Is the 150 showing any signs of cracked inner guards

[krypto Avid PP Poster! Find all posts View Profile Close 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.

[AJ120 Out of control poster! Find all posts View Profile Close 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 Avid PP Poster! Find all posts View Profile Close 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!

[Schniff Member Find all posts View Profile Close 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 Avid PP Poster! Find all posts View Profile Close 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 Member Find all posts View Profile Close 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.

[AJ120 Out of control poster! Find all posts View Profile Close 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

[Peterpilot Avid PP Poster! Find all posts View Profile Close 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.

[KarlCaudwell Junior Member Find all posts View Profile Close 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....

[SWR Banned Find all posts View Profile Close 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

[krypto Avid PP Poster! Find all posts View Profile Close krypto]

I'll have a look at getting a tyredog, sounds like a good idea especially for the camper.

I don't think anyone would dispute that low tyre pressures reduce shock on the chassis. My comment was more about what is a tyre pressure that gives best control for fast travel on corrugated roads. It's fine to run soft tyres but at some point there's a trade off. I would never trade control for comfort.

Unfortunately none of this helps Schniff.

[AJ120 Out of control poster! Find all posts View Profile Close AJ120]

If you want pressures to allow you to travel "fast" on gravel roads aren't you sacrificing safety for speed? So long as speed is reduced along with pressures almost any pressure can be safe. If you want to travel at 80-100k and swerve around the pot holes and bull dust and wildlife whilst sitting on top of the corrugations then it's not going to be safe.

I would encourage everyone to test out the various theories on pressures and then decide for themselves.

Cheers Andrew

[Gordon Member Find all posts View Profile Close Gordon]

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.

it is the temperature of the tyre relative to ambient that indicates how much work the tyre is doing.

Schniff. Wake up and smell the roses.

A. You think you have to get on top of the corrugations because your aftermarket suspension does not work. If you had left your car alone it would ride through the rough stuff, wheels would go up and down and your car's and your own body would be none the worse for it.

B. You have watched your car self destruct and listened to the anecdotes on this forum around tyre pressures, plus you have your own senses of comfort, control and vibration to take notice of. And the indicator you're looking at for the correct pressure is the tyre temperature monitor??? I mean knowing the temperature is handy but it's not the primary indicator of sensible pressure... by far...

And Skywalker... You make some sense, but what's your beef with crash testing the Parados? I don't understand your angle. I's love to see anyone frustrated with the prospect of buying a Parado to find a vehicle that better suits their needs. Or even better go get an engineering degree and show Toyota how it's done.

I'm not brandist or being particularly patriarchal - I'd go buy a Landrover or Mitsubishi if it made sense, just seems to be a lot of negativity around what is truly quite a remarkable vehicle. Maybe its my generation but I'm actually quite thankful that a mainstream, affordable, safe vehicle is so capable in my very marginal environment. And I don't think I'll ever see many of these precious ARB-pimped Parados following me more than half the time.

Anyway back to Dumb, Drunk & Racist...

[SWR Banned Find all posts View Profile Close SWR]

Gday Gordon

Gordon Quote: And Skywalker... You make some sense, but what's your beef with crash testing the Parados?

Skywalkerrun Answer: I think you read my statement wrong as I wasn't bagging Toyota but putting emphasis on how much research Toyota put into making a safe vehicle with a 5 star ENCAP rating. Lol (Basically backing-up Toyota in there defense). Lol

Cheers

PS I was basically being a tad sarcastic with my previous reply due to the lack of acknowledgement that the axle ratings are clearly being over-loaded on the prado when installing numerous heavy aftermarket products without considering the maximum axle load ratings which is promoting to the extra chassis flex/Cracks and that i seen the emphorsist on tyre pressures as a properganda move towards protecting after market products as appose to actknowedging the true cause of the problem.... Hence my indepth detail on explanation of how to read axle loads and kerb ratings. Link below of my prior explanation some threads back.
http://www.pradopoint.com/showthread...l=1#post359454

("Yes" Lower tyre pressures do help to reduce suspention stress and promote traction on corrogated roads).

"Obviously" the up-grading to stiffer suspention inorder to carry the extra weight which has been added to the vehicle (Not to just to lift the vehicle higher for extra ground clearance) it is in turn with the extra weight causes more energy to be transmitted through the chassis instead of the suspention doing its initial job of obsorbing the energy which normally gives a smooth ride and helps to protect the chassis and its body from accessive viabration stress. (Not forgetting the occupants of the vehicle).

PPPS to Gordon. I truly like your open and forward thoughts and for that i respect

[D4D Addicted PP Member Find all posts View Profile Close D4D]

So what of all the other 120s and 150s with aftermarket gear touring around without cracks? Are they just lucky? 1 vehicle with cracks does not prove your point. I acknowledge your point of axle overloading because that is always going to find things to break but I don't think you can prove aftermarket gear is the major contributor.