Tyres "perishing"

50Twuncle

GolfBravo wrote: »

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?

Exactly - I am NOT under-using my car.....
I am not sure about the exact model - I will have a look later
The tyres are at fault.

50Twuncle

Weird_Nev wrote: »

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!

Do you check your tyre pressures (all 4) - at least twice a day ?
I will try to take and post a photo here to show the problem

Ultrasonic

Joe_Horner wrote: »

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.

This is rather splitting hairs, but I think Golf Bravo's figure of approximately 1 PSI per 10°C is about right actually (and being really pedantic, Boyles law relates isothermal pressure and volume changes and so isn't actually relevant here.)

If you take the tyre volume to be fixed (a very good approximation) and assume the air in the tyre to behave approximately as an ideal gas (a reasonable starting point for the accuracy we are concerned with), then if the temperature drops from 15°C to 5°C the pressure will drop by a factor of (273.15+5)/(273.15+15)=0.965, such that a tyre initially at 30.0 PSI would drop to 29.0 PSI (to 1 d.p.).

colino

My apologies for throwing reality into the equation. No doubt when the temperature where you are fluctuates, the carcass of the tyre remains exactly the same as it would at STP, doesn't react elastically and only the gas inside this never changing quasi pressure vessel alternates.

Joe_Horner

colino wrote: »

My apologies for throwing reality into the equation. No doubt when the temperature where you are fluctuates, the carcass of the tyre remains exactly the same as it would at STP, doesn't react elastically and only the gas inside this never changing quasi pressure vessel alternates.

As near as makes no difference from the POV of the pressure. That's why it's made with all those plies you see - if it was just a big rubber bag things would be different but then it'd be a balloon not a tyre

Joe_Horner

Ultrasonic wrote: »

This is rather splitting hairs, but I think Golf Bravo's figure of approximately 1 PSI per 10°C is about right actually (and being really pedantic, Boyles law relates isothermal pressure and volume changes and so isn't actually relevant here.)

If you take the tyre volume to be fixed (a very good approximation) and assume the air in the tyre to behave approximately as an ideal gas (a reasonable starting point for the accuracy we are concerned with), then if the temperature drops from 15°C to 5°C the pressure will drop by a factor of (273.15+5)/(273.15+15)=0.965, such that a tyre initially at 30.0 PSI would drop to 29.0 PSI (to 1 d.p.).

No problem with the hair splitting, it's a long time since I needed any of this stuff and got Boyle and Amontons mixed up

As for the exact figures, my bad - did the sums in bar then converted and it's surprising how big the rounding errors become! :beer:

50Twuncle

I have received a response from my garage - since tyres do not come under the vehicle warranty - there is very little that they can do !!

GolfBravo

50Twuncle wrote: »

I have received a response from my garage - since tyres do not come under the vehicle warranty - there is very little that they can do !!

Car warranties do not cover tyres. Tyres are covered by tyre manufacturer warranties - contact Continental.

dors01

50Twuncle wrote: »

My (not quite) 2 year old car - has done less than 12,000 miles and I noticed this afternoon - that between the treads of all 4 tyres - there are small cracks (lengthwise) in the rubber
Could the tyres be perishing already ?
The tyres are Continental 185/55 R16
Is it worth my contacting Continental to ask why ?

Hi, I have worked in the fast fit (tyre places mainly) for about 20 years and can tell you that in my experience certain sizes and tread patterns of Continental tyres do suffer from premature perishing.

Your best bet is to take your car to a fast fit centre to have it checked, perished tyres are very dangerous.

Can tell you who I work for if you want but will do only in private message.

FLAPJACK

Have exactly the same problem with all four DUNLOP GRANDTREK tyres factory fitted on my Honda CRV 2010.

Had the car from new and not used too much...infact only last weekend did I clock up 17000.

Have had no problems with losing pressure though, I had them inflated with Nitrogen....apparently the molecules air larger than in air so it slows up the deflation process.

I have read that the cracks can be caused by low temps, so I suppose as my car is only used a couple of times a month in the winter (no garage either) it could be a factor.