Is the 150 showing any signs of cracked inner guards

[SWR]

Gday Guys

WOW!!!

So after reading the thread in full can i now safely say that one of the major contribution to the chassis cracks on the Prado's is with the tyre pressures and that the 5 star ENCAP rating is just not good enough and installing heavy after-market products to the vehicle is not contributing to the cracking of the chassis and that it could not possibly be over-loading (is) the maximum axle ratings when looking at the spec sheets... it seems to point more towards over-loading when looking at the axle loads???

My thoughts are solely with the guys who are spending fa-nominal amounts of money on there 60-70-80-90k vehicles and not the aftermarket guys.

I think when you observe the axle ratings against kerb weight before installing all goodies i think the figures speak for them selves and that you would find that the tyre pressures are/could be the final straw that brake the donkeys back.

Just my thoughts against your thoughts that's all!... No propaganda intended.

Apart from your own vehicles courtesy of your selves have the after-market guys rated there products with axle weights put into the equation or is that for you to work out the hard way?

All trucks have to go on a weight bridge to make sure there axle weights are not over-loaded!..... (Front and back)... Shame there is not a compulsory law in place to protect 4x4's from them selves as far as axle weights go!... If there was im am sure peoples mind set on over-loading axles would change! (Axle ratings are put there for a reason!).

Cheers

PS Here is some of Toyota's poor attempts to make a safe good all-rounder With there millions of dollars research!

Crash Test 2010 - 20** Toyota Prado Landcruiser
http://youtu.be/mIxiPhRWHrw

Toyota Prado (2010)
http://youtu.be/GwIVJufJ87M

Crash Test 2010 - 20** Toyota Prado Landcruiser / Lexus GX (Full Frontal) JNCAP
http://youtu.be/qUqTVo4mYq4

Side Pole Crash Test of Toyota Prado
http://youtu.be/Rph_50adMIQ

[KarlCaudwell]

Hey Andrew, I've been reading pp for a while and noticed your various comments on different threads.....you seem to make sense. I'm one of the people reading and wondering if and when my prado is going to crack the guards. I have bar, 2" OME, and tossing whether to tempt fate with a second battery. Low pressure for me....

[Peterpilot]

I agree with Andrew. As a general rule, lowering your tyre pressures is kinder to your vehicle, kinder to the track and kinder to your tyres. I also subscribe to the 4PSI Rule.

[AJ120]

I was referring to actual pressures as well, not just cold pressures.

We shall have to agree to disagree about what pressures to run and how much effect they might have on your vehicle. My posts in this thread are really aimed at people reading this and wondering when / if their prado is going to crack the gaurds, hopefully they learn something and avoid the problem.

In the meantime I will continue to drive my Prado at lower pressures and with fully intact inner gaurds

Cheers Andrew

[Schniff]

I use a tyredog which can be got cheap off eBay. Speed tootling around the bungles was slow, under 60. Up Kulumburu road 40-70 depending how bad the road. Unfortunately the surface is very uneven so speed has to be slow and you cant get on top of the corrugations and let the suspension do the work. Ambient temp also makes a big difference to the pressures. Best way to judge the right pressures (on the highway) is to look at tyre temperature which the Tyredog also provides. As you say, it is the temperature of the tyre relative to ambient that indicates how much work the tyre is doing.

[krypto]

It's mainly side wall flex that causes tyres to heat up. That's why rise in pressure which is directly linked to heat is a precise indicator of how much the tyre is working. (deforming).

Schniff these pressure rises are only around 20% which seem reasonable. My back tyre pressure rises 20% when loaded up and towing my camper, that's on bitumen starting at 50psi.

I've never been able to find really good data on tyre pressures and the 4psi rule seems a bit vague because it's 20% at 20psi and only 10% at 40psi

What sort of speeds were you doing and what pressure monitoring system do you use?

[Schniff]

I pretty much agree with Krypto here. For the record the pressure I quoted were operating pressure as opposed to cold pressure. The coopers heat up a bit more than my road tyres and the pressure always goes up a few psi. The reason i can quote operating pressures in the first place is because I actually monitor the pressures inside the car the whole time I am driving which is more than most people do. When talking tyres to people out on the tracks i get responses that range from "they are round and black and have air in them" to "carrying a bit of weight, so 50 psi all conditions."

In the bungles I aired down to 25f 27r operating in 29 degrees ambient, the next morning (cold) they were 21f and 23.5r. If this makes the difference between the car crumbling to bits or not, then I am in the wrong car. Similar thing on Kulumburu road.

No way would I go below 20 psi at any sort of speed on dirt roads. In touring config the extra weight will make even the Coopers bag out excessively and greatly increase the chance of the tyre coming off the rim. You can feel the car squirming around and steering, braking turn to shite. Ironically, the extra heat from the sidewall movement actually makes the pressure go up too. Sand is a different story.

Agreed we may be splitting hairs here boys :-P

[krypto]

Hi Andrew, I still think its a big leap to put the damage down to tyre pressure. It might be a contributing factor but if it was critical factor then I would be seriously worried about the durability of the vehicle. Mind you this thread has established that there isn't a huge design factor of safety, probably due to the crumple zones.

I think the extra gear mounted on the front of the vehicle plays a significant role in the stress on the body. (Judging by the thickness and design of the guards they would barely be considered part of the chassis)

Incidentally I did a few hundred kms on corrugations over the weekend with a friend who also drives a 150. I wouldn't recommend this but we both did the drive with tyres around 45. Not ideal but we couldn't be bothered letting them down and then putting them back up. Was a pretty smooth ride at around 90, apart from having to dodge a few holes. Our Prados are both pretty standard and he does a heap of dirt driving with no problems so far.

