Highly dispersible precipitated silica The present invention relates to a highly dispersible precipitated silica which has a high surface area, to a process for preparing it, and to its use as a tire filler for commercial vehicles, motorbikes and highspeed vehicles. The use of precipitated silicas in elastomer blends such as tires has been known for a long time. Silicas used in tires are subject to stringent requirements. They should be amenable to easy and thorough dispersion in the rubber, should bond well with the polymer chains present in the rubber and with the other fillers, and should have a high abrasion resistance akin to that of carbon black. Besides the dispersibility of the silica, therefore, the specific surface areas (BET or CTAB) and the oil absorption capacity (DBP) are important. The surface properties of silicas are critical determinants of their possible application: certain applications of a silica (for example, carrier systems or filler's for elastomer blends) demand particular surface properties. Thus US 6013234_ discloses the preparation of precipitated silica having a BET and CTAB surface area of in each case from 100 to 350 m2/g. This silica is particularly suitable for incorporation into elastomer blends, with the BET/CTAB ratios being between 1 and 1.5. EP 0 937 755 discloses various precipitated silicas which possess a BET surface area of from about 180 to about 430 m2/g and a CTAB surface area of from about 160 to 340 m2/g. These silicas are particularly suitable as carrier material and have a BET to CTAB ratio of from 1.1 to 1.3. EP 0 647 591 discloses a precipitated silica which has a ratio of BET to CTAB surface area of from 0.8 to 1.1, it being possible for these surface characteristics to adopt absolute values of up to 350 m2/g- EP 0643015 presents a precipitated silica which can be used as an abrasive and/or thickening component in toothpastes and which has a BET surface area of from 10 to 130 m2/g and a CTAB surface area of from 10 to TO m2/g, i.e. a BET to CTAB ratio of from about 1 to 5.21. Silicas which are especially suitable as fillers for elastomer blends, and in particular automobile tires, are described in EP 0901986 with the following properties: BET surface area 120 - 300 m2/g CTAB surface area 100 - 300 m2/g BET/CTAB ratio 0.8 - 1.3 Sears number (consumption of 0.1 N NaOH) 6 - 25 ml DBF number 150 - 300 g/ 100 g WK coefficient <3 . 4 Particle size of the broken-down particles <1.0 um Particle size of the particles not broken down 1.0 - 100 um Vehicle tires are subject to very different requirements depending on their end use. Given a rough division into automobile and truck tires, the following differences at least must be taken into account: Requirement for automobile tires {recommended values) Requirement for truck tires (recommended values) Principal tread component E- and S-SBR/BR blends NR, in part as BR blend Retreadability unimportant at least 3 times Distance performance 40 000 km in Europe 64 000 km in the USA 3 x 200 000 km Maximum speed 160 - 240 km/h and higher 100 km/h (max. 140 km/h) Filling pressure 2.2 bar 8.5 bar Load-carrying capacity per axle 1000 kg 6300 kg (with single tire fitted) Off-road use low high Heat buildup low very important Rolling resistance very important important Tensile strength low important Automobiles for the purposes of the present invention are vehicles for personal transport for predominantly private use, i.e., not commercial vehicles such as delivery vehicles, for example. This does not include vehicles which are commonly operated at high speeds, even if they might be classed as automobiles on the basis of their construction. These vehicles have different tire requirements again than the automobile tires specified in the table. Tires for motorbikes and high-speed automobiles must likewise exhibit high loads at high speeds and a very good dry and wet traction. Good traction, however, should not be associated with increased wear and/or high rolling resistance. The differing tire requirements of vehicles have corresponding consequences for the fillers that are used in the tires. The admixing of silicas and organosilicon compounds as a filler system, which is long established in automobile tires, results in reduced rolling resistance, enhanced traction, and reduced wear. Transferring these enhanced properties to tires for commercial vehicles such as