Wheels and Tyres
Wheels & Tyres
A usefull contact for people experiencing problems with tyre availability is Longstone Tyres who can be contacted on :
Tel: 01302711123 or www.longstonetyres.co.uk/searchFacility.php
The use of replacement alloy wheels is allowed. They must however remain a period type pattern. This usually means a Minilite style of rim. The chances of obtaining these type of rims from period in a usable condition are fairly remote. The standard steel wheels on some vehicles could well be standard and have been taken on and off the vehicle hundreds of times. This has a weakening effect on the wheel nut tapered seat to the extent of total failure. This is particularly true of large diameter wheels with small P C D´s.
I well remember obtaining some period Mini Cosmic alloys that looked in sound condition. When clamped onto a modern tyre changer the centre broke right out of it. The alloy had degenerated into a powdery dust with no strength at all!
Wheel Rim Widths.
The size of the wheel may not differ from that originally fitted by more than 10% on nominal diameter and by 1 inch (25.4mm) on nominal width. The resultant track measurement shall not differ from the original by more than 1 inch.
Please view MSA Blue book for current permitted wheel rim and permitted tyre sizes.
The fitting of tyres with an aspect ratio of less than 65% is prohibited.
Slick tyres are prohibited. There must be a moulded tread pattern at least 1.6mm deep over the whole width of the tyre.
Definition of moulded tyres.
A moulded tyre is defined as one having a tread pattern with a width of 170mm (85mm each side of the tyre centre line) and a circumference of 140mm. In this area, the surface taken up by the grooves at least 5.5mm deep and 2mm wide must occupy at least 17% of the total.
This Tread Pattern must be moulded.
The sum of the width of the grooves encountered by a circumferential line in the area described above must be at least 4mm. The sum of the width of the grooves encountered by a radial line must be at least 16mm. The bridge blocks and sipes must be considered as part of the tread pattern if they are less than 2mm.
Handcutting is permitted but only for the purpose of introducing additional grooves no deeper than those moulded into a new tyre.
Handcutting in order to increase the depth of existing moulded grooves is PROHIBITED.
At all times during an event the tread depth must not be less than 1.6mm over at least three quarters of the tread pattern.
Tyres marked `For Racing Purposes Only´ are prohibited on Rallies.