Winter tyres (or winter wheels?) on S-Type R

[blackflash]

Loving my new car but of course dreading the winter as much as in the XJR or XKR-S... I have seen and read with interest the earlier posts re winter tyres but my questions are not around brand or price - and i'd be particulaly keen to hear from any fellow STR drivers about success or not in using winter tyres. I suspect the combination of automatic box and engine power means this is never going to be easy...

Standard tyres on 18" rims are 245/40 front and 275/35 rear. I can't get Snowksocks or Weissocks for all four corners so am considering my first ever purchase of winter tyres.

I know some people buy a set of cheaper steel wheels so they can more easily swap them over. A few questions then:

- Has anyone managed to source socks in the right size for an STR?
- If not, is it possible to use 18" wheels with a narrower (higher profile) tyre for better cutting through the snow? If this is possible and you have tried it, please share any stories.
- If I go for winter tyres on my existing wheels, how much difference am I likely to see? Is it like night and day, or just a marginal improvement?

I still remember my first experience with winter tyres which was as a passenger in a Mercedes taxi in Munich twenty years ago. I simply couldn't believe how it turned and drove as if the snow wasn't there! Was it just that particular car/tyre/snow combination?

Brighten my winter.

Nigel

[J44EAG]

I can only comment from my own experience with my own tweaked 4 litre V8.

The car is on 245/35/19 budget Nexens and last year the handling in the snow was truly excellent. I could munch my way up the icy hill to a roundabout and then pull out onto the main road with absolutely no drama at all. Traction control on and with sensible application of power meant J44 was just sheer joy. Have to say, I`ve found an S-type in the snow to be probably the best mannered car I`ve driven under such conditions.

By comparison, a 4x4 2.9 Sierra I once owned was an absolute screaming horror in the snow. Perhaps fairer to say that I probably never mastered the art of that car on ice. It frightened the daylights out of me on a couple of occasions. The S-type I find to be a thousand times more predictable.

Mike

[blackflash]

Wonderfully encouraging, Mike!

Forigve my ignorance re standard wheel sizes on the 4.0 n/a but are those winter tyres on your original wheels or on spare wheels? If the latter, how does the size compare with the standard "summer" setup?

[J44EAG]

My 19" wheels are now a permanent fixture. Originally taken from an X350.

Rim J size is one J larger than anything Jaguar ever fitted to a 4 litre. Standard max is stated at 8.5 J with a max offset of 50mm. My rims are 49mm ET and just clear the arches! The track is therefore widened and the rims fill the space. The car looks rather different in stance as a result.

Tyres are basic all year round items. Nothing special at all. Just budget Nexen at £120 each. I get around 12k miles from them before renewing. I know that sounds a low figure, but I do drive and corner the car quite hard on stiffened and lowered dampers and springs. I wouldn`t expect much more mileage from such tyres. I take the view that the tyres are relatively cheap compared to typical Pirelli types which cost more than double the Nexons and even then I`d only see probably a life of around 18k before they needed to be replaced.

I don`t mind changing tyre sets every year. Nice to have new carcasses each year. Rather reassuring really.

A word of warning though. The STR has rather more grunt than a standard 4 litre and I believe that with such performance available, the option of fitting cheap budget tyres to such a car would not be advisable. Premium brands only as regards the STR.

Memory fades with age, but to answer your question about standard rim sizes, I recall that tyre sizes on my car were 225/55/16 of 8J rims. I might be wrong but I believe the ET on those rims was around 37mm. This might need checking for accuracy of this statement.

Mike

[blackflash]

Brilliant, v informative: thanks for the pics, and for the health warning!

On the case, and will report back.

[GordonJ]

Hi Nigel,
just a another take on this thread. Having returned to the UK in October after 8 years in Germany I can say with confidence that winter tyres definitely give superior grip and traction over summer or all weather tyres. I was not a believer in this till I put them on to my Kia Sportage after two years without. The difference in grip and steering was like night and day. Insurance companies in Germany insist you put them on. I put mine on from October till end of March. I also only use steel wheels for my winter tyres and it keeps my alloys nice and fresh for the summer. (Saves me pollishing to sets of alloys)
I don't have a set for the Jag yet, so it may stay nice and warm in the garage over winter. Maybe just light runs to keep everything free and working.
You are welcome to PM me if you require further information.

[blackflash]

Thanks. I have all but decided to go the winter tyres route, just need to determine whether to do so on existing wheels or on a utilitarian steel or tattier alloy wheels. I won't be taking them on and off myself so it will depend on cost primarily, with protection of my "summer" alloys a bonus if I go for the wheels also.

I'll keep you posted.

