Tyre Pressures Again

Submitted: Wednesday, Apr 07, 2004 at 22:51
ThreadID: 11918 Views:1566 Replies:7 FollowUps:13
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I have looked through the archives and found a lot of formites refering to the 4psi rule. When I use this I find that the rear tyres have somewhere between 3 - 5psi less than the front. I have a DC Hilux with a bullbar and most of the time nothing loaded in the back. The toyota manual only gives recommended pressures for a loaded vehicle with the rear having more pressure than the front. The local tyre outlet says run 40psi all round. Is it advisable to run with less pressure in the rear than the front as the 4psi rule suggests, then increase pressure when loaded ?
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Reply By: DiesAl - Wednesday, Apr 07, 2004 at 22:51

Wednesday, Apr 07, 2004 at 22:51
Sorry where are my manners.

Thanks in advance.
AnswerID: 53637

Reply By: Jimbo (WA) - Thursday, Apr 08, 2004 at 00:48

Thursday, Apr 08, 2004 at 00:48
DiesAl,

I too have a hilux and have been told to run 40 psi all round by my tyre place - on BFG AT KO's.

I have been running that for about 15, 000 kms now and after experimenting with the 4 psi rule only last week found that that is about right for my set-up. My car weighs in at 2420 kg though, with only about 100 kg difference between the front and rear axle weights.

So in other words, 40 psi is right for me. If you only have a bulbar, and not much else added to your car, and you travel unladen mostly, then I would think that what you have discovered playing with the 4 psi rule is about right.

Best thing to do would be to go with it for a while and see what you think - check out your wear patterns in a few thousand k's and see if 40 front / 36 rear is right for you.
AnswerID: 53643

Follow Up By: DiesAl - Thursday, Apr 08, 2004 at 15:45

Thursday, Apr 08, 2004 at 15:45
Thanks Jimbo, nice rig mate. You need to update your rig pic so we can see all those xtra goodies....... Do you have anything in the way of Duel battery setup ? As I would like to include this down the track from my investigations looks like I'll be putting it the tray no room under the bonnet.
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Follow Up By: Jimbo (WA) - Thursday, Apr 08, 2004 at 22:06

Thursday, Apr 08, 2004 at 22:06
DiesAl,

Yeah I know I need a new pic, but have to get off my arts and borrow my mates digital camera to get that done. Soon!

I have been researching (read that as I know what I want but don't have the sheckels yet) the dual battery thing and have decided that it will be going in or under the tray as well.

I need to win the lotto.........
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Follow Up By: DiesAl - Thursday, Apr 08, 2004 at 22:09

Thursday, Apr 08, 2004 at 22:09
I know the feeling I've just streached the budget to book the Hilux in for some scuba gear.....Next week hopefully

Happy Easter & safe travels
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FollowupID: 315415

Reply By: navaraman - Thursday, Apr 08, 2004 at 09:48

Thursday, Apr 08, 2004 at 09:48
I've got a similar vehicle to you and have found 38psi front and back when unloaded is about right for the Navara. When the back is loaded I pump the back to 42-46 psi.
AnswerID: 53661

Follow Up By: DiesAl - Thursday, Apr 08, 2004 at 15:52

Thursday, Apr 08, 2004 at 15:52
Thanks Navaraman, what tyres are you running? I've currently got Bridgestone 693's on and from memory 40psi is the max I can put in them, although when fully loaded I think it could do with a couple more.
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FollowupID: 315370

Follow Up By: navaraman - Thursday, Apr 08, 2004 at 17:39

Thursday, Apr 08, 2004 at 17:39
I'm using Olympic Overlanders which have a max rating of 65psi. I'm tryig to work ut the best pressure for off road work, around 30-28psi seems pretty good but still some work to do to ascertain what is best.
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Follow Up By: DiesAl - Thursday, Apr 08, 2004 at 17:45

Thursday, Apr 08, 2004 at 17:45
Navaraman, are the Overlanders an AT tyre may try them next time 'round
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Follow Up By: navaraman - Thursday, Apr 08, 2004 at 20:26

Thursday, Apr 08, 2004 at 20:26
DiesAl they are an A/T tyre. I've only had these 10000ks and am getting a bit of uneven wear, that may sort itself out a bit once they've been through a full rotation. I've got a fair bit of sand driving coming up after easter so I'll have a better idea of their abilities then, so far they've been good value for the cost.
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Follow Up By: DiesAl - Thursday, Apr 08, 2004 at 21:15

Thursday, Apr 08, 2004 at 21:15
Thanks mate, have fun on the sand. Hope to get to fraser later this year lookin forward to it.

