BMW 3 series E30

Since 1983-1994 of release

Repair and car operation

14.40. Wheel disks

THE GENERAL DATA

The theory

The epoch of steel stamped wheels, apparently, on the sly leaves in the past. The steel is superseded by easy alloys. Than the steel disk is bad? Yes, in general, almost all it is good. Cheap, reliable, strong enough. At very strong blow does not burst, and it is rumpled – means, there is a chance it to restore. If you perceive the car only as the hard worker if you are not confused with a kind of steel punching if your purse is not too burdened by denominations – anything the best to you and it is not necessary. Take. Well and the one who is anxious by own image, clearly, behind the price will not stand, and takes легкосплавный. The kind at it is, of course, more modern, than at the steel. And a variety of kinds is wider. "The know-how" of disks from easy alloys allows designers to embody any imaginations in metal, to do wheels in any style – from a retro to futuristic. Easy alloys give the chance to trace sensitively trick of a technical fashion that you will not tell about a steel – punching it and there is a punching, on it design especially will not play, possibilities are limited, and therefore – with it it is boring.

But not only to it the desire of manufacturers to replace a steel on easy alloys speaks. There are also other reasons, not less weighty. Purely technical. For example, weight reduction. We will notice, the car gross weight – if полуторатонный the device means not and kg will lose to steam of tens, hardly it will be the big achievement. Speech about weight reduction неподрессорных parts, that is all that jumps, shivers and turns under a car body. Here struggle follows each kg.

Accuracy of manufacturing of is easy-floatable disks much more above, than steel. So, and balancing can be spent more precisely. Application легкосплавного wheels improves cooling of brake knot, and not only thanks to high heat conductivity of metals entering into an alloy but also because in it is admissible to do very big apertures (without losing durability and winning in weight) that promotes the best обдуву. The listed advantages quite has sufficed that leading firms have counted on easy alloys – aluminium and magnesian. Despite of their high cost.

Is, the truth, in a camp of steel disks one which can argue with легкосплавными on beauty, ease and "продуваемости". It is classical спицевой a disk. Once it was very popular, it put on the most prestigious cars, on it won races... But eventually it has not sustained a competition even with the usual stamped. First, its manufacture more labour-consuming and consequently, it is more expensive. To stamp a nave and a rim business, of course, simple and inexpensive, but here manual assemblage... Secondly, it was found out that at use спицевого a disk it is very difficult to provide optimum controllability and stability of the car on high speeds. And in the sixties спицевое the wheel has quitted the stage. However now "легкосплавщики" do stylisations under it as the fashion on spokes remained.

As do disks

Not the alloy uniform defines technical characteristics, design and disk cost. Important and what way it is made. The legkosplavnyj disk, both aluminium, and magnesian, can be either is cast, or forged – ковку still name volume hot punching.

Moulding. This way is most extended. Cast aluminium wheels have gone to mass production after 1964 when Americans began to establish them on sports models. Italy and Japan in 1967 have started to equip with cast disks serial cars that has caused chain reaction in other countries – since then aluminium moulding began to supersede steel punching slowly but surely. This way is very technological. It almost does not give a waste that promotes decrease in the cost price of an end-product. Is, of course, and lacks. First, the cast disk demands reliable protection of a surface, without it it quickly loses a trade dress – aluminium becomes covered whitish оксидной by a film. Secondly, it is fragile – at strong blow breaks up. To provide sufficient mechanical durability, it is necessary to increase a 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), manufacturers of serial cars prefer not to communicate with them – requirements to surface protection are too high. Besides, such disks quickly растрескиваются. Magnesium is good not in a cast variant, and in the shod.

Ковка. If not the high cost caused by complexity and power consumption of technology, shod disks, probably, would win for a long time the market – on the majority of characteristics they do not have the equal. At strong blow the shod disk does not burst, as cast, and is rumpled. Cracks on it it is not formed, therefore the probability of depressurization бескамерной tyres is small enough. Air, of course, can leave in a bend place закраины rims, but to rumple закраину a shod disk it is necessary to manage still – ковка provides exclusive durability and rigidity of a design.

