UKH

I have an old car where probably the most valuable parts of it now are the year old and (due to lockdown) not very used all season tyres.

I have a new car (well new to us) that doesn't have all season tyres on it. Both are C-MAXs, but the older one is the older body shape so they aren't identical. The all season tyres are 205/50 R17 W93 and the tyres on the new car 215/50 ZR17 W95.

From my extensive research (googling "car tyre size explained") I think the only difference is the non all-season tyres are 10 mms wider. Is there any reason why I couldn't just swap the wheels between the cars? Or is the different width somehow like to invalidate my insurance and lead me to my inevitable demise in a tragic but all too predictable RTA?

In reply to TobyA:

The rolling radii will be different between the two tyres which affects your speedo readings. I don't think a 10mm difference will be significant though. There are tyre calculators on line you can use to check this.

In reply to TobyA:

I've just checked, only 1.5% difference in tyre circumference between the two widths so not an issue. 

In reply to nikoid:

I understand that the "50" is the percentage of the tyre height compared to width, so one sidewall height will 5mm higher than the other? Is that why you say the radius is going to be different? 

If I've understood that correctly, thanks because I hadn't realised that before.

In reply to TobyA:

Have you checked the PCD (Pitch Circle Diameter) for the two wheels and that the holes are drilled in the same place? I am not too familiar with Fords but I know this is often different between various VAG cars.

Technically any change from factory spec (Other than repair work etc) is classed as a modification as far as insurers are concerned, I am sure cars get sold on all the time with bits changed that have never been declared, most people probably wouldn't ever know.

In reply to TobyA:

Most cars can use a range of tyre sizes depending which model you have, check the handbook or look for a plate or sticker inside one of the doors.

If the all season tyres you have are a listed size for the car you should be fine, assuming the wheels fit as mentioned above of course.

In reply to TobyA:

Your handbook often has a list of tyre sizes acceptable for the model.

Otherwise google c max tyre size to access info from the Ford site.

There is a very slight chance the wheels are incompatable between models.

In reply to Andrew Lodge:

I had sort of presumed this - until 6 years ago I had lived in Finland for a long time and you have to swap between winter and summer tyres dependent on the season. It's normal that if you buy second hand, that the car will come complete with the second set of full wheels (tyres mounted on rims), so I remember on both the cars I had during my time living there, that the winter tyres looked quite different to the summer tyres in size, it may have even been that the rims were different sizes.

I kind of thought I'd like to do the same now and just keep the spare set in the garage, although I'm not quite sure how I can get rid of the old car with no wheels on it! It isn't worth much even with four wheels on it.

In reply to Punter_Pro:

I haven't checked yet, but I'm pretty certain they are the same five stud pattern.

In reply to TobyA:The pcd, bcd, bolt circle diameter are all easily researched but I'd be surprised if the differ -. I know you can fit Mazda wheeels on a Nissan as an example - the dimensions are identical.

I would not be surprised to see different rim sizes between summer and winter set ups-- using a smaller rim allows for a larger tyre to come back to an equivalent wheel diameter

In reply to TobyA:

If you can drive it to a scrapyard they will probably do you a deal to take it off your hands but let you keep the wheels.

Certainly worth asking, alternatively ebay or facebook can be a good place to buy a spare set of wheels.

In reply to TobyA:

Yep that's my understanding. The profile rating is the ratio of tyre wall height to width. Lower numbers mean lower profiles. And more vulnerable to kerb and pothole damage!

In reply to TobyA:

I suppose if you have the time and the space (and motivation) you could register the car as sorn and gradually sell the bits from it?

In reply to TobyA:

My summer tyres are 225/45 y 18, my winter rubber is 205/55x 16. According to gps it only makes a marginal difference to my Speedo readings and really within acceptable margin of error. If the wheels fit, it’ll be fine, and the fractionally narrower rubber may be better in bad conditions.

In reply to Rick Graham:

Another way to find out is to request the "Declaration of Conformity" for your car from the manufacturer.  You should be able to do this through their web site I think.  IIRC from when I requested same for my current car, and the one before, you need to quote your VIN.  They should provide it FoC and it will contain a list of the wheel and tyre size combinations which have been type approved for your vehicle.

In theory, using any other sizes or combinations makes your vehicle non-type-conformant and therefore not road legal, unless you get it type approved as a one-off - which is hardly worth the hassle.  It may also invalidate your insurance.

Note that, when considering wheel sizes, it's not just the diameter of the rim and the PCD of the bolt holes that matter.  There's also the width of the rim, and the offset, which affect how wide a tyre can safely be fitted to the wheel, and whether it will fit over the brakes and (with tyres fitted) inside the arches without fouling anything - which latter is obviously more relevant to the front wheels, since these steer as well as going up and down with the suspension.  However, if you look closely on the wheels on both vehicles you should be able to find the dimensions marked on the wheels (you may need to take a wheel off and look on the back, especially with alloys).  If the marked dimensions match between the two vehicles then the wheels off the old car will be OK on the new one, and it's very unlikely that the narrower all-season tyres wouldn't be as well (though it might still be worth checking the type approval, especially if you're a detail person like me).

In reply to TobyA:

See what wheels and tyres other models in the range take, especially sportier ones. It's highly unlikely that wheels/tyres from a sportier model won't fit. You must consider offset (how far out the wheel rim is compared to the centre) or you risk fouling the brakes or the arches.  Assuming you have both vehicles in your possession just try swapping the wheels around to see what works. You may need to have the alignment altered if the non-standard tyres wear funny.

Winter wheel and tyre combinations are sometimes sized smaller to cater for ice buildup in the wheel arches.