trucks would be desirable, since a reduced rolling resistance is associated with a lower fuel consumption. The different tire requirements of said vehicles, however, lead automatically to different requirements in terms of the fillers used. It has been found that the silicas used in automobile tires are unsuitable for use in truck tires, motorbike tires, and high-speed automobile tires owing to the different profile of requirements. It is an object of the present invention, therefore, to provide precipitated silicas having a profile of properties which is specifically attuned to these vehicles. The skilled worker is aware that, when active carbon blacks are used as a tire filler, with an increase in the surface area, an improvement in the strengthening and thus in the wear resistance of the tire is obtained. The use of carbon blacks with high surface areas (CTAB surface area >130 m2/g) , however, is limited in mixtures with such filling, owing to the sharply increasing heat buildup (hysteresis behavior, described and measurable according to DIN 53535 or according to the references cited in this DIN). It has now been found that a precipitated silica which has a high CTAB surface area is particularly suitable as a filler in elastomer blends for commercial vehicle tire systems, for motorbike tires, and for tires for high-speed automobiles. The present invention accordingly provides precipitated silicas having a BET surface area of 178 - 302 m2/g, a CTAB surface area of >170 m2/g, a DBP number of 200 - 300 g/<100 g), preferably 207 - 276 g/[100 g), and a Sears number V2 of 10-35, preferably 10-25, 10-20, 10-16 ml/(5 g). Owing to the greatly reduced hysteresis when silica of the invention is used as filler, therefore, it is also possible to realize surfaces which are prohibited in the case of carbon black, owing to the higher hysteresis, and so lead to an improvement in the wear resistance. EP 1186629 discloses silicas with high CTAB surface areas which are suitable as fillers for tires. Indications of the Sears number and hence of the concentration of hydroxyl groups on the surface of the silica are not evident from EP 1186629. The precipitated silicas of the invention can have a maximum CTAB surface area of 300 m2/g, in particular a CTAB surface area of 170 - 220 m2/g or 245 - 300 m2/g. The precipitated silicas of the invention can have a BET surface area in the preferred ranges of 178 - 257 m2/g or 257 - 300 m2/g or 190 - 230 m2/g. The present invention additionally provides a process for preparing a precipitated silica having a BET surface area CTAB surface area DBP number Sears number V2 in which 178 - 302 m2/g >170 m2/g 200 - 300 g/(l00 g) 10-35 ml/(5 g) a) an aqueous solution of an alkali metal silicate or alkaline earth metal silicate and/or of an organic and/or inorganic base with pH 7.0 - 8.5 is introduced as initial charge, b) waterglass and an acidifier are metered simultaneously into this initial charge with stirring at 55 - 95°C for 10 - 120, preferably [ 10-60, minutes, e) the mixture is acidified with an acidifier to a pH of approximately 3.5, and f) the acidified mixture is filtered and dried. In addition to the preferential ranges already stated for the BET and CTAB surface areas, the precipitated silicas prepared in accordance with the invention may in each case independently have properties within the following preferential ranges: DBP absorption 200 - 300 g/(100 g), especially 207 - 276 g/(100 g) WK coefficient <3 .4, preferably <3.0, especially <2.5 Sears number V2 10-25, especially 10-20, preferably 10-16 ml/(5 g> . The WK coefficient is defined as the ratio of the peak height of the particles in the size range 1.0 - 100 urn which cannot be broken down by ultrasound to the peak height of the broken-down particles in the size range <1.0 urn (see Fig. 1). The initial charge may amount to around 20, 30, 40, 50, 60, 70, 80 or 90% of the final volume of the precipitation. The basic compounds that are added to the initial charge are selected in particular from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkali metal hydrogen carbonates, and alkali metal silicates. Preference is given to using waterglass and/or sodium hydroxide solution. The pH of the initial charge lies between 7.0 and 8.5, preferably between 7.5 and 8.5. The process of the invention may optionally comprise a holding point. In that case, the following steps