Winter Tyre Section - Less Than Summer?

A snowHead

One for a winter tyre expert, and I know some lurk on the forum. I've understood that winter tyres narrower than summer tyres are fairly normal. Eg 195 instead of 205. As long as the size is one permitted by manufacturer.

A snowHead

@colinstone, I certainly wouldn't class myself as a winter tyre expert Laughing

, but you are correct in your understanding.

Well, the person's real but it's just a made up name, see?

@colinstone, your handbook will often include a size/rating for winter tyres. Not infrequent to be smaller diameter, narrower , higher profile and lower speed rating.

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+1 to what @DJL says

Anyway, snowHeads is much more fun if you do.

I am not an expert but that was what was recommended to me by my local tyre guru.

My BMW 320D estate came fitted with 225/45 R17 runflats, he recommended changing to not only narrower tyres but ones with a deeper sidewall which he claimed would induce a little extra flex in the tyre before it would "break away" from adhesion to the road/snow surface.

The final selection was 205/55 R16 Nokian WR G2's (an approved size combination for the car), being 20mm narrower, smaller wheel centre at 16" and deeper sidewall at 55mm giving the same effective rolling diameter.

As for driving on them, absolutely brilliant and a real pleasure in all cold conditions.

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It often turns out that the tyre width for a winter tyre on a 'performance' car is narrower than for the summer tyre. This is usually because in order to leave space for snow chains to be fitted, you need to release space between the inside of the tyre and the suspension i.e. you have to use a narrower tyre:

Above is the inside front of my A3 with the winter tyres (Michelin Alpin Primacy) fitted. You can see there's about 45mm of free space between the tyre and the suspension strut. You can also see the brake pipes and behind the suspension is the driveshaft to the wheel. As this is FWD there's also the steering mechanism. What you really do not want is for the chain mechanism on the inside of the wheel to hit the suspension and break. Worst case it will wrap itself around all this stuff and cause serious damage. If I fit standard chains, these will consume 20mm of the 45 leaving a safe margin of 25mm.

The winter wheels (below) are 17x7J i.e. 17" diameter and 7" rim width. This width takes 205mm tyres (hence the 205..... in the tyre designation).

The summer tyres (below) are on a wider wheel, an 18x8J (18" wide, 8" rim width) and you put a 225mm width tyre on these. So the tyre width on the summer is wider and leaves about 25mm of space - again a safe margin. But if I fitted my 20mm chains then I'd only have a 5mm margin and that's considered too little, especially since I may not fit them perfectly.

If you look in your Owners Manual you will usually find a chart specifying the various wheel options and indicating which don't take chains. Usually, the Manual indicates that larger wheel sizes are not suitable (although it's really because the larger wheels take wider tyres). So on my A3, you can fit chains to the 16" and 17" wheels but not the 18" or 19" ones.

For any specific model, the overall diameter of a wheel and its tyre is almost always the same, no matter what the wheel diameter is. This is called the 'rolling radius'. This leaves enough space between the tyre and the wheel arch for the wheel to move with the suspension. The odometer will be adjusted to use your specific rolling radius to calculate speed and distance. The dynamics of the suspension will also be adjusted to the rolling radius as built out of the factory. Whilst you might fit a wheel+tyre of greater rolling radius and it still would work, you generally don't do this, as there's the obvious danger of scraping the wheelarch and the less obvious problem of it altering the handling adversely.

So what if you want to fit low profile tyres? These are ones where the height of the sidewall is less in relation to the width of the tyre. The metric here is the aspect ratio which is the % ratio of sidewall to tread width. This is the second number in the tyre designation e.g. a 205/50 or 225/45 etc. In these examples, the first has the sidewall height to be 50% that of the tyre width, while the second has a sidewall height that is only 45% that of the tyre width. The second tyre is 'low profile' in relation to the first.

Why do manufacturers fit low profile tyres? Principally because (i) they turn more easily and (ii) it's fashionable. If you have a high performance car, it's a natural choice to opt for low-profile tyres, as you're probably after better handling. The downsides are (a) harsher ride and (b) greater tendency to aquaplane. The problem is that you can't increase the rolling radius so the only way to fit low-profile tyres is to increase the tyre width. But you can't extend the wheel outside of the wheelarch, so when you design a car which has optional low-profile wheels, you have to have an 'offset' wheel - where there's more wheel+tyre on the inside than the outside.

So your summer wheel+tyre often consumes all the space available between the inner side and the suspension. If you put chains on as well, and given the degree of movement in the suspension, the rotating chains may foul the suspension. If it's FWD you also have the steering mechanicals to worry about as well, so this is even more of a problem. Thus, when you say that you want to fit chains, or if you want to switch to winter tyres, the garage and manufacturer may tell you that you need to reduce the rim width. Which means narrower tyres.