Shod wheel very easy. Compare: the steel disk for 7th model BMW weighs 9 kg, cast aluminium – 7,8 kg (for comparison one of the most easy cast designs is taken), and shod aluminium – 6,8 kg. Korrozijnaja firmness of a shod product it is considerable above, than cast. The aluminium shod disk does not demand protection – if it and do, is faster for the insurance, instead of necessarily. 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 also are applied only on prestigious and by racing cars.

The sizes

So, you have chosen a material, design and the price. Now things are easy – to buy. Also it is desirable so that: on you have not palmed off under the pretext of firm production any самопальную rubbish which should be thrown out through pair thousand kilometres,

The bought disks would approach the car not only on design, but also in the sizes. These conditions to execute simply. It is necessary to buy, first, disks in shops with good reputation. The prices in them, clearly, corresponding, but here to you to solve, on what to hope – at random or on a guarantee. Secondly, it is necessary to know a dimensional number of the disks approaching your car, and to be able to read the marks beaten out on disks. Therefore do not consider the below-mentioned information as a persuasive educational program. It is useful.

The sizes "rim-tyre"

This nomination includes two parametres – 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 in diameter of 10 inches to you will interest only in those cases if you go by legendary Soviet invalid motorised carriage С-3Д or have the small trailer for country needs. Besides, 10-inch castors are put on tiny city micropenalties (them often name microdwarfs), but the given class of cars still for a long time will not be presented to Russia – they can be used only on ideally equal roads, and with it, as it is known, at us напряженка. Disks with assembly diameter of 12 inches too are used редно, but, of course, прочаще. Than 10-inch (on "Oka", for example). The overwhelming majority of modern cars runs on 13, 14, 15 and 16-inch disks. Recently there was a fashion on increase in assembly diameter – those cars for which 13-inch disks are native, for example, translate on 14-inch, 15 on 16 and so on. It speaks aspiration to use the tyre of low series as their rideable qualities it is better, than at tyres of a high profile. And the more low a tyre series, the is less in a wheel of rubber and, accordingly, more metal – it is natural, if external diameter of a wheel remains invariable. At use of steel disks assembly diameter especially you will not increase is will lead to increase of weight of a wheel that is undesirable. Here as it is impossible by the way disks from easy alloys had – their application allows to increase assembly diameter, without making heavier a wheel as a whole. A fashion on rubber of ultralow profiles (the tyre of series 40, 35 and even 30) сподвигла tuning firms on equipment of cars экстракласса disks of very big diameters – 17, 18 and 19 inches. At a sight sideways on such car and tyres it is not appreciable almost – a huge brilliant disk застит eyes, and the tyre looks thin black каемочкой. 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 каемочка should be thicker – at least than 60th series. Otherwise some "iron" will not save enough.

Further. Width of a rim. At the majority of cars this size does not fall outside the limits a following number: 3,5; 4,0; 4,5; 5,0; 5,5; 6,0; 6,5; 7 inches, however on tuning updatings, on off-road cars 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 should be on 25–30 % of less width of a profile of the tyre. As the width of a profile of the tyre usually is underlined in millimetres, and width of a rim – in inches, at purchase of disks you should make simple mathematical calculation. We will admit, you search for a disk under the tyre 195/70R15. Width of its profile of 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 25 % or 30 % and approximate to the nearest value from resulted above a standard number. Receive 5,5 inches – the rim of such width is necessary for the tyre 195/70R15. Use both too wide disks, and too narrow is undesirable: The design profile of the tyre (боковины or are compressed закраинами rims, or are stretched on it) is broken and, hence, its rideable characteristics – reaction to turn, resistance to withdrawal, lateral rigidity worsen. The maximum deviation of width of a rim from regular size makes 0,5–1,0–1,5 inches for disks with a diameter more than 15 inches. But to take better, of course, a disk precisely under the tyre.