N

[blackflash]

And just when I thought I was getting my head around this, I spotted this from Mike on the earlier thread about winter tyres:
"I generally ... 245/35/19 Nexens... If the car was still on its old 235/55/16 rims, I`d never have got away with it."
So what makes the difference? I sort of understand the tyre sizing formula, but are you saying Mike that the key to the difference lies in the tyres being narrower (higher profile)? And therefore of course needing to sit on different wheels?

If so, I think I have three options:
a) buy winter tyres for my alloys
b) buy narrower wheels and fit all-weather tyres like the Nixen
c) buy narrower wheels and fit winter tyres

I guess that (c) is likely to perform best!

Any input much appreciated - hope to make the call to the usual tyre place in next few days...

Nigel

[Montana5]

I can't speak first hand here as I don't use mine over the winter, I therefore can only give my opinion based on what friends say and testaments from members of a few other Jaguar forums, although I am researching the purchase of winter tyres for our rather heavy people carrier just now.
I had hoped Krish (Latebreaker) would have picked up on this thread as I know he has just fitted winter tyres to his STR

As Mike has already mentioned and you know yourself Nigel, the STR is a completely different beast, so I would definitely rule out option b, winter tyres are by far the best option.

I'm not sure if you have the Brembo Brakes or not, but you will have to watch the wheel fit if going smaller, generally most folk go one wheel size down and as skinny as possible, however that might not be an option on the STR, the other factor to take into account is the weight of the Car so any smaller wheels (or tyres) must be of a size / build to carry the weight.

Possibly the option to fit tyres to your existing wheels might be best, however it might not necessarily be the cheapest, having different size tyres front and back doesn't help, 4 same size tyres are probably going to be cheaper.

It is going to be pretty expensive no matter what route you take, remember you are supposed to let your insurance company know as well, most have been ok though some have been known to charge extra.
Hope you get fixed up and let us know how you get on, if I can dig up any more info I'll let you know.

Doug.

[J44EAG]

Rim and tyre comparative sizes then.

Rolling length around the circumference of both 16" and 19" tyres is the same for both rim sizes, so overall gearing for the car is as standard ex factory.

19" rims with 35% tyre profile put on my car to improve general handling. Result is less tyre "squirm" ie carcass distortion during cornering. In other words, the tyre carcass stays inline with the rim rather than distorting under cornering loads. In my opinion excessive distortion occurred on 16" rims and 55% aspect ratio tyres when cornered even at relatively low speeds. On 35% tyres the car now goes where you point it and excessive extra steering input is not required to coax the car around a bend. Less tyre squirm reduces tyre wear as "slip" angles are reduced ie tyre scrubbing reduces and tyres last longer, especially on the inside and outside shoulder areas.

Lowered springs drop the roll centre of my car. This reduces body roll which keeps both the car body and the tyres more horizontal during cornering. The keeps tyres flatter to the road, further reduces under steer, tyre slip and tyre wear.

Stiff 30% uprated gas sport Bilstein dampers provide improved road spring oscillation control, fore and aft body pitching together with reduced suspension movement on bumpy roads. The ride becomes firmer and suspension ball joints, vertical links and bushes see an extended life.

Tyres in snow now. I see it like this. Contradict me someone! It is a question of force, pressure and area. The weight of the car is the force acting downwards. The area is the footprint of the tyre ie length x breadth of the "footprint" area in contact with the ground. Assuming the weight of the car remains a constant, the pressure under the contact area may be increased or reduced by altering the length x breadth of the tyre footprint. ie the larger the area of tyre in contact with the ground, the lower the pressure under the tyre. The converse will obviously apply.

Consider Aircraft A landing on softish tarmac on skinny width tyres. It is likely to dig into the tarmac when landing causing grooves of say 2" depth in the runway. Call this a high load compression sinkage. The aircraft decelerates abruptly, the pilot smashes his nose against the windscreen and spends a week in hospital.

Take the same aircraft (Aircraft B) of the same weight landing at the same speed and and rate of decent onto the same soft tarmac. Consider that that aircraft is fitted with tyres of twice the width of Aircraft A. Simplistically only a 1" depth groove occurs. Call this a moderate load compression sinkage. The aircraft slows less abruptly than Aircraft A and the pilot breathes a sigh of relief as the moderate tarmac sinkage helped slow his aircraft somewhat and he didn`t go through the hedge at the end of the runway. Handy.

Aircraft C is the same as Aircraft A and B except it has great big fat tyres. No damage occurs to the runway, the aircraft does not sink into the tarmac and the pilot gets a medal for landing on the golf course without hitting the club house where a JEC Regional meeting was taking place. Everybody happy.

To my mind the above applies to tyres on cars in the snow. Narrow tyres will tend to sink into soft snow, an abrupt halt might take place and traction will be lost. Fatter tyres would spread the load over a larger area, the car remain on the surface of the snow and traction be maintained. Sheer joy.

