Hoyle Front & Rear Suspension

Written by Geoff King

On first glance the outside my 1972 MGB looks like any other Tartan Red Roadster, however, under the skin it is very different. It’s built on a Heritage V8 SuperSports shell, the engine is a modified Rover V8 with electronic fuel injection and ignition; the gearbox is a 5 speed LT77. To cope safely with well over double the original MGB power it was necessary to consider the brakes and suspension very carefully.

At the front I fitted shortened and stiffened coil springs and modified the bump stops (to obtain the original suspension travel with shorter springs), and exchanged the standard anti-roll bar for one 7/8 inch in diameter. The standard dampers were retained and Superflex blue bushes completed the front suspension. The brakes were modified with 4 pot SD1 calipers, Mintex pads and solid GTV8 discs. 

I initially tried GTV8 rear leaf springs for the standard MGB rear axle, however, these made the ride height of the roadster far too high and were exchanged for lowered rally spec springs that reduced the height to an acceptable level. Again, the standard lever arm dampers were retained.

On the road the handing was as you would expect from a fifty-year-old suspension design, not too bad on smooth roads but bumps could catch it out. The 7/8-inch anti-roll bar limited roll well but the wheels would hop and skip over rough and uneven surfaces and with the addition horsepower and more importantly V8 torque, the rear axle tramped, especially in the wet. The car was easy enough to control but grip was lost at relatively modest speeds and the steering, with 195 section tyres and a quick rack, was heavy at low speed. This was not a situation I was satisfied with and not one I was prepared to accept

I could continue to modify the original suspension with changes to the dampers and springs, I could fit anti-tramp bars and I could install a Panhard rod to restrain the rear axle. However, the front suspension geometry, designed for narrow cross ply tyres, would remain, as would the massive unsprung weight of the live rear axle. Not one who wishes to retain originality the antiquated suspension was not what I wanted, especially when I knew that there was a better, much better, alternative. After just 500 miles I decided to replace both front and rear suspension with an up do date design well able to handle less than perfect roads and the additional power of the V8.

During one of my visits to the MG spares day at Stoneleigh I had seen a new suspension system for the MGB designed by John Hoyle engineering. The front suspension used unequal length double wishbones and coilover dampers, fully adjustable for caster and camber and height. The independent rear suspension utilised a Ford Sierra or Granada diff, wheel bearings, drive shafts and disc brakes in a bespoke sub-frame that bolted into the MGB chassis rails using the existing damper mountings, check straps and forward leaf spring hangers. It too was fully adjustable with double wishbones and coilover dampers. 

The MGB front crossmember was modified to accept the new spring and damper unit; tubular wishbones replaced the lever arm dampers and the original MGB spring pan and bottom wishbone. SuperFlex blue polyurethane suspension bushes (the same size as MGB inner wishbone bushes) were used for the new top and bottom wishbones. The 7/8" anti-roll bar (not shown in the photograph) and the standard kingpin/stub-axle assembly were reused together with the 4 piston SD1 brake calipers. The anti-roll bar is rose jointed to the lower wishbone.

At the rear the independent suspension also has unequal length double wishbones and coilover dampers, adjustable for camber and height and fitted with Superflex bushes, again the same size as MGB front inner wishbone bushes.  The differential, wheel bearings, CV joints, brake discs and calipers are all from the Ford Sierra/Granada parts bin.

On the road the difference was immediately apparent, the car could be thrown about with confidence, gone was the front wheel patter on rough surfaces and of course rear axle tramp was eliminated.

 For more info:

Superflex