Lockers aren't always better.

Submitted: Thursday, Jul 29, 2010 at 16:45
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We are on the way home to Melbourne from Wiluna gathering and Canning.
The car hadn't seen dirt since Marree way and was getting grumpy so as soon as we hit the Vic/S.A. border I intended go south via the Big Dessert roads to home, but not having any coffee for an hour we pulled into the Pinnaroo coffee lounge via the rear entrance and partook.
Shortly after leaving Pinnaroo I realized we were on the road which lead to the less friendly S.A. desserts instead so I looked to turn around, but as we pulled up I noticed that a ute behind us also pulled up.

This young lady gets out and walks up and says, I noticed you lower your tyre pressures on leaving Pinnaroo. So I figured you must be heading into the sand, thats good, I have a map for you, I'm a local Ranger.
Eventually I noticed she had badges on her blouse and well I guess she was a Ranger, and a very observant one I might add.
Then she told me that the tracks were ok but a little cut up at the bottom end where the "Young ones like to play" but this shouldn't worry the older more responsible ones like you !

Well, now that I was offically recognized as a responisible 4wder, we accepted the map, pointed the car towards Firebreak track and a test hill I knew of and headed off on our real mission.

This mission was to determine if my car could get as far up a test sandhill with lockers on as opposed to open diffs.
It was a weekday, we had plenty of time and no else around to worry about so we took our time.

At the base of the difficult testhill the tyres were verified as 24psi, didn't want them to low as 18 would get me over the hill whereas 24 might not.
With open diffs we launch into the steep track which has many huge corrugations and whose surface is damp sand.

Up and Up we go, yes we will, no we didn't, but we almost made it, only 3m from the top, so after a neck twisting 100m long reversal the twin lockers are in and off we go again.
The car tries hard but its obviously struggling early on and ends up falling a significant 10m short of the open diff mark. Interesting, and a confirmation of my suspicions.

Why ?
My theory is that even 200kw pushing the lightly loaded GU's 2 solid axles caused massive axle tramp which quite simply equalled loss of traction!

Bit more playing with the adjustable shocks just re-inforced my conclusion that on this chopped up surface open diffs were better than lockers.

Still in responsibile 4wder mode we picked up some unsightly rubbish, dodged a huge bunch of Emu's who thought the track was made for them and headed for Broken Bucket and a nice warm campfire, our last of this month long trip - tomorrow would be cities, traffic and 492 unopened emails.

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Reply By: Michael ( Moss Vale NSW) - Thursday, Jul 29, 2010 at 17:14

Thursday, Jul 29, 2010 at 17:14
Robin!! So you think the standard Patrol with LSD Rear may have been a little better than two open diffs?? Michael
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Follow Up By: Robin Miller - Thursday, Jul 29, 2010 at 17:43

Thursday, Jul 29, 2010 at 17:43
Hi Michael

I suspect not - because an LSD is part way between and so probably is the performance.

My conclusion was based on the lockers causing the axles to be a big solid lump and removing this via open diffs or independant suspension (if you had same clearance) I think would work better.

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Reply By: gbc - Thursday, Jul 29, 2010 at 18:31

Thursday, Jul 29, 2010 at 18:31
Sounds like you were in auto locker country. :) Just fishing.....

Either way lockers are only going to help once you run out of traction on a given tyre.

If you hang out at a few extreme winch challenges and the like you'll see the drivers run open diffed as far as they can before hitting the switch - unless they know they'll need them of course.

Pro hill climbers use a computer activated traction control system over lockers - Big $$ stuff.

