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There are many uprating options for the suspension on an M.G. Metro which can improve handling and road holding beyond belief. Here Dennis Robinson who runs D&D Motors at Helpringham in Lincolnshire looks at the front modifications, talking from his experience in preparing cars for fast road use and within the Drayton Manor Park M.G. Metro Cup. A second article will feature rear suspension modifications and obviously one should not be uprated without the other.
A standard car with worn front suspension components will begin to handle like it has a mind of its own. It will lack grip on turn in, will wallow under cornering and straight-line stability will be affected, with the car tramlining on the road. All these problems can be overcome by replacing bushes and renewing worn parts, but if this is necessary it gives the owner the option also to uprate the suspension and replace with a much stiffer and more responsive set up as used in competition cars. All the modifications discussed here are road going and allowable under MOT.
Assuming that you have no accident damage you would start by checking ball joints and track rod ends for play and general wear replacing as necessary. To remove the front suspension, release the front anti-roll bar clamps, separate lower joints and remove the long bolt from the rear of the front subframe. Supporting the engine and subframe as this is done is essential. Remove the rubber bushings in the lower arms, these may now be replaced with nylatron, the inner bushes being available as offset. When correctly fitted these will increase static negative camber by up to 1.1/4 degrees. Nylatron bushes can be very noisy but using silicone grease when assembling will reduce this. The subframe mounts can be replaced at this stage using either nylatron or machined alloy bushes. If you have a pre 1985, non turbo car the front anti-roll bar will be approx. 17.5mm, post 1985 cars are 18.5mm, the latter being an advantage to use. When refitting always use new front anti-roll bar clamp bushes, these are often worn badly even on lower mileage cars.
To lower a standard car and keep it to the factory pressures within the Hydragas units (which are approx. 420 to 520 psi) depressurise the unit using a Hydrolastic pump, remove the Hydragas units and machine up to 12mm off the cone strut. When refitted and refilled to factory pressures the ride height will be approximately 1.5” inches lower. Different Hydragas units were fitted to the front of Metros. Early units, some MG’s and turbos combined use with shock absorbers. Later models apart from GTA's and turbos didn't use shock absorbers. The damping on later units was done with internal valving, the later units i.e. NAM 5759 can be used with or without shock absorbers depending on models but it is beneficial to use them with. All Metro’s have the facility to accommodate shock absorbers so if modifying an early car it would be an advantage to use later Hydragas units plus some shock absorbers. You can according to your budget, fit shock absorbers ranging from a quality Gasmatic to an all adjustable gas shock absorber.
Moving on to race car set ups, and modifications allowed within the regulations of the Drayton Manor M.G. Metro Cup cars, gives scope for tuning of the front suspension. Depending on which class the car will race in, and rim and tyre size, tuning is mainly confined to castor, camber and stiffness changes. The castor angle changes are achieved by moving the anti-roll bar forward or backwards by adding or removing shims from the front bar clamps. Some anti-dive characteristics can also be achieved by shimming the bar up or down according to the ride height chosen. Camber is set by the use of offset bushes within the lower standard arm.
There are two schools of thought on the Hydragas unit pressures. At very low pressure, below 200 psi the suspension would be very stiff, but loss of droop control would result if larger droop stops were not fitted. Very high pressures above 650 psi would also make the suspension very stiff but at the risk of bursting the unit. My own preference is to run the unit between these figures depending on which class of car is being modified. The turbo class C car like my own runs a lower pressure than a class A or B car. The shock absorbers used are fully adjustable units.
Bump stops at the front are a matter of driver preference, some cut down the originals when the ride height is to the lowest setting, but most including myself opt for progressive type bump stops which allow for a more forgiving ride when kerb hopping.
Metro Suspension Modifications - The Rear
Dennis Robinson, of D & D Motors, Helpringham revisits the theme of MG Metro suspension modifications.
Following on from the article on front modifications we will now turn our attention to changes that can be made to the rear suspension of an MG Metro for fast road or competition use such as in the Drayton Manor Park M.G. Metro Cup.
Initially I would check the wear on the rear radius arms for excessive play. If in doubt fit new radius arms. The cheapest modification to start with is to solid mount the rear subframe, these join the subframe to the body of the car at a point In front of the rear wheel. Standard construction is of rubber sandwiched between two metal plates. One could either weld across the two metal plates or alternatively relieve the rubber and replace with an alloy spacer block. In addition I would drill through the floor, to the rear of the Hydragas displacer unit and bolt the subframe to the floor pan. These alterations prevent the subframe moving around under cornering, It must be noted that the tracking of the rear wheels should be checked afterwards and rectified to parallel or slight toe-in.
If the car you are modifying is a non-turbo it will not have a rear anti-roll bar. Fitment of a rear anti-roll bar is straightforward, but if fitting a second hand bar ensure that the bushes are in good order or replaced. Larger diameter adjustable rear anti-roll bars are available but are usually only used in competition cars, however a substantial improvement in anti-roll stiffness can be achieved by the addition of a standard bar combined with the modifications discussed here.
Another improvement in reducing roll at the rear of the car is to use progressive rear bumpstops. Ideally cutting off the originals and drilling through the radius arms at a point halfway down the arm where it is already semi-drilled, (the Metro van rear radius arms are already drilled as they are fitted with a large triangular bumpstop). The progressive bumpstop I prefer is found on the rear axle of an MGB. It is a hollow tapered bumpstop, which gives it a progressive nature.
To enable independent suspension to be achieved remove one of the Hydragas pipes where it joins the three way adapter, fitting another three way adapter to the pipe and blocking off both the spare points. This allows the Hydragas suspension to work independently preventing the fluid transferring from side to side when cornering. It also facilitates more accurate independent ride height adjustment. In this situation suspension pressures should be 250 to 350 psi, depending on ride height chosen. Lowering further can be achieved by machining the struts attached to the displacer; for example machining 10mm off will reduce ride height by approximately 27mm.
All these modifications are allowable within classes A and B of the Metro Championship or for road use. Class C, the Metro Turbos would follow much the same route as this, but would add turreted rear suspension to facilitate the use of rear shock absorbers, preferably adjustable ones. Adjustable camber and toe plates fitted to the outer radius arms will provide far superior wheel alignment. I prefer to have four wheels in contact with the road in a corner so to try and prevent wheel lift I use a reduced droop stop fitted on the main subframe) contacting the radius arm.
As mentioned in the previous article these modifications must be carried out in conjunction with any front suspension modifications and ride height suited front to back as required.
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