LOW INFLATION LIFTS COSTS
Page 80
Page 81
If you've noticed an error in this article please click here to report it so we can fix it.
The message that tyre costs can be controlled often falls on deaf ears. Now manufacturers are trying a different tactic.
Tyres are the second largest running cost after fuel and perhaps one of the most neglected areas when it comes to cost control. For years the tyre manufacturers have been putting out information aboutmaximising tyre life, but it seems to no avail. Now the battle is being taken into the operators' yards instead of their 'In' trays.
Mainly through their distributors, many of which are wholly-owned, tyre manufacturers are offering regular tyre checks on operators' fleets. Workshop accompanied Central Tyre on a visit to find out what is involved in the service and how it benefits the operator.
Central puts fleets into five user groups: general haulage; car transporters; fuel tankers; tippers; and coaches. In this case the fleet was in general haulage category.
On this first visit all vehicles available will have each tyre inspected and its size, make and position noted while the remaining tread depth and inflation pressures are measured. The plate/fleet number, maximum axle weights and any visible defects are noted. In this case as the operator provided loaded vehicles: portable weigh pads were used to measure the laden axle weights and determine the optimum pressures.
A chart is drawn up for each vehicle showing the make, size, position, condition, inflation pressure and remaining tread depth of each tyre. Any defects are noted as are any obvious causes. From this data a report is drawn up which highlights problem areas such as incorrect inflation, short valves on twin wheels, miss-twinning, irregular wear and missing valve caps.
Repeat visits continue on a regular basis depending on fleet size and type of work undertaken. Large tipper fleets could get a daily visit while trunking vehicle require less frequent checks. There are three types of subsequent checks: visual; visual plus tread depth; and visual, tread depth, pressures and wheel torque checks.
Central's technical manager Mike Swain compiled a typical report as an illustration. This covers a typical hub-and-spoke type of operation with 58 tractive units and 76 trailers-788 tyres in total—being inspected. Such a report would probably show one in four tyres (197) cannot have their pressures checked because of valve extensions missing, damaged/defective valves or badly aligned twins. How can the driver be expected to do his checks. One in three of the tyre pressures checked (234) would be more than 10% below the recommended pressure for the axles plated weight—although this could be correct for the load they carry. About 15% of valves would not have caps.
There would be a scattering of badly twinned tyres, some showing uneven wear, a few with less than 3mm of tread remaining, a flat or two and possibly a GV9-type of defect. Some fleets regroove, some do not and the ratio of new to remould tyres will vary with the fleet's policy.
UNDERINFLATION CUTS LIFE From these observations Swain points out that a tyre running 10% under-inflated only gives 88% of its optimum life. So 431(197 + 234) tyres under-performing by 12% is the equivalent of losing almost 52 tyres. At a trade price of £200 this represents a staggering £10,400 off the bottom line.
But the usefulness to the fleet does not stop at these regular checks picking up things that are going wrong—it can also forecast future expenditure. From many thousands of such checks. Central has corn piled graphs of tyre wear against distance for drive, steered and trailing axles by the types of vehicles and useag-e. By comparing the remaining tread depth against the chart, the remaining tyre life can be determined.
Factors such as tyre size, annual mileage, engine power, the balance between motorway against urban useage and typical axle load have a bearing on such forecasts.
The forecast mileage left in the tyre is cross-referenced against annual mileage and the time to replacement can be calculated to build up a budget for tyre replacement.
These predictions accept that the problems highlighted in the check are corrected, with pressures and so on being kept in line with recommendations. Having ensured that the operator will get maximum life out of the existing tyres, the replacement policy must be examined.
All new truck tyres rolling off the production line can be regrooved, but many think this is a false economy. According to Michelin, regrooving a tyre can extend a tyre's life by another 36%, Central works on a more conservative 20% figure.
However, many retreaders point to incorrect regrooving as a reason for casings being rejected.
This is not necessarily backed up by a survey where only 17 out of 286 (6%) regrooved tyres had been so badly cut as to prevent the casing being remoulded.
The usual problem is setting the regrooving tool too deep and cutting through to the wire bracing. Once the cut has been made water will get in and travel round the wires of the bracing plys causing them to rust In order to combat this problem Michelin is incorporating depth indicator holes round the tread. The depth of the hole indicates the maximum limit for regrooving—if you don't go deeper than the hole, you won't ruin the tyre. Central recommends regrooving takes place when there is 4mm of tread left and cut lmm less than recommended by the tyre manufacturer (hence 20% extra mileage against Michelin's 36%).
While the operator must take this small loss of potential life on the chin, scrap casings due to bad regrooving are virtually eliminated.
The 286 regrooved tyres were out of a sample of more than 2,000. In Central's view
this is about par for the course our fictitious fleet has less than 10% regrooved. Most manufacturers do not recommend regrooving steer axle tyres while only the
centre axle of tri-axle trailer is suitable for using regrooved tyres (lateral forces can chip and chunk recut treads).
This still means that on a 2+3 combination using wide singles, at any one time half of the tyres could be recut: four on the drive axle and two on the trailer's centre axle. With tyre husbandry it is possible to ensure that, with rotation, all tyres can be recut.
UNCUT IMPLICATIONS If our typical fleet did not recut tyres because of the potential of a 6% rejection rate for casing remolds, the cost implications would be: 788 tyres loosing 20% of their potential life (36% on Michelin's figures) is equal to 158 tyres at 1200 each: 431,600 lost savings.
But 6% of 788 tyres being rejected for remoulding would cost £9,456; the difference is £22,064 Putting these costs into perspective, on each tractor/trailer combination 10% underinflation would cost ..£288 and the loss through not regrooving would be between Z480-£864 depending on which figures you use, While the remoulding vs retreading debate rumbles on, it is clear to see that good tyre maintenance pays dividends whether you do it in-house or have it done by the manufacturer/distributor.
Tyres are such a large expense that all operators need to keep records. These will cover invoicing, which tyres are fitted to each vehicle and when, which tyres are new and which remoulded, which have been regrooved and what has happened to scrapped casings.
With so much information to keep some operators are seeking to computerising the records. In addition to making the record-keeping easier the computerised data can have the ability to draw off reports and pick up problems that might otherwise go unnoticed. Keeping track of casings is one advantage but it is also easy to spot rogue vehicles, compare different makes of tyres on different jobs and find out if there is a particular reason for casings being scrapped. All the vehicles' details would be loaded on to the computer including their tyres. Workshop tried the Leomar system which, once the data is loaded in, has a report menu with vehicle and tyre listings, tyre and inspection history, tyre costs by manufacture and vehicle, tyre condition and projected life. Each time the vehicle has its tyres checked the computer records such as odometer reading, remaining tread depth and so on can be updated Whether the new information is put in on the tyre record or the vehicle record, the tyre costs, predictions and other records are automatically updated.