The present invention relates to highly disperse 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 high¬speed 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 (DBF) are important. The surface properties of silicas are critical determinants of their possible application: certain applications of a silica (for example, carrier systems or fillers for elastomer blends) demand particular surface properties. Thus US 6 013 234 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 0 643 015 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 70 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 0 901 986 with the following properties: 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: 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). 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 170 - 350 m /g, a CTAB surface area of >170 m2/g, a DBF number of 305 - ,' 400 g/100 g and a Sears number of 23 - 35. 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. 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 according to the invention may in each case independently have properties within the following preferential ranges: The wk coefficient is defined as the ratio of the peak height of the particles in the size range 1.0 - 100 pm which cannot be broken down by ultrasound to the peak height of the broken-down particles in the size range <1.0 pm (see Fig. 1}. EP 1 186 629 discloses silicas with high CTAB surface areas which ' ard 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 1 186 629. The present invention additionally provides a process for preparing a precipitated silica having a 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 > 9 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, 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, preferably 20 - 80, 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. Silica prepared in accordance with the invention may have properties in the preferred ranges mentioned. The initial charge may amount to 20, 30, 40, 50, 60, 70, 80 or 90% of the final volume of the precipitation. The basic compounds that are added 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 > 9, preferably between 9.0 and 12, especially between 9 and 10.5. An additional addition of organic or inorganic salts during steps b) and d) is also 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, 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 all combinations of the following ions: Li% Na, K% Rb% Be*, Mg, Ca\ Sr% Ba*, B.*, F~, CI", Br", I", S03", SO', HSO4", P03", P04", NO3", NO2", C03', HCO3", OH", TiOs", SrOs", ZrO", AIO2", Al204", BO,". 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 rate 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 rate of addition in step d) is 125 - 140% of the rate of addition in step b), the components being used in each case in equimolar concentration in both steps. It is pceferred 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 HCl, HNO3, H3PO4 or CO2. 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 \im, in particular more than 80 pm, with particular preference more than 200 ]im. After drying it is also possible to carry out granulation using a roll compactor. In this case the average 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/ox delivery vehicles and also trailers. In respect of wear resistance such as bar tear resistance, bar tear propagation resistance, 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 therefore 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. 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, methacrylate, organosilane radicals, it being possible for R and R 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, X is a number from 2 to 8, to 20 carbon atoms, preferably from 2 to 8 carbon atoms, and Alkenyl is a monovalent unbranched or branched unsaturated hydrocarbon jradical 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 R-nSiXn (with n = 1, 2, 3), [SiRXyO]z (with 0 < x < 2; 0 < y < 2; 3 < z < 10, with x + y = 2} , [SiR\XyN]z (with 0 < X < 2; 0 5 y < 2; 3 S z < 10; with x + y = 2} , SiRnXOSiRoXp (with 0 "Si"-ONa + HCl HCL + KOH => KCl + H2O. Determination of the CTAB surface area Application: The method is based on the adsorption of CTAB {N-cetyl-N,N,N-trimethylammonium bromide) on the "external" surface, which is also referred to as the "rubber- active surface", in accordance with ASTM 3765 or Janzen and Kraus in Rubber Chemistry and Technology 44 {1971) 1287. The adsorption of CTAB takes place in aqueous solution with stirring and ultrasound treatment. Excess, unadsorbed CTAB is determined by back-titration with SDSS {dioctylsodium sulfosuccinate solution, "Aerosol OT" solution) using a titroprocessor, the endpoint being indicated by the maximum clouding of the solution and determined using a phototrode. For the calculation, an occupancy of 0.35 nm2 per CTAB molecule is assumed, corresponding to 578.435 m2/g. The phototrode is set to 1 000 mV before commencing titration, corresponding to a transparency of 100%. Reaction equation: {back-titration) Apparatus: IKA universal mill M 20 Titroprocessor, e.g. METTLER, type DL 55 or DL 70, equipped with: pH electrode, e.g. Mettler, type DG 111 Phototrode, e.g. Mettler, type DP 550 Bulb buret, 20 ml volume, for SDSS solution Bulb buret, 10 ml volume, for KOH, 0.1 N Titration beakers, 100 ml, made of polypropylene