The old Tyre debate

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02 Nov 2012 21:55 #1 by dandjcr
dandjcr created the topic: The old Tyre debate
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Dave and Pauline Gray
Member
Posts: 84
Good day Dean i thought it best to start a new topic i.m still a bit confused on the sizeof the wall issue i assume your measuring the wall from the bead to the crown of the tread and you are saying the longer the measurment the taller the tyre the cooler it should run because the tyre has a bigger volume of air for a given pressure an interesting theory one which i hadnt given any thought to , your quite right about people who go out on these trips and believe that high pressures and a rooster tail of sand from each wheel and speed is the anwser to conqering every sand hill but usally old mother nature has the final say with usually a repair bill that you wouldnt get if if they put the brains back in, we encoutered our fist sandhill problem just south of well 12 I still was running 40 psi but one look at it told it was time to adjust things during the course of this [waiting for my tyre deflater to do her bit] i grabed a handfull of sand from the wheel tracks and it had the consistensy of flour virgin sand alongside was quite coarse this caused an immediate re think on the pressureswe had decided to try and let them down a nother 5psi i may have got over at the higher pressure i dont know but we did the oka .thing and went over slowly. We all think we have best fomular but really it amounts to what ever works for you is right, Iv waffeled on enough again it must be getting that time of the year when i start looking to the north ha ha cheers Dave
February 3, 2011 at 1:22 PM Flag Quote & Reply

Dean & Kaye Howells
Member
Posts: 79
G'day Dave, Just a theory of course, I'll try and explain a bit better (not one of my strong points). Tyre wall height is measured as a percentage of tread width. eg 255/100R16 Michelins have a tread 255mm wide and a wall height 100% of this, 255mm. All 19.5" tyres (mainly for use on prime mover trailers) are '70 series' tyres, that is with a wall height 70% of tread width; so a 265/75R19.5 has a 265mm tread width with a wall height of 185mm. So whilst the tread is marginally wider the wall height is substantially less, 60mm less, for the 19.5" tyre. Whilst this is good for carying heavy loads on the bitumen, ie. small wall height equals small wall flex which results in less heat generated compared to a higher aspect ratio tyre, (more rubber to flex creates more heat). This is a good thing for highway travel.
Off road it's a different story, when you let your tyres down they 'bag'. This gives you a longer and slightly wider footprint which is the main aim of the exercise, a decrease in ground pressure. It also allows the tyre to act as a damper or shock absorber particularly when driving on corrugated surfaces. The more you bag the tyre the greater the tyre flex and the greater the heat generated. The more air you've got in the tyre the greater the heat required to increase its temperature so the more air volume the better (within reason). The bigger wall height also gives more room for tyre deformation. ie. when crossing rough terrain the chance of 'pinching' a tyre or tube against the rim is less. The bigger the wall surface area the greater the the ability to dissipate heat as well. This is fine for relatively low speeds off road. The faster you go the more rapid the wall flex, the greater the heat generated ..............................bang (blowout).
Hope that makes some sort of sense, I am quite happy to listen to counter views.

One of the reasons I went for 305/70R19.5's was the increase in wall height compared to say 265's or 285's. Wall height for the 305 is 213mm, for the 265 is 185mm and for the 285 is 200mm. Another reason is that the rolling diameter of the 305 is pretty much the same as the old 900R16.

The need and desirability of running lower tyre pressures 'off road' is to me quite obvious and normal, unfortunately this is not the case for drivers more used to driving 'on road'. This may be because, to urban drivers, deflated tyres are synonomous with blowouts. Another reason is that 4WD hire car companys invariably tell their clients to keep tyres pumped up hard (greater tyre life) or maybe just ignorance but is very common.
I spoke with a lady in a high roof Troopy at the Gibb River ford on the Kalumbaru Road last year who complained bitterly of the (quite deep) corrugations and how she could not 'cope' with the discomfort of driving any further. She had the usual 7.50R16's which were perfectly round, 60 psi minimum probably more. She was quite indignant and regarded my suggestion of reducing tyre pressure as a very foolish proposition. "Didn't I know anything about driving on dirt roads ?", she took off in a hail of stones obviously one of the 'speed is best over corrugations' school.................sigh.
This mis-understanding of tyre pressures and dirt road driving is very common amongst travellers today.

