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Thank you for clarifying that, I’m relieved to know my car has the correct tyres. I’m slightly confused as to why the MO marking was in any way significant, this is a 7 year old, 70,000 mile car, so the original Continental 225/40R18 tyre probably didn’t have a MO marking (but that was probably 2 tyres ago). Whenever it was changed I’d have just told the garage to fit the same tyre, I have no idea why it would have supplied one marked MO, but if it doesn’t make any difference then why should I be in any way concerned? I’ll check the other 3 tyres tomorrow to see if they are also marked MO (I suspect there will be at least one more as I normally buy them in pairs, unless it has been to fix a puncture). Alan

Ah, that was just my fat fingers typing on an iPad, it should say 225/40R18. Do we agree that is the right size for the car? I’m not sure I understand the ‘MO’ issue, are you saying my motor car could not have come with Continental tyres (in that case you would be mistaken - I am the only owner)? What is the significance of the ‘MO’ marking (apart from being approved by MB), are you saying they are unsuitable for my motor car? I’m a bit confused. alan

Hi, Thank you for that, but it seems (to me) unlikely that the car should have come with 225/45R18 tyres when the sticker inside the fuel flap lists 225/40R18 (see the photo below). I’ve owned the car from new, it has had a few new tyres over the past 7 years, but I have always had them replaced with the original size. I think you must be mistaken about the 225/45R18 tyres - I have no idea about the MO bit, the tyres would have been supplied by a reputable garage either to replace a worn out one or a puncture. Does it make any difference? Alan

... are we saying that Skoda do not fit Continental 225/49R18 as OE? See above, I bought the car new from a Skoda dealer so I’m the first owner, that is what it came with. Alan

I bought the car new, it came with the same Continental tyres as I have now (I suppose about 8 tyres have been changed over the past 7 years and nearly 70,000 miles through punctures and wear).

Many thanks. You have already exceeded my knowledge of car tyres (I'm better at motorbike tyres, they are a bit more critical). Whenever I need to replace 18" tyres I always just ask for an exact match (I think it is best to keep with the OE, manufacturers don't often get it wrong).

Okay, here are some photos of both tyres, the Continental (18”, on an alloy rim) and the Yokohama winter (on a 16” steel rim). I measured the consumption using the onboard computer. It was on a route I do quite often from Corby to Pentney (near King’s Lynn) - about a 140 mile trip, probably half dual carriageway and half good A roads. I normally get just about 50 MPG (maybe a tiny bit more) with the summer tyres, driving exactly the same way (60-70 MPH, just me and the dog in the car, full tank of fuel, no stops) gave 58 MPG on the winter tyres. Akan

Okay. I'll photograph both tyres when I get back. The 18" wheels are alloy, the 16" are steel. Alan

... I'll have a look after I've taken my son to school - does it make that much difference? Alan

Many thanks, the calculator is really useful. I’ve just put in 225/40R18 and 205/55R16 and get rolling circumferences of 2001 and 1985mm respectively, 6mm difference is 0.3%, and the 16” wheel has the slightly smaller dimension.

Agreed, I don’t think this is anything to do with summer and winter rubber, just the narrower and higher profile tyres.

See above. I have checked, and the width is indeed reduced from 225 to 205, so about a 10% reduction. The running pressure for the 16” tyre is also higher at 2.4 bar (as opposed to 2.2 bar for the 18”). The car runs well on the winter tyres, they are certainly quieter (due to the higher aspect ratio I think). It is easier to spin the front wheels with them, particularly in the wet, which is unsurprising.

See above for the details. The sizes are both standard for the car (225/40R18 and 205/55R16 - which is the same as my full size spare), so I’m pretty sure the rolling circumstances will be the same (although I have not checked). I can only put it down to a 10% narrower tyre and slightly higher standard inflation pressure. Alan

Yes, of course: the summer tyres were Continental 225/40R18 (OE fitment ) running ar 2.2 bar, the winter tyres are Yokohama 205/55R16 at 2.4 bar. I checked the pressures were exactly as per the recommendations myself. I was pleasantly surprised at such a big improvement. Alan

One unintended but most welcome consequence of changing to my winter wheels and tyres has been much improved fuel consumption. On the 18" alloy wheels (225 width I think) my Superb diesel would return just about 50 MPG, I took the car to Norfolk last week (130 mile round trip) and it did 58 MPG (on 16" wheels, 205 width I think). That was a nice surprise. Alan

That is a very good price. I have Dunlop Sport Maxx tyres on my Porsche Boxster, they work very well - good grip (similar to the Pirelli equivalent). I don't think they will last as long as Continental on your Skoda (although that may not be an issue for you). Alan

That will probably work, but this is quite a common problem with alloy wheels as they get a bit older (I've never heard of it on a steel wheel, but normally they are painted all over).

Well, they need changing anyway (particularly of you are going to use them in the winter), so that makes sense now. If you tell the tyre fitter to check the rims then that will probably solve the problem. If the fitter will let you check that rim with the tyre off that would be a good idea, VAG don't bother to paint the wheels inside the rims, so they are a bit prone to corrosion as they get older, so check around the bead for that. New rubber will probably solve the problem by fitting better into the surface even if it is a bit corroded. In my experience powder coating solves this issue completely and the scuffed up old alloys look like new. It would be a good idea to check the valve (I can only think of one or two occasions in decades when a valve leaked, but it is such a cheap and easy fix it is worth trying first (before even getting the tyre changed so you can eliminate a possibility). Good fortune. Alan

I had a very slow puncture in one of my summer tyres, fitted on 18" alloy wheels. I couldn't find it, but it disappeared after I had the wheels powder coated, so I think it was leaking from the bead. VW wheels are pretty poorly finished (not much paint or lacquer, none inside the rim) - it might be worth checking that.

Good morn, The thieving bit concerns me a little (although I live in a nice, residential area with very low crime). I’ve stored the summer wheels in my motorbike shed, which is attached to the house, has a cantilever roof, brick walls and a lockable gate at each end. I’ve installed an IP camera inside and outside at the front gate. I’m not sure what more I could do (apart from store the wheels in the kitchen). :-)

... I'm at a loss to understand why that might be the case. Tyres on the car are going to be subject the UV light, wind and rain, wear from contact with the road and damage by nails etc, whereas my summer tyres stored in a dry, well aired and pretty secure motorbike shed will be subject to... what? I'll get a small tarpaulin to keep the dust off them and out of sight today. Alan

... the motorbike shed (where they are stored) has a roof, so UV shouldn't be a problem. I might get a cheap tarpaulin (the £land sort) to keep the dust off them (and maybe not attract prying eyes when the bike shed door is open). :-)

All done for the winter :-)

I was just having a look at the (very good) metcheck app; it looks like the ideal time to change will be the week after next (4/5 November). Many thanks, that was helpful. Alan

That is a useful website - many thanks. alan