Be very suspicious of chain suppliers who don't seem to understand all this and don't check that your specific wheels are certified for chains. You should be uneasy if they say anything like "They should fit ..." and be particularly concerned if they say "Well, try them out first.". How exactly do you 'try them out' and what if you do come up with a realistic test scenario and they cause some damage? You certainly don't want to have problem going down a mountain, in the dark, with a fully-loaded car and passengers, on an Alpine hairpin bend.

Then you can post your own questions or snow reports...

After all it is free

I'm with you there, Alastair. I'm sure that I'm not the first owner who has found themselves reluctant to switch back to the Original Equipment low-profile wheels after their first winter on higher-profile wheels. I don't have the Audi A3 any more, and when I replaced it I opted for 'standard' 17" wheels rather than the flashy 18". Yes, they don't handle quite as dynamically as the 17" but they are hugely more comfortable on standard pot-holed British roads. And safer in the wet, etc.

And surprisingly, a lot of 4x4 SUVs sold in the UK can't take chains on any of the factory build options. One of my previous cars was a Jeep Grand Cherokee. When I asked for the wheel option that could take chains it transpired that these weren't available on UK builds. I was told that (a) no one wanted this and (b) we don't get snow. Looking in the manual it clearly said that even if fitted with winter tyres, a 4x4 may still need chains in conditions such as ice, steep slopes or deep snow.

@msej449, @Alastair Pink, something gone wrong here. Two sensible posts in a row giving good advice and no argument. Is this really Snowheads? And a winter tyre thread to boot.

*Ski* the Net with snowHeads

Just about everything you wanted to know about tyres:

http://www.carbibles.com/tyre_bible.html

snowHeads are a friendly bunch.

@colinstone, get them off as soon as practical in spring, they can be F1 slicks after a few corners on hot tarmac.

snow reports

You know it makes sense.

Otherwise you'll just go on seeing the one name:

Thanks for all the useful responses. I've got 195/65-15 winter tyres on wheels for my MkIV Golf. Splashing out on a new MkVII, don't know why!, which has 16 inch wheels. Unfortunately wheels won't fit new car, so for cost reasons I was going to stay on 15 inch wheels for winter.
From the new car info, it seems that each inch increase of wheel size, with wider tyre, increases CO2 By around 2gm/km.
Let's go F1 with 13 inch wheels!

A snowHead

A snowHead

Did it the easy way...
car (Seat Leon, so virtually identical to one of those Golfs) came with 205/55-R16. Binned the pirelli summer tyres (they wear out too quick), and put on Conti Winter Contact in same size, on the same alloys (so no nonsense with insurers regarding "mods").

ADAC shop will explicitly not even sell chains without seeing the car reg document, and confirming that your wheel and tyre size fitted is still in line with that reg doc.

Better economy IME, but that could eb due to driving within the capabilities of the tyre rather than the compound (if that makes sense). With the Pirelli sporty tyres, I'd be squeeling them at every light and spooling the turbo to max boost (aka not very much on Leon Cupra/Golf GTi).

Still have the same winter tyres on that I fitted for the first Birthday Bash in Campitello, and used them all year round, in case anyone comes out with the BS that winter tyres wear out quicker in summer. Call it about 50,000 miles so far. I managed 16,000km on a set of pirelli summer tyres.

PITA fitting chains though. It's not the clearance to suspension etc. but the fact that clearance between tyres and bodywork is rather slim on VAG cars of that sportiness, and you can't fit wrists in with useful dexterity. 195's might give me a cm extra space for fitting hands in.

Well, the person's real but it's just a made up name, see?

Pirelli, like Conti, Michelin, Bridgestone or others has different tyres for different types of cars - (a) so called performance tyres, (b) cruising all rounders (c) fuel saving tyres - these are very broad categories, with lines between them shifting depending on a maker or specific tyre model (some are on the border lines). So saying "Pirelli" does not automaticaly denotes a high performance or sport tyre - there is a big difference between Rosso Zero and P7 types of tyres at Pirelli. Same for other manufacturers. Just like not all Rossignol skis are race oriented Smile

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Thanks Andy. I've some tyre cables from USA. Much slimmer and easier to fit than chains. Also have some Michelin Easy Fit kevlar "chains". Even easier to fit, but not yet used them. Also a bargain from Tesco. - £13 instead of £90, but a couple of years ago now.

Anyway, snowHeads is much more fun if you do.

@Piste View, I don't understand. There is plenty of evidence to show that winter tyres have a marginally worse stopping distance in the summer (<10>25%). II have driven on winter tyres in the summer with no problem at all.

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@welshskier, our winters will go on by Oct 15 and this year didn't come off till end April, and we'd had quite a few bbqs in shorts by then. no issues, like you.

Help!!

Winter Tyre Section - Less Than Summer?

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