Opening a can of worms....(tyres pressure)

[tonto73]

Hi all,

I know i am opening a can of worms but.....

I am trying to look up some info regarding next choice of tyres and also pressures for my existing set (michelins). When i bought the Disco a couple of months ago the previous owner had the tyres at around 38 psi all round. I changed the pressure to what it calls for in the handbook. 28 Psi front and 38 Psi on the back. I had a steering wheel vibration at around 100k's per hour and i have changed the spare over as one of the rear tyres was almost bald so i have set it back to 38 Psi all round until i get a wheel balance.

What does everyone else run ???

I looked up tyre pressure in the common threads however it led me nowhere. In the meantime i will do a search on tyre pressure and hopefully get some feedback from you guys.....

[George130]

I have BFG Mudds and run them at 50psi on road. This is higher than most of the users on the forum.

[one_iota]

Hi all,

I know i am opening a can of worms but.....

I am trying to look up some info regarding next choice of tyres and also pressures for my existing set (michelins). When i bought the Disco a couple of months ago the previous owner had the tyres at around 38 psi all round. I changed the pressure to what it calls for in the handbook. 28 Psi front and 38 Psi on the back. I had a steering wheel vibration at around 100k's per hour and i have changed the spare over as one of the rear tyres was almost bald so i have set it back to 38 Psi all round until i get a wheel balance.

What does everyone else run ???

I looked up tyre pressure in the common threads however it led me nowhere. In the meantime i will do a search on tyre pressure and hopefully get some feedback from you guys.....

There is a rule called the "Pirelli 4 psi Rule" that applies to highway driving. Measure the tyre pressure when the tyre is cold. If after 20 minutes of driving at 100 kph the tyre pressure is 4 psi above the cold temperature pressure then the pressure is right. Any more then the cold temperature is too low and if it is less then the cold pressure is too high.

Nice theory....start with the placard pressures at cold tyre temperatures and experiment.

If you air down for off road it depends on the surfaces (rock, sand, corrugations, loads carried)....more experimentation.

[discoute]

here ya go old debate.

http://www.aulro.com/afvb/showthread.php't=27684&highlight=recomended+tyre+pressures

glen

[harro]

There is a rule called the "Pirelli 4 psi Rule" that applies to highway driving. Measure the tyre pressure when the tyre is cold. If after 20 minutes of driving at 100 kph the tyre pressure is 4 psi above the cold temperature pressure then the pressure is right. Any more then the cold temperature is too low and if it is less then the cold pressure is too high.

Nice theory....start with the placard pressures at cold tyre temperatures and experiment.

Live & learn, haven't heard that one but I will certainly try it!;)

[Slunnie]

I think that you will find that tyres will operate through a fairly broad range of pressures. In my opinion there isn't a great deal of difference when you get over about 30psi through to 40psi or so. Some tyres are more sensitive than others though, especially those with thin sidewalls. LR recommend 28psi, I run 36-40psi and both will probably drive on the road well - 28 being softer and doughier, 40 stiff and precise.

Back to your question though..... 36 - 40 psi all round on radials. I think about 36 is good though.

For lower pressures when offroading, you may also find this interesting (Simex bias ply related):
http://www.slunnie.com/phpBB/viewtopic.php't=4

[one_iota]

I think that you will find that tyres will operate through a fairly broad range of pressures. In my opinion there isn't a great deal of difference when you get over about 30psi through to 40psi or so. Some tyres are more sensitive than others though, especially those with thin sidewalls. LR recommend 28psi, I run 36-40psi and both will probably drive on the road well - 28 being softer and doughier, 40 stiff and precise.

Back to your question though..... 36 - 40 psi all round on radials. I think about 36 is good though.

For lower pressures when offroading, you may also find this interesting (Simex bias ply related):
http://www.slunnie.com/phpBB/viewtopic.php't=4

And it gets more complicated when you have been driving at 23psi off road and the tyres are warm and you fill them up with cold air to highway pressures...you end up way below the ideal highway pressures by about 4psi.;)

I can tell by fuel consumption :eek:

[LoadedDisco]

I have BFG Mudds and run them at 50psi on road. This is higher than most of the users on the forum.

Interested what size tyre are they and how much on road work do they do at that pressure and what the where on the tread is like after ? Km.

I have B . F. Goodies Muds and run them at 41 psi on road (255x70xR16).
Off Road I run them around 28psi.

[DiscoDave]

First thought... How accurate is your gauge? Never trust the gauge at a servo.
Second thought... I run a D1 with 235/70R16 Michelins so my specified pressures may be different. (I think it's 28 psi front, 34 psi rear) To be honest I don't bother about it much. Before I got off-road tyres I used to inflate the Michelins to 30-something all round when airing up and never noticed any difference (I have almost no load in the rear). The only time I did notice anything was on the second set of Michelins when the installer put about 40psi in them and the ride made my teeth rattle before I realised what it was.
Bottom line - no tyre pressure combo has ever caused me steering vibration, it's far more likely to be due to balance, alignment or mechanical problem.

