650B

The Ground Control Sport is an exceptionally versatile trail tire that uses a tread optimized using Finite Element Analysis. This means that it rolls fast and provides increased grip and traction in nearly all conditions. - Casing: 60 TPI - Bead: Wire - Compound: 60a - 27.5 x 2.1", psi 25-50 - 27.5 x 2.3", psi 25-50

The Nimbus 2 Sport Reflect tire features an updated tread and compound that rolls even faster and has more grip than ever before. It comes in many widths to accommodate different bikes, riding styles, and comfort levels, so it's the perfect choice for riding on any road or bike path. And with BlackBelt flat protection and reflective accents that increase your visibility to motorists in low-light conditions, you get an added dose of that good ol' peace of mind. - Casing: 60 TPI - Bead: Wire - Compound: 60a - Flat Protection: BlackBelt - 650b x 2.3", psi 25-50