Tire loads rating are shown in 'pounds' because the primary purpose of the load rating is to indicate how much *load* (vehicle weight) a tire can support....in pounds.

There are no doubt other considerations (some mentioned in this thread) when designating a particular load rating for a particular car but the ability to support xxx-weight in the essential aspect.

Sure there is !

Jaguar specified 98 load rating. Doing so satisfied *their own* various requirements.

Not varying from factory spec satisfies the (legal) requirements of the tire vendors....because they know that there's a whole world of people out there looking for any excuse to find deep pockets. Talk to any tire manufacturer rep *off the record* and I'll bet a week's pay that they'd recommend a variety of suitable tires that, technically speaking, do not meet 'specification'.

When I buy a set of tires I'm more concerned with *my* requirements

For one example, I my neck o' the woods we have tons of rain. From a safety aspect, a tire with exceptional wet traction characteristics is a far great concern to me than the specified load rating ...and vastly more important than a V/W/Y speed rating.

For another example, my XJR tramlined horribly with factory spec tires ...a common issue....to the point of being nearly treacherous. It's was bad enough that I wouldn't let my daughter drive the car on the highway. Long story short I went with tires that were not factory spec (different cross section, aspect ratio, and load rating) and ended up with a car that I could comfortably let my daughter drive.

We have choices. it's up to each of use to make decisions. Personally I won't be a slave to 'factory spec' when I know there are better choices out there...ones that suit *my* needs and do not pose any safety threat to me or the world

Cheers
DD

 

Doug,
I'm all for you doing it your way, and for everyone else doing it their way too.
That unfortunately doesn't alter a couple of facts:
- fitting non spec tyres can invalidate your insurance ( at least in the UK it can)
- Jaguar know more about it than I do.
I know from previous posts that you have a healthy degree of cynicism when it comes to manufacturers and their self interests, but even the most cursory review of the market would show that all manufacturers are moving to put more and more rubber on the road in increasingly strong tyres ( do you have XL rated extra load tyres in the US?) and that since the XJR appeared with ZR speed rated tyres, they have introduced two higher speed ratings ( counter intuitively, W and Y). I suppose it could all just be a global conspiracy, and that tyre related failures are at an all time low for another reason, but .....
We haven't directly discussed brands, but even though I don't drive the car anywhere near its potential, I always fit a premium brand, in the correct size, load, and speed rating . In the same way as I use premium, correct spec brake and steering parts. Pretty much everything else I am open to debate about, but in the primary safety areas, I don't feel I know enough or want to take the risk.

 

You're right, of course. Good catch!

Cheers
DD

 

I can't tell you how often I've asked on internet forums if anyone has ever heard of that *actually happening*. Silence is the inevitable result

In the USA, as you imply, it is a non-issue.

Anyhow, what becomes of, let's say, the Series III owner who can no longer find 'specified' tires? Throw the car away? In the USA, at least, we look to alternatives. In this case fitting non-spec tires that we known darn good and well will get the job done, safely. How do we know it'll be safe? Common sense and observation.


Are you sure?

It isn't rocket science by any means. No magic.

Probably because of the public's love affair (which often turns to hate) with super low profile tires which need the extra strength due to their vulnerability to road hazard damage.




Not sure about ROW but tire related accidents are extremely rare in the USA even without, and before, the very latest trends in tire design. It's because tire quality in general has improved over the decades, and more to point, our speed limits, roads, and drivers themselves do very little to challenge their tires.

When that spec is no longer available what do you indeed to do?


Fair enough.

I feel I DO know enough.

It's not that I'm anything special. It's just that you don't need to be a Jaguar engineer nor a tire engineer to select a safe tire. You can stick to factory spec (which in-and-of itself really doesn't guarantee safety, after all) or do some research and independent thinking, review your *actual* needs and driving conditions, and make your own choices.

As for 'premium brand' I generally agree. Or try to, clinging to the past a bit. With today's global marketing and manufacturing, label engineering, and ever changing corporate ownership it's increasingly difficult to know what you're buying even with a well known name attached. And, let's face it, even the premium names have some dud designs from time to time. For just one example, the Pirelli P4000/4000E....for years the mainstay tire for owners of older Jags due to the V-rating....was far too slippery in the wet for me to feel safe and they were a bit notorious for belt separation and going lumping when about half worn. They met factory specs (for awhile there was even a P4000J variant--"J" for Jaguar) but I wouldn't regard them as particularly safe by any stretch of the imagination. I eventually deviated from factory spec and found a safer tire, the Michelin X-One.

Years ago you wouldn't never caught me dead with "Sumitomo" tires. Now that I've had a couple sets, and found them to be perfectly satisfactory, the strength of my convictions regarding name brands is being challenged!



Look at tire failure/accident stats. I'm betting you'll find there isn't all that much risk. You'd probably reduce risks much more by simply avoiding roads that have lots of taverns!