[Redback]

Funny thing about tyre pressures is what suits one person doesn't suit another, (ie) me and Slunnie (we have the same springs and lift) our Discos are pretty much the same, only differance is tyre size and type, now i've found that the Land Rover recommended pressures are good for me, 28psi front 38psi rear, i increase the rear to 42psi and the front to 30psi when loaded and the trailer on, for me this is the best handling wise, i find the Disco tracks better at these pressures.

Offroad is a whole other can of worms:tease:

Baz.

[JDNSW]

Like One Iota, I would start with the placarded pressures. Any pressure is a compromise - you are trying to get a comfortable ride, good handling and maximum tyre life, and these probably require three different pressures (and all vary with speed, load and road conditions) so you have to decide how you want to balance the tradeoffs.

Note that the "best" pressure will not usually vary very much for different brands of tyre or even size (within reason) - the variation with load and speed will probably be a lot more. Handling is likely to be more affected by ratio of front to rear pressure than actual pressure once the pressure is high enough for the tyres to stand up reasonably well.

I find it interesting that since Landrovers were introduced, the recommended tyre pressure has steadily increased - The 80" recommended 20/26, 20/30 (F/R,loaded), my S2a handbook has(109) 25/25, 25/36 or for radials 20/20, 20/35, and my S3 handbook for essentially the same vehicle and the same tyres, has increased the radial pressures to 25/25, 25/42. My 110 has pressures from 35/35 up to 45/65 depending on load and speed, radials only. To some extent I think this increasing pressure is because of increased typical highway speeds.

I don't think there is a single or simple answer to your question - as I think you realise given the comment about worms!

Steering wheel vibration at 100km/hr in my experience is often due to out of balance front wheels.
John

[George130]

Interested what size tyre are they and how much on road work do they do at that pressure and what the where on the tread is like after ? Km.

I have B . F. Goodies Muds and run them at 41 psi on road (255x70xR16).
Off Road I run them around 28psi.

They are 285x75xR16.
Since I bought the vehicle its done 60,000km, They were on it when I bought it. Most of that has been highway travel. The tyres are now down to 5mm at best on the tread.
I have foud at the high pressure it is harsh but the thing is presise and goes exactly where you point it, It's also noticbly better on fuel consumption and seems to maintain its pace more easily.
As for the accuracy thing I normaly use a servo to pump them up so accuracy is ????

[LoadedDisco]

They are 285x75xR16.
Since I bought the vehicle its done 60,000km, They were on it when I bought it. Most of that has been highway travel. The tyres are now down to 5mm at best on the tread.
I have foud at the high pressure it is harsh but the thing is presise and goes exactly where you point it, It's also noticbly better on fuel consumption and seems to maintain its pace more easily.
As for the accuracy thing I normaly use a servo to pump them up so accuracy is ????

Thanks I will test them at 45psi for two weeks and see what happens with feel and fuel. :)

[tombraider]

Honestly... Speak to a tyre expert. (A real one not some pimply faced bloke at Bob Jane)

28 psi is too low for a 4x4 tyre.

I have had several meetings with Cooper and Mickey T guys and all of them have commented that manufacturers recommendations are based on ride quality goals for their specs..

Nothing to do with handling and tyre wear etc...

On Michies I'd say 34 F/ 38R

On 285-75-16s 36-38 front/36-40 rear.

Tyre design plays a part in ride, number of plies, actually thickness of plies, tread depth, siping, tread pattern, thickness of rubber in carcas...

All play a major part...

Tombraider

[tonto73]

Thanks to all for the replies. I will try some different pressure on my Michelins. They are the 235 70R 16's.

I will also look into the 4 psi cold/warm thingy-me-jig rule and give that a try as well. Just got to remember to test them before and after with the same guage.....

Cheers:D

[stevesub]

On the Rangie we run the standard pressures 28/38 all the time on and off road - using the standard expensive Lichelin tyres.

On the Troopy, we run 35/55 as per the handbook on and offroad. We did run them for a couple of years at 40 all round but had several blowouts on the rear that indicated too low a pressure

Don't listen to the tyre people as it was their recommendation to run lower - several tyre shops and talking to the managers all say that I am mad to run at 55psi but I don't have blow outs and that is what the handbook says. We are running 750-16 tyres which are different from most other tyres anyway.

Even offroad, they work well at that pressure, getting up a sandhill last weekend with no problems where 2 Discos could not even get halfway up. Also towed a dead Landie we found on the beachover 100m or so of soft dug up sand at the beach exit with no problems when a Disco had 2 attempts to get through.