are carried out between steps b) and e): c) stopping of the metered addition for 30-90 minutes, during which the temperature is maintained, and d) simultaneous metered addition of waterglass and an acidifier, preferably sulfuric acid, at the same temperature with stirring for 20 - 120, preferably 20-80, minutes. An additional addition of organic or inorganic salts during steps b) and d) is optional. This can be carried out in solution or as a solid, in each case continuously over the time of addition of the waterglass and the acidifier, preferably sulfuric acid, or in the form of a batch addition. It is also possible to dissolve the salts in one or both components and then to add them simultaneously with these components. As inorganic salts it is preferred to use alkali metal or alkaline earth metal salts. In particular it is possible to use combinations of the following ions: Li + , Na+, K+, Rb\ Be2 + , Mg2\ Ca2+, Sr2\ Ba2\ H+, F", CI", Br", I", S032\ S0„2~, HSCV, P033", PO„3", N03", N02", C032", HCOf, OH", Ti03z~, Zr032", Zr04"", A102", A12042", B043_. Suitable organic salts are the salts of formic, acetic, and propionic acid. Cations that may be mentioned include the specified alkali metal ions or alkaline earth metal ions. The concentration of these salts in the solution for addition can be from 0.01 to 5 mol/1. As an inorganic salt it is preferred to use Na2S04. It is possible to supply the acidifier in steps b) and d) in the same way or in different ways, i.e., with the same or different concentration and/or rates of addition. Similarly, waterglass as well can be supplied to the reaction in the same way or in different ways in steps b) and d). In one particular embodiment, in steps b) and d) the acidifier and waterglass components are supplied such that the rates of addition in step d) is 125 - 140% of the rates of addition in step b), the components being used in each case in in each case equimolar concentration in both steps. It is preferred to add the components at the same concentration and rate of addition. Besides waterglass (sodium silicate solution) it is also possible to use other silicates such as potassium silicate or calcium silicate. In addition to sulfuric acid it is also possible to use other acidifiers such as HC1, HN03, H3PO4 or C02. The filtration and drying of the silicas of the invention are familiar to the skilled worker and can be read, for example, in the documents cited, The as-precipitated silica is preferably dried in a pneumatic conveying drier, spray drier, rack drier, belt drier, rotary tube drier, flash drier, spin-flash drier or nozzle tower. These drying variants include operation with an atomizer, a single-fluid or two-fluid nozzle or an integrated fluid bed. After the drying step the precipitated silica of the invention preferably has a particle morphology with an average diameter of more than 15 urn, in particular more than 80 urn, with particular preference more than 200 urn. The average particle diameter is defined such that 50% by weight of the particles have a larger or smaller diameter. After drying it is also possible to carry out granulation using a roll compactor. In this case the average particle diameter is >1 mm. The silica of the invention is preferably used in tires for commercial vehicles, trucks, high-speed automobiles, and motorbikes. Commercial vehicles for the purposes of the present invention are considered to be all vehicles whose tires are subject to stringent demands in respect of distance performance and/or wear. With regard to the requirement of a high distance performance, mention is made in particular of tires for buses, trucks and/or delivery vehicles and also trailers. In respect of wear resistance such as bar tear resistance, chipping, chunking, for example, tires for off-road vehicles, construction and agricultural machines, mine vehicles, and tractors are to be mentioned. Reference here is in particular to vehicles having an axle load of more than 1 tonne or with a permissible overall weight of more than 2, 4, 7.5 or 15 tonnes. The silicas of the invention can be used in particular in traction tires for heavy trucks or their trailers. Vehicles of this kind frequently have axle loads of more than 5 tonnes and/or a tire diameter of more than 17". Tires for commercial vehicles such as trucks are classified according to speed. The silicas of the invention are particularly