tyre pressure

[dullbird]

hi

can someone give me an idea of what sort of pressures we should be running the disco on here in this heat as we are not sure the disco is on 16's i think and is running a/t

we have been running he 90 on 35 in the uk but not sure here with the heat and stuff

thank you
dullbird

[one_iota]

Hi again,

Tyre pressures and the Meaning of Life eh :wink:

There is the 4 PSI rule that says that the tyre pressures are right if after say 20 minutes of highway speed driving the pressure of the tyre when measured warm is 4 PSI higher than the pressure when measured cold....hmmmmm...far too scientific for me (I'm into Intelligent Design Not).

35 PSI is a good start and then experiment as it depends on the load and the road temperature and the speed and the roughness of the road and the ambient temperature etc etc

Start with the placarded recommendations.

Don't to be too precious about pressures for day to day driving except if they are below 30 PSI and above 40 PSI on road.

You're on the right road though. https://www.aulro.com/afvb/

[DEFENDERZOOK]

<span style="color:blue">lurch runs 40psi front and rear when i remember to check them........



your recommended tyre pressures should be 28 front and 38 rear.......

most of us reckon that 28 in the front is way too soft for on road......</span>

[George130]

In the ford we run 32psi and in the fenda I run between 40 and 50 psi. Good on the fuel but might be a hard ride but then muds on a defender aint designed for the ultimate ride comfort anyway 8)
I up it to 50 for long trips and just check them every now and then normally and up them to at least 40 if they are low.

[weeds]

i run

hi way 40
long drves onthe dirt 30
sand 20

[LandyAndy]

Hi Dullbird
Chasing fuel economy I put my Disco2 tyres(Cooper Discoverer ST 255/70x16) up to 34 front and 36 rear.I have just dropped them back to 32 front 34 rear as it was too harsh with our POO QUALITY ROADS(I work on roads for a living and there is a huge room for improvement,roadtrains are destroying our roads)
I was running30/32 and will drop back to that if the ride is still too hard.
My Disco has done 205000Ks so it probably needing a set of new shocks.
Andrew

[disconut]

I like simple numbers, so I run the fender 300kpa rear (280 placard), and 200 kpa front (190 placard).
In english that translates to 29psi and 43.5 psi.

Tyres are 235/85/16 Grabbers, (standard rubber off the showroom floor).

Trev.

[CraigE]

I generally run 38-40psi front and 40-42 psi rear. I find too low in the front makes the steering less responsive and causes premature wear. Sometimes there is a big difference in what the car manufacturer and the tyre manufacturer recommend. Most 4x4 tyres I have used recommend 35-40psi and some up to 50psi. On normal sedan tyres it is lower and I normally runn these at 32-35psi.

[MickG]

I have 265/75/16 Muds on my D2 with fairly firm suspension and I normally run the following.

Road (day to day) - 30psi all round
Longer road trip - 35psi all round if empty, 35fr 40r if loaded
Short gravel road sections - 28 all round
Off road, rocks, low range stuff - 22psi

I have just gone by feel really but have found these to be adequate. Speed is really the dictating factor when dropping pressures.

Good luck

[rick130]

wow, I'm running much lower pressures in the 'fender with BFG MT 255/85's than the majority.
Generally 1/2 tonne+ in the back, fully loaded with bar work, winches, etc. 30-32 psi in the front 30-34 psi in the back, 26 psi on pure gravel.
A little bit sloppy in turn in response, (I put this down to tread squirm on a full tread depth muddy. This can really be felt when going from less than 3mm tread depth to new 14mm tread ) but best overal tyre wear/grip for this combination in the 130. Just replaced them and was at 57,000km, and almost down to the tread wear indicators with even wear. I travel a mixture of gravel/broken rough bitumen/highway everyday, and am known to push on a bit in corners (momentum is my friend https://www.aulro.com/afvb/)

FWIW, we run 34psi front, 30-32 psi rear (empty) (36-38 towing) in the Patrol ute with BFG AT 265/75/16's. Running similar pressures in Cooper ST's went 80,000km with relatively even wear.

[p38arover]

I run the recommended pressures in my P38A and did the same in my previous RRs (classics), i.e., 28 front/38 rear. On a long trip (500km) at highway/freeway speeds I may add 4 psi front and back.

Interestingly, this question came up on the RR forum and John Robison (JE Robison Service - LR specialists) says there should be a differential between front and back. Don't run the same pressures. See http://rangerovers.net/forum/viewtopic.php...a376ba465240062 (http://rangerovers.net/forum/viewtopic.php't=4968&sid=8ea908bc935abdda8a376ba465240062)

Robison claims the difference in tyre pressures provides stability. I had a rear tyre blow on the freeway (in the P38A). I heard it and wondered what the noise was. It wasn't until I saw the smoke that I realised it was my car. By tthe time I'd stopped, the tyre was shredded - not just missing a tread - and I hadn't even felt it. The P38A was rock steady.

