Continental and VDL Bus & Coach have pooled their expertise and jointly developed initial prototype tires.
These tires are currently being tested at Continental’s Contidrom proving grounds. VDL Bus & Coach launched its first electric Citea urban bus back in 2013.
“As with all electric vehicles, these bus tires are exposed to higher torque when moving off and accelerating,” said Ben Hudson, automotive engineer at Continental Truck Tires. “In downtown traffic in particular, vehicles need to run very quietly, so that the comfort offered by quiet electric drive isn’t diminished by loud road-tire noise.”
In addition, the deceleration of electric buses in urban traffic is a key factor in the energy recovery or ‘recuperation’ process, Continental says. Here, the electric motor acts as a generator and, driven by the deceleration of the bus, produces energy to charge the battery. This leads to a marked increase in the vehicle’s range. Compared to conventional brake management systems, this process of recuperation puts added strain on the drive axle tires.
Consequently, tires for electric buses have to cope with tougher requirements than their counterparts for buses with combustion engines, Continental says.
“At the same time, they need to deliver the same mileage and meet the same safety standards as bus tires for conventional drive systems,” Hudson says. “We are up against new requirements here, but obviously we’re not going to accept any compromises in terms of robustness or braking performance. Safety takes top priority for us.”
Right now, the tires on the VDL vehicles at the Contidrom are still running on tires built by the prototyping department in Hanover-Stöcken with hand-carved tread patterns, Continental says, adding that as a rule, the tire development cycle from initial prototype to volume production takes three to five years.
For the e-bus tires, Continental says the aim is to shorten that cycle.
“When developing this concept tire, we’re not restricted by what has gone before in previous generations of tires,” Hudson says. “That gives us the freedom to try out entirely new concepts and ideas. If these prove successful, we’ll put them into practice very quickly and feed them into the development of the next line of tires.”