Heidenau K74 M+S 120/90-17 68M RF TT

K74 120/90-17 is the only reinforced size among the Heidenau K74 M+S versions. It is a 68M TT tyre with an M+S marking, built for off-road terrain, from hard, stony surfaces to soft sand.

What the 68M Reinf. marking tells you

• Rear axle only: the price list lists 120/90-17 for rear-wheel use, and every K74 size is a rear tyre. There is no K74 front size to match it.
• Reinforced casing (Reinf.): among the K74 M+S sizes, 120/90-17 is the only one specified as RF. The 130/80-17, 120/90-18 and 140/80-18 sizes come without reinforcement.
• Speed rating M: M is the speed rating on the K74 M+S sizes; it is not unique to this size.
• Tube-type, 17-inch, 5.28 kg: a cross-ply tyre for a 17″ rim, part number 11170241, listed by Heidenau under MOTO / OFFROAD and shown in the catalogue as motocross.

Tread and behaviour off-road

K74 is designed for unsurfaced ground whether it is hard and stony or soft and sandy, which is why it uses a versatile rather than surface-specific tread pattern. It is intended to work across contrasting surfaces while keeping handling predictable. The tread clears mud effectively, so the blocks keep working as the surface softens, and traction stays dependable. Every K74 size shares this behaviour — the marking, not the tread, is what separates 120/90-17 from the rest.

How 120/90-17 differs from 130/80-17

120/90-17 and 130/80-17 are not interchangeable in specification. 120/90-17 is the reinforced one, rated 68M and weighing 5.28 kg; 130/80-17 is wider, unreinforced, rated 65 and weighs 5.44 kg. If the reinforced casing is what you are after in 17 inches, 120/90-17 is the single M+S option.

The front tyre that goes with it

The matching front size is 90/90-21 54M TT, and it comes as two different models. K69 front M+S (11170247, 3.55 kg) is intended for stony ground and hard surfaces: its particular block layout, the reinforcements between the blocks and a firm carcass are designed for that type of terrain. K79 front M+S (11170246, 3.31 kg) is intended for sandy ground — the wider-spaced blocks aid self-cleaning and traction, and the transverse blocks down the centre provide lateral bite on loose surfaces. A rear 120/90-17 and a front 90/90-21 pair up only on a machine whose standard front size is 90/90-21, so check the front size on your own bike before ordering the set.

Which inner tube fits

Tube-type means the tyre needs a tube, and for this size it is the 17F Cross (61020329, 1.18 kg) from Heidenau's competition group. Its size list runs 5.10, 100/100, 110/90, 120/90, 130/90, 130/80, 140/80 and 150/70 in 17 inches, so 120/90-17 is covered. Note that the Heavy-Cross tube is not made in 17 inches at all — it starts at 18 — so 17F Cross is the tube to order here.

Where K74 does not belong

K74 tyres are pure off-road tyres and they are not designed for permanent road use. That limit applies to the model as a whole, and neither the reinforced casing nor the M+S marking changes it: M+S is a mud-and-snow marking; it does not make the tyre suitable for regular road use. If most of your mileage is on the road, this is the wrong tyre for it. It suits riders using a 17-inch rear wheel off-road on mixed terrain who want the reinforced casing that the other K74 M+S sizes do not offer. Available with delivery across Kazakhstan; pair it with the 17F Cross tube.