I believe that improvements of my car in the snow have occurred changing from smaller footprint areas of the narrower 225mm width tyres on 16" rims to 245mm width tyres fitted to my 19" rims. Across an axle then, I have additional tyre rubber of 40mm in width. (Two tyres x 20mm extra width rubber each) It is late now and I`m fatigued. My calculations may be duffers, but my increased tyre width amounts to an increase of an extra 18% tyre area compared to my old 16" rim tyres. So nearly one fifth extra surface area for each axle tyre set. Useful grip indeed in the dry, the wet and in the snow.

From my own personal experience, I would not fit narrower tyres for the winter for reasons above. Winter tyres do afford extra grip in adverse conditions. They are well worth having. In Germany, I believe that domestic regulations insist that winter tyres are fitted to cars during certain winter months. I further understand that many car owners have two sets of wheel rims for their cars. One set with summer tyres, the other with winter tyres. That type of regulation may come to the UK eventually! Start saving............

The aspect ratio (percentage) of the tyres in slow moving snow conditions is somewhat academic. Very different to summer conditions where we drive rather faster than in the winter and handling under higher cornering forces influences the aspect ratio of the tyres we fit to our cars.

Aspect ratio (side wall height of a tyre compared to its width) is measured as a percentage of the tyre sidewall height. As an example, a tyre of 100mm width manufactured as a 35% side wall height, would have a sidewall height of 35mm.

I`m off to bed. MOT time early tomorrow.

Mike

[GordonJ]

From my own personal experience, I would not fit narrower tyres for the winter for reasons above. Winter tyres do afford extra grip in adverse conditions. They are well worth having. In Germany, I believe that domestic regulations insist that winter tyres are fitted to cars during certain winter months. I further understand that many car owners have two sets of wheel rims for their cars. One set with summer tyres, the other with winter tyres. That type of regulation may come to the UK eventually! Start saving............
[quote][/quote]

In Germany every vehicle comes with the rim and tyre size written into the vehicle registration document. This has to be adhered to. Hence summer and winter tyres and rims are the same size.
To change wheel and tyre sizes without notifying the licensing authorities and the TüV (MOT) is an offence and would invalidate the insurance policy. Plus if you do change the size of any tyre or wheel you then have to have the vehicle type approved again. "Trust me not worth the hassle"

Gordon

[blackflash]

Wow, thanks guys - this is a forum working at its very best!

I will look into the cost of winter tyres on my existing rims. I will in slower time keep my eye out for a spare set of same size wheels to put the winter boots on.

That was a really helpful discussion about narrow/wide - mentally I had it the other way round, with narrower tyres "cutting through" the snow... This was based on my experience many years ago of driving smaller cars ok but struggling to gain any traction at all on my subsequent cars. I now guess this difference may be more to do with the greater weight and power of those later cars and the fact that they have been rear wheel drive versus the front wheel drive lighter less powerful cars in days of old.

I would always have told my insurance company of a wheel size change of course. I had thought this was part of the secret but it not being makes life easier.


I will let you know how I get on with sourcing winter tyres - and in time with driving on them!

Thanks again,

Nigel

[latebreaker]

Hi Nigel,

I have recently fitted winter tyres to my STR.

Jaguar recommends the following winter tyre sizes for the standard supercharged staggered 18" Rims(Not sure of name I think its Vulcan?):

- 235/40R18 95V X/L (2.0 Bar) up to 100mph
- 265/35R18 95V X/L (2.3 Bar) up to 100mph

I have fitted a set of Kumho KW27 winter tyres last weekend onto my standard 18" Rims. I have a set of 19" Barcelona's which are now my summer sets of wheels & tyres.
I'm still running in the tyres so I cant comment fully on their performance, but from past experience of using winter tyres there are IMO the best option if you want to use your RWD cars in the winter months without getting stuck.

Krish

[blackflash]

Had my Vredenstein winter tyres fitted a week ago. Drove to Bracknell (290 miles round trip) in normal weather and am pleased - no noticeable change in driving experience on snow-free roads and the comforting thought that when the white stuff falls I'll be able to move. Seriously, I'm hoping that the next time we get snow I'll be able to think "ah, how beautiful" rather than "oh $h1t, how am i going to get out of the village?"

Apart from faster tyre wear (I beileve the winter tyres are a softer compound), is there any disadvantage to using winter tyres in snow-free conditions?

Nigel

[GordonJ]

From my time in Germany I am sure temperature played a part in the fitting of winter tyres and not just the snow. The compound is suited for temperature and snow and ice. I have them on my Kia Sportage at the moment but not on the jag. I'll see what use the jaguar gets over this winter before I decide on whether to buy a set of wheels and tyres. In saying that if the jaguar was my every day car I would.

Gordon