2019-04-01 BMW Car

APRIL 2019 43

DRIVING TIPS

The friction disc is connected to the
gearbox input shaft, while the fl ywheel
and cover-plate assembly are bolted to
the engine crankshaft, and thus rotate at
engine speed.
As the driver starts to ease the clutch
pedal to the biting point, the rotating
cover-plate clamp surface is inched
towards the corresponding fl ywheel
surface, and this starts to clamp the
stationary friction disc between them. As
the engine is running, and usually slightly
above idle speed, the diff erence in speed
is in the region of 15 metres per second.
The friction between the surfaces starts
to accelerate the friction disc to match
the speed of the engine and, in turn, this
accelerates the gearbox internals, the
wheels and, therefore, the car.
But this process creates quite a harsh
environment and generates heat. During
matching speeds, the rubbing action
wears the surfaces and, as heat is
generated, generally this becomes worse.
This is why you should avoid ‘slipping the
clutch’ for extended periods with partial
pedal pressure, as it promotes extra
sliding wear and heat generation, which
will further increase the problem.
You can also wear the release bearing
and diaphragm spring system through
excessive time spent with the clutch pedal

In reality, as soon as the temperature
drops to below 7°C, winter tyres perform
better and summer tyres start to struggle.
So, for maximum grip and safety, a winter
tyre will always be superior when the
temperatures are low.
So, what is it about a winter tyre that
makes it work better at these lower
temperatures? Well, they’re made using a
rubber compound that’s better suited to
winter weather. The rubber used remains
more fl exible at low temperatures, which
improves the interaction between tyre and
road. In contrast, a summer tyre becomes
harder and loses performance as ambient
temperatures head towards freezing.
Additionally, the tread pattern on a
winter tyre is often more ‘V-shaped,
which helps to displace water and slush
to prevent the rubber from rising off the
road and aquaplaning. Further still, the
tread incorporates multiple ‘sipes’ – the
grooves, or cuts, in each individual tread
block that allow the rubber to fl ex more
eff ectively, and provide multiple gripping
edges. These are particularly eff ective for
traction and under braking.
So, are they required in the UK? Until the
heavy snow/ice arrives we still manage to

months. This is because, in my

experience, the majority of drivers

genuinely don’t adapt their driving

style signifi cantly enough in cold,

damp conditions, from that of warm

dry weather.

It’s only when the snow and ice

appear that people start to go to the

other extreme, and crawl around,

struggling to make any progress at all.

That’s when they’ll wish they had fi tted

winter tyres proactively. Those who are

already in on the ‘secret’ have been

better off all season!

depressed while the engine is running.

I once experienced the release bearing

collapsing into the spring on a second-

hand car that had clearly had some

previous clutch abuse!

In order to minimise clutch wear and

maximise its life, the main ‘normal driving’

things to avoid whenever possible include:

stop/start driving in traffi c; bringing the

car to a complete stop instead of ‘idle

driving’ – creeping forwards in gear with

the engine ticking over at idle speed;

spending more than a few seconds with

the clutch pedal depressed when the

engine is running; unnecessary stopping

at give-way junctions and roundabouts,

when good planning would allow safe

drive around on summer tyres but, since the

more grip a tyre has the greater the margin

for error, I’m defi nitely a fan.

Whether we admit it or not, there’s

always the opportunity for us to miss a

developing hazard, and rely on last-minute,

heavy braking and/or steering. In the lower

temperatures that we experience in the UK

between October and March, winter tyres

may just make the diff erence between a

nasty accident and a near miss.

For these reasons, I’d like to see

winter tyres or all-season tyres become

compulsory in the UK, during the winter

There’s no question that winter tyres are more effective and safer when the weather’s bad, but they also work

better than normal tyres under all conditions when ambient temperatures drop below 7°C. Winter driving can

be diffi cult enough at the best of times, without limiting your car’s grip by continuing to use summer tyres

during bad weather.

progress; holding the clutch pedal at

the biting point for extended periods of

time when pulling away; holding the

car still on a hill using the clutch at the

bite point, or using the clutch as a brake

when the car is still rolling backwards

and you start driving forwards.

In addition, every time you change

down a gear in the ‘normal’ way, you

are using the clutch as a brake, adding

yet further wear. Changing down less

frequently, and later in the braking

phase with low engine revs will improve

this, but learning how to heel-and-toe

or the double-declutching technique,

can eliminate this aspect altogether and

prolong the life of your clutch.

Clutch wear can be directly linked to the way you drive. Mechanically sympathetic drivers will typically get

above average life from their vehicle’s clutch. Maximising clutch life is all about good technique and effi cient

use of the gears.