Wheel start. This distance between a longitudinal plane of symmetry of a rim and a fixing plane of a wheel. For each model of the car the start pays off so that optimum stability and controllability of the car, and also the least loading on bearings of naves were provided. The majority of serial cars is issued with starts of wheels on 0 mm (ГАЗ-3102) to +38 mm (Opel Corsa, Toyota Corolla, Mitsubishi Colt, VAZ-2109), but the range, of course, is not settled by it – there are models a start and-46, and +59. To put on the car disks with supernumerary for the given model a start manufacturers do not recommend. Its reduction does a track of wheels more widely – though it a little and raises stability of the car, gives it more racing kind, but at the same time sharply reduces a resource of bearings of naves and creates additional loading on a suspension bracket (to increase a start that is to narrow a track of wheels, it is impossible more often – the disk will rest against a support or in a brake drum).

The sizes "wheel-car"

With it usually problems do not arise – each automobile owner perfectly knows, what bolts, nuts, hairpins the wheel to its car fastens. In number of fastening apertures too it is difficult to be mistaken – hardly you buy a disk with four apertures if on a nave of an axis of the car 5 hairpins stick out. Happens, make the wrong choice diameter of the central aperture of a disk (if an error in a minus, the wheel simply does not sit down into place) and diameter of an arrangement of apertures of fastening. Both that, and another is specified in catalogues 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 aperture of a disk, as a rule, is precisely adjusted to an axis nave: at factories 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 that the central aperture can appear more put. Manufacturers of spare parts often do its obviously increased diameter (a wheel in this case align on diameter of an arrangement of apertures of fastening – it is designated PCD – Pitch Circle Diameter) and supply a disk with a set transitive колей that allows to use it on different models of cars. But it is better to do without rings. Though in them big криминала is not present, all the same the it is less in knot of "superfluous" details, the it is more reliable.

Marks

The full information full or nearly so on a disk is given by marks which should be cast or beaten out in a prominent place. That is on any surface of a disk, except that part of a rim which is turned to the tyre. To put marks on a landing surface it is not meaningful, as disks often are on sale in gathering with tyres which close inscriptions. In our market you can face different variants of marks – as a rule, with Russian, American and European. They differ from each other an execution manner a little, but it should not confuse you – simply same information reaches the buyer by means of different, depending on concrete national standards, symbols. We will consider as an example marks of an off-road car of a disk of American firm ALCOA.

The first. It, of course, the firm name, its emblem (something reminding a sand-glass), a sign protecting the right of the manufacturer to be called by itself (letter R in a circle), and the country of manufacturing of a disk (Made in USA).

Further. A standard size – 15х10JJ. It means that the given disk has assembly diameter of 15 inches and width of a rim of 10 inches. Consider that on the European and Russian disks these parametres are specified in return sequence – 10JJх15, and in a tail of this inscription also any letters (for example so are attached: 10JJх15CH). In an index, the put down ambassador of value of width of a rim (in our case it JJ), the information on design features onboard закраин this rim – every possible angles of slope, radiuses закругления and other is coded. Instead of JJ can be written J, JK, K or L – depending on what form закраин rims is chosen by designers for the given disk. Well and what mean the letters which have been put down after assembly diameter? Before to answer this question, it is necessary to recollect, in what the basic difference of a disk for the chamber tyre from a disk бескамерной consists. Have recollected? Available at "бескамерного" хампов – special ring ledges on the regiments of a rim keeping the tyre from соскакивания from a disk at lateral blow and at loss of pressure. Designs хампов very much – there is an idle time хамп (it is designated H – Hump), is flat хамп (FH – Flat Hump), asymmetric хамп (AH – Asymmetric Hump) and still set of others. Sometimes on rims do a special shelf (SL – Special Ledge) which parametres are verified so that the tyre reliably keeps and without хампа. Happens, on a rim outer side хамп one type, and on internal – another. All these combinations also make a reservation in a dimensional inscription. In the European variant of marks – 10JJх15CH – letters mean that on the given disk system Combi Hump (combined хамп) is applied. To penetrate that with what is combined, to the buyer it is not obligatory, it is the information for experts. Remember values of these буковок you can as required to flash only erudition in conversation with colleagues on a wheel.