Even when you reckon you've got it all figured out it's still easy enough to mess it up. Kaye and I were travelling North up Knolls Track in the Simpson Desert in July 2009. It was just after lunch and I had checked the tyre pressures before setting off. We were running 16psi front and rear in Kayes Landrover Discovery. Shortly after I noticed that I had the steering wheel at approx. 60 degrees from straight and I was 'ploughing' or 'crabbing' through the loose sand. Damm, flat tyre thinks I................nope, steering problem...........nope. When I'd checked the tyres at lunch time the front RHS was 1psi greater than the LHS, which I ignored as not worth worrying about. I was wrong. With the sun on the RHS of the vehicle the tyre pressures on this side had gone up a further 2psi giving a difference of 3psi which was enough to create the problem. Another lesson learnt.


Dean
February 3, 2011 at 5:06 PM Flag Quote & Reply

Dave and Pauline Gray
Member
Posts: 84
Hi again Dean dont put yourself down mate that is a very understandable explanation and it supports the old saying in my case your never to old to learn and also now i fully understand where your coming from your therory is certainly valid,
I was fortunate enough to make my first trip up the Gibb River Road in 1972 i took a small rigid truckload of station stores to Doongan it and Drysdale had only been established a year or so so i didnt have to contend with corrugations in that area there mayhave been a bit of uneven road suface here and there but generally once north of the Mt House turn-off it was just a couple of wheel tracks to follow, to be honest i had no idea where i was till i saw perhaps a drum on the side of the track that said ie gibbriver or mt elizebeth then i would think well i.m still on the right road but the point im trying to make is i didnt have to contend with people like you met with no idea how adjust to the road conditions listen to somebody who does and make their trip an enjoyable expierience instead of a disaster or worse still an accident which affects a lot more people than just them, I think I was very fortunate to see when i did because it does not have the same apeal to me now mainly because of people like the lady you met. Cheers Dave
February 3, 2011 at 8:17 PM Flag Quote & Reply

John & Laura Szkoruda
Member
Posts: 112
Agree with what Dean says , we always run our tyres at lower pressure on rough dirt, corrugations & sand . Especially sand . As stated speed is not always necessary the bigger footprint from lower air presssure and a slow & steady pace will normally win out every time. Thats been our experience over the last 28years or so of 4WDing only the last 7 with the Oka.
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John & Laura Szkoruda OKA 147

February 8, 2011 at 3:08 PM Flag Quote & Reply

Dave and Pauline Gray
Member
Posts: 84
Hi all I came across an interesting article on explor oz site much along the lines we were discussing last week with some technical detail from the maufacturers on tyre pressures and heat buildup etc the web site is www.netspeed.com.au/rob.dobson/
cheers Dave
February 9, 2011 at 5:45 PM Flag Quote & Reply

Peter & Sandra James Oka 374
Member
Posts: 413
374 has 16" rims and 255/900x16 Michelin XZL's which are approx half worn, howl like anything on the highway and definately feel suss on a wet road. They are approc 880mm diameter.
I'm seriously considering fitting 16" alloys but rather than fitting tyres of the same diameter I'm thinking of dropping back to a 285/75R16 which is around 840mm dia. The Oka's were originally fitted with 825x16 tyres and the 285/75's are about the same size. I'm thinking the slight reduction in diameter will help the gearing and maybe the Oka won't have a heart attack when a hill appears in the distance. Any thoughts? I realise revs will increase but as we rarely go over 90kph I don't see that as a problem.
Peter
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Oka 374 LT Van

March 16, 2011 at 11:07 AM Flag Quote & Reply

Hal Harvey
Site Owner
Posts: 510
Peter,

Some diameters to compare:

825/16 has a diameter of 32.4" and looks plain wrong on a bus!
285/75R16 has a diameter of 32.8".
265/70R19.5 has a diameter of 34.1" (standard LT)
315/75R16 has a diameter of 34.6" (see #147, but they'll go up a size next time).
900/16 has a diameter of 35.2".
285/70R19.5 has a diameter of 35.2" (standard LT bus)
305/70R19.5 has a diameter of 36.3" (requires wider-than-std rims)
325/85R16 has a diameter of 37.8" (as per okadoc import)
355/80R16 has a diameter of 38.4" (mine, and as large as you can go without a body lift). 1100/16 is similar.

