Tyres "perishing"

GolfBravo

50Twuncle wrote: »

Or a fault (as appears the situation in my case).....

Apart from the cracked side wall rubber that you see there are also radial plies underneath - this is what holds the rubber in one piece. So as long as the plies are OK, the tyre should be fine.

Overinflation doesn't cause the side walls to crack as the plies prevent the tyre from expanding (too much). You would need to inflate it way over 50psi to cause any damage.

If these cracks are on all tyres and on both inside and outside walls my guess would be under inflation in winter - as the temperature drops from 25ºC to -5ºC, the pressure is likely to drop by about 3psi. Not a big deal really, except for if this is a summer tyre, the rubber compound loses flexibility in low temperature, and the sidewalls start to crack (especially on under inflated tyres as they flex the sidewalls more). Unfortunately, all summer tyres suffer from this in winter, and the only thing you can do to minimise the damage is to keep checking the tyre pressures at least every fortnight.

Just take your car to a reputable tyre place (i.e.. not Kwik Fit) and ask them to take a quick look. I'm sure it's nothing to worry about.

Joe_Horner

OP was talking about cracking in the tread band, GB, but apart from that absolutely agree. In fact, the tread band can be more susceptible to cracking when cold and under-inflated because of the way the tread flexes.

I'm also quite surprised that anyone doesn't realise that tyre pressures drop as the temperature drops and need adjusting accordingly, seeing as the opposite is true as they heat up. Makes you wonder how many people are happily checking their tyres hot after a run and ending up under-inflated as a result!

GolfBravo

Joe_Horner wrote: »

OP was talking about cracking in the tread band, GB, but apart from that absolutely agree. In fact, the tread band can be more susceptible to cracking when cold and under-inflated because of the way the tread flexes.

Oh, my mistake.

In that case there is only one other possibility that I can think of: lack of use.

My (not quite) 2 year old car - has done less than 12,000 miles

For the rubber to crack it needs to lose its flexibility, so either very low temperature or lack of use. Inflated tyres age faster (the air pressure keeps stretching the tyre outwards) so to keep elasticity you need to work them.

PS
This is exactly why you need to drop the tyre pressure by 30% when storing summer tyres in winter.

Iceweasel

Joe_Horner wrote: »

OP was talking about cracking in the tread band, GB, but apart from that absolutely agree. In fact, the tread band can be more susceptible to cracking when cold and under-inflated because of the way the tread flexes.

I'm also quite surprised that anyone doesn't realise that tyre pressures drop as the temperature drops and need adjusting accordingly, seeing as the opposite is true as they heat up. Makes you wonder how many people are happily checking their tyres hot after a run and ending up under-inflated as a result!

This may well be the origin of the expression 'Perishing Cold'

Summer tyres do go very hard at low temperatures and not only suffer cracking, but may well lose parts of the tread on rough tarmac.

colino

To all those thinking their houses will expand, possibly needing an increase in council tax, when summer comes around, do Boyles Law or Bernoulli's Principle have a remnant of memory in their physics lessons?

Joe_Horner

So what exactly does Bernoulli (concerning the pressure of an inviscid moving fluid) or Boyles law (concerning a contained gas) have to do with the size of your house, which is presumably constructed of solid material?

Boyles law does apply to gas in tyres and it shows that a change of 10 deg C will give approximately 1.5 psi change for a tyre intitally inflated to 30 psi. Which is around 2 - 3 psi difference between average summer and winter temperatures in the UK.

50Twuncle

GolfBravo wrote: »

Oh, my mistake.

In that case there is only one other possibility that I can think of: lack of use.



For the rubber to crack it needs to lose its flexibility, so either very low temperature or lack of use. Inflated tyres age faster (the air pressure keeps stretching the tyre outwards) so to keep elasticity you need to work them.

PS
This is exactly why you need to drop the tyre pressure by 30% when storing summer tyres in winter.

What does "lack of use" mean - how is 7000 miles per year (average) ?

Weird_Nev

Joe_Horner wrote: »

So what exactly does Bernoulli (concerning the pressure of an inviscid moving fluid) or Boyles law (concerning a contained gas) have to do with the size of your house, which is presumably constructed of solid material?

Boyles law does apply to gas in tyres and it shows that a change of 10 deg C will give approximately 1.5 psi change for a tyre intitally inflated to 30 psi. Which is around 2 - 3 psi difference between average summer and winter temperatures in the UK.

Or 6 Psi between day and night temperatures in Australia, which if you've been running your tyres at 12Psi on sand in the evening can be a problem in the morning!

OddballJamie

Not surprised the tyres are older than the car. You're going by the date the car was registered to you not the date it was built, could be many months apart.

In any case they shouldn't be doing this at two, three or four years old.

GolfBravo

50Twuncle wrote: »

What does "lack of use" mean - how is 7000 miles per year (average) ?

7000 miles is just below the national average for private cars (8500 miles). Apparently a fifth of all cars on British roads cover only 5000 to 7000 miles.

Are these ContiEcoContact by any chance?