre was in the sun all day, or in the shade, both were up at least 4 psi, and evenly.

Been watching tyre pressures quite a bit, had the old terra tracs on, they were great off road on stony tracks, and monitered temps and pressures whilst getting to know them, and am doing the same with the Cooper ST's ive now got.
Have to say, Im very impressed with them so far.

Trains
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Follow Up By: Splits - Sunday, Feb 01, 2009 at 16:21

Sunday, Feb 01, 2009 at 16:21
"and reckons it is a lot of bunk! "

glids

I was told exactly the same thing during a long conversation with a tyre technician from another manufacturer. He said he is constantly involved in tyre testing programs covering pressures, different terrains and even deliberately trying to destroy them. He said there are far too many variables for a 4 psi or any other temperature related rule to be accurate.

The "wear" rule definitely works though. Too little air and the outer edges wear. Too much and the centre wears. If it is even, the pressure is correct.

Brian
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Reply By: RobAck - Sunday, Feb 01, 2009 at 11:05

Sunday, Feb 01, 2009 at 11:05
Having used the 694's on our last two vehicles and just completed a year of durability testing, Japanese vs Australian spec tyres, for Bridgestone I can offer the following guidance.

Test vehicle is a 120 Prado weighing in at 2400kg for daily use and when full loaded we run up to around 2950 kg. We average 20,000km off bitumen each year by the way.

Tyre pressures we use are:

Sand. Start at 16-18 psi

Off-bitumen/rocky terrain. 26 psi

Normal bitumen driving. 34 psi

One thing for all tyres is to ensur they are rotated and balanced every 10000kms to ensure even wear and tyre life

Regards

RobA
AnswerID: 347016

Reply By: ross - Sunday, Feb 01, 2009 at 17:47

Sunday, Feb 01, 2009 at 17:47
Ive been using 18psi in my 694 b/stones on the beach. I got a little stuck last week near the water so I went down to 10 psi and the landcruiser walked out .

So far I think they are great in the sand,maybe even better than the BFG a/t
AnswerID: 347104

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