Thoughts? Depends how much time you spend on hills. I've been happy to go down through the gears as required and go slower over hills; but mainly because the larger diameter tyres are better on beach sand, and I do a fair bit of that.
--
Hal

March 16, 2011 at 9:21 PM Flag Quote & Reply

Peter & Sandra James Oka 374
Member
Posts: 413
With the 255/100R16 it feels overgeared most of the time and I know originally they came with 8.25x16 hence the question. I've been told that most fitted the taller tyres so that when used for tourist duties they could sit on 100kph on the highway. I agree the smaller tyres do look silly but the smaller sizes might be more obtainable outback if needed.
The second problem is that with 374 having a GVM of 6 tonne most tyres do not have a high enough weight rating.
We need a tyre with a minimum 124 and preferably 126 to be legal and also not destroy the tyres when running lower pressures on rough and/or sandy terrain. I've yet to find a 305/16 or 315/16 tyre that has a 126 rating where there are quite a few in the 285/75x16 that do. Most only have a 121 rating which isn't even legal on a standard 5500kg Oka.
I've looked at Okadoc's tyres but they are too tall to expect a Perkins to pull, ok for Doc with a 6.6 lt turbo diesel V8 and all of you that live in flat country but over here in the east we have hills and mountains ;-)))
As we do plenty of very remote travelling I've no wish to use tyres that are nigh on impossible to replace either, never mind the cost of the big tyres if staked.
I intend to replace the split rims with wider 16x8 alloys so they will handle a larger tyre than the standard rim.
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Oka 374 LT Van

March 17, 2011 at 7:08 AM Flag Quote & Reply

Hal Harvey
Site Owner
Posts: 510
Not sure on the load rating of these babies, but the staking problem is gone...


--
Hal

March 17, 2011 at 9:14 AM Flag Quote & Reply

okadoc
Member
Posts: 98
Hi all, if we didnt leave the bitumen we would not have Oka"s, the 325/85/16 are supurb off road rubber with the multi operational qualities required for our operations out back, thats why we now have sufficient tyre no's at a very good price that will ensure the long gevity of reliable transport in our areas of operation.One of the Okaa's has at present 19.5/265 /80 psi mitchies on and the difference offroad is like steel wheels instead of rubber so we restrict its areas of operation until rigged with our choice of rubber. Our experiences tell us No matter where you are out back if your not carrying priority spares, fan belts,filters,oil fuel and tyres then your not fair dinkum about the realities of high temperature remote travel reliability and safety.Nothing is bullet proof but the tyres we selected are the next best thing when correct pressure is maintained whilst moving, its self defeating only knowing pressures when your stopped and having to wait until the rims and tyres are considered cold enough for testing pressures, its absolutley a must to be able to monitor pressure and temp whist on the move cause they dont get punctures while standing still unless hit by a bullet, its truly a no brainer.The 325/85/16 are four big comfortable air bags that are designed to run from 65 psi / 5300lb /tyre down to 3 psi if required in the quick sand, safely and as our Oka,s are 5500 kg all up max then running at 50 psi is ideal and sooooooo comfortable we wouldnt have anything else. The 1100reds are the same but I believe a better suited all terrain tyre and our first selection when operating on firmer terrain as their not as wide in tread and give the same running qualities of its wider cousin on or off highway.We have opted for the 6.5l optimiser V8 unit simply because our research on the GM range of engines points to the optimiser being the most fuel efficient and reliable engine ,(you gotta believe at some time what you read and listen to until time proves otherwise).Ok,Ok there is that bit of rev head still lurking in this 60 yr olds attrified mind which is suffering tunnel vision but they sure got the effortless grunt and when its applied through a torque converter and seamless gear changes the rest of the drive train can relax a bit from sudden surprises as long as you keep it "cooooool"' with the correct clean oil. The majority of the surplus tyres we have at present have been soaked up by Canter owners wishing to soften there ride(understandable) hence our forward order for the other 180 units, they have ample room to carry multible spares and it gives there rigs monkey glands with wide singles and major elimination of there harsh tight ride.The fact that these tyres are mostly unobtainable else where should dictate to any perspective owners that obtaining just 4 on the pavement and one spare would not be a wise choice, MHO is they would be safe with 7or 8 tyres for the duration of there travels as they probably would not travel the K's to wear them out and only destroy them after imbibing one to many reds in snakewood country.Its horses for courses here folks and Lyn and myself wish all happy travels.
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March 17, 2011 at 10:33 AM Flag Quote & Reply

