Autosocks

Ultrasonic

OddballJamie wrote: »

Fuel economy is a good point, but I wonder if there's much in it during cold or wet weather as a winter tyre should get more grip and cut down on wheel spin.

Would make an interesting study. I didn't really look too much into that as I don't do enough miles to worry and the savings from not wearing my more expensive larger summer tyres would compensate for any loss.

European tyre label info. suggests a difference in fuel economy of 0.26 to 0.41 L/100 km between my B rated summer tyres and E or F rated winter tyres. Along with poorer wet braking ratings, which I guess when the roads are above 7°C?

I've also got no idea how rolling resistance may vary with tyre temperature now that I think of it, I bet the ratings are for summer temps.

Obvously safety is more important than fuel, but it is in part a question of how much difference there really is for the sort of driving I'll be doing.

forgotmyname

In a lab tthere will probably be a measureable difference in mpg. In real life the difference maybe less. No 2 days will be the same. You may have a journey with crosswinds at road level that further decrease the temperature. High speed high traffic flow roads may actually add some heat to the surface?

Never had winter tyres, So i cannot comment on them. I wouldnt mind testing a set like the snow dome video i watched a while back.

But test both in my car with me driving exactly the same.

Cynical me dod wonder if the driver with the winter tyres was just a better driver? Smoother with the clutch/throttle and knew to feather it not just plant it down.

WTFH

My fuel economy changes by about 2-3% between summer and winter (same size tyres). Now, how much of that is due to the tyres and how much is due to aircon etc is hard to say.
In summer, my climate control is set to 18, so on a day when it's 25 outside, it's got a delta of 7.
In winter, if the outside temp is 0, then the delta is 18, so it needs to work harder for longer to get to & maintain that temp. I suspect that accounts for more fuel than the tyres

Gloomendoom

WTFH wrote: »

In winter, if the outside temp is 0, then the delta is 18, so it needs to work harder for longer to get to & maintain that temp. I suspect that accounts for more fuel than the tyres

Delta smelta

In the winter it doesn't have to work at all. It uses heat from the engine to heat the inside of the cabin that would otherwise be wasted heating up the air outside the cabin.

GlynD

Why not just use snow chains? More effective I would have thought and certainly wear better.

Gloomendoom

They are noisy, nasty things that chew up the road... and your nice alloys.

GlynD

Gloomendoom wrote: »

They are noisy, nasty things that chew up the road... and your nice alloys.

You're not supposed to use them on the road. The clue is in the name "Snow" chains.

WTFH

Gloomendoom wrote: »

Delta smelta

In the winter it doesn't have to work at all. It uses heat from the engine to heat the inside of the cabin that would otherwise be wasted heating up the air outside the cabin.

Good point - I never thought of that!

InsideInsurance

OddballJamie wrote: »

My summer wheels have 225/45/17 tyres where as my winter wheels are smaller and take 205/55/16 which is a nice common cheap size.

Out of curiosity, how do you find out the acceptable wheel sizes for a car?

My car's fronts are 255/35/19 and rears 285/30/19 which are the smallest option for new build and would be a none starter for winter tyres even if I wanted to keep that size of wheel as there dont appear to be any made in that size for the rear end

forgotmyname

Look at similar cars in the range and see what the smallest wheel is.

Of course you need to check on things like brake sizes. Your model have have larger wheels to cover bigger brakes so the wheels of a low spec model may not fit.

Several tyr calculators on the net. Most recommend you stay within 2.5% of the original rolling radius.

Fitting a narrower tyre usually means fitting a higher profiles one to make up the size difference.

255/35x19 = 661mm diameter. 205/70x15 = 668mm diameter.

Probably no such tyre as a 205/70x15 though. but if there was a 15" wheel/tyre would be taller than your 19" one. But only 7mm.