On a disk manufacturing date (year and week) necessarily is underlined. Number 0294 means that the wheel is let out in the second week 1994.

Inscription PART NO 150410-A is number of that party отливок from which preparation for a disk is taken. If while in service factory defect is found out in a disk, trading inspection can define under this number, in what link of a technological chain marriage is admitted. The Russian and European manufacturers usually designate casting number four-unit number.

N48 T-DOT – a brand of supervising body (saying our way, Quality Department), confirming that the goods are checked up on all parametres and годен to the use. DOT means that the disk corresponds to the American standards of safety. Some firms brand the production not dry indexes, and birdies, florets and an other art.

On cast disks for бескамерых tyres besides a brand of usual Quality Department it is put also a brand рентгеноконтроля which testifies that the disk has no internal defects – литьевых bowls.

MAX LOAD 3000 LB – limiting static weight loading on a disk. Having translated 3000 pounds in measures habitual to us, we will receive 1362 kg.

FORGED in a translation from English means the shod. Presence of such inscription in marks is not obligatory, it is not provided by any standards. As a rule, it do on the superfashionable disks forged from an easy alloy. It means that the firm-manufacturer simply wishes потрафить the vain buyer and to involve monetary clientele. After all shod, and especially shod magnesian disk – madly expensive (in the West) and prestigious – a sign of a solvency of the owner. And without inscription FORGED here not to manage in any way. Say, let all see, what I abrupt...

There is in the American marks one more interesting inscription: MAX PSI 50 COLD. It means that pressure in the tyre which is put on this disk, should not exceed, in our example, 50 pounds on square inch (3,5 kgs/sm sq.); the word cold reminds (cold) what to measure pressure in the tyre follows, when it cold, that is to a trip or not right after it.

It would seem, what for to specify on disk pressure of air if it is stipulated in requirements to the tyre and is defined first of all it, instead of a disk, a design? Experts have explained that it is a thin insurance course. We will admit, at drift at great speed the car flies sideways in a border – the tyre comes off a rim, the disk bursts (if it cast, shod is rumpled). The Cause of accident you. Naturally, consider quality of a disk (rotten have palmed off, the tyre does not hold) and address in court with intention вчинить the claim to its manufacturer. But the court will solve business in your advantage only in the event that you accurately observed ALL instructions and the restrictions, concerning a dispute subject. And if it will be found out that in the tyre which has been put on a disk with inscription MAX PSI 50, these most PSI was though for pound more (it will find out, having measured pressure in the escaped tyres, – it is meant that it identical on all four wheels) – indemnification not to see.

For the come off tyre will not pay. It is logical: the rim reliably holds the tyre, only when that is not pumped over, and the rating limit see in disk marks (in this sense, by the way, inscription MAX PSI on a disk is quite justified technically). And that is interesting, for the burst disk too will not pay. Why? Yes all therefore. Instruction non-observance. It seems, what communication? And it is unimportant. Ministry of Health warned...

As we see, the inscription – is good зацепка in judicial dispute. Not to pay superfluous under claims. Americans have known inside out insurance affairs. Europe is yet cunning before similar pettifogging – anyway, шинное MAX PSI on disks there nobody specifies. Or nearly so anybody.

You, probably, have paid attention that in marks of a considered disk there are no such important things, as a start and the connecting sizes "wheel-car". Generally the start without fail is underlined all European firms and the majority American (our example in this sense is atypical). Germans designate start ET (it is admissible, ET 30, if its size positive, or ET-30 if negative), Frenchmen – DEPORT, all the others manage English OFFSET. The sizes "wheel-car" are specified seldom enough. If you can see an inscription on any disk, for example, PCD 100/4, know that diameter of an arrangement of apertures of fastening of this disk to an axis nave is equal 100 mm, and apertures 4. The last, however, is visible and without helps.