James & Usha (THEByleDuct)
Administrator
Posts: 161
Another good tyre size comparison calculator which will allow you to compare up to 4 tyre sizes with you original giving all sorts of information can be found here. It includes 1/2 inch sizes such as 19.5" which is good for us
Info includes: Section width, Rim diameter, Rim width range, Overall diameter, Sidewall height, Radius, Circumference, Revs per mile, Speedo compared to 100km/hr on original, Speedo difference, Diameter difference. Pretty comprehensive really.
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OKA #072

March 17, 2011 at 10:01 PM Flag Quote & Reply

Peter & Sandra James Oka 374
Member
Posts: 413
That is a good site, makes it very easy to compare different combo's
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Oka 374 LT Van

March 18, 2011 at 6:58 PM Flag Quote & Reply

Tony Lee
Member
Posts: 540
" its absolutley a must to be able to monitor pressure and temp whist on the move"

Agreed. But how do you do that?
--
Tony

picasaweb.google.com/114611728110254134379

March 18, 2011 at 7:10 PM Flag Quote & Reply

Seamus and Cate
Member
Posts: 21
Hi - Tyre Pressure and Temperature Monitor - there are a few on the market. We got this one a year or so ago
www.tyredog.com.au/store/4-wheel-wtpms/4...-0-to-180-psi-1.html
and have been quite happy with it, although lately it doesn't like corrugations at all and won't read pressures while driving over bad corrugations.
OKA tyres being as expensive as they are, having the monitors gives me peace of mind - you can set an alarm for high pressure too

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www.boldacious.com.au/

www.serendipityprojects.com.au/

www.portlandroadsbeachshack.com.au/

www.capeyorkblog.com/

www.sandfly-mosquito-repellents.com/







March 18, 2011 at 8:11 PM Flag Quote & Reply

Alister McBride
Member
Posts: 97
Hi all,
Hal, you're using Pro Comps and have had them for a while, any idea on the wear rate yet?
Doc, do you know the tread depth of the XMLs (I can't see it on the mich website)? Also, i'm assuming you're working on the tyres being well under their weight rating so the 100km/h speed rating on these (i don't go much faster anyway...) wont worry you? Have you upgraded the brakes with the new dynatrac diffs, bigger wheels and tyres etc?
Cheers,
Alister
March 25, 2011 at 12:18 PM Flag Quote & Reply

okadoc
Member
Posts: 98
we have gone to air over hydralic with the dynatracs gear and much better braking systen and exceeds DOTAR standards, the tread depth of xml/xzl are 21 mil. we have 1ncreased overall track by 100 mil , reduced from 115mil negative offset to 65 mil neg and kept the protrusion at 123 mil from standard config which is easily covered with flares, much less work load on the wheel bearings even though there beefed up in the 80's , just our preference believing we have engineered in bullet proof specs for reliability, no probs with the 16 in rims and brakes either, 4 pot calipers etc. photos on the board before, during, and after. when all set, cheers Doc and lyn Davey
March 25, 2011 at 8:38 PM Flag Quote & Reply

okadoc
Member
Posts: 98
Hi again all, yes the 325/85R16 dash 1100/16's meet our tyre selection criteria. This being load capacity parameters matching speeds and pressures, lower inflation pressures so they can act as air bags and have large footprint and stay on the rim when the terrain gets extreme and highly resistent to foreign material penetration. We wear steel capped safety boots for that reason but even then some manage to defy the odds, we is who we is,Neanderthal employees are more common than we would like to believe Im afraid and our vehicles are speed limited to 100 klms/hr.We use the Davies Craig tyre guard temp,pressure monitors and have saved countless tyres from destruction and have experienced very little grief with them over all terrain including water.We would not go back to the old days of guessing when the vehicle doesn't feel quite right so you stop and its too late to save the tyre'because its way over temperature and although still togethor its structual composition integrity has been eroded sufficiently to rush forward its inevitable untimely end, perish the thought.We also found whilst traveling lifes highways that obtaining any type tyre suitable for the Oka's when in need there and then is at the very least the old broken record ,""Sorry we would have to get it from the big smoke"" so we have commenced rectifying this problem by wholesaleing tyres to outlets all over the less travelled out back and judging the response so far have no doubt that our efforts will asisst in erroding the tyre issues in most areas to a negligble level. Most fortunatly there are many 16 in rims on other vehicles and trailers that can utilise the tyres so demand should ratify there existence at remote outlets. We have unlimited supply of the tyres now and would not be surprised if Michelin gets in on the act after weve done the ground work and picks up any slack so to speak, only all good for everyone, cheers and hope everyone is relaxing and enjoying the week end in our fabulous Australian back yard. Doc and lyn.
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March 26, 2011 at 11:24 AM Flag Quote & Reply