Glass titration vessel, 150 ml volume, closable with snap-on lid Conical flasks, 100 ml volume, closable with screw lid or standard ground stopper Ultrasound bath (Bandelin Sonorex RK 106S, 35 kHz) Pressure filtration device Membrane filter of cellulose nitrate, pore size 0.1 pm, 47 mm 0, e.g. Sartorius, type 113 58 Reagents: Potassium hydroxide solution, 0.1 N CTAB solution, 0.0151 mol/1: 5.50 g of CTAB are dissolved with stirring in about 800 ml of warm (about 30-40''C) demineralized water in a glass beaker, the solution is transferred to a 1 1 graduated flask and made up to the mark with demineralized water, after cooling to 23-25''C, and this solution is transferred to a stock bottle. The solution must be stored and the measurement conducted at >23*'C, since below this temperature CTAB crystallizes out. The solution should be prepared at least 12 days before use, but not stored longer than 2 months. The concentration of the CTAB solution is assumed to be exact: 0.0151 mol/1. SDSS solution 0.00426 mol/1: 1.895 g of SDSS (dioctylsodium sulfosuccinate) in a glass beaker are admixed with about 800 ml of demineralized water and the mixture is stirred until all the material has dissolved. The solution is then transferred to a 1 1 graduated flask, made up to the mark with demineralized water, and transferred to a stock bottle. The solution should be prepared at least 12 days before use, but not stored longer than 2 months. The concentration of the SDSS solution should be determined daily by means of a blank titration. The solutions can be purchased in ready-to-use form from, for example, Kraft, Duisburg {telephone 0203-58-3025) {order No. 6056.4 CTAB solution 0.0151 ml/1; order No. 6057.4 SDSS solution 0.00423 mol/1). Procedure: Blank titration (determining concentration of the SDSS solution), The consumption of SDSS solution for 5 ml of CTAB solution should be checked 1 x per day before each series of measurements. Pipette precisely 5.00 ml of CTAB solution into titration beakers. Add 50.00 ml of demineralized water. Titrate with the titroprocessor until the end of titration. Each blank titration should be performed as a duplicate determination; where values do not agree, further titrations should be carried out until the results are reproducible. Adsorption: 10.00 g of the granulated, coarsely particulate sample are ground in the mill. Weigh in precisely 500.0 mg of the ground sample to a precision of 0.1 mg. Transfer the sample amount weighed out quantitatively to a 150 ml titration vessel with magnetic stirrer bar. Add exactly 100.0 ml of CTAB solution, close titration vessel with lid, and stir on a magnetic stirrer for 15 minutes. Screw the titration vessel onto the titroprocessor and adjust the pH of the suspension to 9+0.05 using KOH (0.1 mol/1). 4-minute treatment of the suspension in the ultrasound bath. Filtration through a pressure filter fitted with a membrane filter, using a nitrogen pressure of 1.2 bar. During adsorption, it must be ensured that the temperature is held within the range from 23°C to SSC. Titration: Pipette 5.00 ml of the above-obtained filtrate into a 100 ml titration beaker and make up to about 50.0 ml with demineralized water. Screw titration beaker onto the titrator. Titrate with SDSS solution in accordance with the method defined above until clouding reaches a maximum. Each titration should be performed as a duplicate determination; where values do not agree, further titrations should be carried out until the results are reproducible. Calculation: CTAB surface area in g/1 = (Vi + V2)*E*115.687/Vi Vi = blank sample (ml of SDSS when using 5 ml of CTAB) V2 = consumption (ml of SDSS when using 5 ml of filtrate) E = initial mass of CTAB, g/1 The measurement is normally to be given corrected for the anhydrous substance: CTAB surface area (water-corrected) = CTAB surface area *100/(100 - water content in %) wk coefficient: aggregate size distribution by laser diffraction (Coulter) Apparatus: Laser diffraction instrument LS 230, Coulter Bandelin ultrasonic finger, type HD 2200, with DH 13 G horn Cooling bath 80 ml Eppendorf pipette, 5 ml Centrifuge glass, height 7 cm, 0 3 cm Petri dish, height 4 cm, 0 7 cm Dewar vessel, height 21 cm, 0 4 cm Digital thermometer, accuracy ±0.1 K Chemicals: Ethanol, p.a., Merck Triton X-100, Merck Sodium hexametaphosphate. Baker Sample preparation: Granules are introduced into a mortar and the coarse granules are compressed, not mortared. 1 g of unaged silica (produced no earlier than 10 days before) is weighed into a 30 ml rolled-edge glass vessel, and 20 ml of dispersion solution (20 g of sodium hexametaphosphate made up to 1 000 ml with demineralized water) are added. The sample is then placed in a cooling bath, which prevents the suspension from heating up significantly, and treated with ultrasound for 4.5 minutes (100 W output, 80% pulse). Three dispersion solution specimens are prepared in succession for each silica. Until the sample is added to the liquid module, the suspension is placed in a petri dish with magnetic stirrer in order to prevent any sedimentation. Procedure: Before the beginning of the measurement, the instrument and the liquid module are allowed to warm up for at least 30 minutes, and the module is rinsed automatically for 10 minutes (menu bar "Control/Rinse") . In the control bar of the Coulter software, the menu item "Measurements" is