I do agree that lower tyre pressure makes for a softer ride, but with really soft tyres things can start to get interesting if you need to take evasive action at 80-100.

edit: I just read the post by Steve further up and I agree that the type and design of tyre plays a big role. So at the end of the day its probably a case of finding out what works for your individual set-up.

I think the people on this forum probably pay more attention to these things than the average person. I was on a mine site last week where they do a lot of dirt driving and no-one checks the tyres. In a random check I found one vehicle with one tyre at 24 and another tyre at 38!

[AJ120]

I agree with your method for determining presssures krypto, I do basically the same thing, however we have both come to completely different answers. Anyone can test what suits them best pretty easily, drive for 5 minutes on a rough rough at low 30's them drop to 26ish and compare, should be eay for everyone to make up their own mind then.

Probably I wasn't clear when I said look at the corrugations, I was really referring to how far apart the peaks are in reference to high pressures and sitting on top of the corrugations; and how little contact your tyes have with the road with this technique. Having done a few hundred k's this morning, much of it on dirt roads with fortunately only mild corrugations I took the opportunity to measure one, roughly 350mm between peaks and thats a very small corrugation. Not much road contact if you are sitting on top with high pressures.

Yes you need to sit on top of them most of the time rather than drive through them, but lower pressures can allow lower speed and more road contact as the tyre deforms better, hence lower pressures means better safety on gravel roads, rather than it being more dangerous as you suggested.

In the context of this thread low 30's didn't stop the cracking issue, whether it is the only cause or not is only for speculation, but my suspicions are that it was a fairly significant factor.

Cheers Adnrew

[krypto]

Great chart done by the people at the Pink Roadhouse, especially the different pressures dependent on wheel size, tyre type and vehicle.

Sitting stationary on a corrugation does not in any way resemble what a tyre does at 80km/hr. We are probably splitting hairs but I base my tyre pressure on how fast I'll be driving, the load, type of tyre and track/road conditions. I usually stick to low 30s for corrugations, unless they are really bad or I won't be going over 60km/hr I will drop to 20s. To get a feel for how hard the tyre is working its worth comparing the cold/hot pressure change.

Each to his own, after years of driving on dirt roads around SA and more recently WA I like to drive corrugations a bit fast so that you are driving on top of the corrugations rather than through them, but it does makes things interesting if you come across an unexpected obstacle like a big hole.

[Sambo150]

Thanks for posting that pdf, very cool Have to visit that place one day.

Was going to ask about 18's until I got to the bottom!

[AJ120]

But hey I'm not an expert however these guys are and they have seen more blown tyres than any of us will in our lifetime
http://www.pinkroadhouse.com.au/Pink...essure-pdf.pdf

Yep Adam Plate at the Pink roadhouse was probably the first person that gave me the good oil on tyre pressures, although he reckoned I wa already in the 5% that had it pretty right already, but I still learned a bit from him. I have had a couple of good talks with Adam, and spent around half an hour chatting with his wife Lynnie last time I was in Oodnadatta (she was admiring my awning).

Had similar conversations at Dyrsdale river in the Kimberly, Archer river on Cape York and a few others as well, same story everytime.

Cheers Andrew

[D4D]

I agree with AJ who agrees with me that tyre pressures would accelerate any vehicle damage due to fatigue.

I disagree with your comment about sacrificing comfort for grip as a lower pressure tyre has a larger contact area therefore increasing grip. Obviously you slow down to suit the pressure.

But hey I'm not an expert however these guys are and they have seen more blown tyres than any of us will in our lifetime
http://www.pinkroadhouse.com.au/Pink...essure-pdf.pdf

[AJ120]

With pressure in the 20s on a good gravel road you are actually giving up control for comfort, unless you are driving very slowly. With low tyre pressure the contact shape deforms causing the tyre to float more, have a look to see what happens to the bottom of tyre as the pressure drops. This reduces steering control and can increase braking distance. As well low tyre pressure causes more sidewall deformation and fatigue, and causes the tyre to heat up excessively.

So you need to be careful with pressures, it's not the same as slow 4wd driving. Definitely drop them on dirt roads but be careful by how much.

Sorry but I disagree. On any gravel road that is less than perfect lower pressures will improve control. High tyre pressures combined with high speed (80k) on even a slightly corrugated road will cause significant loss of control as you sit on top of the corrugations. Stop and get out and look at the corrugations some time, if you sit on top of them your tyres are not in contact with the road as much, hence less grip and less control. Lower pressures in the same scenario will allow tyres to deform over the top of the rough sections and give you more contact, better control, a smoother ride and most importantly as far as this thread is concerned, less stress on the vehicle.

A good rule of thumb is speed can be 3 x psi. So 25 - 26 psi = 75 - 80km/hr, adjust speed accordingly when you drop pressures. Being a country boy and an experienced out back traveller I travel rough dirt roads regularly, if not quite daily.

If you talk to people who run outback roadhouses they will all tell you the same thing, most tyre damage, vehicle damage, and accidents on outback roads are caused by people driving to fast and with pressures too high.

Cheers Andrew

[smakb]

A lot also depends on the brand of the tyres. Coopers have much harder side walls than BFGs, so the Coopers do not deform as much.


Steve