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Follow Up By: Robin Miller - Thursday, Jul 29, 2010 at 19:46

Thursday, Jul 29, 2010 at 19:46
I'm thinking that as issue is wheels bouncing off the traction surface that suspension control mods are way to go to get more out of this situation GBC
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Follow Up By: gbc - Thursday, Jul 29, 2010 at 22:34

Thursday, Jul 29, 2010 at 22:34
You already said you left too much air in the tyres. You'll have to go back to the hill and run it at lower pressure.
Adjustable shocks will help, because unfortunately the long single rate springs that the comp guys run are just what a load carrying tourer doesn't want.
Everything's a compromise........especially with the unsprung weight of a patrol axle, and the varying loads of a touring vehicle.
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Follow Up By: Member - Russnic [NZ] - Saturday, Jul 31, 2010 at 18:20

Saturday, Jul 31, 2010 at 18:20
Hi Robin
I am at Marla waiting for the roads to dry, I have my own reason for diff locks, only any use for conditions where a wheel may leave the ground.
Changing the subject, have you checked the back brake pads?. The wet might have made the dunes easy but the mud build up on the discs did nothing for the brake pads. I had the same problem as Howard did, a while later.
Pleased you had a bit of fun on the way to the Home Paddock.
Cheers
Russ
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Follow Up By: Robin Miller - Sunday, Aug 01, 2010 at 12:15

Sunday, Aug 01, 2010 at 12:15
Hi Russ

Just changed wheels here in readiness for snow trip and brake pads here seem to have not suffered like yours - maybe my several runs thru the about to be closed Todd river and its clean water dig the trick - I'm sure the car weighed 30kg less afterwards.

I am hoping to test lockers out again in deep snow soon and past experience indicates that axle tramp won't be an issue there and tyre pressures drop automatically in snow with below zero temperatures.

I guess your on closing stages - but if you wish to ad snow to your trip our Vic trip is the place next week.
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Reply By: Crackles - Thursday, Jul 29, 2010 at 20:14

Thursday, Jul 29, 2010 at 20:14
There is a perception even amoungst some experienced drivers that lockers are an advantage in sand and that's certainly not the case for most situations. Sand gives plenty of traction & thats why even bald tyres work as well if not better than mud tyres. If you engage a locker & turn a corner even slightly the wheels on the outside are going to need to travel further so will naturally dig in. If pressures are set correctly there is very little diagonal wheel spin so why would you need to engage a locker anyway.
The exceptions I've found are when restarting on a soft beach where I take the locker out as soon as I'm up to speed & on dune crests where a wheel may be lifted over a hole in which case it's put in & taken out immediately after.
On two occations now I've heard 1st hand of 100 series Cruisers blowing up CV joints as they engaged lockers while turning on full lock under power. The ironic thing was the locker was obviously not needed as both vehicles continued to drive out in 2wd for the rest of the desert unaided.
On my last crossing of the Madigan we didn't engage a locker once. Simply not required. I'm yet to see a locked diff car go any further up a dune or along a beach where the same type of open diff car couldn't and your little experiment appears to back that up Robin.
Cheers Craig................
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Follow Up By: Robin Miller - Thursday, Jul 29, 2010 at 21:06

Thursday, Jul 29, 2010 at 21:06
Yep agree with some of those observations Craig.

In this test I specifically went for the straight line but heavily corrugated section to see if axle tramp was the limiting factor , and it seems that it was.

It would really cheese you off if that after breaking a CV you could drive out on 2wd - I'd never live that one down.

For me now I need to investigate how to reduce the axle tramp - actually the whole car is feeling a little loose after its heavy pounding on corrugations lately and a few new bushes and kingpin bearings might need some attention as a first step.
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Follow Up By: ross - Thursday, Jul 29, 2010 at 21:59

Thursday, Jul 29, 2010 at 21:59
I remember pulling a locked 100 series off the beach a few years back with my trusty old FJ73.
Admittedly the 100 had rubbishy tyres but with them deflated and with lockers I thought it would have done better than my unlocked front and landcruiser rear LSD : )
The owner was a 4th time LC owner and had never been bogged there before.