Cheers
DD

 

Guess I'll jump back into the fray... Working in the defense industry for years and years, dealing with load stress was one of the specs I learned way too much about. For instance, if you happen to load a certain antenna system on to a k-loader and then insert it in to the cargo area of a C 130, you had best be sure that the tires are inflated to 105 psig. Tire deflection during maneuvers and landings can cause some pretty good g force and the tire deflection is amazing. You should see what happens when a load shifts in an aircraft. The force on tires as one tools down the road is more than you think, i.e., uphill, downhill, potholes, fast maneuvers, high speed cornering through the mountain roads of Colorado....

Couple of articles I found interesting and personally, I will never use a tire that doesn't meet my vehicle spec but you are more than welcome to use whatever tire you think is right for you. And yes, I do exceed 100 mph quite often.

TurnFast! Race Driving Techniques for Heel Toe Downshift, Driving Line, Cornering, Braking, and More ? Weight Transfer

Tires | ConsumerWatch.com

http://www.aa1car.com/library/tirefail.htm

 

Yes indeed! But are you saying that the only way to safely deal with such forces is unwavering adherence "factory spec" ? I'm assuming not



A person who regularly drives over a 100 mph would likely have different requirements and expectations from a tire than a person who never exceeds 70 mph, just as a person who regularly drives in wet weather has different requirements, as would a person who places large emphasis on low noise and soft ride, as would a person who places more importance on long tread life, and so forth.

Cheers
DD

 

While I am not an attorney, and this post should not me misconstrued as legal advice, I think that having non-spec tires is a huge liability issue in the USA.

Say a car is involved in an accident, that has nothing to do with the tires. Say there is litigation, trying to establish the party at fault. One of the cars gets examined by an expert witness, and the witness testifies that the tires don't comply with the requirements of the car's manufacturer. With a little investigative work, the attorney for one of the plaintiffs was able to determine that the owner of the other vehicle knowingly installed tires that were non-compliant. At this point the owner of that car is screwed, because any trial attorney should be able to easily argue "willful disregard for safety". The guy might be found at fault, even though he wasn't and even though the accident had nothing to do with tire performance. Things like that don't look good in front of a jury.

I am not saying that this is right/just/how it should be. But this is how the system works, whether we like it or not.

 

And, obviously, any attorney representing the car owner can present his own expert witness to explain and prove what is already known....that the tires had nothing to do with the crash....and simultaneously expose the other attorney's nefarious deceit! Telling the truth works with jurists, too !

USA car insurance companies, who have the most at stake it would seem, don't care about tire specification in the least. I know because I asked, read, and researched.

I know that our sue-happy society can come up with some twist-it-into-a-pretzel lawsuits such as you've described. That's why so many tire vendors won't install a non-spec tire. It's not that they truly think they are putting the customers' safety at risk. They've simply been advised to avoid doing so for the exact reason you described. They're serving their own interests much more than the consumers'.

Anyhow.... in leading our lives and making choices we each determine for ourselves how much to let such possibilities control our decision making.

Cheers
DD

 

You should look up the term "proximate cause".

It basically means that you have to establish a relationship between
the factor and the result.

One can also argue "community standards", "industry practice" and the
list goes on.

But first, you have to establish proximate cause.

 

At the risk of this descending into an entirely legalistic debate, I am not sure that it is a s simple as your proximate cause comment suggests, principally as your insurer can void your insurance cover under the terms of the policy as it is normally a condition of the policy that you have to declare any departures from the manufacturers specification. As Doug has mentioned, there is no evidence that insurers do this often, but once would be enough if you find yourself in the position of having to make a claim...
And yes, you could argue that the tyre and vehicle manufacturers are wrong, and on the right day in the right court, you might win, but I don't fancy your chances, nor the cost of lining up the necessary experts.
Factor in that even Doug agrees that the correct spec tyres are safer, and that the cost savings from fitting lower spec tyres are very modest, to use another legal expression, I rest my case!
In reply to Doug's question about what to do when the standard spec tyres are not available, fortunately that is not a situation faced by X300 owners for the moment. However, having encountered it on another vehicle, I fitted the next speed rating up, and would have done the same with load rating had the correct one not been available.

 

I'll hazard a guess that Steve never imagined his post would turn into an "oil thread"

 

Actually, with respect to the USA, what I said is that insurers flat-out don't care. Tire spec, disclosed or not, is not an issue with them.

With respect to UK/ROW, when I've asked, nobody from the UK/ROW has ever heard of this actually happening....even though it is mentioned quite often.



Did I say correct spec tires are safer? I don't recall saying that, specifically. The point I've been trying to make is that, with some rudimentary thought and research, you can vary from factory spec without compromising safety and, in some cases actually increase the margin of safety.

The issue has never been about saving a few dollars on a set of tires.


Good answer, as long as those choices are available.

