spring is not wound as tight providing a higher (stiffer) spring rate. This prevents excessive suspension compression and prevents dangerous body roll, which could lead to a roll over. Variable rate springs are used in cars designed for comfort as well as off-road racing vehicles. In off-road racing they allow a vehicle to absorb the violent shock from a jump effectively as well as absorb small bumps along the off-road terrain effectively. Suspension travel The severe handling vice of the TR3B and related cars was caused by running out of suspension travel. (See below.) Other vehicles will run out of suspension travel with some combination of bumps and turns, with similarly catastrophic effect. Excessively modified cars also may encounter this problem. Tires and wheels In general, softer rubber, higher hysteresis rubber and stiffer cord configurations increase road holding and improve handling. On most types of poor surfaces, large diameter wheels perform better than lower wider wheels. The depth of tread remaining greatly affects aquaplaning (riding over deep water without reaching the road surface). Increasing tire pressures reduces their slip angle, but lessening the contact area is detrimental in usual surface conditions and should be used with caution. The amount a tire meets the road is an equation between the weight of the car and the type (and size) of its tire. A 1000 kg car can depress a 185/65/15 tire more than a 215/45/15 tire longitudinally thus having better linear grip and better braking distance not to mention better aquaplaning performance, while the wider tires have better (dry) cornering resistance. The contemporary chemical make-up of tires is dependent of the ambient and road temperatures. Ideally a tire should be soft enough to conform to the road surface (thus having good grip), but be hard enough to last for enough duration (distance) to be economically feasible. It is usually a good idea having different set of summer and winter tires for climates having these temperatures. Track and wheelbase The axle track provides the resistance to lateral weight transfer and body lean. The wheelbase provides resistance to longitudinal weight transfer and to pitch angular inertia, and provides the torque lever arm to rotate the car when swerving. The wheelbase, however, is less important than angular inertia (polar moment) to the vehicle's ability to swerve quickly. The wheelbase contributes to the vehicle's turning radius, which is also a handling characteristic. Unsprung weight Ignoring