Eufori: a good idea that falls flat (Pirelli Tyres)

Member Name: Alfettaman

Product:	Pirelli Tyres
Date:	30/07/09 (301 review reads)
Rating:

Advantages: You can drive on, even with a punctured tyre

Disadvantages: Unstable handling; poor wet grip; harsh ride; weak carcass; expensive

I should say straight away that this is a relatively technical overview of the Pirelli Eufori run-flat tyre, based on my own personal experiences.

'Run-flat" technology:
These 205/45x17 tyres came as standard equipment on my BMW MINI Cooper S, and - on paper at least - have quite a bit going for them. In essence, Euforis have extra rigid sidewalls which mean that they can support the weight of your car even when fully deflated. Pirelli market this as a safety feature, and BMW use it as an excuse not to supply a spare wheel - not even one of the skinny 'space-savers' that many manufacturers now use.

The reality of all of this is actually rather different.

It's true that a punctured car tyre is an inconvenience and can - in some circumstances - be dangerous too, so let's tackle the safety issue first.

In a bygone era, car tyres had inner tubes and a puncturing object (say, a nail) would pierce the tyre then pop the tube, a bit like a pin in a balloon. The result could be a very sudden and catastrophic 'blow-out' and, at high speed, the car could veer violently and uncontrollably towards the punctured side.

Modern cars use tubeless tyres, and the puncturing object usually stays in the tyre causing a much more gradual deflation: even if it comes out, the air escapes through a relatively small hole, rather than through a shredded inner tube. So punctures nowadays are unlikely to be the terrifying prospect that they were fifty years ago.

Which leaves us with 'convenience'. Changing a tyre at the side of a rain-swept dual carriageway is certainly no fun, so the appeal of the run-flat technology is pretty obvious: but modern tyres are commendably puncture-proof and I've driven almost a million miles without ever having to change a wheel at the side of the road. That said, if Pirelli can offer the convenience of run-flat technology without any downsides, then of course I'll have it.

Trouble is, there is a big downside - several, in fact.

A compromised design:
A car tyre works by pressing a small patch of rubber onto the road, which then resists the forces of steering, braking and acceleration, all of which are trying to make the tyre slip. The cars springs, dampers and flexibly-walled tyres are all designed to assist in keeping the tyre on the road, as otherwise it can't do its job: this is what engineers call 'compliance' - making the tyre tread 'comply' to the undulations and contours of the road.

Pirelli have accepted a huge performance compromise with the Eufori, because the extra-stiff sidewalls play a much more limited part in keeping the rubber patch uniformly pressed against the road. Think what would happen if you put solid rubber tyres on a racing bicycle and rode it fast around bumpy corners, and you'll start to understand the problem: less grip, especially on wet, uneven or undulating surfaces, and a harsh and uncomfortable ride.

Handling:
Another issue with these run-flat tyres is the day-to-day handling. The designers have tried to ameliorate the problem of the very stiff sidewalls by making the tread blocks relatively soft and 'squishy' - essentially putting back a little bit of that missing compliance. Unfortunately though, the tread blocks squish sideways as well as up and down which robs the car's steering of all its feel and immediacy.

This is particularly noticeable during the initial turn-in to a corner, as the soft tread resists the steering's order to turn. It makes the car feel as though the steering wheel has been fixed to the column using a block of rubber and also makes the Euforis 'tramline' quite badly as they are deflected by the grooves worn in the road: this is memorably bad once the tyres are more than half worn.

Any 'press-ahead' driver will find these handling characteristics deeply frustrating and at times unnerving, because it makes the car's behaviour less predictable.

An inconvenient convenience:
There are yet more reasons to avoid these tyres: Pirelli say that you can only drive about 90 miles on a punctured Eufori, and then only at 50 mph. They also recommend that you fit it only to vehicles with a tyre pressure monitoring system (because you need to know when they're punctured, and drive accordingly), and a Eufori that's been run whilst flat has to be discarded as it cannot be repaired.

In 40,000 miles of driving on Pirelli Euforis I had two puntures: perhaps an ironic consequence of the soft tread. In contrast, a conventional radial ply tyre can often be safely repaired if cleanly punctured near the centre of its tread.

Since there is specialist equipment needed to fit run-flat tyres (not all tyre dealers have a suitable machine) and only a limited number of cars that use them, you could have trouble getting your tyres replaced at short notice.

Sum-up:
I finally gave up on these tyres when I had to discard two half-worn Euforis that were less than six months old, in order to get my (then) three year old MINI through its first MOT test. I was horrified when the test technician showed me that the tread on each rear tyre had split down the middle and round the entire circumference, virtually dividing the tyre into a left and right half. Not an easy fault to spot (there was lots of tread left on these tyres and superficially they looked fine) so I remain exceptionally grateful to that MOT tester for his skill and diligence.

As if all this wasn't enough, the Euforis cost about £120 each. I now use Falken's excellent ZIEX 512 (it's now called 912) which provide loads of grip, compliance and comfort for £72 per tyre and outperform the Pirellis in almost every way. I've also made a one-off purchase of a tyre inflation kit for £25 which has a bottle of tyre sealant and a mini air compressor, just in case I get a puncture one day.

Summary: Could compromise safety for convenience

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