More Star Cars - Movie Flyers, On Tyres

The star cars that make some movies memorable often start life as completely standard vehicles. They rarely stay that way and they always attract a following. So let us follow in the tyre tracks of some Hollywood luminaries.

Our first diva was in fact six cars, of which four still exist. In many respects it was ahead of its time; by the end of the first movie in which it appeared, it was running on rubbish. This early green machine, Doc Emmet Brown’s time-travelling car was a DeLorean DMC12 and it first burst on to our movie screens in 1985. A trilogy of movies and many years later, Christopher Lloyd (Doc Brown) is 71, and Michael J. Fox (Marty McFly) is 49, has Parkinson's disease and an honorary doctorate from the Karolinska Instituet. Of the four DeLoreans remaining, two are studio tour stars at Universal, one lives on the ceiling of Planet Hollywood in Honolulu - and the last one is being restored. Some of the cars that John Z. Delorean made still set tyres to tarmac, and some among their number have attained a degree of immortality.

'So cool it hurt' is an epithet that applied to the late Steve McQueen, and his handling of the 1968 Ford Mustang GT390 Fastback he used in 'Bullitt' did his reputation no harm at all.

During the seven-minute, tyre-burning chase sequence with the baddies' Dodge Charger R/T440, McQueen did most of the driving and there was no camera trickery. Both the Mustangs used were given tuning tweaks so they could keep up with the more powerful Magnum Chargers, and one of each was given beefed-up suspension and a full roll cage.

All that drifting car tyre smoke was real, as was much of the San Francisco traffic. One thing, however, was a later addition. The full-blast V8 engine sounds came from an example of the GT40, Ford's four-times Le Mans winning racing car.

Now for a quirky one. What has massive tyres, ten carburettors with gold plated intake pipes, and a huge, Ford Cobra motor? Need more clues? How about Jahns high-domed pistons and an Iskendarian camshaft? Still too techy? Ok then.

Customizer George Barris built the idiosyncratic vehicle in question. It was based on a lengthened 1923 Model T ford chassis and had a custom body. Still struggling? Alright, here are some names. The car was featured in a 1960s TV comedy starring Fred Gwynne, Yvonne De Carlo; Al Lewis played Grandpa. Those who are thinking of Clive Dunn at this stage can go to dunce's corner right now. However, the names Herman and Lily might ring some bells. Yes, it's the Munster’s Koach.

This unique car toured the 'States extensively in the 1970s, and pre-tour, George 'Batmobile' Barris gave it a new paint job. The car now rests in peace, in the 'Cars of the Stars' museum, in Keswick, Cumbria.

Finally, a vehicle with just 114 horsepower from its 4.9-litre, six-cylinder engine is hardly likely to set tyres or tarmac alight, especially with its three-speed automatic transmission. However, the very same vehicle had its charm and made us laugh, even if it was slow. The film 'Dumb and Dumber' featured this 1984 Ford Econoline van, complete with floppy, furry ears, a lolling tongue and a full fur coat. Jim Carrey and Jeff Daniels' 'Mutt Cuts' van didn't stay long but the movie wouldn't have been the same without it!

Merityre are a leading UK independent supplier of car tyres. Why not visit their website at www.merityre.co.uk and see where you can buy your next set of tyres.

Car Tyre Clearance: Making Sure Your Wheels Measure Up

There’s nothing in the rule book that says you must keep the wheels your car had on when it arrived. Many people change their wheels, for a variety of reasons. Some want a different style of wheels, some want wider wheels and most want alloy wheels. A change of wheels usually means a change of car tyres. That is no problem in itself but there is a trap into which a lot of people have fallen with a resounding clatter.

The thing is, any car wheel will accept one or more different sizes of car tyre. There is, however, more to car wheels than just rim diameter and width. Ignore the other measurements or get them wrong and disaster looms. In short, you can find there’s a clash between your car tyres and its bodywork. This can happen with steering or suspension movement and often, it happens just the once, immedately before the tyre and bodywork wreck one another.

The first measurment is Pitch Circle Diameter, or PCD for short. This is nothing to do with car tyre to bodywork clearance but if you get this wrong, the wheels won’t fit. The PCD is the diameter of a circle drawn through the centre of your wheel mountings, be they studs or bolts. The wheels obviously need the right number of stud or bolt holes but you also need to ensure that the wheel nuts or bolts have the right thread and profile for your car’s hubs, and that they are correct for use with the wheels you’re using.

Now for the easy ones: rim width and diameter. You could go for the standard measurements here. However, many people want bigger wheels and low profile tyres. Fair enough – just ask the wheel supplier, who you can always blame if something doesn’t fit. It’s also important to make sure that the wheels can accommodate your brakes. Big wheels and low profile tyres were invented, in part at least, to allow for bigger brakes to be crammed in. These days, clearances are close and it’s problematic if your wheels and disc calipers rub each other. This makes only one difference to the car tyres: they won’t work too well if the wheels can’t rotate.

So, we come to the tricky one, the knotty problem of wheel offset. This is most easily understood with a little bit of theory. Imagine a car wheel sawn in half across its diameter. If you were to draw a line through the centre of the wheel rim, and this line was to coincide with the wheel’s hub mounting face, the wheel offset would be zero. If, as is common, the hub face lies outboard of the centre line, the wheel has positive offset. Conversely, if the hub face lies inboard of the centreline, the offset is negative. The degree of offset, apart from altering wheel clearance, has a profound effect on the behaviour of your car tyres.

Visually, positive offset places the car tyre further under the car’s wheelarch. Negative offset makes the tyre carcass sit further outboard. In either case, provided you don’t choose a seriously large figure in relation to what is standard, the car tyres won’t cause difficuties. That said, there is a danger in choosing too radical an offset, as this figure (usually expressed in millimetres) affects steering. You could find that your steering has becomes mysteriously heavy. Worse still, you could find it’s become over-light, to the extent that straight line driving becomes a thing of the past.

Merityre are a leading UK independent supplier of car tyres. Why not visit their website at www.merityre.co.uk and see where you can buy your next set of tyres.