Tyre chains are designed to allow a vehicle to climb a gradient that's beyond the grip level of the tyres. In countries other than South Africa, tyre chains are normally fitted to snow tyres, not summer tyres
The ‘Owners manual' of your vehicle will detail what wheel and tyre combinations are approved for the fitting of wheel chains. The safety of any vehicle, especially the braking performance, is compromised if wheel chains are fitted to summer tyres and if wheel chains are used on a ‘bare' road that is free of snow and ice.
Wheel chains fitted to summer tyres on the front wheels of a 2WD or AWD will increase traction for take-off and driving but cannot assist with lateral stability. Because of the inadequate grip on the rear tyres the vehicle will oversteer and when braking the ABS system will be activated, further increasing the stopping distance. The problems are always worse when driving downhill than uphill.
Wheel chains fitted to summer tyres on the rear wheels of a 2WD or AWD will increase traction for take-off and driving but cannot assist with steering or lateral stability. Because of inadequate grip on the front tyres the vehicle will not ‘turn in', it will understeer and when braking the ABS system will be activated, further increasing the stopping distance. Again the problems are always worse when driving downhill than uphill.
There are issues when diamond pattern snow chain systems are used on high performance 2WD or AWD ‘summer' tyres. On summer tyres snow chains will grip to the snow/ice but the tyre can slip or spin the chain even when they are correctly tensioned on to the tyre. The problem is worse when the vehicle has been parked at the resort because the low ambient temperature makes the tyres harder and therefore has even less grip to the chain.
The issue is compounded by the camber of the road, the weight and torque of the vehicle and the amount of tread on the tyre. The tread compound in Nokian snow tyres, however, is designed to remain flexible in extremely cold conditions, making wheel chains on snow tyres more effective.
For wheel chains to work effectively they must be able to rely on the tread of the tyre for grip to help prevent the wheel from spinning inside the chain or the chain ‘rolling' off the tyre due to the lateral loads when cornering. Given the superior tread on snow tyres, its commonplace in countries other than South Africa for the wheel chains to be fitted to snow tyres, not summer tyres.
Here in South Africa, it makes just as much sense to fit them to snow tyres. Wheel chains need to have firm compacted snow or ice to penetrate to provide the maximum amount of traction. Traction is often lost when the snow and/or ice begins to break up or melts and wheel spin is experienced. In certain situations, i.e. on a ‘bare' road, the vehicle can slide on the wheel chains. In order for wheel chains to work effectively they must penetrate in to a compacted surface