Abstract Cycloid drives are widely used in the in-wheel motor for electric vehicles due to the advantages of large ratio, compact size and light weight. To improve the transmission efficiency and the load capability and reduce the manufacturing cost, a novel cycloid drive with non-pin design for the application in the in-wheel motor is proposed. Firstly, the generation of the gear pair is presented based on the gearing of theory. Secondly, the meshing characteristics, such as the contact zones, curvature difference, contact ratio and sliding coefficients are derived for performance evaluation. Then, the loaded tooth contact analysis (LTCA) is performed by establishing a mathematical model based on the Hertz contact theory to calculate the contact stress and deformation. Finally, based on a numerical example, the two gears are manufactured by using additive manufacturing methodology (3D printing), the meshing characteristics are analyzed and the contact stress and deformation are calculated by using the analytical models and validated by the finite element method (FEM), which shows a good agreement. Meanwhile, a comparison with the conventional cycloid drive is conducted, which demonstrates a salient feature of the proposed cycloid drive. The design and analysis in this study could help designers to design suitable cycloid drives and provide an alternative cycloid drive for the application in the in-wheel motor of electric vehicles. Introduction As the environmental issues such as global warming, air pollution and the depletion of fossil fuel are widely recognized, fuel-cell electric vehicle (FCEV), electric vehicle (EV) and the development of in-wheel motor are attracting attention in recent years. In order to respond to the global demand for more energy efficient and environmentally-friendly electric vehicles, many car manufacturers have developed an in-wheel motor axle unit [ 1]. This axle unit consists of a cycloid reducer and a high-speed axial gap motor to achieve a compact and lightweight design [ 2]. The conventional cycloid drive consists of cycloid planet gears that have an equidistant curve to the epitrochoid and multiple ring gear rollers placed at equal intervals on the circumference as shown in Figure 1. The rotational movement of the eccentrically revolving cycloid planet gears is transmitted to the disc pin, located inside the cycloid planet gears. A cycloid drive has been adopted that not only requires less space but also provides a large ratio with only one stage. It is superior to other drives for its compact size and light weight. However, due to the sliding contact between the ring gear roller and ring gear pins and double sliding contacts between the ring gear rollers and cycloid planet gears with large sliding coefficients, power loss often occurs unavoidably in the meshing gear pair. Furthermore, because of the existence of the movable components such as the pins and rollers, it is hard to form a good oil film. Hence, the two defects will lead to a low transmission efficiency. Even though all the teeth of the cycloid planet gear are theoretically in contact with the ring gear rollers and half of them transfer loads, in practice, such a meshing does not exist due to the modification of the tooth profiles and assembly and manufacturing errors [ 12]. Normally, there are only small a number of teeth in contact and transferring loads, which will cause higher surface contact stresses. Moreover, the double shear stresses may exist at the interface of the rollers and the pin. Hence, the conventional cycloid drive will have a lower load capability due to the defects mentioned above. There are many research works reported in the open literature, which are typically focused on the methods for the tooth profile generation [3, 4, 5, 6, 7], the effects of machining tolerances on output speed [ 9], the analysis of meshing characteristics, force and efficiency [ 11]. For example