suitable for (truck) tires which are approved for speeds of between 80 and 140 km/h and carry the symbols F, G, J, K, L, M or N. Tires for high-speed vehicles (motorbikes or automobiles) are those approved for a speed of more than 180 km/h. These are (automobile) tires bearing the symbols S, T, U, H, V, W, Y and ZR. The invention further provides elastomer blends, vulcanizable rubber blends and/or other vulcanizates comprising the silica of the invention, such as, for example, shaped structures such as pneumatic tires, tire treads, cable covers, hoses, drive belts, conveyor belts, roll covers, tires, footwear soles, gaskets, and damping elements. Moreover, the silicas of the invention can be used in all applications in which silicas are commonly used, such as, for example, in battery separators, as antiblocking agents, as flatting agents in inks and paints, as carriers of agricultural products and foods, in coatings, in printing inks, in fire-fighting powders, in plastics, in the nonimpact printing sector, in paperstock, in the personal care sector, and in specialty applications. By use in the nonimpact printing sector, such as in the Inkjet process, for example, is meant the use of the silicas of the invention in printing inks, for thickening or for preventing splashing and offset, paper, as filler or coating pigment, lubricant paper, heat-sensitive paper, in thermal sublimation, for preventing strikethrough of printing inks, for improving imaging background uniformity and contrast, and for improving dot definition and color brilliance. By use in the personal care sector is meant the use of the silicas of the invention as filler or thickener, e.g., in the pharmaceutical or body care sector. The silica of the invention may optionally be modified with silanes or organosilanes of the formulae I to III [SiR1n(RO)E(Alk}m(Ar)p]q[B] (I) , SiR1n(RO)3.n(Alkyl) (II) , or SiR:n (RO) 3_n (Alkenyl) {III) , where B is -SCN, -SH, -CI, -NH2, -OC(0)CHCH2, -OC(0)C(CH3)CH2 (if q = 1) or -S„- (if q = 2) , B being bound chemically to Alk, R and R1 are aliphatic, olefinic, aromatic or arylaromatic radicals having 2-3 0 carbon atoms which may optionally be substituted by the following groups: hydroxyl, amino, alkoxide, cyanide, thiocyanide, halogen, sulfonic acid, sulfonic ester, thiol, benzoic acid, benzoic ester, carboxylic acid, carboxylic ester, acrylate, methacrylate, organosilane radicals, it being possible for R and R1 to have an identical or different definition or substitution, n is 0, 1 or 2, Alk is a divalent unbranched or branched hydrocarbon radical having from 1 to 6 carbon atoms, m is 0 or 1, Ar is an aryl radical having from 6 to 12 carbon atoms, preferably 6 carbon atoms, which may be substituted by the following groups: hydroxyl, amino, alkoxide, cyanide, thiocyanide, halogen, sulfonic acid, sulfonic ester, thiol, benzoic acid, benzoic ester, carboxylic acid, carboxylic ester, organosilane radicals, p is 0 or 1 with the proviso that p and n are not simultaneously 0, q is 1 or 2, w is a number from 2 to 8, r is 1, 2 or 3, with the proviso that r + n + m + p=4, Alkyl is a monovalent unbranched or branched saturated hydrocarbon radical having from 1 to 20 carbon atoms, preferably from 2 to 8 carbon atoms, and Alkenyl is a monovalent unbranched or branched unsaturated hydrocarbon radical having from 2 to 20 carbon atoms, preferably from 2 to 8 carbon atoms. The silica of the invention may also be modified with organosilicon compounds of the composition SiR24_nXn (with n = 1, 2, 3), [SiR2xXyOh (with 0 < x < 2; 0 < y < 2; 3 < z < 10, with x + y = 2) , [SiR2xXyN]z (with 0 < x < 2; 0 < y < 2; 3 < z < 10; with x + y = 2), SiR2nXm0SiR2oXp (with 0 < n < 3; 0 < m < 3; 0 < o < 3; 0 < p < 3, with n + m = 3, o+p= 3) , SiR2nXmNSiR20Xp (with 0 < n < 3; 0 < m < 3; 0 < o < 3; 0 < p < 3; with n + m = 3, o + p = 3), SiR2nXm [SiR2xXyO] zSiR20Xp (with 0 < n < 3; 0170 m2/g DBP number 200 - 300 g/(100 g) Sears number V2 10-35 ml/(5 g) 2. The precipitated silica as claimed in claim 1, wherein the CTAB surface area is not more than 300 m"7g. 3. The precipitated silica as claimed in either of claims 1 or 2, having a WK coefficient of <3.4 (ratio of the peak, height of the particles which cannot be broken down by ultrasound in the size range 1.0 - 100 um to the peak height of the broken-down particles in the size range <1.0 um). 