used to select the file window "Calculate op. model", and the refractive indices are defined (liquid refractive index real = 1.332; material refractive index real = 1.46, imaginary = 0.1). In the file window "Measuring cycle" the output of the pump speed is set to 26% and the ultrasound output to 3%. The items of ultrasound "during sample addition". "before each measurement", and "during measurement" are to be activated. Additionally, the following items are selected in this file window: Offset measurement (1 x daily) Adjustment Background measurement Adjust measurement concentration Enter sample info Enter measuring info Start 2 measurements Automatic rinse With PIDS data When calibration is complete, the sample is added. Dispersed silica is added until a light absorption of about 45% has been reached and the instrument announces OK. The measurement is made using the evaluation model "Si02_i.rfd". For each sample added, three duplicate determinations of 60 seconds are conducted. The software calculates the particle size distribution from the raw data plot, on the basis of the volume distribution. Typically a bimodal distribution curve is found, with the mode A at about 0.2 pm and the mode B at about (2-5) lam. From this it is possible to calculate the wk coefficient in accordance with Figure 1. DBF absorption The DBP absorption (DBF number), which is a measure of the absorbency of the precipitated silica, is determined as follows in accordance with the standard DIN 53601: The dibutyl phthalate number is determined using the Brabender plastograph with the Multi-Dosimat E 415 (50 1) plotter from Metrohm. The absorbency is dependent on the moisture content, the particle size, and the amount of material analyzed. Procedure: 12.5 g of silica are introduced into the kneader of the Brabender plastograph. With continued mixing (kneader paddle speed 125 rpm), dibutyl phthalate runs into the mixture at a rate of 4 ml/min. The force required for incorporation is low. Toward the end of determination, the mixture becomes poorly free-flowing. This fact is documented in an increase in the required force, which is indicated on a scale. When the scale has moved by 300 units, DBP metering is shut off automatically. Evaluation: The density of DBP is 1.047 g/ml. The DBP absorption is based on the anhydrous, dried silica. When using precipitated silicas with relatively high moisture content, the value must be corrected using the correction table unless the silicas are dried prior to the determination of the DBP number. The correction figure corresponding to the water content is added to the experimentally determined DBF value; for example, a water content of 5.8% would mean an add-on of 33 g/100 g for the DBF absorption. Moisture determination Description: The silica is dried to constant weight in an IR drier. The loss on drying generally consists predominantly of the water moisture of the silica, and only of traces of other volatile constituents. Apparatus: IR drying unit, Mettler, type LP 16 Aluminum weighing boats Measurement procedure: 2.0 g of silica are introduced into the aluminum boat, tared beforehand, and the lid of the drier is closed. Measurement begins when the start button is pressed and is ended automatically when the decrease in weight per unit time falls below a value of 2 mg/120 s. The following values must be checked and/or set on the Result: The loss on drying in % is indicated directly and/or printed out by the instrument. The following examples are intended to illustrate the invention without restricting its scope. Example 1 A reactor is charged with 1 480 1 of water and also 0.41 kg of waterglass (density 1.348 kg/1, 27.1% SiOz, 8.00% NaaO) . Then 8.791 kg/min of waterglass and 1.160 kg/min of sulfuric acid (density 1.84 kg/1, 96% H2SO4) are metered in at 63°C for 22 minutes. Following a 60-minute waiting phase, again, 8.791 kg/min of waterglass and 1.160 kg/min of sulfuric acid are metered in for 45 minutes. Thereafter the addition of waterglass is stopped while that of sulfuric acid is continued until a pH of about 3.3 is reached. The product obtained is filtered in the usual manner, subjected to long drying or flash drying (rotary tube drier, rack drier, spray drier, nozzle tower drier, spin-flash drier), ground where appropriate, and granulated where appropriate. In the granule form the product obtained has a BET surface area of 235 m2/g and a CTAB surface area of 185 m2/g. Example 2 The precipitated silicas of the invention from Example 1 are investigated in an S-SBR/BR rubber blend. As state of the art, the silicas Ultrasil 7000 GR and Zeosil 1205 MP were selected. The formula used for the rubber blends is that indicated in Table 1 below. In the table, the unit "phr" denotes parts by weight per 100 parts of the crude rubber used. The reference silica Ultrasil 7000 GR in mixture Rl was modified with 6.4 phr of Si 69. In order to take account of the higher surface area of the reference silica Zeosil 1205 MP and of the silica of the invention, in mixtures R2 and A the amount of silane was raised to 8 phr and the amount of sulfur was reduced accordingly. The general procedure for producing rubber blends and their vulcanizates is described in "Rubber Technology Handbook", W. Hofmann, Hanser Verlag 1994. The rubber blends are prepared in an internal mixer in accordance with the mixing specification