Driving a BMW with Run Flat Tyres – The Good and the Bad
BMW’s decision to collaborate with Bridgestone and fit run flat
tyres on all future car models as standard in 2009 was a sensible move that has
provided their customers with improved fuel economy and a safer method of
punctured tyre replacement.
The
benefits, however, are not widely agreed upon as a number of brand evangelists
dislike the run flat tyres mostly because of their comfort, or
lack of, whilst driving but also because of the hefty price tag attached to
replacement tyres.
To help prospective BMW owners decide on whether or not they’d
like to keep the run flat tyres that come fitted on models produced in 2009
onwards, we’re going to highlight the pros and cons of driving with them for
you to draw your own conclusions.
Brief Explanation of Run Flat Tyres
There are two main types of run flat tyres. One is a
self-sealing tyre and it contains a layer that automatically seals any puncture
holes. Created by Continental, the technology used reduces the amount of air
lost compared to a standard tyre with a puncture wound. It is, however,
criticised as being the less efficient type of run flat because it allows air
to leave before the sealing layer becomes active.
The other is a self-supporting tyre and contains a lightweight metallic support
ring inside of it which supports the car’s weight once a puncture has been
made. These run flat tyres also have thicker, reinforced side walls to ensure
that the bead stays in contact with the rim of the wheel at all times – this
often slips away on punctured conventional tyres, creating contact between the
rim and the road surface.
The self-supporting tyre is the technology used by Bridgestone
and fitted on current BMWs with tyre pressure management systems installed to
notify the driver of any sudden tyre pressure changes that signify a puncture
has occurred.
Reasons For Driving On Run Flat Tyres
The major benefit of driving a BMW on run flat tyres is you can
continue to drive and maintain control of your car with punctured run flats for
about 50 miles at a speed of 50mph – more than enough time to find a qualified
tyre fitter for a new one.
This 50 mile grace period is especially useful for motorway
drivers who won’t need to immediately pull over onto the hard shoulder and wait
for roadside assistance or even worse take the risk of changing the tyre
themselves, which is never recommended.
By installing run flats, BMW has also reduced the weight of
their cars by removing the heavy spare wheel and tyre that us motorists are so
used to carrying. This improves the fuel economy of their vehicles and provides
more cabin space for your belongings.
Although they are not impervious to blow outs, the support ring
still protects BMW’s wheels from making contact with the road. This means
drivers can continue travelling to find a convenient place to have their tyres
changed without worrying about the far more expensive cost of replacing damaged
alloys.
Reasons Against Driving On Run Flat Tyres
Many online BMW communities and forum threads provide enough
evidence to suggest that a considerable number of BMW evangelists dislike run
flat tyres for a number of reasons including drive quality and cost.
The most popular point raised against them was the harsh and
uncomfortable ride they provided compared to regular tyres, caused by the
stiffer tyre wall. Drivers that took turns at quicker speeds identified that
the car jumped/ jittered because of the lack of flexibility in the tyre wall
that you get from a standard set.
It was also suggested that the tread wears down quicker due to a
limited choice of tread patterns for different driving conditions, which could
mean more frequent tyre replacements in order to comply with UK driving laws.
Another significant argument against using run flats is the
price of replacing them – around twice as expensive as regular tyres.
Considering that a punctured run flat is a temporary fix and the tyre still
needs replacing, price is a big problem that spectators hoped would reduce as
demand increased for these tyres alongside BMW sales.
Should I replace my run flats tyres with regular tyres?
Before making this decision, it is worth learning from other
people’s experiences first. The Z4 is an older yet popular BMW model that has a
number of owners who have replaced their run flats with regular tyres because
of the harsher ride issue.
The “fail safe” that these drivers rely on is called the
fix-a-flat kit which fills the punctured tyre with sealant and inflates it back
to the recommended PSI. The only problem with this backup is for the tyre
fitter who has to clear away the mess it leaves so inform them when replacing
the tyre to avoid nasty surprises. Remember also that like the run flats, this
is only a temporary fix for punctures.
If you are keen to swap run flats for regulars, check the
documentation of your manufacturer’s warranty and insurance policy first to
find out whether or not a change will make either of them void.
Which is Better for Your BMW?
To conclude, the safety benefits that run flat tyres provide in
the event of a blowout or puncture are obvious and can potentially save you
from a risky need to swerve from the inside lane on a main road to stop in the
hard shoulder.
The
issue of high replacement prices compared to regular tyres is commonly felt,
however, if you consider the savings that accumulate from the improved fuel
economy they provide in addition to how many times you actually suffer from a
puncture, the one-off cost of a new run flat becomes less of a worry (“the
average driver does only get a flat tyre once every 44,000 miles or five years”
In regards to the problem of comfort, unless you are a dedicated
petrol-head and love to test your BMW’s performance limits, the uncomfortable
ride might be less noticeable and even less of a concern if you are a regular
everyday driver.
