Chipping of BFG tyre

[voyager Junior Member Find all posts View Profile Close voyager]

I am running 275/65 R17 BFG A/Ts and they have done just on 30,000km and look to be only about half worn.

I have just completed a trip from Brisbane down to the Clare area in SA, up to the Flinders Range, back up the Strezelecki Track through Cameron Corner to Quilpie and back to Brisbane towing a Kimberley Karavan - approx 2,000kg loaded.

There would have only been about 1,500 km out of the total 5,500km on gravel roads. I was checking tyre pressures all the time and maintained 42 in the rear tyres on the bitumen and dropped them to 28 on the gravel keeping speed down to 80 - 85 kph.

Three of the tyres went well but the driver's side rear has a lot of little chips out of it - about 6mm in diameter. All four tyres have the same build date code. There were none of these chips evident before the trip.

Has anyone any ideas why this would happen and should I be doing anything about it?

Harry

[Guest Close Guest]

Maybe its got to do with temperature with that tyre being closer to the exhaust.

[voyager Junior Member Find all posts View Profile Close voyager]

You might be right Andrew.

I use Tyredogs but really only monitor the tyre pressures. I will keep an eye on the temperatures in future.

Harry

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

Exposure to sunlight will advance deteriation that one tyre may have been stored on the end of a rack. What a lot of people aren't aware of is that tyres have a shelf life just like other products.

Richo.


Sent from Richos iPhone using Tapatalk

[404pug Avid PP Poster! Find all posts View Profile Close 404pug]

Those South Australian roads really knock your tyres around. My 265/65 BFG AT at 40,000 are so severely chipped that I just replaced the back 2 with 2 new ones [10mm] in preparation for a Simpsom trip in July and relegated the back 2 to spares. The front ones had about 1.5 mm more tread [6.5mm] than the backs [5mm] and were nowhere near as chipped. The chips that they did have they got on a previous trip when they were on the back. The back has the load and cops the rocks chucked up by the fronts. Neil

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

Maybe its got to do with temperature with that tyre being closer to the exhaust.

I would be surprised if the exhaust made much difference to the tyre temperature, looking at the temps on my tyre dogs I haven't noticed that one being much warmer. It is very noticable though when travelling East or West that the tyres on the North side of the vehicle can be anything upto 20 degrees warmer than the south (shaded) side.

It does seem strange that only 1 tyre had the issue, probably worth running it past your tyre dealer, it could be a problem with the tyre!

As a rule the left rear normally cops the biggest hiding, more weight added to more stones on the edge of the road than in the middle. Take note when you travel and see people changing flats, its surprising how often its the left rear, Adam Plate at the Pink Roadhouse pointed this out to me many years ago and he should know!

Cheers Andrew

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Weren't there rumours of a batch of BFG that didn't come from the USA or something? Do you guys have Made In USA on your BFGs? <Did I just start a rumour?>

[Milti 1974 Junior Member Find all posts View Profile Close Milti 1974]

Heard today whilst enquiring about BFG's (retailer was a cooper retailer) that tyre quality may have become an issue??????

[Bellyup Junior Member Find all posts View Profile Close Bellyup]

Like some of the boys from S.A. said - the dirt roads, especially Flinders/ Arkaroola and north of, are murder on tyres. My BFG A/Ts copped a hiding up around there. I reckon the big chunky tread could work against you on those roads.

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

Heard today whilst enquiring about BFG's (retailer was a cooper retailer) that tyre quality may have become an issue??????

That's what all Cooper retailers will tell you about every other brand - they are liars, the lot of them.

[gxl_d4d Advanced Member Find all posts View Profile Close gxl_d4d]

I have the same chipping problem on both rear tyres running 32psi cold on gravel roads. My front were run at 30psi and had no chipping.

I've have to try 34 or 35psi next time. I wore off 3mm rubber on the rears in 3000km.

My grandcraps didn't chip at all running at 26psi on a 1000km gravel run a few years ago.

[Moz Junior Member Find all posts View Profile Close Moz]

[...] looking at the temps on my tyre dogs I haven't noticed that one being much warmer. It is very noticable though when travelling East or West that the tyres on the North side of the vehicle can be anything upto 20 degrees warmer than the south (shaded) side.
[...]

Cheers Andrew

That's bloody amazing! i wouldn't have thought it would get anywhere near a 20deg difference!!!

what sort of pressure change will you see in that situation? ...i'd imagine a considerable amount?

[Guest Close Guest]

For an ideal gas, pressure is proportional to temperature (PV=nRT http://en.wikipedia.org/wiki/Ideal_gas_law)
Note that the units for T is in Kelvin (not degC). Now use the following formula:
P1/T1 = P2/T2

If the tyres are 40psi at 25degC (298K) and the temp rises to 45degC (318K), the values in the formula becomes:
40/298 = P2/318

Therefore, P2 = 42.7psi

To put it in english, if the tyre's cold pressure is 40psi at 25degC, when the tyre temperature rises to 45degC, the tyre pressure goes up to 42.7psi.

[Moz Junior Member Find all posts View Profile Close Moz]

For an ideal gas, pressure is proportional to temperature (PV=nRT http://en.wikipedia.org/wiki/Ideal_gas_law)
Note that the units for T is in Kelvin (not degC). Now use the following formula:
P1/T1 = P2/T2

If the tyres are 40psi at 25degC (298K) and the temp rises to 45degC (318K), the values in the formula becomes:
40/298 = P2/318

Therefore, P2 = 42.7psi

To put it in english, if the tyre's cold pressure is 40psi at 25degC, when the tyre temperature rises to 45degC, the tyre pressure goes up to 42.7psi.

thanks for the extremely informative answer... i'm currently on an electricians course…. with all sorts of formula's i can't get into my head… i don't think i can go trying to shove another one in there! but i'm sure i'll be able to plug some numbers into a calculator... my shock of hearing of a 20deg difference in opposite sides of the car stands tho... that's a massive difference!

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

Without wishing to look like a pedant the pressure in Boyle's law is absolute pressure too not gauge pressure so the calculation should add 14.7 psi before the ratio'ing for temperature rise and then take 14.7 psi off to give gauge pressure that you can read.

So 40 psi gauge pressure is 54.7 psi absolute, calcualtion then becomes 54.7/298 = P2/318, so P2 is 58.3 psi ab or 43.7 psi gauge. Pretty close but this is an education thread. I just love mixing imperial and metric. At least in this instance it works.

Sorry it didn't work did it........... The pedant bit.............

On the opposite side of the coin if you have a TPMS in the snow or overnight in the depths of winter the pressures cold can be 10 psi (gauge) lower than at temperature.