▁the ▁inside ▁face ▁of ▁the ▁t ire . ▁ ▁This ▁shoulder ▁was ▁sever ely ▁limited ▁in ▁size ▁as ▁it ▁had ▁to ▁pass ▁over ▁the ▁wheel ▁centre ▁for ▁assembly . ▁ ▁T ires ▁of ▁different ▁designs ▁were ▁fitted ▁to ▁whe els ▁with ▁wooden ▁cent ers ▁( M ans ell ▁whe els ▁in ▁the ▁UK ) ▁and ▁to ▁various ▁other ▁types . ▁ ▁The ▁use ▁of ▁t ires ▁is ▁becoming ▁ob sole te . ▁ ▁The ▁util isation ▁of ▁traditional ▁fre ight ▁w ag ons ▁was ▁often ▁so ▁low ▁that ▁t ires ▁never ▁needed ▁renew al , ▁so ▁it ▁was ▁che aper ▁to ▁fit ▁a ▁one - pie ce ▁(" mon ob lock ") ▁wheel . ▁ ▁Mon ob lock ▁whe els ▁are ▁l ighter ▁and ▁offer ▁better ▁integrity ▁as ▁there ▁is ▁no ▁t ire ▁to ▁come ▁loose . ▁Modern ▁flow - line ▁repair ▁lines ▁are ▁dis rupted ▁by ▁the ▁ins pection ▁of ▁the ▁wheel ▁centre ▁once ▁the ▁t ire ▁is ▁removed , ▁possibly ▁generating ▁extra ▁rect ification ▁work , ▁and ▁the ▁need ▁to ▁make ▁each ▁t ire ▁fit ▁its ▁allocated ▁wheel ▁centre . ▁ ▁Mon ob lock ▁whe els ▁are ▁now ▁more ▁econom ical . ▁ ▁C aus es ▁of ▁damage ▁ ▁The ▁most ▁usual ▁cause ▁of ▁damage ▁is ▁drag ▁bra king ▁on ▁severe ▁grad ients . ▁ ▁Because ▁the ▁bra ke ▁blocks ▁apply ▁directly ▁on ▁the ▁t ire , ▁it ▁is ▁he ated ▁up , ▁relax ing ▁the ▁inter ference ▁fit . ▁ ▁It ▁is ▁not ▁feas ible ▁to ▁fit ▁the ▁t ire