Cando
Member
Posts: 199
Hi Doc,
can you tell me if the Davies Craig tyre guard system works all the time ,, corrigations etc?
cheerrs and let us know when yiu have the new shipment of tyres
cando
--
Happy trails

Cando and Bron XLT 112



March 26, 2011 at 10:21 PM Flag Quote & Reply

okadoc
Member
Posts: 98
Hi Cando. the senses on the tube stems have shown intermitently a break in continuity with the monitor but only on the 19.5 rims with /80 psi tyres this could have been that our eyes were jumpin around out of their sockets and couldnt focus on the monitor properly, we have not experienced any problems on the flexible 50 psi xl,xzl,xml 's as that sharp intolerable vibration is dramaticaly dampened to allow trouble free communication in all areas on board, nil feces. The 1100r16 sit perfect on the Oka 16 inch rims with a tube and your in business, we will have 34 1100reds lob on the 7th April, brand new tyres, XZL all terrain, enjoyable travels to all, Doc and Lyn
March 27, 2011 at 3:40 PM Flag Quote & Reply

Tony Lee
Member
Posts: 540
"the senses on the tube stems have shown intermitently a break in continuity with the monitor but only on the 19.5 rims with /80 psi tyres this could have been that our eyes were jumpin around out of their sockets and couldnt focus on the monitor properly"

Well, I don't run at anywhere near 80psi, but I do have 19.5" rims so looks as if the Davies Craig system is likely to give the same problems as the Zartronics system with losing communications but without the benefits of the Zartronics system. Add the hassles of having external sensors to remove and refit every time you change the pressure, and the lack of dual range setting capability requiring resetting the range every time you change pressure and the long time to notify of a communications fault and I'd say I'll be looking for a suitable system for quite a while yet.
--
Tony

picasaweb.google.com/114611728110254134379

March 27, 2011 at 8:44 PM


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Posts: 39
G'day all I am running the 19.5 rims with new set of Toyos, not sure of the other dimensions at present as I am away working for a while so can't check, but does anybody know the correct tyre pressures for the highway and the soft sand. I have been told for the sand dunes by different people 16 to 35 pounds and an army bloke told me to remove the valve from the stem and when it starts to whistle thats the right pressure. As for the highway I am getting anywhere from 50 psi to 100 psi, the man who sold me the tyres had no idea what to put in them, but I have also been told by a truck driver that I had them too hard as they were buldging in the middle and would wear out unevenly, they were then running on 70psi. Gets a bit confusing. Thanks Darren Lilly
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March 27, 2011 at 10:20 PM Flag Quote & Reply

Aussie Bight Expeditions
Member
Posts: 109
Hi
I run 265 Hankooks and when I am really soft beach sand I go to 32 psi, if I get stuck then I will go down to 20 psi but then pump up again asap, to a pressure that suits the conditions, that usually means when one is not getting bogged. If I am doing sand dunes the pressure depends on the conditions, ie on how dry or wet or the type of the sand that one is trying to transverse there is no set pressure as your weight has to be taken into consideration and the type of tread pattern also influences the pressure. I run on the highway from 60 psi up to 110 psi depending on what I am carrying, in people numbers and also in weight, and were the road is and how long before I get to sand or off road.
In general beach 32psi to 40 psi
sand dune work 20 psi to 40 psi
highway 60 psi to 110 psi with general running around at average 5 ton I have found 70 psi to get good wear on mine, at 60 psi I wear the outside quicker than the middle so that is a little under inflation.
I have 1800,000 klm's on mine and they are 60 to 70% worn but will have to replace due to being nearly 5 years old. I can only go to 6 for roadworthy each year, one of the pains of being a tour operator.
Also usually if you run 19.5 rims and with the 3 choices of common tread width we have available, the wider the tyre the more pressure you can run as the width makes it easier in sandy conditions.
I know clear as mud as no 2 vehicles or conditions are the same, but that is what I have found to work for me over the past 7 years as a tour operator, good luck in your pursuit to find the best pressures, just play around with the pressures as 2 psi can change allot of things off road.
Regards
Tony ABE
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March 28, 2011 at 8:00 AM Flag Quote & Reply

