Tyre Blowout

Yes, I have Tyre Dogs and continually monitor my tyre pressure.

Although the cold inflation pressure was 45psi, it had risen to about 50psi at the time of the blow-out. This was the same as the pressure on the other rear tyre.

I was watching my tyre pressures more closely than usual because I thought I might have a slow leak in one of the front tyres. As it turned out it was not a problem.

No warning - wow. Must have been a faulty tyre then that suddenly exploded.

BFG KM2's have a E load rating which is rated at 80psi (550kpa) at 45psi wouldn't the load rating be considerably reduced?

Yes the load rating is reduced, I have a chart relating load, speed and pressure and I use that all the time.

We were very lucky that there was nothing else coming in the opposite direction. If there had been something coming, then to avoid a head on collision, I would have had to continue off the other side of the road and into the scrub. It would have almost certainly wrecked the truck and caravan and injured both of us.

And some one made post joking about gray haired nomads doing 90 now if you had been doing 110 this may have ended differently

will you try for warranty with the tire if so let us know how it goes

I don't think I will bother as I have on previous occasions tried to communicate with BFG and have been totally ignored.

I would be more interested in finding out why the tyre blew in the first place. I do not want to have this frightening experience again.

I don't think I will bother as I have on previous occasions tried to communicate with BFG and have been totally ignored.

that is interesting and says a lot about the company thank you

I think Michelin owns BFG now. Trycontacting them.

Even though B.F. Goodrich is still a popular brand name of tires, the Goodrich Corporation exited the tire business in 1988. The tire business and use of the name was sold to Michelin

The outside

I have checked it on a weighbridge and I know that the load, speed and pressure were all within manufacturer's specifications.

I always thought that the GVW for an LC100 was close to 6700kg so how was it within specs.

I am referring to the load, speed and pressure of the tyres being within specification.

Rob,
I now note you posted below:
"A few weeks earlier I travelled over some rough terrain at reduced tyre pressures and reduced speed on the Walker's Crossing track between Innamincka and Birdsville. This may have somehow damaged the tyres."

Cal me a mind-reader but that's exactly why I posted above. You have hit something hard, got a small split in the sidewall and it's let go on the highway with the extra heat and pressure. Seen it happen before - but mostly with the old BFG muddies.

The 7 tonne is gcm not what he had on his drive wheels.

Good input thanks Brad.

I have a number of photos of the failed tyre, I will have a further look to see if I can discern any blue colour tinge.

I was aware of the need to increase pressure in Light Truck tyres compared to passenger tyres.

The BFG LT 285/75 R16 KM2 have a load index of 126 or 1700kg at 80psi. At 90kph and 45psi they have a load rating of about 1220kg per tyre.

The 45psi was the cold reading first thing in the morning, at the time of the blowout the rear tyres were reading 50psi on the tyre dogs.

I purchased two new tyres at Barcaldine and pumped them up to 60psi just in case.

Hi Rob
Air pressures is a touchy subject and everybody has their own opinion, I have been in the tyre industry for over 25 years as part of a family business, we have a few retail stores plus some import companies in NSW and Vic, in which I manage. As a guideline from the tyre manufactures they recommend that you go no lower than 25% from the maximum pressure without discussing weight carrying capacity. When you involve weight it doesn't work on ratio as such, If tyre rated at 1700KG but vehicle is only 850KG doesn't mean you can run 40 psi if recommended max 80psi. As for your tyres on your 100 series me personally would run 65psi daily all round, when towing on tour I would run 75 rear and 70 front. Remember the rating is based on maximums, for yours 126Q which is 1700Kg @ 160Km p/h since you won't be driving at 160 you have some leeway with pressures, as mentioned that's what I would run personally
Brad

Thank you Brad.

Brad S7 replied:
"all L/T tyres require more pressure,"

I don't think that applies right across the board with all tyres. The specifications in the handbook for my car lists a street tyre and an LT that are both the same size. It mentions eleswhere in the book that using the street tyre on rough roads is not recommended. Both have the same recommended pressure at the front at all times. The rear pressures vary depending on load but the street tyre pressures are 7 psi higher than the LT when the car is empty and 10 higher when fully loaded.

Almost all tyre manufacturers have issued safety warnings stating that LT tyres need to inflated to higher pressures than the equivalent P metric tyres to carry the same load.