In reply to TobyA:

It's also possible that (if you haven't owned both cars from new) that the tyres fitted to the wheels are not the correct size anyway.  They may not even be the original wheels.

In reply to TobyA:

Those are basically the same size tyre, 10mm here or there on ~200mm width makes next to no difference*. I'd lazily assume from one generation of Ford to the next the stud pattern should be the same and they're unlikely to have changed the wheel offset. I'd just try one on the front (where the most likely clashes will occur), check it clears the caliper while jacked up and everything else at full lock each way with it on the ground.

*trying to persuade 4" mud and snow tyres to inflate on a 6" rim is a different matter

If you're a worrier you can check the wheels are identical (or not, I didn't bother) https://www.wheel-size.com/size/ford/c-max/

I have no idea what your insurance policy says but I've never worried about it when choosing wheels tyres.

jk

In reply to jkarran:

Just been outside in the sleet to swap the wheels and see if they fit, of course it turned into one of those disheartening episodes of things going wrong in a series, the end result being the original problem unresolved and the discovery of some other problems you previously didn't know you had!

The old car (with the good tyres on it) has one security nut per wheel which you need one of those special sockets to undo. I loosened off the four nuts on one wheel, got the special key-socket thing on my tyre iron but couldn't get it to grip the security nut properly. Looking at it the 'key pattern' inside was all chewed up. Obviously at the garage last year when they had used it to loosen the security nuts, probably with hydraulic wrench or a massive long tyre iron has stripped it. So it turns out if I had had a puncture over the last year I wouldn't have been able to change the wheel anyway as I have no way of undoing the security nut!

Then I remembered in the garage I had some snow socks that since getting the winter tyres I hadn't needed at all. Thinking I could chuck them in the boot of the new car (without all season tyres on it) for snow emergencies, I tried putting them on but was struggling to do it. Looking carefully at the instructions my snow socks are "L", whilst for the tyres on the new car I would need "XL". So that's not going to work either.

Anyway, any winter climbers out there want to buy a 58 plate C-Max with 149k on it? The back nearside brake recently started making a noise so might need new pads, at worst a new caliper and pads. MOTed to July. BUT! It has a new clutch in it and four Michelin Cross Climate tyres which must have only done maybe 2000 miles, still just under a year old, which are bloomin' brilliant in the snow. With a bit of work a mountain approach road-cruising machine and yours for just 500 quid. Basically buy the tyres and get a car thrown in for free.

In reply to TobyA:

Damn, that's a bargain. In case you still want to pull those wheels out, most decent tyre fitters can get the locking nut out for like £20 each if it isn't the spinning collar type. If it's the collar type then you need to drill the stud and replace it (a couple of quid for the stud and a couple of minutes work).

If it's the key that is chewed up rather than the nut then Ford dealerships have master keys to get them out, but they probably charge a kidney per nut.

ETA: It's a coupe of minutes to replace the stud. Drilling it out takes rather longer than that...

In reply to Mr Lopez:

Thanks for advice.

Don't need a project car do you?

I was thinking despite jkarran's soothing words of expertise above, that the failure of the snowsocks to fit on the new cars tyres, and actually those tyres listed as being XL for the snow sock, while the tyres on the old car would only be L - did make me think that perhaps the wheels aren't basically the same size anyway, although I guess the winter ones are very slightly smaller and that seems less likely to cause problems than slightly bigger.

I guess if I can flog the car for about the price I've said, I could afford to get Cross Climates fitted to the new one, although I reckon actually getting a full second set of wheels and swapping them like I did in Finland might make sense. There was a quite a lot of snow just a bit up from us today as you go up on the Eastern Edges in the Peak, so it suddenly seems a lot more pressing than a few weeks ago!

Photo of the socket-key-thingy below. It used to be a pretty flower shape in there, but now it is all mangled up. I might go and moan to the local garage who put the winter tyres on the car this time last year, although I'm not sure what they could actually do now.

In reply to TobyA:

Wish i could. I'm being done by the London ULEZ extension so not allowed anythng that isn't EURO 6

The alloys are the same according to this website and by what you have fitted. They'll be 5x108 (stud pattern), 7j (width which means 7 inches), ET50 (Offset) and 63.4mm center bore

58 plate https://www.wheel-size.com/size/ford/c-max/2008/

12 plate (mk2) https://www.wheel-size.com/size/ford/c-max/2012/

16 plate (mk3) https://www.wheel-size.com/size/ford/c-max/2016/

Tyre size difference you can enter the details here as it doesn't save the entered data in the URL, but regardless evertything is within tolerance. 215/50/17 wasn't a standard size for your car anyway, so you've done the testing already

https://tiresize.com/comparison/

You could budget for a set of alloys in the sale price. Should be easy to find cheaply as it's the same alloys as many cars of similar vintage. Volvo V50's, s40's, and Ford Focus of that era for example all have the same alloy fitment as they share the components. They can be commonly had for about £100 a set.

Also Range Rover Evoque alloys will work if you want to bling it up!

They'll deny any wrongdoing but worth a try. If you feel lucky, you can hammer that key into the nut with the biggest sledge hammer you can get and sometimes is all it takes to be able to unscrew the nut. Unlikely it will last 4 goes though, so maybe see if it works in the other wheels the traditional way first

In reply to TobyA:

You can ge 'universal sockets' basically a socket full of tough spring loaded pins that grip whatever you push them onto, they're a crap solution to most problems but they should grip a security stud. A tyre shop will get them out with similar tooling or by welding a bolt onto the stud. Wouldn't cost much but I expect it'll sell at that sort of price.

Jk