Snowchains...is there any overlap with sizing?

A snowHead

Hi folks thinking of heading off in the motorhome this month. I have winter tyres but thought i should get some chains just in case, have fitted them before when i worked in france so quite familiar with them but what i'd really like to know is if there's any 'overlap' amongst sizes?

Basically i've seen two sets brand new on ebay which could save me a small fortune.

My tyres are 205/75/16

The closest size quoted that these two chains fit are;

Set 1: 205/65/16

Set 2: 205/75/17.5

So would either of those two fit with a bit of persuasion? Am i correct in thinking the only problem with option B would be the chain overlapping onto the wheels and could potentially damage alloys? (which isn't a concern) As the overall width and diameter are identical. Thinking any slack could be pulled in with a bungee?

Or should i stop being a tight ar$e and bite the bullet (think of the wine)

Would appreciate comments, thoughts or experiences as trawled everywhere and can't seem to find a definitive answer.

Cheers all

A snowHead

Usually on the side of the box there's a whole range of sizes that those chains will fit.

If you look up the manufacturer's details of the chains your looking at and enter the model name then you should be able to find the whole list I would have thought.

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

Many brands of chain fit multiple tyre sizes, but not all. The sizes are usually listed on the bag or container. Unfortunately, many sellers just list their own vehicle's tyre size. So it's hard to know. If you can contact the seller ask them whether they chains they are selling fit multiple tyre sizes, and to send you a photo of the label e.g.

One factor to bear in mind is that cheaper chains often have two issues: 1. They are more prone to snapping under stress and 2. They tend to fit a narrow range of sizes, sometimes only one. So more expensive ones (like those with the above label) may turn out to be more cost-effective if they're likely to be transferable to your next, or your other vehicle if you have one.

Re your question of whether chains not certified for your tyre size will fit - probably not, unless the chains are designed for a wide range of sizes. And as you can see from those above, your 205/75-16 tyres aren't listed, although various sizes 'around' yours are.

A 205/75 tyre has 21mm or 2.1cm extra height to each sidewall compared to a 205/65. This probably means that chains for a 205/65 wont fit your 'thicker' 205/75 tyre. But it all depends on the design - this is why it's important to see the original manufacturer's label.

The second figure is the tyre's aspect ratio % which is the height as a % of the width. Your 205/75 tyre has a width of 205mm and a height of 205x0.75=153.75mm. The third number is the diameter of the wheel onto which the tyre is fitted, not the radius of the tyre from the centre point to the tread, which is the rolling radius. The rolling radius is usually kept the same whatever wheels and tyres you fit because any change will change the speedometer and odometer readings, as well as handling characteristics.

If you have a 205/75 tyre on a 17.5" wheel then the rolling radius will be 0.75" greater i.e. a tyre that has a greater circumference (you'll have to do the pi r² calculation and conversions to work out how much more, but it's probably not trivial). So again, probably not viable - my guess would be that the chains would be too big.

You need to Login to know who's really who.

There are few less pleasurable experiences than being at the side of a dark mountain road in a blizzard trying to fit chains that are the wrong size.

Anyway, snowHeads is much more fun if you do.

Thanks @LaForet for such a detailed reply, very informative. It's looking like i may have to bite the bullet!

You'll need to Register first of course.

Oh and a final tip - some chains that fit a range of tyre sizes need to be adjusted before fitting in order to match your specific tyre size. Others adjust themselves once they’re on. In the former case it’s not always obvious from the translated manual that ‘try them out first’ isn’t just desirable, it’s essential. This is a lot easier using a spare, laid flat on the ground at home (the spare, not you).

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

Unless it had the exact size on the list I wouldn't risk it because you either run the risk of not being able to get the chains on the wheels or the chains could come off and damage the car (e.g. brake lines).

PS turn off the ESP when using chains so they can dig/cut into the snow & ice when needed.

Help!!

Snowchains...is there any overlap with sizing?

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