The following is quote from the Nitto tire company.

"Load Comparison Example, P vs. LT:
P265/75R16 114 Max Load = 2,601 lbs @ 35 PSI

In order to carry the equivalent load, a LT265/75R16 Load Range C must be inflated to 50 PSI.

Using this example, even LT265/75R16 Load Range D, or E must be inflated to 50 PSI to carry the P-metric load at 35 PSI.

LT tires do not offer any benefits of being "heavy duty"
when under-inflated."

Rob

It still may not apply to all tyres. My little pocket size 205x16 LTs have a load rating of 112 which is 1120 kg according to charts that I have found on the net. The maximum pressure written on the sidewall is 65 psi. I always ring the tyre manufacturer whenever I buy new tyres and discuss pressures, loads, road surfaces and the weight supported by each 1 psi. That is what their customer information number is there for. I was told to use the factory pressures and never exceed them by more than 4 psi. That means 25 front at all times and 25 to 34 rear depending on load. The tyres are near the end of their life now, the tread wear has always been even and those factory pressures that I initially thought were too low have worked perfectly.

The street tyres in the book are 25 front and 32 to 44 rear.

Hi 671

It is correct that your hand book would recommend the same size tyre either PCR or LT, this would be for correct speedo reading it shouldn't recommend same pressure. Car makers always recommend lower pressures this is to give a smoother ride, a fuel supplier would recommend higher pressures to give you better consumption. Everybody would recommend different to help their own product standout and give best results for them. As for my recommendation for the front to be higher when towing is that when towing although most trailers have there own brakes it still puts more pressure on the front tyres as you are braking especially on down hill decents this should give you better handling with pressure. I think Rob D7 has answered in above reply

Regards
Brad

"Car makers always recommend lower pressures this is to give a smoother ride, a fuel supplier would recommend higher pressures to give you better consumption. "

In that case I would expect a tyre manufacturer to also recommend a pressure that would give the best performance from their product. I wonder why mine recommended the same pressures as the car manufacturer?

I have heard that claim about manufacturers recommending lower pressures for a smoother ride many times over many decades but I have yet to see any proof of it. It sounds like an urban myth to me. It does not seem logical that they would spend millions developing a suspension system in which the tyre and its pressure play an integral part of the design then, when they have it just the way they want it, they specify a lower pressure for a smooth ride. Why not design the thing with a smooth ride in the first place?

671 - what car? That information and pressure recommendation sounds contrary to anything I've ever been told or read. Not saying you are wrong, we might all learn something here, just I've never heard of it.
I have attached a link to a toyo tyre bulletin which is pretty much standard across the manufacturers. No particular tyre size is an exemption from this that I have ever heard, so I'd be interested to know which vehicle manufacturer assumes a p and an lt would both be happy at the same load and same pressure under any circumstance at all?

http://toyotires.com/sites/default/files/page-files/TSD-12-011%20Replacing%20Tires%20on%20Light%20Trucks.pdf

"671 - what car? "

2003 Hilux 4x4. Goodyear Wrangler TG 205R16 LT 112 load rating.

Two other tyres are listed in the book in addition to the 205 street tyre. One is a 255/70x15 LT 112 load rating. The pressures are 28 psi front at all times. The rear is 28 to 34 depending on load. That tyre would probably be standard on the SR5 version. My car is the basic no frills variety.

The other is a 195R14C presumably for the 2wd version. Its pressures are 32 front at all times and 32 to 65 rear depending on load.

I was still not convinced that these pressures were correct even after talking to Goodyear but I thought both they and Toyota knew more about the car and its standard size tyres than I did so I did what they said. The result has been a 100% success.

Goodyear also told me NOT to reduce the pressures on unsealed roads so I don't. The only exception was on a climb to the top of Big Red and back down again. I reduced them to 14 front and 18 rear at the bottom of the hill then re-inflated them to the same previous hot pressures when I went down again. The car went straight up in third low at the first attempt.

The car has been to the top of Blue Rag in the VHC back in 2008 when the track was still very rough. It has been graded recently. Last year it went through Dalhousie, Mt Dare, the Sandy Blight and the Gunbarrel on the same factory pressures that I left home with in Sydney. There have been plenty of mountain and desert trips between those two trips. All have been on the same pressures that I left home with.

