One thing to check is the date of manufacture of the tyres. DOTXXXX 4907 for instance indicates the tyre being manufactured on the 49th week of 2007. Worth checking such details to ensure you haven`t some ancient tyres being fitted.
Tell us. What model of Dunlop tyres and sizes are fitted and at what pressures you are running?
Do you carry heavy loads in the rear of the car. If so, what pressures do you then run at?
Once we have a few more hard points to work from we can look at the issue in further depth.
For every fault, there is a cause and effect. We know what the effect is. Now we need to establish a cause.
The cracking was on the inside walls. The DOT No. DN5V JA 1R5012 and are the tyres are 255/35R20 97Y SP Sport MAXX J XL MFS. I have spoken to the Director of the dealership and he said the first owner of the car is quite a responsible person who looked after the car. i have just checked the pressures the one original tyres which 33.5psi, the correct pressure should be 34psi all round.
J is one characteristic, XL is another and MFS indicates a limited run flat ability. I wonder if that limit may have been exceeded at some point in these tyres life. Side wall cracking can occur if tyres are run at markedly low pressures. Dunlop appear to market their tyres offering various combinations of those particular specifications to different product models. As I found when looking, you can for instance buy a tyre with just the J spec or with XL and with or without MFS spec.
From previous experience, certainly with a Pirelli tyre, the J indicated that it was suitable for a Jaguar car. Maybe this is also the case with Dunlop products but I cannot confirm that one way or the other.
The problem with low profile tyres is that it is often very difficult to visually gauge a low pressure tyre. I have that problem myself on 35% tyres. That being the case, I try hard to do what the car hand book advises. Namely weekly pressure checks. Inevitably, I suppose we can all be less than diligent in that respect on occasions. Perhaps the previous owner could have let that slip. A dealers assurances that the previous owner was responsible stands for little in my opinion. The dealer cannot realistically verify the statement can he? One over long trip on an overly soft set of tyres may have been enough to cause a structural failure of the tyre carcass to occur with cracking of sidewalls becoming visible at a later date.
Other issues that affect sidewall cracking are UV attack from sunlight and exposure to an ozone rich atmosphere. Close proximity to electric plant can cause that effect.
The interesting aspect to this thread is the cracking you note on the inner sidewalls. Perhaps someone else could offer and explanation on why this has occurred.
Whether 34psi or 33.5psi has been maintained matters little. As much as 4psi is often allowable by manufacturers under typical driving conditions. Higher pressures are generally recommended for faster driving and higher load situations.
As regards the DOT digits you have given, this perhaps needs verification. As I see it, 12 would perhaps indicate manufacture in 2012 which seems logical and the 50 indicating the fiftieth week of that year. So those tyres are not aged beyond acceptability as a safe or legal prospect.
Maybe you will have to bite the bullet as regards replacement costs or look at the small print as regards your purchase contract with the dealer. If there is an argument to get the dealer to fund replacements, it might be from a "merchantable quality" aspect.
After sending a reply letter to Dunlop outlining my thoughts on the problem and said I will be seeking to send the tyres to an indepedant specialist to ask their opinion on this issue. I received a phone call today saying that they still stick to their initial decision, but as a goodwill jesture they will refund an amount after deducting allowance for wear. So I will get 60%, 45% and 40% back on tyres that cost £210 each. It is better than nothing, but I will have to think hard when I need to replace the tyres as to which manufacturer I choose. Anyway thank you for your help on this matter and it is good see the Forum working as it should with other Jaguar Enthusiasts taking the time to reply and help.
Ultimate Black XF 5.0 V8
It is difficult to fathom quite what is causing several manufacturers problems with tyres disintegrating whilst at very early years of service.
As I surfed the issue I was rather astounded to find many of the premium brand makers were also being slated for sidewall cracking problems.
Technology moves on. Sometimes not for the benefit of the end user although the environment appears to win hands down.
Brakes. Now we have an issue with brake pads and discs since asbestos was taken out of pad material.
My last set of discs and pads wore out together. Previously, to the introduction of asbestos free pads, I had no difficulty getting three pad sets to one disc set before replacing the whole lot at the fourth reline session. Now it appears to be almost one pad set per disc set.
So, could it be what we are seeing with tyre degradation has something to do with the compounds that are now being used for tyre manufacture?
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