Another time my 73 series(now with a 1HZ) went within cooee up steep sand dune against a hzj75 with lockers and turbo
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Reply By: Muntoo - Thursday, Jul 29, 2010 at 20:38

Thursday, Jul 29, 2010 at 20:38
Might be a little off the subject, but i got a question for ya.

My old Landcruiser Trayback was useless on sand, and still is i am told. It just digs in, and then the rear starts jumping, like its axle tramping. This is with 31''x10.5 and with pressures down to 20psi even. With or without weight on the back it was always the same. I would always go out with an 80 series, 120 Prado and they never had any probs. They didnt even need to drop there pressures, and most of the time the 80 was towing a dinghy.

Any suggestions, it really struggled to hold revs/speed once you got some up, but if you stopped it sank. Low 4 was needed and heaps of backing up and going forward.
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Follow Up By: Robin Miller - Thursday, Jul 29, 2010 at 20:59

Thursday, Jul 29, 2010 at 20:59
Hi Muntoo

I really think that if you went down a lot further it would help - not for the traditional long contact patch reason but for a similar reason to what this test showed. Check it out one day at no more than 15 psi.

This is that above a certain point the tyre/suspension cannot confrom to the surface and this causes axle tramp and loss of traction , cars with longer travel suspension can lower this point with tyres up harder.

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Follow Up By: ross - Thursday, Jul 29, 2010 at 22:11

Thursday, Jul 29, 2010 at 22:11
I too would try 15-17psi but I have gone as low as 8psi to get off the beach and away from an incoming tide.

As Robin pointed out suspension is also big a factor.
Good articualtion allows the drive wheels to maintain contact with the ground.
The more you deflate the tyres,the more it can make up for lack of articulation
There is also a big difference when you go the next size up in a tyre.

The other big factor in sand driving is horsepower/torque.
To get on top of the sand and "surf" you need the power to get the speed.
This is one instance when petrol engines (generally) do better than their diesel brethren.
Any Landcruiser with HJ or BJ in its desgnation will not be great on sand (except a HJ61)
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Follow Up By: Muntoo - Thursday, Jul 29, 2010 at 22:50

Thursday, Jul 29, 2010 at 22:50
Thanks fellas, i will past that onto the new owner as he wont go near sand with it. I always thought a lower pressure would be better.
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Follow Up By: Member - Bucky - Friday, Jul 30, 2010 at 07:20

Friday, Jul 30, 2010 at 07:20
ross
I totally agree !
8psi will get you out of trouble, if you need to.

A little momentum is also handy, and that does not mean speed.

Cheres
Bucky
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Reply By: Member - Bucky - Friday, Jul 30, 2010 at 07:17

Friday, Jul 30, 2010 at 07:17
Robin
Nice lesson learnt, and demontrated !.

Yes I remember at the base of Big Red, in 2006, 2 blokes in the bleep at 10:00 am were gunna eat the dune,
" we god diff locks and a 200 kw chip" weree the words of the driver

I just let them go and dig heaps of holes.
After 10 or 12 goes, I just checked my tyres at 15psi, and went straight up, one go.

That was bad enuf, for them...so then we had a 16 year old L plate driver with us, and I let his tyres down to 12 psi (I told him they were 15) and after 3 goes he went up ( lack of experience )

Those guy's almost cried, then they listened, and they too got over.

Hope all went well with your trip. It's abeautiful country out there.

Did you do any of the CSR ?

CheersMate
Bucky

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Follow Up By: Robin Miller - Friday, Jul 30, 2010 at 07:55

Friday, Jul 30, 2010 at 07:55
Hi Bucky

Like your comment "you told him they were 15" , why is it some seem so concerned about really dropping pressures all the time - even experienced that on our Canning trip , although the arguement was presented that high pressures were preferred to sidewall bulges.

Did go up Canning , tried to take our time but weather wasn't inviting so we keep moving and went thru in under 10 days , wil go back one day though !
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Follow Up By: Member - Bucky - Friday, Jul 30, 2010 at 08:41

Friday, Jul 30, 2010 at 08:41
Robin

Nothing erks me more than when people are mis-informed, then become experts.