Ron

[rick130]

<div class='quotetop'>QUOTE</div><div class='quotemain'>The difference in tyre pressures provides stability.[/b][/quote]

never heard that before. I had a blow out a few years back on the Putty road (Colo Heights end) on the right front @110km/h in a right hander.
Luckily it was the more lightly loaded side, and the 'fender tracked dead straight even under braking until the stop. It was an instant deflation, and I was driving on the rim. I was also running almost the same pressures front and rear. (IIRC @ 36 psi Bridgestone 235/85 MT's)

Generally, the tyre placard is a very good starting point, although the tyre placard for the 130 recommends 75psi in the rear in ALL conditions. (laden and unladen) If I ran that I'd have no tread in the centre of the tyres in about 5000km, the back end would be skipping all over the road, and I'd probably slash them to bits before that distance on our lovely gravel roads. Even with the OE Michelin XZL's, I started @ 50psi and dropped from there. Different tyres from OE also have differering constructions, with some being quite a bit stiffer or softer in the carcass, and so need a slightly different pressure to suit a given situation. Of course if the tyre size is different to OE, everything changes. Generally, a larger tyre (taller/wider) doesn't need as high pressures as a smaller one due to its greater internal volume, although this doesn't always hold true if the tyre uses a realtively soft sidewall/pliable case. More pressure may be needed here for support.

In road cars, I always ran more pressure in the front than the rear as there was much more weight over the front axle, as I do in our Patrol. (unless carrying a load) Any front engined race car I had anything to do with always ran more presure in the front than the rear for this reason. This was also borne out with lap times. Mid engined cars, even with their greater width/larger volume rear tyres always ran the opposite. e.g. Formula Fords run 17psi front, 19 psi rear hot pressures. Race tyre pressures are always checked hot, and adjusted accordingly. e.g. Cold days/weather, starting pressures may be higher, or a non abrasive track surface would use a higher starting pressure to achieve your hot optimimum running pressure. Differing suspension setups also require differing starting pressures, as they can work the tyre carcass differently, generating lesser or greater temperatures and consequently pressures.

Interesting fact on wet weather pressures. Any race car I ran that didn't use specialist wet weather tyres used much higher pressures in the wet than the dry
It didn't matter wether they were bias ply (Formula Ford, Historic Touring Cars, etc) or radials (production cars)
Any time I'd let the tyres down (at the request of a driver, 'cause everyone else was doing it) I'd be abused and we'd be as slow as everyone else. (I was accused by the driver at my first Historic meet with an XU1 of trying to kill him after setting the pressures where he insisted. He then proceeded to drive through the field in the second race and place, and he was a very cautious driver who hated the wet https://www.aulro.com/afvb/)
A couple of things are happening here. One is that the channels in the tyre are more defined with the higherpressure, the second and main one I think is that the reduced contact patch worked the centre portion of the tread much harder and actually was able to generate some sort of heat to generate grip. The tyres were always too cool after a race to actually check this with a pyro, but the fact remained that the cars were always much nicer to drive and much faster with silly high pressures.

[CraigE]

It seems there are some discrepencies between what vehicle manufacturers recommend and what tyre manufacturers recommend. I find that if I run the front at around 28-30psi it is a lot harder on the turns and sluggish. Also find that tyres tend to wear. I usually run the fronts at 40 and rears at 42. I find light responsive steerin better, but it would be each to their own as long as it is safe. As previously mentioned tyre design and construction varies so refer to the tyre manufacturer ratings. Some tyres even say to run at 50psi.
At 2-30psi the front tyres actually look flat to me. :?:

[Defender200Tdi]

<div class='quotetop'>QUOTE</div><div class='quotemain'>wow, I'm running much lower pressures in the 'fender with BFG MT 255/85's than the majority.
Generally 1/2 tonne+ in the back, fully loaded with bar work, winches, etc. 30-32 psi in the front 30-34 psi in the back, 26 psi on pure gravel.[/b][/quote]

As with Rick, I'm also running much lower pressures than the rest of you. BFG M/T 255/85s with ARB bar and winch on the front. Normally 32psi front and 35psi rear, unless really heavily laden, in which case I might bump the rears up to 40psi. On straight gravel, 25psi all round, and on sand, 18psi all round.


Paul https://www.aulro.com/afvb/

[incisor]

I spent many many hours and miles playing this game and found that running the placard trye pressures were the best settings...

definetly agree that the pressure difference between front and back makes a major difference to stability, slightly more so in the v8's than the tdi's but there is a very measureable difference.

[DEFENDERZOOK]

Originally posted by incisor
I spent many many hours and miles playing this game and found that running the placard trye pressures were the best settings...





[b]<span style="color:blue">running the recommended pressures will work best with the original tyres and setup of the vehicle.....

when accessories are added(more weight) and better off road tyres....
different pressures will be needed for best results......


there is no right or wrong for the vehicles once things have been changed from standard.....
all there is is a guide like you will find on this thread from different experiences......


so there is no real or simple answer....only a guide....</span>