PRP Tyre Services
GOOD TYRES ARE VITAL Tyres   are   the   vehicle's   only   point   of   contact   with   the   road.   The   actual   area   of   contact   between   the   car   and the   road   through   the   tyres   is   small,   roughly   equivalent   to   four   size   eight   men's   shoes.   Bald   tyres   -   'slicks'   - may   be   fine   for   a   race   car   on   a   dry   track,   but   no   good   at   all   for   road   vehicles   on   a   wet   road   surface.   Tyres treads   are   designed   to   pump   water   from   the   road   surface   and   provide   maximum   grip.   By   the   time   the tread   is   worn   down   to   the   legal   limit   they   will   be   unable   to   perform   this   task   efficiently   and   MUST   be replaced.   RoSPA   recommends   that   worn   tyres   are   replaced   with   an   equivalent   new   unit   well   before   the legal minimum tread limit of 1.6mm is reached - ideally as soon as they reach 2.5mm. The Right Tyres for the Vehicle Motor   vehicle   manufacturers   choose   the   type,   make,   size,   profile,   load   carrying   capacities   and   speed ratings   to   match   their   vehicles,   adjusting   the   tyre   pressures   to   give   the   optimum   grip,   ride   and   handling characteristics. Only change the type of tyres on your vehicle on expert advice. Tyre Maintenance Tread Depth Pay   special   attention   to   the   amount   of   tread   remaining   on   your   tyres,   and   measure   them   regularly   (details of minimum legal tread depths is given below). Always replace tyres before they reach the legal limit. Pressures The    vehicle’s    handbook    provides    guidance    about    how    to    look    after    your    tyres.    It    will    also    contain information    about    vehicle    loading    and    the    required    adjustments    to    tyre    pressures    which    should    be followed   for   safety.   Tyre   pressures   should   always   be   checked   and   corrected   (if   necessary)   when   they   are cold.   It   is   vital   that   tyre   pressures   are   maintained   at   the   levels   recommended   by   the   manufacturer   to ensure maximum tyre life, the best ride and handling characteristics.  Over   or   under-inflating   tyres   is   likely   to   seriously   impair   their   performance   and   may   prejudice   the   safe   use of   the   vehicle.   Over-inflation   increases   overall   tyre   diameter,   decreases   the   amount   of   tread   in   contact with   the   road,   decreases   sidewall   flexibility   and   affects   road-adhesion.   Under-inflation   decreases   overall tyre    diameter,    increases    sidewall    flexion,    generates    higher    tyre    operating    temperatures    and    difficult vehicle   handling   characteristics.   Under   extreme   conditions   running   an   under-inflated   tyre   may   cause premature tyre failure. Both over and under-inflation adversely affect tyre life. Cleaning Treads Keep   tyre   treads   clean   of   stones   and   other   foreign   bodies,   and   check   regularly   for   damage   to   the   tread and   side-walls.   It   is   vitally   important   that   any   damage   is   checked   out   by   a   tyre   expert   and   any   necessary repairs or replacements are carried out immediately. Tyre valves Check   tyre   valves   carefully.   Ensure   the   caps   are   in   place   and   that   there   is   no   evidence   of   cracking   or damage to the valve stem. Part-Worn Tyres What are part-worn tyres? Part-worn'   tyres   are   those   which   have   been   used   previously   -   in   other   words   they   are   'second-hand'.   Most part-worn tyres are imported, mainly coming from continental Europe. What are the potential problems with part-worn tyres? Part-worn   tyres   are   usually   sold   with   about   50   per   cent   of   their   original   tread   remaining   and   may   have several    thousand    miles    more    motoring    in    them.    However,    despite    their    remaining    tread,    it    must    be appreciated   part-worn   tyres   are   nevertheless   USED   TYRES.      As   such   their   purchase   and   use   should   be treated   with   a   degree   of   healthy   scepticism.   In   many   cases,   such   tyres   will   be   perfectly   sound.   However,   it is   possible   that   they   have   been   bumped   up   and   down   kerbs   and   over   other   obstacles.   They   may   have been   run   over   or   under-inflated,   and   may   have   sustained   irreparable   and   invisible   damage   to   their structure.   The   cost   of   part-worn   tyres   reflects   their   second-hand   state   and   this   no   doubt   contributes   to their   attraction   to   motorists.   The   purchase   and   use   of   part-worn,   instead   of   new,   tyres   may   enable   some owners   to   afford   to   keep   their   vehicles   on   the   road.   The   tyre   industry   continues   to   express   concern   about the   sale   and   use   of   part   worn   tyres.   However,   it   is   important   to   consider   the   issue   objectively   and   make   a reasoned   judgement   about   the   real   risks   of   using   such   tyres.   RoSPA's   advice,   like   that   of   Trading Standards   Officers,   is   'let   the   buyer   beware'.   Whether   the   purchase   of   part-worn   tyres   is   a   good   economic proposition   or   not,   there   can   be   little   argument   that   a   tyre   which   is   only   half   worn   but   is   in   all   other   aspects sound, is likely to be safer than a tyre worn to the legal limit. Remoulded Tyres What is a remould tyre? A   remould   tyre   is   made   from   an   old   tyre.   Old   tyres   which   are   not   sound   should   never   be   used   as components   for   remould   tyres.        The   essential   building   block   for   a   remould   tyre   is   a   used   tyre   whose   tread is   worn-out   but   whose   carcass   (basic   structure)   is   sound.   Preparation   for   remoulding   involves   stripping away   the   tread   of   the   worn-out   tyre. The   final   part   of   the   process   moulds   a   new   tread   onto   the   old   carcass using a new rubber compound. What problems are there with remould tyres? In   the   majority   of   cases   remould   tyres   perform   satisfactorily   provided   the   manufacturer’s   guidance   about maximum   vehicle   loadings   and   maximum   speeds   is   followed.   Overloading,   sustained   high   speeds,   and under or over-inflation all contribute to increased tyre wear and/or premature failure. The Tyre Law Tyre Pressures Tyre pressures should be maintained at or within a very close tolerance of the recommended pressures. Tyre Tread Depth and Damage When   tyres   become   worn   or   damaged   they   must   be   replaced.   There   must,   by   law,   be   at   least   1.6mm   of tread   depth   across   the   centre   3/4   of   the   width   of   the   tread   throughout   the   entire   circumference   of   the   tyre. There must be no damage to the tyre body - sidewalls or tread, no bulges or cuts. Tyre Types It   is   illegal   to   mix   tyres   of   a   different   construction   (cross-ply;   bias   belted   or   radial)   on   the   same   axle. Cross-ply   and   bias-belted   tyres   are   seldom   used   on   production   cars,   and   are   not   widely   available   in   the UK.   Cross-ply   and   radial   tyres   should   never   be   mixed   on   the   same   vehicle.   Where   a   mix   is   necessary, radial   tyres   MUST   only   ever   be   used   on   the   rear   axle   and   cross-ply   tyres   on   the   front. This   mix   of   tyres   will produce   'over   steer'   whereas   the   opposite   will   produce   'under-steer'.   (Over-steer   refers   to   the   car   turning more   tightly   into   a   corner   than   it   is   steered;   under-steer   indicates   that   the   vehicle   turns   at   less   of   an   angle than it is steered). Of the two conditions, over-steer is generally accepted to be easier to control.
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