keeping them running
Page 71
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by Trevor Longcroft
3 u have had to put a vehicle ugh the annual test more than
because the new linings/ ns you have fitted haven't time to bed in sufficiently, you should consider brake ing.
lr P. Rivers of Rivers Trustop, isley, maintains that for less the cost of one day's down an operator can have his cle's brake units trued to give 90 per cent lining area /drum tact required for optimum :e unit efficiency.
edding-in brakes correctly is time: if it is rushed, the n can become distorted or ked, crazing and hot spots appear and reduced lining ice will result.
irther, because the drum and to which it is attached argo different machining :esses it is unlikely that their re-lines will coincide prey when they are assembled.
Mr Rivers has found that drum friction surfaces are etimes not machined true to drum axis. The net effect of is that the braking load is avenly distributed around and across the drum, and braking between wheels is unbalanced.
This is more probably noticed by drivers as brake judder or a tug at the steering wheel at each brake application, or by fitters as uneven tyre wear caused by the brakes of lightly laden wheels locking under only light pedal pressure.
To make maximum use of brake trueing it is advisable to machine both the shoes and drum, though some operators prefer to grind the shoes only, if the drum is in reasonable condition.
To true the drum, it must be firmly bolted to its hub and the complete assembly mounted on a drum lathe. The drum friction face is then machined concentric and parallel to the hub axis. On certain types of vehicle the wheelnuts may be required to clamp on to the drum during machining to minimize the effects of drum distortion when refitting the wheel.
Relined shoes are mounted on a special jig which has the , particular mountings applicable to the type of back-plate used. The linings are machined to match the drum diameter.
For this service Mr Rivers charges El per inch width of drum and El per set of shoes regardless of their size. The complete operation, matching one drum to a pair of shoes, takes on average less than one hour though badly worn drums and some patterns of shoe take longer.
From their base at Carlton Road, Barnsley, Yorkshire, Rivers Trustop operate 24 hour pick-up and delivery service for operators within reasonable distance.