Living in Sydney means the tyres see plenty of freeway use. Even at the recommended 25 in the front, they don't overheat or wear the outside edges as they would if they were under-inflated.

The difference with these tyres is they are commercial sizes. The TG only comes in a 14 inch, a 205 x16 and two 7.50 x16 in different load ratings. I have lived in the bush for many years and worked in the motor industry for part of it. The majority of locally owned 4x4s used 7.50 x16 tyres and the owners did not change pressures from one road surface to another. It would drive you crazy in some areas if you had to do that. I can only assume that these tyres have been designed to work in those conditions at the same low pressures all the time. Maybe that is why Toyota still fits a 7.50 x16 to the basic Cruiser ute and the Troop Carrier. The whole Outback seems to run on that size in both steel belted radial and very heavy cross ply for cross country work.

The magazines don't cover the 205 and the 7.50 x 16 so going everywhere at the same pressures never gets mentioned. Companies like Cooper and Micky T do recommend changing pressures but they don't make those two commercial sizes.

A lot of tyres look the same but are they? You can't tell by looking. This is why I will always recommend talking to the tyre manufacturer, not the tyre service, when you buy new tyres. The dealer who fitted my tyres said the pressure should be 40 psi. That would have shaken the body off the chassis.

There is always a lot more to the design of both suspensions and tyres than meets the eye. The standard tyre and the recommended pressures is part of the design. It is not an after thought intended to keep the car off the ground until the owner buys something better.

I had that model hilux. I think you should check the nomenclature on the door card. The oe tyres were Bridgestone HT in both the sizes you mention. The load 112 is correct, however I am sure you won't find the LT specification on the original tyres nor the door card. I don't doubt that you might be running LTs in that size now, but the oe door placard should be ignored because of the change in tyre construction. Yes they recommend lower than normal, but they are on P/C rated tyres. If you voluntarily change to LT rated tyres then check the tyre manufacturers inflation recommendation and not the car manufacturer's.

"If you voluntarily change to LT rated tyres then check the tyre manufacturers inflation recommendation and not the car manufacturer's."

I have already said that I did that. The door placard lists one tyre only and that is the 205R16C HT which the hand book says is not suitable for off road use.

That is why I rang Goodyear when I decided to use their light truck Wrangler TG. As I have said before, I was told to use the same factory pressures as recommended for the "205R16 reinforced" that was also listed in the book. That is 25 front at all times regardless of load and 25 to 34 rear depending on load. Who am I to disagree?

I had a very informative twenty minute conversation with one of Goodyear's tyre engineers that day and learned a lot about tyres. He told me not to reduce those factory pressures on any road surface but if I really wanted to go higher then never go any further than an extra 4 psi. I have yet to find a reason to increase them

He also said every 1 psi increase would support an additional 70 kg. The only increase allowed is a 9 psi variation in the rear tyres. The handbook says the car is considered to be empty when carrying two people and up to 100 kg of luggage. The car weighs 1610 kg with a Toyota aluminum tray and a full tank of fuel. My wife and I have a combined weight of 140 kg. Add 100 kg of luggage and that becomes 240 kg. making the total weight 1850 kg. The insurance papers state a GVM of 2500kg. That leaves 650 kg still to be added. 9 divided into 650 kg is 72 kg. That is where the 70 kg for every 1 psi increase comes from.

It sounds like he had all the information in front of him while we were talking and was not giving his own opinions

That makes it very easy to keep an eye on weights when loading the car and setting the correct rear pressure. I had it out on roads like the Gunbarrel last year. It was 190 kg under GVM. Nothing was overstressed, there was no excess weight bouncing up and down right on the rear end that could lead to chassis damage and I did not have to stuff around with tyre pressures.

The manufacturer has your 205r16 wrangler tg as not being an LT either? No wonder they said to use the same pressures as the oe tyre - they are the same construction. Only the 7.5r16 wrangler is available in LT?
No wonder people get confused about this stuff.

"The manufacturer has your 205r16 wrangler tg as not being an LTeither"

My TGs have 205R16 LT clearly written on the side wall in letters so big nobody could miss them. They are Goodyear's off road mud/rock tyre for all utes that use a 205x16 as original equipment.

