Series IV - Technical Information

The Series IV is the most advanced and only system that has been developed to date which addresses the whole tuning issue, e.g. if you modify or improve the suspension and brakes at the front end of a Morris Minor then you must balance this by upgrading the rear end as well.

All of the improvements are in keeping with good sound engineering practice.

Structural Condition

As with any major improvement, before Series IV installation the vehicle must be structurally sound, and any necesary repairs thus made. This of course is a very important point with the Morris Minor considering the last one came off the production line back in 1971.

The Series IV System consists of:

Front Brakes

The donor parts needed are the 9.75 inch discs as fitted to a Morris Marina or Ital vehicle.

The major breakthrough was to re-engineer the Morris king pin to accept the correct Marina or Ital stub axle, which will then accept the complete disc brake assembly directly, and of course allows the use of easy to obtain off the shelf replacement parts.
                
Note. The Marina or Ital stub axle has been specially developed for fitting discs. It is much stronger than the original Morris stub axle, and it is obvious that if the BLMC could have used the Morris unit, why then go to the lengths of developing a new part. The point of shear, or moment when complete failure will be reached is a lot earlier with the Morris stub axle, so for safety the correct type approved stub axle is used.

A further bonus is that the locking system for the hub nuts does not require left and right handed nuts, special bearings, or hubs, and you can obtain spares at reasonable costs.

The Master Cylinder

             
The standard master cylinder is used, but has to be modified to release residual brake pressure inherent in drum brakes. Together with the master cylinder, a special header tank unit is fitted under the bonnet which allows ease of topping up, early warning of system leaks, and most of all because of the large swept area of the calliper pistons which with a standard cylinder supply could lead to fluid starvation, allows a safety margin of fluid.

Servo

With the fitting of disc brakes, the line pressure should be raised to a level giving the same braking effort for a given pedal pressure as that of an equivalent drum brake arrangement. To achieve this, a Servo is fitted on a Series IV system.

Telescopic dampers are fitted using the integral lower bottom arm which is modified and fitted with a location pin welded in the optimum position. Location of the dampers upper mounting are made by special fabricated 11 gauge steel brackets which are welded against the end of the engine bay cross beam, to dissipate stress energy build up.

Not only is it correct engineering practice, but brackets should be welded in place to eliminate possible movement of the dampers out of their optimum damping geometry.

Upgrade 30% – 60% torsion bar kits. Infinite micrometer adjustment. A vast improvement over the standard torsion bars as fitted to Morris Minors.
        
            
Rear Brakes and Axle

             
To complement the updated front suspension and brakes, the obvious thing to do was to transpose the Marina / Ital rear axle arrangement onto the Morris Minor.

The axle has to be reengineered to make it compatible with the Morris Minor, and as this is a live axle arrangement, extra location is required.
        
            
For this, two top fitting radius arms are used, and when fitted form an A frame location. Not only do they tie in the axle, but help prevent axle tramp, exhausting energy through reinforcing plates welded to the chassis. The energy is further dissipated through special sections into the upper rear seat base.

Rear Dampers

            
Damping is carried out by special telescopic dampers rated for the body and unsprung weight, mounted in the ideal location – outboard and vertically. They are located with the aid of pins installed on the modified axle, and upper brackets of welded 11 gauge steel.

Wheels and Tyres

With the upgrade, the use of a wider 13 x 4.5 inch J wheel is employed. This not only allows a wider selection of radial tyres, but also lowers the vehicle and therefore gives the vehicle a better roll height and centre of gravity.

The Series IV Ford System

This system uses the Marina front disc units with the PCD of the wheel stud altered to Ford wheels.

A modified Ford Timken or Salisbury axle is fitted to the rear. The rest of the Series IV parts are matched to the Ford parts.

Installation

Our systems are fitted in our workshops, although you will need to source your own donor vehicle parts, and we offer excellent after care and technical back up support.