The density of the carcass fabric is expressed in EPI or TPI (Ends Per Inch, Threads Per Inch). The range of carcasses used for Schwalbe tires are 24, 37, 50, 67 and 127 EPI.
In principle, the more close-meshed a carcass is woven, the higher the quality of the tire. A dense carcass is important for low rolling resistance. At the same time, puncture protection increases because carcasses with a high strand density are difficult to puncture.
This does not apply in the case of extremely fine 127 EPI carcasses as each strand is sheer and quite vulnerable. The best compromise for low weight and resistance is around 50 to 67 EPI.
In most of our top tires we use a 67 EPI carcass. Weight and rolling resistance can be reduced even further by using a 127 EPI carcass. But at the same time, these tires are a lot more vulnerable to damage. Therefore, we intentionally use the 127 EPI carcasses only for extremely light-weight tires or in combination with extremely highperformance puncture protection materials.
Exercise caution when comparing EPI of different tire brands as it is common that the total of all carcass layers are added together. An indication of 200 TPI results from 3 layers of 67 EPI each underneath the tread. With all EPI numbers above 127, it should be assumed that the figures have been calculated by adding up the strands in all layers. Schwalbe only indicates the material density in one carcass layer. Commonly, there are 3 carcass layers underneath the tread.