I also have a very old but never used Dunlop Road Gripper in 205R16C size. It is a 6 ply with a 110 load rating. That is lower than my TGs at 112 but it has the words Light Truck written on it.

I have no doubt that the suspension and tyre engineers know what they are doing so I just do what they say and so far it has always worked. I think I would go mad trying to work it out myself.

25 psi in the front tyres on a hilux that's dangerous I use to drive a short wheel base cruiser on the beach with 25psi and it went well and they weigh a bit over 1,600 kg. Maybe you should get into the passengers seat of another car and drive beside your hilux and see just how dangerous that is especially on a windy road how much your tyre is flexing and rolling. I jumped in my nephews 4 cylinder disco a few yrs ago now because his father said it didn't steer or handle very well he said they followed the tyre placard which stated 28psi. Well what a shocking drive it wouldn't turn it wanted to go straight into the other lane on corners the steering was heavy I pumped them up to 39psi and it was a lot better. My brother in law was concerned I put too much in he called the tyre manufacturer and they said 42psi unloaded please pump your tyres up you're not driving a Gemini. At least put 34psi all round for everyone's sake.

The sidewalls looked perfectly normal.

I had the Tyre Dogs on measuring the pressure and temperature. The cold inflation pressure was 45psi and at the time of the blowout was 50psi. I had been watching the pressures extra closely as I thought I may have had a slow leak in one of the front tyres; this turned out to not be the case.

Although the pressure measurement is reasonably accurate with these devices the temperature is measured at the tip of the valve stem which is a long way from where the rubber hits the road.

A few weeks earlier I travelled over some rough terrain at reduced tyre pressures and reduced speed on the Walker's Crossing track between Innamincka and Birdsville. This may have somehow damaged the tyres.

By the way Rob D (NSW) and Rob D7 are one and the same. At the moment ExploreOz is having a problem recognising my email address so I have to log in through FaceBook which gives me a new alias.

I'd suggest that you were probably doing nothing wrong when the tyre blew but had damaged the tyre in a previous incident like you have mentioned.
Have a look at your intact tyres and see if there is any fine sidewall cracking / crazing. You will often see it close to the rim/ bead area.

I fail to see what this has to do with the Load vs Speed vs Pressure characteristics of a BFG KM2 LT285/75 R16 and whether the limits of those parameters were exceeded.

It was the tyre that failed, not the truck.

This post is about tyre failure not GVM or GCM. You will find plenty of other posts on those subjects if that is your interest.

It is a heads up on what is legal side concerning insurance, as it appears the vehicle was over the allowable GCM. Nothing to do with tyres just adding some information that it would seem that a lot of people have no idea about. Have a single vehicle accident and you MAY I repeat MAY get away with it but if there is another vehicle involved or someone hurt or killed then you are in serious trouble from the insurance company and the law. I run a towing company and this is becoming prevalent to have crashed vehicles weighed that are suspect on GVM and GCM.
This is an open forum so I can add in anything I want and don't have to stick to the exact subject.

First sign a tyre is under inflated is heat. 5 degrees from cold to running temp to me would indicate just about perfect inflation for an LT rated tyre. Rule of thumb has them at 6 odd degrees and p rated tyres at 4 degrees (4 psi rule). The facts don't support your supposition. Tyres weren't overloaded by a long way going by the op's numbers. Heavy yes, but not even close to the tyre's load rating.
Some days you just get unlucky I guess?

Absolutely spot on BunderDog . Also on another note some people get very defensive and think it's horrible and disturbing if you comment on their dangerous driving habits that they proudly post for all to see and playing the poor innocent fool who can't understand what went wrong why did my tyre blow when it was clearly under inflated and he admitted the vehicle was overloaded. Sometime experience doesn't make people wiser we were still shaking 4 hours after it happened what a cry for sympathy my heart bleeds for you your just lucky it wasn't the person you could have smashed into heart who was bleeding.

Yep.............Would have been interesting to read the Coroner's Report if they had have wiped out a mother and her two kids going to school.

Oh yeah and no compensation for any innocent survivors when the dangerous driver's insurance drops them and they decide to use bankruptcy as an escape goat and leaves the injured to struggle for the rest of their lives. Yeah it's just too difficult for some to comprehend how dangerous arrogance it is until something happens.