4. The precipitated silica as claimed in any of claims 1 to 3, whose surfaces have been modified with organosilanes of the formulae I to III: [SiRln(RO)r(Alk)m(Ar)Pl(|[Bl I, SiR'n(RO)3.n(Alkyl) II, or SiR'n(RO)3.n(Alkenyl) III. where B is -SCN. -SH, -CI, -Nl 12, -OC(0)CHCH2, -OC(0)C(CH3)CH2 (if q - 1) or -S„- (if q = 2), B being bonded chemically to Alk, R and R1 are aliphatic, olefinic, aromatic or arylaromatic radicals having 2-30 carbon atoms which may optionally be substituted by the following groups: hydroxyl, amino, alkoxide. cyanide, thiocyanide, halogen, sulfonic acid, sulfonic ester, thiol, benzoic acid, benzoic ester, carboxylic acid, carboxylic ester, acrylate, meth-acrylate, organosilane radicals, it being possible for R and R1 to have an identical or different definition or substitution, n is 0, 1 or 2, Alk is a divalent unbranched or branched hydrocarbon radical having from 1 to 6 carbon atoms, m is 0 or 1, Ar is an aryl radical having from 6 to 12 carbon atoms, preferably 6 carbon atoms, which may be substituted by the following groups: hydroxyl, amino, alkoxide, cyanide, thiocyanide, halogen, sulfonic acid, sulfonic ester, thiol, benzoic acid, benzoic ester, carboxylic acid, carboxylic ester, organosilane radicals, p is 0 or 1 with the proviso that p and n are not simultaneously 0, q is 1 or 2, w is a number from 2 to 8, r is 1, 2 or 3, with the proviso that r + n + m + p=4, Alkyl is a monovalent unbranched or branched saturated hydrocarbon radical having from 1 to 20 carbon atoms, preferably from 2 to 8 carbon atoms, and Alkenyl is a monovalent unbranched or branched unsaturated hydrocarbon radical having from 2 to 20 carbon atoms, preferably from 2 to 8 carbon atoms. A process for preparing a precipitated silica having BET surface area 178 - 302 m2/g CTAB surface area >170 m2/g DBP number 200 - 300 g/{100 g) Sears number V2 10-35 ml/(5 g) in which a) an aqueous solution of an alkali metal silicate or alkaline earth metal silicate and/or of an organic and/or inorganic base with pH 7.0 - 8.5 is introduced as initial charge, b) waterglass and an acidifier are metered simultaneously into this initial charge with stirring at 55 - 95°C for 10 - 120 minutes, e) the mixture is acidified with an acidifier to a pH of approximately 3.5, and f) the acidified mixture is filtered and dried. The process as claimed in claim 5, which comprises carrying out between steps b) and e) the steps of c) stopping of the metered addition for 30-90 minutes, during which the temperature is maintained, and d) simultaneous metered addition of waterglass and an acidifier at the same temperature with stirring for 20 - 120 minutes. The process as claimed in claim 6, wherein the acidifier and/or the waterglass in steps b) and d) each have the same concentration or rate of addition. The process as claimed in claim 6, wherein the acidifier and/or the waterglass in steps b) and d) each have a different concentration or rate of addition. The process as claimed in claim 8, wherein, where the acidifier and/or the waterglass have the same concentration in steps b) and d), their rate of addition in step d) is 125 - 140% of the rate of addition in step b). 10. The process as claimed in any of claims 5 to 9, wherein drying is carried out with a pneumatic conveying drier, spray drier, rack drier, belt drier, rotary tube drier, flash drier, spin-flash drier or nozzle tower. 11. The process as claimed in any of claims 5 to 10, wherein drying is followed by granulation with a roll compactor. 12. The process as claimed in any of claims 5 to 11, wherein during steps b) and/or d) an organic or inorganic salt is added. 13. The process as claimed in any of claims 5 to 12, wherein the granulated or ungranulated precipitated silicas are modified with organosilanes in mixtures of from 0.5 to 50 parts per 100 parts of precipitated silica, in particular from 1 to 15 parts per 100 parts of precipitated silica, the reaction between precipitated silica and organosilane being carried out during the preparation of the mixture (in situ) or outside by spray application and subsequent thermal conditioning of the mixture or by mixing the organosilane and the silica suspension with subsequent drying and thermal conditioning. 14. Elastomer blends, vulcanizable rubber blends or vulcanizates. tires for commercial vehicles, high speed vehicles and motorbikes comprising the precipitated silica as claimed in any of claims 1 to 4.