BMW 3 Series E30

since 1983-1994 release

Repair and operation of the car

Theory

The era of steel stamped wheels, apparently, slowly consigns to the past. Steel is forced out by light alloys. Than the steel disk is bad? Yes, in general, almost everything it is good. Cheap, reliable, rather strong. At very strong blow does not burst, and it is rumpled – means, there is a chance to restore it. If you perceive the car only as the hard worker if you are not confused by a type of steel stamping if your purse is not too burdened by notes – nothing the best is necessary to you. Take. And the one who is anxious with own image clear, behind the price will not stand, and will take light-alloy. The look at it, of course, is more modern, than at steel. And a variety of types is wider. The production technology of disks from light alloys allows designers to embody any imaginations in metal, to do wheels in any style – from a retro to futuristic. Light alloys give the chance to sensitively monitor trick of technical fashion what you will not tell about steel – stamping it and there is a stamping, on it design especially will not play, opportunities are limited, and therefore – with it it is boring.

But not only to these desire of producers to replace steel with light alloys speaks. There are also other reasons, not less weighty. Purely technical. For example, weight reduction. Let's notice, not the gross weight of the car – if the polutoratonny device means and will dump couple of tens of kilograms, hardly it will be big achievement. The speech about weight reduction of not subspring parts, that is all that jumps shivers and turns under a car body. Here fight goes for each kilogram.

Accuracy of production of light-alloy wheels is much higher, than steel. So, and balancing can be carried out more precisely. Application of a light-alloy wheel improves cooling of brake knot, and not only thanks to high heat conductivity of the metals entering alloy, but also because in it it is admissible to do very big openings (without losing durability and winning in weight) that promotes the best obduv. There were quite enough listed advantages in order that the leading firms relied on light alloys – aluminum and magnesian. Despite of their high cost.

Is, however, in a camp of steel disks one which can argue with light-alloy on beauty, ease and "produvayemost". It is classical spoke a disk. Once it was very popular, it was put on the most prestigious cars, on it won races... But eventually it did not sustain the competition even with usual stamped. First, its production more labor-consuming and consequently, he is dearer. To stamp a nave and a rim, of course, business simple and inexpensive, but here manual assembly... Secondly, it became clear that when using a spoke disk it is very difficult to provide optimum controllability and stability of the car at high speeds. And in the sixties the spoke wheel quitted the stage. However now "easily raftsmen" do stylizations under it as the fashion for spokes remained.

As do disks

Uniform technical characteristics, design and cost of a disk are defined not by alloy. Important and in what way it is made. The light-alloy wheel, both aluminum, and magnesian, can be either is cast, or forged – forging is called still volume hot stamping.

Casting. This way is most widespread. Cast aluminum wheels went to mass production after 1964 when Americans began to establish them on sports models. Italy and Japan in 1967 began to equip with cast disks serial cars that caused chain reaction in other countries – since then aluminum casting began to force out steel stamping slowly but surely. This way is very technological. It almost does not give waste that promotes decrease in prime cost of the final product. There are, of course, also shortcomings. First, the cast disk demands reliable protection of a surface, without it it quickly loses a trade dress – aluminum becomes covered by a whitish oxidic film. Secondly, it is fragile – at strong blow breaks up. To provide sufficient mechanical durability, it is necessary to increase thickness of walls, and it reduces so desired prize in weight.

Pour also magnesium. But in very limited quantities. In spite of the fact that cast magnesian disks give solid economy of weight (about 2,5 kg on a wheel), producers of production cars prefer not to contact them – requirements to protection of a surface are too high. Besides, such disks quickly crack. Magnesium is good not in cast option, and in shod.

Forging. If not the high cost caused by complexity and power consumption of technology, shod disks, probably, would win long ago the market – on the majority of characteristics they do not have equal. At strong blow the shod disk does not burst as cast, and it is rumpled. Cracks on it are not formed therefore the probability of depressurization of the tubeless tire is quite small. Air, of course, can come out in the place of a bend of a zakraina of a rim, but to rumple a zakraina of a shod disk it is necessary to manage still – forging provides the exclusive durability and rigidity of a design.

Shod wheel very easy. Compare: the steel disk for the 7th BMW model weighs 9 kg, cast aluminum – 7,8 kg (for comparison one of the easiest cast designs is taken), and shod aluminum – 6,8 kg. Corrosion firmness of a shod product is much higher, than cast. The aluminum shod disk does not demand protection – if it and do, then it is rather for an insurance, but not as necessary. Magnesian shod, of course, it is necessary to protect, but not so seriously and carefully as cast. Shod disks, especially magnesian, in the West – very expensive pleasure are also applied only on prestigious and on racing cars.

Sizes

So, you chose material, design and the price. Now things are easy – to buy. Also it is desirable so that: did not palm off on you under the guise of company production some homemade rubbish which should be thrown out through couple of thousands of kilometers,

b) the bought disks would suit the car not only on design, but also by the sizes. It is simple to execute these conditions. It is necessary to buy, first, disks in shops with good reputation. The prices in them, clear, corresponding, but here to you to solve what to hope for – at random or on a guarantee. Secondly, it is necessary to know a size range of the disks suitable your car and to be able to read the markings which are beaten out on disks. Therefore do not consider the following information a persuasive educational program. It is useful.

