A method of controlling operation of a winder for a fiber web, in which method while forming at least one fiber web roll: - fiber web is brought on the web roll via a nip formed by a first support drum and the web roll, which first support drum is driven by a first drive assembly applying controllable torque to the drum; - winding force is applied to the web roll by a second drive assembly; characterized in that - the winding force is controlled by executing at least the following steps: (a) an initial value for an indicative coefficient (μ n) is set; (b) a set value for the winding force is determined using a function F s = f μ n N where F s = set value for winding force [N/m], μ n = the indicative coefficient, N = nip force [N/m] at a nip over which the winding force is transmitted, (c) at least the second drive assembly is controlled by using the set value for the winding force; (d) an indicative speed of the first drive assembly and/or the first support drum is determined, and an indicative speed of the second drive assembly is determined; (e) the indicative speed of the second drive assembly is compared with the indicative speed of the first drive assembly, and (f) in case the difference between the indicative speed of the second drive assembly and the indicative speed of the first drive assembly is smaller than a predetermined set difference, the indicative coefficient value is increased, and; in case the difference between the indicative speed of the second drive assembly and the indicative speed of the first drive assembly is greater than a predetermined set difference, the indicative coefficient value is decreased; and (g) the steps (b) to (f) are repeated. - fiber web is brought on the web roll via a nip formed by a first support drum and the web roll, which first support drum is driven by a first drive assembly applying controllable torque to the drum; - winding force is applied to the web roll by a second drive assembly; characterized in that - the winding force is controlled by executing at least the following steps: (a) an initial value for an indicative coefficient (μ n) is set; (b) a set value for the winding force is determined using a function F s = f μ n N where F s = set value for winding force [N/m], μ n = the indicative coefficient, N = nip force [N/m] at a nip over which the winding force is transmitted, (c) at least the second drive assembly is controlled by using the set value for the winding force; (d) an indicative speed of the first drive assembly and/or the first support drum is determined, and an indicative speed of the second drive assembly is determined; (e) the indicative speed of the second drive assembly is compared with the indicative speed of the first drive assembly, and (f) in case the difference between the indicative speed of the second drive assembly and the indicative speed of the first drive assembly is smaller than a predetermined set difference, the indicative coefficient value is increased, and; in case the difference between the indicative speed of the second drive assembly and the indicative speed of the first drive assembly is greater than a predetermined set difference, the indicative coefficient value is decreased; and (g) the steps (b) to (f) are repeated. (a) an initial value for an indicative coefficient (μ n) is set; (b) a set value for the winding force is determined using a function F s = f μ n N where F s = set value for winding force [N/m], μ n = the indicative coefficient, N = nip force [N/m] at a nip over which the winding force is transmitted, F s = set value for winding force [N/m], μ n = the indicative coefficient, N = nip force [N/m] at a nip over which the winding force is transmitted, (c) at least the second drive assembly is controlled by using the set value for the winding force; (d) an indicative speed of the first drive assembly and/or the first support drum is determined, and an indicative speed of the second drive assembly is determined; (e) the indicative speed of the second drive assembly is compared with the indicative speed of the first drive assembly, and (f) in case the difference between the indicative speed of the second drive assembly and the indicative speed of the first drive assembly is smaller than a predetermined set difference, the indicative coefficient value is increased, and; in case the difference between the indicative speed of the second drive assembly and the indicative speed of the first drive assembly is greater than a predetermined set difference, the indicative coefficient value is decreased; and (g) the steps (b) to (f) are repeated.