Tyre Pressure?

Submitted: Wednesday, Jan 14, 2004 at 10:13
ThreadID: 9727 Views:1879 Replies:5 FollowUps:4
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Please tell me if this sounds right?

I have Hancook 31x11.5x15 tyres on my fj55, on the tyre wall it was pointed out to me by a mate that the tyre pressure when the tyres are cold should be 50psi, i used to take them to between 38-42 when re-inflating, until i saw this.

What do you guys think?
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Reply By: Member - Ed. C.- Wednesday, Jan 14, 2004 at 10:49

Wednesday, Jan 14, 2004 at 10:49
Synergist,
I think you'll find that the pressure marked on the sidewall will be the pressure at which the tyres' Maximum load is rated.. This will usually be marked on the sidewall as well...
38-42 psi seems about right for light-to-moderate load on a FJ55...

Regards, Ed. C.Confucius say.....
"He who lie underneath automobile with tool in hand............
Not necessarily mechanic!!"
AnswerID: 42907

Follow Up By: Synergist - Wednesday, Jan 14, 2004 at 11:34

Wednesday, Jan 14, 2004 at 11:34
Cheers, i thought it sounded a bit high.
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FollowupID: 305221

Follow Up By: Member - Ed. C.- Wednesday, Jan 14, 2004 at 12:25

Wednesday, Jan 14, 2004 at 12:25
BTW,
I was thinking of the back tyres when I replied earlier..
I reckon you could run 28-30 psi on the front with no problem...
It all depends on speed & load...
Would certainly soften the ride a bit..

Regards, Ed. C.Confucius say.....
"He who lie underneath automobile with tool in hand............
Not necessarily mechanic!!"
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FollowupID: 305225

Reply By: jemima puddle duck - Wednesday, Jan 14, 2004 at 12:31

Wednesday, Jan 14, 2004 at 12:31
gday synergist.
that pressure is wayyyyy to high.
with out a load run around 34psi.
then add according to your load.you reckon your cute
richard(eskimo)
but im a lot cuter

AnswerID: 42927

Reply By: Synergist - Wednesday, Jan 14, 2004 at 13:12

Wednesday, Jan 14, 2004 at 13:12
Cheers guys, being a newbie to this game, any help or feedback is much appreciated. So if anyone out there has advice or info on the old girl (fj55 76') that would be great!
AnswerID: 42930

Follow Up By: Synergist - Wednesday, Jan 14, 2004 at 13:18

Wednesday, Jan 14, 2004 at 13:18
Ha Ha, obviously a newbie to this site aswell, i just realised i sent that post to myself (idiot).
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FollowupID: 305227

Reply By: Andrew - Wednesday, Jan 14, 2004 at 16:15

Wednesday, Jan 14, 2004 at 16:15
Hmm Tyre pressures..
Quite simple really, you just need to take into account, the load on the tyre, the speed you are travelling at, the type of terrain, the type of tyre, The tyre size, colour and gender orientation then multiply it by the phase of the moon and divide the answer by two.

OK maybe not.

Starting point for tyre pressure is the tyre placard on the vehicle, this will give you the minimum recommended pressure for the standard vehicle, usually loaded and unloaded. This information is also available in the Tyre and Rim Association manual based on the tyre size.
On bitumen roads increasing the pressure will reduce the rolling resistance, however you should never go over the maximum printed on the sidewall. The stiffening effect of the higher pressure also improves steering responsiveness but the vehicle can become more nervous as well as riding harshly. The higher pressure also reduces heat buildup.
On gravel and dirt the higher pressures can lead to impact damage due to rocks and stones etc being forced into the tyre because the tyre can’t mould itself around the object.

The tyre and rim manual also shows the effect on load carrying of differing tyre pressures. The 31x11.5 R 15 LT varies from 665 kg @175 Kilopascals (app 25psi) to 1060 kg @ 350 kilopascals (app 50 psi). This applies for road speeds up to the design limit of the tyre.

When off road it is common to go lower than recommended to gain traction and improve the ride and this is possible because the ability of the tyre to handle a load goes up as the speed comes down. This requires a serious commitment to monitoring pressures and being aware of that dreaded tyre killer, heat buildup.

Where to start? Weigh the vehicle loaded, they are usually a lot heavier than you think. Get separate reading for front and rear axle then divide each by two to get the tyre load.
Check the tyre & rim manual (tyre services should have them) or the manufacturers website for minimum pressures for that load then add pressure till the vehicle feels good to you. If you get a large difference between hot & cold then you are probably running too soft for the conditions.

Off road depends on surface and speed, just remember that road pressures destroy sand tracks.

Enuff for know. I hope I got enough right to get you thinking

Regards

A
AnswerID: 42962

Follow Up By: Synergist - Wednesday, Jan 14, 2004 at 16:40

Wednesday, Jan 14, 2004 at 16:40
Yeah, it has got me thinking.

Seems to be alot more to it than the old "yeah that'll do gauge"

Thanks!
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FollowupID: 305256

Reply By: Dmitri - Sunday, Jan 18, 2004 at 19:51

Sunday, Jan 18, 2004 at 19:51
Hi Synergist !

Tyre pressure mostly depends on the load rather than other things.
There is one very simple and reliable way to maintain the correct pressure - the rule of thumb - cold pressure should be increased by 4psi after 1 hour of driving on bitumen.

Check out this link:
Tyre Pressures

Cheers,

Dmitri.
AnswerID: 43443

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