Your Trip Right presents
The Great Central Rd Guide
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Space and weight are very valuable resources when travelling.
My biggest purchasing lesson came from buying what I thought were the best shocks on the market.
Speed. First of all I was wrong. From my testing, going faster did not make the corrugations any smoother in the Prado. Perhaps on a different corrugation the results may vary but from the evidence I collected high speed made corrugations worse.
Time to defend my assumption, whilst it does actually make the corrugations worse, a higher speed reduces the duration you feel the corrugations for and the duration of your trip, which is why I believe that many of us out bush feel as if speed helps the situation.
Given the evidence, you clearly should slow down over the bad corrugations. 80km an hour seems like a fair speed to travel at over corrugations for skilled drivers. You are going to have to make a call about what speed you choose for corrugations. If you are not experienced I recommend 60km or lower as you can really get thrown across the road through corrugations.
Tyre pressure. I nailed this one! What I was hoping to find though, was an ideal tyre pressure, say 28PSI. I didn’t and simply the lower you go the better it gets. I would never recommend driving at 20PSI along these roads nor would I recommend 25PSI. The lower your tyre pressure the more vulnerable I feel you are to creating heat in your tyre and weakening your sidewalls. As you know I completed the test in 32 deg temperatures. In the testing that I did at 20PSI my tyre temperature hit 49 deg. I have only seen my tyres get that hot previously if the day is over 40 deg. I will have to turn the decision on tyre pressure over to you. You're going to need to make a decision based on how fast you plan on travelling, what your legally able to run in your tyres and what you feel is best for your car.
Now that I have completed my fence sitting I will tell you what I now run in my Prado. This is not a recommendation to anyone it is simply what I do.
Rear 30 PSI
Front 28 PSI
Tyre Pressure: By sight
If you do find the need to do your tyre pressure by sight, make sure you have a good in-car tyre monitoring system so you can make sure all is going as per the program in each tyre.
Compare 120km at 25PSI to 80km at 25PSI. The danger of high speed just is not worth it.
As my world came crashing around me I did need to figure out if going faster did ever make the corrugations better so I decided to push the envelope and take 25PSI to 120km per hour. Never recommended. This is what happened.
The lower the tyre pressure the less the vibrations we detected in the cabin. Below is the lowest tyre pressure test I preformed 20PSI at 60km an hour.
Now we come to tyre pressure. Lets have a look at what 80km an hour looks like at 35 PSI (on the left) compared to 25 PSI (on the right).
As you can see, 80km an hour was an optimal speed at 40 PSI. Through the tests, 80km preformed really well however once the tyre pressures were below 35 PSI 60km became very comparable.
The picture on the right is of 30 PSI at 80km the left is 30 PSI at 60km.
Finally we have a picture of the car at 60km with 40PSI in the tyre.
As you slow down you will notice the corrugations get slightly better. The next picture is at 80km with 40PSI in the tyre.
Now lets show you what happens to your car at 100km with 40PSI in your tyres over some punishing corrugations.
Jess and I are in an unusual position where we have been able to sink 100k into our Prado. I explore what accessories I would have if i could only choose 5.
All people have set assumptions in all areas of life. I like to test my assumptions as often as I can.
Jess and I have been living on these roads for years and whilst we think we know how to best handle the conditions all we have is a bit of hear-say and opinions. Not really what I should be basing my opinions on.
How to handle the corrugations is a topic that comes up between locals every fortnight and when tourist season is here, every tourist gets told 100 different things. So to help you out on your next trip I put some science into my theory so you know exactly what you’re talking about when it comes to corrugations.
Leading into the test I believed that lower tyre pressure and high speed was the cure to the vibration of the corrugation. My theory was "you are going so fast you only hit the top of the corrugation, not the whole thing". I estimate 85% of my bush friends will tell you the same thing. We are wrong. In general this is how my set up of corrugations looked.
General speed: 95km-80km
Rear Tyres: 32 PSI
Front Tyres: 28 PSI
About the test.
I wanted to do the test in conditions similar to what most tourists experience in the tourist season so I was waiting a long time for a day that stayed below 35 deg in January. I headed out of Docker River to a notorious patch of corrugations 15km from Docker River, definitely up there with the worst on the road. I picked a section that I would do my test on. I started with my tyre pressures at 40PSI I then tested the pressure at 100km, 80km, and 60km. I completed the test reducing tyre pressure by 5PSI until I got to 20 PSI. I then measured the vibration in the car with a vibration monitor. After each round of testing I let the car sit for 15min to allow the shock absorbers a decent amount of time to recover.
Lets get into it. The first picture I’m going to show you is what driving on the tar looks like inside the Prado. You may even be able to spot where I have gone over a speed hump.