The reason I asked is that, as you know, this topic s nothing new. I first became aware of it in the late 1990s when 'factory spec' tires were becoming scarce for the 70s-80s vintage Jags. 'Scarce' then morphed into 'extinct'. We were having the very same conversations back then and the solution for the majority of us, in the USA at least, was to fit non-spec tires. This choice was met with the very same dire predictions, mostly from the ROW/UK owners: Jaguar knows what's best for you, tire failures, lawsuits, attorneys' fees, highway tragedies, you're taking your life into your own hands, voided insurance cover, mayhem

None of which has ever materialized!

Cheers
DD

 

I am in the UK. When I wanted to run on winter tyres I spoke to my insurance company about the rating of the tyres. They allowed me to put tyres on that were rated SLIGHTLY lower than originally designated by Jaguar. I got them to send me a letter accepting this. So in the UK beware!

 

So much fun from from just one tyre delaminating!
Doug,
I do not recollect you ever saying in as few words that correct spec tyres were safer, but it is the clear and only inference from your line of argument on this and other tyre related threads, but your latest comment that below spec tyres might in certain circumstances be safer affords an opportunity to clarify the matter. Can you tell me when, say a V rated tyre might be safer than a Z, or a Z safer than a W? Or a 94 load rating safer than a 97?
As for the attitudes of insurance companies, I can only speak for the UK, but I would not be so sure, although I am sure that I do not want to take the risk of finding out the hard way. I would be interested to know whether you have ever actually asked your insurer to "bless" any of your departures from standard spec?
My most recent experience of a departure from standard tyre sizes was on a BMW 635 CSI from 1988, which had the dreaded metric wheels fitted, with worn out Michelin TRX tyres on them. (Jaguar and BMW seemed to put a toe in the metric pond at around the same time.) The wheels themselves were in astonishingly good original condition, but tyre availability was a known issue, as the TRX was the only tyre made for the wheel, which had a unique rim/ wheel well design. Investigation revealed that there had in fact been some recent remanufacture of the tyres, and they could be purchased for a mere £350 each! Before taking the plunge, I googled reports on the TRX tyre, and they seemed a fairly mixed bag, with the only consensus being that the tyres went "off" fairly quickly with age and lack of use. I began to wonder whether it made sense to stick with what had been seen as high tech in the 1980s but had conspicuously not been pursued subsequently. ( how many modern tyres have a tread pattern that looks remotely like a TRX?)
In the end, I replaced the wheels to allow fitment of modern tyres,
But:
I bought a BMW wheel of near equivalent diameter and width, and identical offset. The wheel type had been fitted to the M6 from new.
I fitted continental sport contact 5 tyres, with a Y speed rating ( originally Z) and a 97 load rating ( originally 94)
All for about £500 less than the cost of the TRX tyres.
My insurer was perfectly relaxed about this, as the tyres were demonstrably higher spec than original, but I would not have expected the reverse to be true.

 

Yes, very easily.

For example, as already mentioned, if a person does lots of wet weather driving, a tire with exceptional wet traction attributes would be safer than a tire with merely average wet traction attributes, even if the former technically has a lower spec. (unless, of course, one plans 150+ mph cruising in the rain!)

Another example, already mentioned, is my own XJR. It was very clearly safer to drive with non-spec tires (smaller size, lower load rating) because the infamous and treacherous tramlining was eliminated. Keeping the car in your own lane is a safety issue, after all!

Still another example, already mentioned, is the infamous Pirelli P4000 tires. They absolutely met Jaguar 'specification" but were prone to belt separation. Belt separation is not safe at all. A tire less prone to belt separation would certainly be safer, even if it had a lower speed/load rating.

If you believe that tire safety springs *only* from speed rating and load rating 'specification' (and it appears you do) then, naturally we'll be in disagreement.


Yes, as mentioned earlier, I have researched the issue.

I called my insurance company a number of years ago. They don't care about tire specification....or most anything else. Thanks to my years in the repair business I have easy access to insurance adjusters. I asked several about the issue and they looked at me as though I just landed from outer space. They don't care about tire spec or modifications. I read my insurance policy and a couple others from other carriers. No mention of tire specification and/or other spec changes compromising the coverage.

They DO want to know if you have a custom installed stereo, custom paint, fancy aftermarket wheels, 4x4 lift kit, and other accessories/spec changes for the purpose of imposing a surcharge.... as they assume they be more expensive to replace if stolen or damage. If not informed, and you don't pay the surcharge, they certainly won't deny coverage but they'll pay only what it would cost to replace factory installed parts.

That's as far as their interests go.


There are any number of other choices you could have made without compromising safety. But it appears that appeasing your insurance company is your main concern and, indeed, requirement. I'm not hindered in that respect. This accounts for a lot of our disagreement on the issue.

I'll stop beating the dead horse

All's well.

Cheers
DD

 

Doug,
At last, two things on this thread that we can both agree on: the horse is dead, and all is well!
In the interests of us both enjoying the remainder of our weekend, I will not take the bait to re-open our tramlining discussion!
With best wishes
F

 

Just to throw in another factor - did anyone check the guilty tire to see if it had a nail or similar object in it?