Roadrunner uprated
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• Leyland Trucks has made major changes to its Roadrunner range, first introduced two years ago.
Out goes Leyland's own 98 series engine. In its place is the more powerful Cummins B series engine. The 5.9-litre, straight-six, naturally aspirated unit is offered at two power ratings of 86kW (115hp) and 97kW (130hp) — delivered at a relatively high 2800rpni. Torque outputs are 348Nm (2571bft) and 386Nrn (285Ibft) at 1300rpm respectively.
Leyland and Cummins have collaborated over the last four years to develop the original B series design to match Leyland's requirements.
Ancillary equipment, such as the large-capacity compressor and alternator, have been tailored to suit the Roadrunner chassis. The engine has also had to pass the severe standards set by Leyland's 1500hour engine test programme. This includes repeated cycles of overspeeding, running at rated torque and then at maximum power.
The new Cummins engine has 20% fewer parts and is 18% lighter than the old 98 series. Its crossflow cylinder head has an integral inlet manifold and the single-piece block is of linerless construction.
Leyland says that there should be no need to lift the head during the life time of the vehicle. The design, however, does allow for two rebores after which there is the option to then fit liners.
To match the output of the higher-powered B series, Leyland has specified a larger, 330mm diameter clutch and revised gearing with a high overdrive ratio to suit motorway cruising.
Roadrunner becomes the first British-built 7.5-lonner to be equipped with front disc brakes. The German. Perrot air/hydraulic braking system has ventilated front discs with four cylinder calipers, and drum brakes on the rear axle.
It was chosen in preference to the Lucas Girling disc brake system used by Volvo and Ford. Iveco has fitted the Perrot system for some time to its Z-range light middleweights.
Leyland claims that the large, 500cm2 frictional area of the 7.5-tonner's disc pads last twice as long as the previous drum brakes. With the wheels off, pads can also be replaced in seconds.
Leyland engineers were unable to ensure parking security with disc brakes on all wheels without going to high operational pressures. So instead, the Roadrunner has new, larger diameter rear brake drums with thicker linings which give a longer service life.
Z1: Power steering is now standard on all Roadrunners in place of the previous optional Burman system. Anti-roll bars are fitted to both axles.
Detailed changes to the cab include heated mirrors and new acoustic trim fitted to the roof and rear panels. This combines with the quieter Cummins engine to reduce the noise level, in an already quiet cab, by a further 4d13(A) at maximum engine speed.
The Cox driver's seat, with pump-up lumbar support, has been modified with extra padding at either side of the squab. The interior colour scheme has also been changed in keeping with the damask and grey trim materials used in heavier Leyland trucks.
Prices range from 213,300 for the 6.2-tonne 6-12 tipper to 215,400 for the heaviest 10-tonne 10-13. The 97kW 7.5-tonne 8-13 haulage model is priced at 214,650.
The first public showing of the new range will be at the Paris show early next month where it may also be exhibited with Daf badging as part of the recent LeylandiDaf joint marketing agreement (CM. March 29).