As standard there are 225/45/17 tyres on the sputnik's, they are not the cheapest tyre size, so has anyone changed the tyre to a narrower say 215 or 205 tyre width which should improve mpg and as I am a motorway hauler I don't need cornering grip etc..

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I have changed tyres on other cars etc e.g.

A2 guide

You can go down to a 195 section without over-stressing the new tyre sidewalls. You clearly understand aspect ratios, so I'll say kudos for that rather than insulting your intelligence.

I will suggest that you check that you're getting a suitable speed rating (maybe OEM or the one below) and load rating for the car though.

Thought 225/45/17 were quite a reasonable price myself. They're also popular for VAG vehicles, and others - Ford included.

Don't see why you couldn't drop to a 205/45/17 or 215/45/17 though, if the price represented a reason to move. The rolling radius and speedo accuracy should be within tolerance for those.

Steve

If you check on 'my tyres' etc. you will see that there is a wide price span for that size. If price is that important you could still get a decent brand say Avon, for a lot less money than Michelin, which tends to be the most expensive. If you are not fussy about the brand then the world's your lobster. I bought Michelin after I found a good deal at a local independent.

I like to buy decent rubber and have stuck with Bridgestone er30 for a while which are a bit soft but grip is what they are there for and have not really trusted budget buys, even though Avon are well known etc.

Would anybody have an idea if going 225 to 195 would give lower rolling resistance and better mpg for motorway miles?

Cheers

Would anybody have an idea if going 225 to 195 would give lower rolling resistance and better mpg for motorway miles?

Nah the wider tyre will be better - because they'll have a narrower profile, there will be less sidewalk flex.

Tyre width itself doesn't really factor into rolling resistance. You want something that doesn't deform. If you think about a plastic bottle rolling on it's side, it's easy to roll until you slightly overcome it's strength with weight. Now you have to roll harder to compensate for the rolling resistance of the bottle - caused by the deformation. If you pumped the bottle up to avoid deforming under the same weight, it'd roll much easier again. It doesn't really matter whether the bottle is 10cm wide or 200% wider.

Sorry Mute, but I have to disagree. The wider tyre will give you reduced mpg due to two factors, the greater contact patch (which is why all eco specced cars have narrow tyres) and the aerodynamic impact of having a larger frontal area.

However, the idea of pumping the tyre (bottle) up is accurate as you are effectively reducing the tyre contact patch and causing the centre of the tyre to wear out quicker, but you "normally" inflate a tyre to give even contact across it's tread width (within reason).