Aussie Bight Expeditions
Member
Posts: 109
Should proof read, 180,000km for the distance on the tyres so far, pity they do not do the previous figure.
Tony ABE
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March 28, 2011 at 8:02 AM Flag Quote & Reply

Hal Harvey
Site Owner
Posts: 510
>>Hal, you're using Pro Comps and have had them for a while, any idea on the wear rate yet? <<

Sorry for the belated response Alister, I'm away at the moment and (I think) have just worked out how to post a response on here via an iPad (have to use the HTML button alongside the smiley face for others' future reference)...

My best guess at the moment is that Pro Comp's Xtreme A/Ts will give me 70,000km. Other styles of Pro Comps would no doubt be different. That doesn't sound like much compared to some other tyres discussed, but for me it will actually be just what I want; I want the tyres to only last me six years, and I average around 10,000km a year. One of the reasons I wanted to get rid of the truck tyres was that they lasted too long, and being human I never did bin them when they were six years old and not even half-worn, but then they were letting me down by disintegrating at odd times, which could reasonably be put down to the structural integrity of an over-old tyre not coping with being run at all sorts of pressures dependent on circumstances.

I'm very happy to have gone to LT tyres, but then I'm not running at maximum weight and not doing 30,000km a year.
--
Hal

March 28, 2011 at 8:59 AM Flag Quote & Reply

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Posts: 39
Thanks for your replies I'll just have to experiment abit when I finally get it back on the road which is approaching the 3 year mark in the shed tidying her up, looks like work may pick up a bit so I can warrant registering it (no use if I can't afford to use it). Took it to Fraser Island twice and as those who have been there know that 99.9% of the driving is sand but the resort areas are tarred probably lucky to be a kilometre all up but can be a real pain with the tryes deflated but not far enough to bother pumping them up. Got it stuck big time once in the Stockton sand dunes in the quick sand and nothing would have prevented it sinking like it did, it just fell through the ground and laid on the chassis with the tryes swimming in water. I have lived in this area all my life riding motor bikes and 4wd's for approx 30 years and never had I come across this quick sand nor did I believe it existed but it is real. Thats where I met the army man who was driving a new V8 diesel troopy and he snatched strapped us straight out backwards no problem. I had wondered if I ever got stuck whether the majority of the 4wd's getting around would be of any assistance, now I know they can so it was a good lesson. There was no indication of the quick sand being present at the time as the ground looked the same all around but then all the sand around me darkened as the water was forced up. This was the man who told me to remove the valves and stated that this is what they did in the army when they used the OKA's, his position was 4wd instructor. Does someone know the procedure for setting up the bus stair compressor to utilise it also for pumping up the tryes. Thank you Darren Lilly
March 28, 2011 at 10:54 AM Flag Quote & Reply

Dandj
Member
Posts: 367
"Does someone know the procedure for setting up the bus stair compressor to utilise it also for pumping up the tryes"
Darren you would need to tap into the compressor (or tank) output line with a tap and air socket for connecting an air line to, and the compressor would need to be turned on while pumping.
However, Oka tyres require a large volume of air, and assuming you have an electric compressor, it's capacity would be fairly small. Also the air step tank is quite small and would not add much benefit. It would be better to fit an engine powered compressor (eg Endless Air or similar) and large (>20 litre) tank if you plan to raise and lower tyre pressures regularly.
FYI we run our Michelins at 60 psi on bitumen, 40 on gravel and 25-30 on soft sand. We have an engine powered compressor (actually an ex air conditioner compressor) and even with that it can take several minutes to raise the pressure in 4 tyres after sand driving.
Removing the valves to lower the pressures sounds a bit extreme and you loose control of the pressure. There are pressure reducing devices available (Staun Deflators) but it's almost as quick to use the air gauge.
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David and Janet Ribbans, Oka 148

March 28, 2011 at 7:45 PM Flag Quote & Reply

Stephen Knowles
Member
Posts: 3
To Set the correct tyre pressure ( michlein website under tyre tips) read tyre pressure cold,drive for half an hour and check pressure should not have increased more than 4psi. If increased more, lower pressure. If less increase pressure. Driving on sand When pressures are right you should be able to roll to a stop when you deprss the clutch. Not feel like you have applied the brakes.
Hope this helps
Steve Knowles
March 28, 2011 at 8:12 PM Flag Quote & Reply

Tony Lee
Member
Posts: 540
"If increased more, lower pressure. If less increase pressure."