Rim tire sizes

This nomination includes two parameters – the assembly diameter and width of a rim. The complete series of assembly diameters of automobile and off-road disks looks so: 10, 12, 13, 14, 15, 16, 17, 18 and 19 inches. The disk with a diameter of 10 inches to you will interest only in those cases if you go by the legendary Soviet S-3D microcar for disabled or have the small trailer for country needs. Besides, 10-inch castors are put on tiny city micropenalties (them often call microdwarfs), but this class of cars in Russia will not be presented for a long time – they can be used only on ideally flat roads, and with it, as we know, at us a crunch. Disks with an assembly diameter of 12 inches are used redno too, but, of course, to a pro-thicket. than 10-inch (on Oka, for example). The vast majority of modern cars runs on 13, 14, 15 and 16-inch disks. Recently there was a fashion for increase in assembly diameter – those cars for which a family are, for example, 13-inch disks, translate on 14-inch, 15 on 16 and so on. It is explained by the aspiration to use tires of low series as their riding qualities it is better, than at tires of a high profile. And the tire series is lower, the it is less in a wheel of rubber and, respectively, more metal – is natural if the outer diameter of a wheel remains invariable. When using steel disks especially you will not increase assembly diameter – it will lead to increase of mass of a wheel that is undesirable. Here as it is impossible by the way disks from light alloys had – their application allows to increase assembly diameter, without making heavier a wheel in general. The fashion for rubber of ultralow profiles (the tire of series 40, 35 and even 30) moved tuning firms on equipment of cars of top-class disks of very big diameters – 17, 18 and 19 inches. At a view sideways of such car and tires it is almost not noticeable – the huge brilliant disk zastit eyes, and the tire looks a thin black kayemochka. Looks beautifully and it is technically quite justified, but start up this fashionable animal on our roads – to the first pothole will reach, and further? Such tuning, alas, not for us. Under our conditions the kayemochka has to be thicker – at least than the 60th series. Otherwise you will not save enough "iron".

Further. Rim width. At the majority of cars this size does not go beyond the following row: 3,5; 4,0; 4,5; 5,0; 5,5; 6,0; 6,5; 7 inches, however on tuning modifications, on SUVs and on sports models are applied also wider disks – to 13,5 inches. How to choose the necessary width of a rim? There is a golden rule: it has to be of 25-30% less than tire profile width. As width of a profile of the tire is usually specified in millimeters, and rim width – in inches, upon purchase of disks you should make simple mathematical calculation. Let's say you look for a disk under the tire 195/70R15. Width of its profile is 195 mm. In inches it will be 7,68 (it is necessary to divide 195 on 25,4). Now take away from the received size of of 25% or of 30% and round to the next value from the standard row given above. Receive 5,5 inches – the rim of such width is necessary for the tire 195/70R15. Use of both too wide disks, and too narrow is undesirable: the design profile of the tire (sidewalls or are compressed by rim zakraina, or are stretched on it) is broken and, therefore, its riding characteristics – reaction to turn, resistance to withdrawal, side rigidity worsen. The rim width tolerance from regular size makes 0,5–1,0–1,5 inches for disks with a diameter more than 15 inches. But it is better to take, of course, disk precisely under the tire.

Wheel departure. This distance between the longitudinal plane of symmetry of a rim and the fixing plane of a wheel. For each model of the car the departure pays off so that optimum stability and controllability of the car, and also the smallest load of bearings of naves were provided. The majority of serial cars is issued with departures of wheels on 0 mm (GAZ-3102) to +38 mm (Opel Corsa, Toyota Corolla, Mitsubishi Colt, VAZ-2109), but range, of course, is not exhausted by it – models meet a departure both-46, and +59. Producers do not recommend to put for the car disks with a departure, emergency for this model. Its reduction does a track of wheels wider – though it a little and increases stability of the car, gives it more racing look, but at the same time sharply reduces a resource of bearings of naves and creates additional load of a suspension bracket (to increase a departure, that is to narrow a track of wheels, most often it is impossible – the disk will rest against a support or against the brake drum).

Wheel car sizes

With it usually problems do not arise – each car owner perfectly knows what bolts, nuts, hairpins the wheel to its car fastens. In number of fastening openings it is difficult to be mistaken too – hardly you buy a disk with four openings if on a nave of an axis of the car 5 hairpins stick out. Happens, make the wrong choice of diameter of the central opening of a disk (if the mistake in minus, wheel simply does not sit down on the place) and diameter of an arrangement of openings of fastening. It is both specified in catalogs which are in any decent shop – before purchase of disks ask the seller to be verified with them. At native wheels of the car the central opening of a disk is, as a rule, precisely adjusted to an axis nave: at the plants it is accepted to align a wheel on it – its diameter is landing. But if you buy disks in the secondary market, be not surprised to the fact that the central opening can appear more put. Producers of spare parts often do it obviously increased diameter (a wheel in this case align on diameter of an arrangement of openings of fastening – it is designated by PCD – Pitch Circle Diameter) and supply a disk with set transitional Kolya that allows to use it on different models of cars. But it is better to do without rings. Though in them there is no big crime, after all than it is less in knot of "excess" details, it is more reliable than subjects.

Marking

Full or almost full information on a disk is given by marking which has to be cast or beaten out in a visible place. That is on any surface of a disk, except that part of a rim which