Replacing Runflats With Conventional Tyres

We are receiving a number of queries from tyre dealers concerning customers who want to replace the runflat tyres fitted on their vehicles as original equipment with conventional tyres

Some people, it seems, do not like runflats, for a number of reasons; one of which is the higher price of runflats when they have to be replaced. Another reason is that the availability of runflat tyres could best be described as patchy and, when one has to be replaced, if the tyre dealer cannot supply one straight away then the motorist is stuck.

The situation is exacerbated by the confusion – in the tyre trade and among the general public – about whether or not runflat tyres that have suffered a puncture can be repaired. Take BMW, many of whose vehicles are fitted with runflats as OE, who recommends that punctured runflats are not repaired "as additional forces and wear have been incurred within the tyre whilst being driven deflated". The motorist may feel aggrieved that his runflat tyre not only costs more than conventional rubber, but also that the tyre dealer refuses to repair it, whereas if it were a conventional tyre, then it could be repaired.

However, by far the most common reason for replacing runflats with conventional tyres is not down to economics, but is the perceived quality of the ride – take a look at any online message board and, when it comes to runflats and comfort, hardly anyone has a good word to say about them.

The sidewall is stiffer on runflat tyres and, where these are fitted as OE, it forms part of the suspension, giving a harder ride, according to runflat critics. Of course, much depends on the driving style, but a typical message board comment is along the lines of "I couldn't believe the ride improvement when I got rid of the runflats". One suggestion is that fitting a non-runflat when the suspension had been set up for runflats makes the ride "wallowy" which contrasts with the original hard ride.

Whatever the reason for changing to conventional tyres, it is interesting that some motorists are willing to forgo the undoubted safety advantages of runflats. Also, as more and more cars are fitted with runflats as OE, presumably there will be more motorists wanting to switch.

For those who do decide to switch, what happens should they suffer a puncture? The tyre pressure monitoring systems – which are mandatory with runflats – will work equally well with conventional tyres, so a slow leak can be checked in time, but what if there is a sudden blowout? This is another question frequently asked on the message boards and the answers given are "carry a spare in the boot" (presumably given that there is room) or "carry a can of sealant".

INDUSTRY THOUGHTS

So much for why people want to change over from runflats, but what do the various sectors of the tyre industry, vehicle manufacturers and insurers have to say on the subject?

Back in 2005, the British Tyre Manufacturers' Association issued a statement concerning self-supporting runflat tyres (SSTs). On the subject of retro-fitting conventional tyres to SST-equipped cars, it points out that this "would remove the runflat capability, potentially leaving the driver immobile in a case of deflation and could compromise vehicle handling. It is therefore recommended to consult with the vehicle manufacturer or tyre manufacturer before replacing SSTs with conventional tyres."

Tyre manufacturers' websites have little to say about replacing runflats with conventional tyres. Most recommend replacing runflats with runflats and not mixing different runflat brands. One thing they all agree on is that runflat and conventional tyres should never be mixed on a vehicle.

Regarding the criticism of ride comfort, no doubt tyre manufacturers would argue that, in the early days of runflats, this may have been the case, but would point to the improvements in construction and materials since then, making the latest generation of runflats the most comfortable yet.

It should be remembered that the growing use of runflat tyres is because they are popular with vehicle manufacturers, not because the tyre industry wanted them. The BTMA statement suggested contacting the vehicle manufacturer, so we approached BMW, as an enthusiastic supporter of runflats, for their thoughts on changing to conventional tyres.

Their statement began by listing the reasons that they chose to utilise runflat technology in the first place, which primarily focused on driver and passenger safety and comfort. The statement went on:

"All of our vehicles that use runflat technology have their suspension and braking components set up to accommodate runflat tyres. Should you decide to change to non-runflats, it may alter the driving and handling characteristics of your vehicle. It is for this reason that this modification is not recommended by BMW as a manufacturer.

"However, it is possible to have standard tyres fitted. You will additionally need to purchase either a spare wheel with jack and brace set or a mobility kit, which can be ordered from the parts department of your nearest BMW Approved Dealership.

The illustration above shows a normal tyre deflated and on the left a run-flat tyre deflated clearly showing the additional sidewall support from the run-flat.

"Converting a vehicle from runflat tyres to conventional tyres will not invalidate its warranty, although this could give rise to a warranty claim being rejected where the fitment of conventional tyres is found to be directly attributable to the occurrence of any fault or defect."

So that's it – it can be done, but BMW doesn't recommend it.

TyreSafe statement

What about TyreSafe, the UK tyre safety group – where do they stand on this issue? We contacted them and, a few days later, a statement was released. In it, TyreSafe warns motorists that they could be compromising their own safety if they replace the run-flat tyres fitted to their vehicle with standard tyres that do not include run-flat technology.
The statement goes on: "With many motorists looking to reduce their vehicle maintenance costs, some have been tempted to economise by selecting tyres which do not incorporate the added technology and features found in run-flat tyres. By choosing these standard tyres, drivers risk significantly changing the handling characteristics of the vehicle which could increase their chances of being involved in an accident.

Stuart Jackson, Chairman, TyreSafe says "As a general rule, we would always recommend that drivers only replace run-flat tyres with a similar product. Run-flats have much stiffer sidewalls than those in traditional tyres and this is taken into account by vehicle manufacturers when they design their suspension and steering systems. By switching to tyres that do not use run-flat technology, the handling of the car can be dramatically altered and it may become unsafe, particularly during extreme manoeuvres."

In addition to the performance changes which may occur as a result of switching to non run-flat tyres, drivers can also cause themselves other problems. Run-flat tyres give drivers the ability to continue their journey for a limited time when they have no pressure in the tyre. Standard tyres cannot do this and must be changed as soon as there is a sudden loss of pressure.

SAFETY AND INSURANCE

The most powerful argument against getting rid of runflats is the safety angle. While punctures at high speeds are relatively uncommon, the results can be devastating without runflat capability. However, this is not the only safety factor, as, back in October 2006, Auto Express carried out a tyre test comparing runflats and standard tyres against each other on a wet and dry track.

A sentence in the report said that “fitting the wrong tyres to your vehicle could also invalidate your insurance”. Is this, in fact, the case? We contacted insurance giant Aviva and asked whether swapping from runflat to conventional tyres would affect a motorist’s cover.

The answer was unequivocal, with the Aviva spokesperson saying: “I can confirm that there would be no issue with a motor insurance policy purchased directly with us if a car was changed from runflat tyres to conventional tyres, with the only stipulation being that the tyre was road legal. We would only advise the client to call us so that this was noted, but there would be no additional terms imposed.”

We tried to obtain an industry-wide comment, but without success and the sensible course of action would be to check with your insurer before changing over tyres, to be on the safe side.

WHAT ABOUT RETRO-FITTING RUNFLATS?

In addition to replacing runflats with standard tyres, some NTDA members have been approached with requests to retro-fit runflats to cars that normally carry conventional tyres.

There is little information on this subject, but one thing for sure is that some sort of tyre pressure monitoring system will be needed. As you might imagine, the Royal Society for the Prevention of Accidents (RoSPA) seems to be a fan of runflat technology and it has the following to say about retro-fitting runflats:

"You should seek expert advice from your vehicle manufacturer before retro-fitting a runflat tyre if your vehicle has TPMS. As the tyre is more rigid, vehicles that have them as standard may require softer suspensions to compensate for the lost ride comfort. Guidance should also be sought from the tyre manufacturer."