"dennis@home" wrote in message
news
I *thought* that a spacesaver spare tyre was always (nominally) the same
OD as the wheel that it is replacing, allowing for different amounts of
tread wear, and that it was only the tyre *width* that was narrower. I
agree that one wheel may be a different size to the other, but that is
immaterial as long as the OD of the tyre is the same.

They are frequently smaller all around.
The limit to how small they can make them is the clearance on the brakes.

And how much the car sags at one corner because one wheel is smaller. When I
can be arsed, I'll go and measure my spare against a full-size wheel. They
look the same OD and the car looks level, without a dip at one corner making
the opposite corner high and hence less downward force on that wheel.

Certainly I've not felt any pulling to one side on the steering, with the
spare on the front or the back - I was amazed at how little it affected the
handling of the car, though I'd be more cautious on cornering and I'd
restrict myself to the 50 mph and 50 miles limit that they always say.

Gone are the days when your spare is fully-interchangeable with the four
running wheels and can be driven as far and as fast as you like without any
limit. I really wish the UK would mandate cars to be designed so they can
accommodate a full-side spare (steel rather than allow wheel, but otherwise
normal tyre) as used to be the case until corner-cutting took over. Cars
always had a recess in the boot floor or else a cage under the boot for the
full size wheel - or on some cars like the Ford Zephyr and some small
Renaults it was under the bonnet. Nowadays the boot doesn't seem any more
capacious but there's allegedly no room for a full size wheel in boot - all
the pain, but with no perceivable gain.

I think even our big Honda CRV has a space-saver spare, and that's got
plenty of space below the boot floor to take a full-height spare.

Car manufacturers say "oh, it's not a problem - put the spare on and drive
to a tyre place". Not at 10 PM on a Sunday when you're about to start on a
long journey. I don't think I've ever in all the years I've been driving had
a puncture that's happened during shop opening hours - it's always late at
night or on a Sunday that I discover it. Until recently it was a minor
nuisance which delays me setting off by 10 mins or so to fit the spare, and
then take the dead tyre in to be repaired at a later date when I'm not in a
rush to be somewhere. Now it's a show-stopper which means waiting till the
following morning to set off after I've been to the garage - hoping that
they actually have the right size in stock and I don't have to wait another
24 hours till they've ordered one in.