The way I see it, tyres are expensive, but no where near as expensive as, say blowing clutch, because you cannot be told. Drop your pressures, and slow down, it's the best way to preserve your vehicle. And above all, drive defensively in rough going.
One bloke told me that he was not prepared to drop tyre pressures below 28psi because of weight. What a load of crap. !... He too could not get up Big Red.

Get good tyres ( a whole new debate ) and if you need to drop pressures to get the job done, then also drop your speed accordingly.. My combinatioon of 12, 15 and 12 psi means a top speed of 50-60 km/h, in good going, works incredibly well. Don't want tocook them.
We were loaded up and I run 15 in the rear of the Patrol, and I am still using those tyres today, a little sad for wear, but the integtity of the tyre is still 100 %.

Cheers
Bucky
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Follow Up By: ob - Friday, Jul 30, 2010 at 12:29

Friday, Jul 30, 2010 at 12:29
Agree 100% Bucky and well said, irks the hell out of me too when I find some track, sand or otherwise corrugated to hell by some a- hole who is too lazy or too stupid to get out and lower tyre pressures and speed to suit the conditions and charges repeatedly doing more and more damage and making it harder for those that follow.
On the subject of diff locks my personal preference is for manual operation that I can control rather than auto "unlockers" that make their own minds up as to whether they are locked or not.
Diff locks or not good suspension travel is extremely important.

ob
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Reply By: garrycol - Friday, Jul 30, 2010 at 09:54

Friday, Jul 30, 2010 at 09:54
About 12 years ago when Land Rover introduced four channel traction control to their cars a car mag did a test to evaluate the usefulness of various forms traction aids. The test was basically driving up a sandy (big red type sandy) hill. They had a number of cars drive up and down first to chop it all up then groomed the slope (like a ski slope) before each run so that each test would be driving on a similar surface.

They used discoverys as the purpose was to test the effectiveness of the silly decision to remove the centre diff lock on the D2s. They also had a modified D2 with a CDL activated.

The results were basically:

Open diffs - no traction aids - no CDL - about half way up
Open diffs - no traction aids - CDL on - just a little bit further (only about a m or so)
Open diffs - traction control on - no cdl - about the same as the previous test
Open diffs - traction control on - cdl on - about another m further up the hill
Diff locks on - traction control on (but it does not activate with diff locks on) - cdl on - all the way to the top.

The test showed that Land Rovers decision to remove the CDL was a bad decision (actually a BMW decision) (later corrected) and that Traction Control works well but the best traction aids were Diff Locks.
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Follow Up By: Member - Bucky - Saturday, Jul 31, 2010 at 03:16

Saturday, Jul 31, 2010 at 03:16
Diff locks are no good in sand mate !
Drop your pressures, that's all you have to do ..15 psi is common ,but be prepared to go 8 psi, if you have to..

You can feel the vehicle climb out of the soft stuff, and easily go up the dunes, on the top of the sand.

I liken it to a ski boat "plaining"..

Cheres
Bucky

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Reply By: River Swaggie - Monday, Aug 02, 2010 at 14:49

Monday, Aug 02, 2010 at 14:49
Hiya Robin longtime no see...

I was always under the impression (read articles) that diff locks in the sand are basically crap...Sure its a quick summary...lol


Catch-ya..
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Follow Up By: Robin Miller - Monday, Aug 02, 2010 at 17:47

Monday, Aug 02, 2010 at 17:47
Hi Swaggie

It is a while.

Their are various sand conditions , some of which I think a locker may help in like this straight line run I setup on rough ground , but I think all I did was show up suspension issues and this probably masks the result.

I was hoping someone may have results that remove this from the picture , because I guess whereever 1 wheel spins first the locker should be able to provide some assitance.

Hope we here more from you !

Robin Miller

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