in Table 2, while Table 3 compiles the methods used for rubber testing. The blends are vulcanized at 165"C for 20 minutes. Table 4 shows the results of rubber testing. The polymer VSL 5025-1 is a solution-polymerized SBR copolymer from Bayer AG having a styrene content of 25% by weight and a butadiene content of 75% by weight. The copolymer contains 37.5 phr of oil and has a Mooney viscosity (ML l+4/100°C) of 50±4. The polymer Buna CB 24 is a cis-1,4-polybutadiene (neodymium type) from Bayer AG having a cis-1,4 content of at least 97% and a Mooney viscosity of 44±5. As an aromatic oil, Naftolen 2D from Chemetall is used. Vulkanox 4020 is 6PPD from Bayer AG, and Protektor G35P is an ozone protector wax from HB-Fuller GmbH. Vulkacit D/C (DPG) and Vulkazit CZ/EG (CBS) are commercial products from Bayer AG. Perkazit TBZTD is available from Akzo Chemie GmbH. Si 69 is the coupling reagent bis(3-triethoxysilyl-propyl)tetrasulfane from Degussa AG. The dispersion coefficient is determined by a light-optical method. The measurement can be carried out by the Deutsche Institut fiir Kautschuktechnologie e.V. [DIK], Hanover, Germany. In addition, the method is described in H. Geisler, "Bestimmung der Mischgiite", presented at the DIK Workshop, November 27-28, 1997, Hanover, Germany. As is evident from the data in Table 4, as a result of the higher surface area of the silica of the invention, the Mooney viscosity of the mixtures A is slightly increased as compared to Rl, but is still better than the prior art reference mixture R2, which has an increased viscosity and poor processing properties. The vulcanization characteristics (Dmax-Dmin, t90%, tlO%) of the mixtures Rl and A are very similar to one another, which suggests trouble-free vulcanization, while mixture R2 exhibits a significantly shortened scorch time tlO%. The strain values of Rl and A are comparable, whereas R2 possesses a much higher hardness and strain value 100, indicating a markedly higher silica network owing to the poorer dispersion. Advantages of the mixture A over the reference Rl are evident in the increased dynamic moduli E* OC and eO'C. These higher stiffnesses are particularly important for high-speed automobile and motorbike tires, since they indicate improved dry handling and higher cornering stability. Despite the higher silica surface area in mixture A, the hysteresis loss tan 5, which is inversely proportional to the rolling resistance value, is - advantageously - virtually unchanged, while mixture R2 in accordance with the prior art shows a significantly higher hysteresis loss. The good reinforcement in combination with the high CTAB surface area of the silica of the invention suggests an improved road abrasion of the mixture A. This improvement in road abrasion is also to be expected when using the high surface area silicas of the invention in natural rubber blends, such as are employed in truck tread mixtures. Particularly in combination with a high surface area, highly structured carbon black such as N 121, excellent road abrasion in the case of truck tires can be predicted. WE CLAIM: 1. A precipitated siliqa characterized by BET surface area 170 - 350 m2/g CTAB surface area >170 m2/g DBF number 305 - 400 g/100 g Sears number 23-35. 2. The precipitated silica as claimed in claim 1, wherein the CTAB surface area is not more than 300 m2/g. 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 ym). ' 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: arylaromatic radicals having 2-30 carbon atoms which may be substituted or un.substituted by the following groups: hydroxy1, amino, alkoxide, cyanide, thiocyanide, halogen, sulfonic acid, sulfonic ester, thiol, benzoic acid, benzoic ester, carboxylic acid, carboxylic ester, aerylate, 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, X is a number from 2 to 8, r isl, 2or3, with the proviso that r + n+in + 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. 5. The process for preparing a precipitated silica having a 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 > 9 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, 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, e} the mixture is acidified with an acidifier to a pH of approximately 3.5, and f) the acidified mixture is filtered and dried. 6. The process as claimed in claim 5, wherein the acidifier and/or the waterglass in steps b) and d) each have the same concentration or rate of addition. 7. The process as claimed in claim 5, wherein the acidifier and/or the waterglass in steps b) and d) each have a different concentration or rate of addition. 8. The process as clairned in claim 7 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). 9. The process as claimed in any of claims 5 to 8, wherein drying is carried out using a pneumatic conveying drier, spray drier, rack drier, belt drier, rotary tube drier, flash drier, spin-flash drier or nozzle tower. 10. The process as claimed in any of claims 5 to 9, wherein drying is followed by granulation with a roll compactor. 11. The process as claimed in any of claims 5 to 10, wherein during steps b) and/or d) an organic or inorganic salt is added. 12. The process as claimed in any of claims 5 to 11, 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. 13. Elastomer blends, vulcanizable rubber blends or vulcanizates comprising the precipitated silica of any of claims 1 to 4.