Tyre Pressures

[the BuTch3R]

Very interesting article (albeit from a Landy site) about recommended tyre pressures and common misconceptions.

http://www.landyonline.co.za/techtalk/t ... ssures.htm

How many of you are this meticulous about your own tyre pressures?

[ThysdJ]

What the man says is half right.... You need to drop tyre pressures in sand... Do we go to those extremes to calculate it? No, for 1 reason... Sand is not sand is not sand... It changes all the time... moisture content, time of day, heat, wind all plays a roll to make the surface, and traction abilities of sand different all the time... therefore, the optimum pressure is the one that allows your vehicle to move forward in soft sand... at that time...

[the BuTch3R]

Thanks Thys. That makes sense yes.

I actually stumbled across this article while researching tyre pressures for my own vehicle. With the 31" takkies on my SFA I could comfortably play around with off road tyre pressures anywhere between 1.4 and 0.5 Bar. Now with the 265 65 r17 on the Prado, I'm not as comfortable and struggling to find the balance between good traction and damage

[Johan Kriel]

As said sand there is sand and sand. Deflate only till you have good traction.

Sand is either water or wind polished smooth pebbles, and have very little resistance to pressure on it, but moisture, and temperature, and other material in it change that property drastically. Pre 4x4's, farmers used to stabilize loose sand with old kraal manure, and land lovers were not allowed to use the tracks, because they didn't spoor.

[the BuTch3R]

Now with the 265 65 r17 on the Prado, I'm not as comfortable and struggling to find the balance between good traction and damage

Anyone else running this size tyres?

What's you average offroad pressure for gravel, rocky trails, mud, sand ?

[Tenk]

Ek het nou 265/65/17 met brigestone duelers ek struggle om weg te kom in sand en moet langer aanloop vat. Onthou die tipe band maak ook n verskil. My 31/10.5/15's le in die garage wil hulle maar weer terug sit, is baie meer responsive met bfg's op.

[Tenk]

O ja en ek het altwee afgeblaas na 0.7 in sand.

[Hangover]

Volgens daai ding moet my standard driving pressure 0.9 bar wees op my 35 geo muds... Dink my trokkie sal lekker sag loop dan...

[ThysdJ]

A BFG only starts working in sand from 0.6bar or less....... because of the firm sidewalls

[4x4BEES]

Ek het die naweek wat verby was, by Outrekpad, 0.7 voor en 0.5 agter geloop op my BFG's.

Ek het oral saam met die groep gegaan en die selfde obstacles gedoen as hulle sonder probleme.
Ek was ook enigste diesel daar gewees.

Die voertuie was soos volg:

Ek het n 2.4D SFA sonder diff-lock en raised suspension op 33" bande
Franscois het n 3.0 straight 6 (cressida motor) SFA met diff-lock en raised suspension op 33" bande
Alex het n Colt Rodeo 3000i V6 met diff-lock en raised suspension op 33" bande
Eben het n 4.0 V6 Vigo met diff-lock en raised suspension op 32" bande

Volgens daai lys voertuie, moes ek baie gesukkel het, maar die regte band druk help n mens geen einde nie.

[ThysdJ]

Kevin hoekom 0.7 voor en 0.5 agter?

[Rianc]

Dis interresant. Ek was laas jaar op Kosibay met my boot, ek moes 'n midde weg kry met pressure, want ek het elke tweede dag dorp toe gery op die swart pad vir paar biertjies. So ek het besluit om my bande tot selgs 1.5bar te sak. Ek is met die boot en trailer oor lekker duineveld en het gevoel dit kon beter maar het oorleef. Het paar keer bietjie diep spore gemaak (onnodig sou my druk laer gewees het). Dit was nogals 'n groot uitdaging omdat my gillie my vertel het hoe hy vir meer as 5 ure 'n voertuig met 'n boot uitgrawe op die roete. Ek gaan nou Julie weer af en gaan die laer bandruk toets. Sal dan maar net vroer opstaan en begin pomp.

[4x4BEES]

Kevin hoekom 0.7 voor en 0.5 agter?

Daai bakkiekie van my het nog nie kragstuur nie.

So die bietjie hoer druk voor maak dit makliker vir my om hom te stuur.

Nog n rede is dat die enjin voor sit en ek kompenseer so bietjie vir daai extra gewig

[ThysdJ]

Jou redenasie is goed....

[the BuTch3R]

At vaatjie the weekend, started at 1.4 because of the lower profile tyres on the Prado.... got to the first sandy incline and no further. :roll:

Dropped to 1.2 and adjusted the loud pedal slightly and glided through those hills and turns.

......oh, and the 4.0 v6 under the bonnet didn't mind either.

[ThysdJ]

We deflate tyres to gain footprint size, and in doing so to gain traction, right?

Now, we have done this many many times to prove the point and those who did training with us can concur.. The biggest gain in footprint happens below 1 bar.

Come lets say you gain 20mm in footprint length with every 0.1 bar you go down below 1 bar....

Once you get to around 0.8 bar, you gain 20mm in footprint length for every 0.05 bar you go down and it increases "exponencially"...

So the gain in footprint length between 1.4 and 1.3 bar is 1/4 of the gain between 0.8 bar and 0.75 bar..

So especially for sand driving, if you only deflate to 1.2 bar, you might as well not deflate at all... Your biggest gains lie below 1 bar.. adn on BFG's they only start working at 0.6...

[the BuTch3R]

I hear you Thys. With the SFA I would usually have deflated to 0.8 bar. But surely with a lower profile tyre (265/65/17) one should be more cautious....not so?

[ThysdJ]

I hear you Thys. With the SFA I would usually have deflated to 0.8 bar. But surely with a lower profile tyre (265/65/17) one should be more cautious....not so?

Yes one should... One cannot use bar alone to deflate one must also use profile height..