Happy and Safe Easter

Al
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FollowupID: 315407

Reply By: Paul's lot - Thursday, Apr 08, 2004 at 10:02

Thursday, Apr 08, 2004 at 10:02
The bull bar because it hangs forward of the axle and not over it likke most weights will put load on your tyres and if you talk to suspension people they will tell you the same which is why they recommend heavier springs when you have a winch bar.
Your pressure in the front is paramount as this is where the load is when the vehicle is unlaiden. I run 40 in the front and 35 in the back on my unlaiden hilux and this gives great results for comfort and tyre wear. When laiden with a heavy load I increase the rear to 40 as well but to run 40 in the rear unlaiden will make it more prone to axle hop on uneven surfaces.
Having said all that these pressures are for bitchumen running and are all out the window when i get on rough tracks where I reduce the pressures.
Hope this helps sunshine
AnswerID: 53663

Follow Up By: DiesAl - Thursday, Apr 08, 2004 at 15:59

Thursday, Apr 08, 2004 at 15:59
Thanks Paul, I'm running nearly 40 in the front now and have found this to be about right. Just of interest what do you run offroad on gravel, sand & mud?
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FollowupID: 315371

Reply By: Reynard - Thursday, Apr 08, 2004 at 12:24

Thursday, Apr 08, 2004 at 12:24
I run at about 32-34 in the rear of my hilux xcab with no load (BFG AT's), if I run the pressure at 36+ the rear tends to skip & breaks traction easy - particulary in the wet.
Do suffer from wear on the outside shoulders on the front so if anyone else suffers from this???? Running standard torsion bars with winch, steel bar and scrubbies so am wondering if the extra weight is rolling the tyres onto the shoulders when turning as the front is bit soft??

see you in the scrub...
AnswerID: 53675

Follow Up By: DiesAl - Thursday, Apr 08, 2004 at 15:41

Thursday, Apr 08, 2004 at 15:41
Gday Reynard, I also have steel bar and srub bars no winch & I'm currently running 39.5psi in the front on Bridgie 693's so far no signs of wear. What are you running in the front?
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FollowupID: 315367

Follow Up By: Reynard - Friday, Apr 09, 2004 at 15:25

Friday, Apr 09, 2004 at 15:25
About 34-36. The wear is only on the outside shoulder & I would expect if it was related to the pressures it would be either both shoulders or the center, although I guess if I'm running to low the tyres would be rolling onto the shoulders when turning.
The front suspension is soft & dosn't take much to bottom out on washouts etc so I am at a loss as to the wear - regular alignments don't seem to change much????
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FollowupID: 315440

Follow Up By: DiesAl - Saturday, Apr 10, 2004 at 08:35

Saturday, Apr 10, 2004 at 08:35
Just a thought Reynard, have you asked them to pay particular attention to the camber angle as I believe too much positive camber angle can also cause what you describe, not sure if the tyre places check this as a matter of course, they may be only checking toe-in when doing wheel alignment, but then again I'm no expert on the subject and maybe they have to check camber angle as part of a wheel alignment.
Just a thought anyway

Happy Easter Mate
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FollowupID: 315499

Reply By: Paul's lot - Thursday, Apr 08, 2004 at 17:05

Thursday, Apr 08, 2004 at 17:05
It changes depending on the surface. My own preferences are 18psi heavysand 15 psi soft sand but I do go down to 10 to 12 in certain circumstances in this terrain but the lower you go the more prone you become to rolling a tyre off the rim and you must keep this in mind and avoid sharp turning with pressures that low for safety reasons.
22 to 24psi is what I use for general offroad. I used these pressures on the cordillo from Birdsville to innaminka kept the speed at around 90kph and never had any problem. Over sharp gibber like that your speed becomes as critical as your pressures.
There are probably hundreds out there that would rubbish my phylosophies but it has worked for me and as yet I haven't rolled a tyre off a rim or shredded one so I'm either lucky or somewhere around the mark.
Good luck with your ventures, there is no right or wrongs but just preferences and guidelines it's up to you to wade your way through them and decide what works for you. See ya buddy.
AnswerID: 53712

Follow Up By: DiesAl - Thursday, Apr 08, 2004 at 17:21

Thursday, Apr 08, 2004 at 17:21
Thanks Paul, do you apply the same rule for all brands of tyre or do you find some tyres handle these pressures better than others.
Mate whether anyone rubbishes your philosophies or not as you said it works for you and that's all that counts, I find it's good to speak to people and find out their views as it then gives me a starting point to begin the wading.

Have a Happy Easter and safe travels
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FollowupID: 315387

Reply By: Paul's lot - Thursday, Apr 08, 2004 at 19:52

Thursday, Apr 08, 2004 at 19:52
I have only used Kumho ventures, Kumho powerguards and olympic overlanders all in the 31x10.5x15 variety and all worked the same for me you take care too.
AnswerID: 53724

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