[ak]

When I use to get the car serviced with the stealer they use to drop the pressure to 32 - 34 psi. When I asked why they said it's a good pressure for comfort. I run 36 - 38 all round. I just try and stay in that range. Find it's a good compromise between comfort, handling and tyre wear.

[LandyAndy]

Hi
I have 255/70 Cooper ST's Front 36 Rear 38.If towing a big load or she is loaded up for a trip I go 40 to 42 on the rear.
It rides alot harder with the 36 upwards pressure but its a hell of a lot safer on our crappy country roads.
Andrew

[Kenjo]

I found that Land Rover got it right with my D1 which is specified 28 psi front & 34 psi rear (cold pressures). Good ride/handling and 100,000km life span for both Michelins and BFG A/Ts. I do put in a few pounds more when towing and naturally drop down for gravel and sand.

I used to own a Michelin dealership and found most customers were more interested in tyre life rather than ride comfort or even road handling. Most vehicle manufacturer’s tyre pressure recommendations tend to ere toward the comfort end. This is generally 4 to 6 psi below optimum pressure for longevity. The lower than optimum pressures result in outside edge wear with heaps of tread left in the middle (assuming alignment and balances are correct. Of course the opposite happens when over pressured – the center tread wears first.

Cheers,

[discoute]

On the Rangie we run the standard pressures 28/38 all the time on and off road - using the standard expensive Lichelin tyres.

On the Troopy, we run 35/55 as per the handbook on and offroad. We did run them for a couple of years at 40 all round but had several blowouts on the rear that indicated too low a pressure

Don't listen to the tyre people as it was their recommendation to run lower - several tyre shops and talking to the managers all say that I am mad to run at 55psi but I don't have blow outs and that is what the handbook says. We are running 750-16 tyres which are different from most other tyres anyway.

Even offroad, they work well at that pressure, getting up a sandhill last weekend with no problems where 2 Discos could not even get halfway up. Also towed a dead Landie we found on the beachover 100m or so of soft dug up sand at the beach exit with no problems when a Disco had 2 attempts to get through.

If your 750x 16 tyres are 8ply "RATING" the pressure limit as stated in the Australian Rim & Tyre Association Standards Manual is if fact 50 psi. these standards are normal tyre and rim engineering and a point of law. You will find these managers are giving you safe information based on the manual and experiance. All tyres sold for use on Australian roads must fall into the engineering guidelines as set out in this manual.

glen

[harro]

Defender xtreme.
High 30's front
40'ish rear.
25 all round off road (mainly for comfort) but I will go down into the high teens if I need the traction.
Really depends on the surface.

[barney]

I run BFG muddies on my defender yoot. 255/85/R16 which have a max pressure of 65psi. i run these at around 45psi. i do this mainly for the simple reason that i don't have power steering and any lower pressures thn that and you just about pop a shoulder trying to turn the wheel. a this pressure i got 90,000km from them. this included a 7000km innamincka/birdsville/simpson/ghan/mereenie loop/oodnadatta track trip. on this trip pressures were maintained at 45 to 50 depending on load except in the sand where they were run between 23 and 28 psi. no problems with bogging or fuel consumption (V8 in the simpson averaged 22l/100k). the weight in the ute kept the tyres bagging and the footprint large.
other roads (ood, diamantina, mereenie, ghan) were run at typically around 80km/h-100km/h on which the tyres were run at 45-50psi.
4 weeks, 4 cars with similar rated muddies, no punctures. 1 with bigger, lower load rated muddies=10 punctures.....running 32psi. draw your own conclusion!

[DEFENDERZOOK]

I found that Land Rover got it right with my D1 which is specified 28 psi front & 34 psi rear (cold pressures). Good ride/handling and 100,000km life span for both Michelins and BFG A/Ts. I do put in a few pounds more when towing and naturally drop down for gravel and sand.

I used to own a Michelin dealership and found most customers were more interested in tyre life rather than ride comfort or even road handling. Most vehicle manufacturer’s tyre pressure recommendations tend to ere toward the comfort end. This is generally 4 to 6 psi below optimum pressure for longevity. The lower than optimum pressures result in outside edge wear with heaps of tread left in the middle (assuming alignment and balances are correct. Of course the opposite happens when over pressured – the center tread wears first.

Cheers,




about 90% of the tyres we change at work are from worn edges due to underinflation......
basically....people dont check their pressures.....

all they seem to check is the fuel guage (occasionally).....and their wallets....
the other 8% is from damage/slashed carcasses....mainly from hitting kerbs.....
and about 2% actually worn evenly across the tread.....
these tyres are the only ones that ever seem to have any air in them.....

when checking tyre pressures on regular services.....most cars only have between 12 and 22psi.....
and the spare is usually dead flat.....
and these are the people that complain that their tyres dont last long and want a different brand.......