Not what I would expect.

I weigh each axle (each tyre would be better but not always possible) and then use the tyre manufacturers pressure/load tables (Michellin) to set the pressure for highway driving. I also follow their recommended reductions for other road conditions.

My understanding of the 4psi rule is it applies for normal sedan tyres but needs to be higher for larger tyres carrying more load. For instance, 6psi for standard 4WDs
--
Tony

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March 28, 2011 at 8:41 PM Flag Quote & Reply

Peter & Sandra James Oka 374
Member
Posts: 413
374 doesn't have an air operated step but does have an ARB compressor with integral tank to run the exhaust brake. The compressor is pretty tired so I've got a Boss Pro7 compressor from www.probag.com.au . I've had one of these compressors in the Humvee for about 7 years now and it is a very good unit, rated for continuous duty and 3CFM. On the Humvee it ran the CTIS system as well as air tools.
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Oka 374 LT Van

March 28, 2011 at 8:57 PM Flag Quote & Reply

John & Laura Szkoruda
Member
Posts: 112
Darren,
yes the quick sand is definately there at Stockton have had to pull several people out of it over the years and its as you say you cant see it but you know when you hit it.Thankfully #147 hasnt been sunk in it yet. The picture on the sandhill in our album is at Stockton Beach, great spot not too far to travel just for the weekend.
Laura & John
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John & Laura Szkoruda OKA 147

March 30, 2011 at 3:47 PM Flag Quote & Reply

Peter 334
Member
Posts: 118
We are in the mist in figuring out what tyres to get for our beast , we have 16 " alloys on the list and going to purchase when they arrive ,tyres are another thing and ive gone back some time to see what everyone has said still confused Okadoc has mentioned he was getting tyres in ,do you still have some ,what brand ,tread width ,dia,load rating, i know this debate keeps poping its head up but it keeps us on our toes with tyres thanks peter 334
May 7, 2011 at 5:25 PM Flag Quote & Reply

Tony Lee
Member
Posts: 540
I would question the wisdom of getting any tyres from a specialist one-off source half way across the country (especially if they happen to have been manufactured several years ago).
--
Tony

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May 7, 2011 at 6:11 PM Flag Quote & Reply

Peter_n_Margaret
Member
Posts: 198
I also run a Big Boss Pro 7 compressor.
With my 305R19.5 XDE2 Michelins, I run pressures strictly in accordance with Michelin charts which quote pressures Vs actual loads for Highway, Dirt (65 kph) and Sand (20kph). I have had first class results using their recommendations.
I turned their info into a graphed easy reckoner.
Any one want a copy, drop me a line
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Cheers Peter, OKA196 Motorhome. www.oka4wd.com/xt196.htm



May 7, 2011 at 7:40 PM Flag Quote & Reply

Peter 334
Member
Posts: 118
A tyre service in Melbourne have the rims comming in and he trying to sell me BFG all terain tyres with a load rate of 120-122 im not so sure , i did notice peter and sandra you have Hankook tyres so they must be to your liking as there weight capacity must be good ,no one at the tyre service tell you anyhting about others than the ones they sell ? peter
May 8, 2011 at 9:55 AM Flag Quote & Reply

Peter & Sandra James Oka 374
Member
Posts: 413
Technically the Hankooks are only 121 in the 315 size but as we don'tintend to run at anywhere near GVM I don't think it will be a problem.
I was going to get Toyo's as they are a very good tyre and are available in the correct load rating but Toyo lost a full shipment of tyres in the tsunami and production has been virtually stopped as a result so they could not give any idea of a delivery date except itcould be six months or more.
Both the tyre guy I've dealt with for over 25 years and several friends recommended the Hankooks so bought them instead. They did balance well and ran very true on the rims but as yet I've not driven the Oka with them on as I'm still fitiing it out.
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Oka 374 LT Van

May 8, 2011 at 5:38 PM

David and Janet Ribbans - Oka 148
Oka148 profile here.
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