Suspension Bushes

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If there’s one thing that differentiates a classic from an old banger it’s the way it drives. Here’s how to get back that factory fresh feel

Aclassic can look like it belongs in a showroom inside and out, and a rebuilt engine will make it perform like new too, but unless the suspension is brought up to standard it will always be a clunker to drive.

It’s amazing how many overlook the suspension when rebuilding their classics, particularly the mounting bushes and springs. A motor can look new inside and out but unless the suspension is brought back to standard spec it will always feel loose and sloppy. Trouble is the deterioration process is so gradual that a car’s owner hardly detects the deterioration taking place.

BUSH TUCKER TRIAL

Insulating bushes (sometimes referred to as compliance or void bushes) are fitted to a car’s steering and suspension assemblies to provide a degree of ‘padding’ between various linkages and joints, essentially for comfort and quietness. Without them, refinement would be minimal but the chassis would prove very positive and sharp, much like a racing car.

What you ideally need is a compromise and this is decided by the car designers for the type of car and motorist it is aimed at.

Suspension bushes are some of the most highly stressed components fitted to a motor car. They undergo enormous strains and in the most arduous of conditions with no maintenance or lubrication.

The standard material they are manufactured from is a rubber compound containing natural products which deteriorate with age. It becomes softer and more pliable, resisting the forces placed on it less and less. As a result this allows more and more movement of suspension components and less control over the suspension’s geometry, says leading maker Powerflex.
This as a consequence causes inferior handling and stability plus accelerated and usually uneven tyre wear, many people think that if they look okay and passes the annual MoT, all is well. However, bushes gradually wear out and replacing them will instantly give any classic that ‘as new’ tight feeling.

Bushes are traditionally made from rubber but you have the option of either replacing them with standard types, or as it’s becoming the norm, modern ‘poly’ alternatives that are made from polyurethane which is tougher, impervious to oil and grease and lasts longer. Poly bushes come in road or racing hardness designs.

There’s numerous companies marketing a range of bushes for road and track use, coming in different firmness grades. Another bonus is that because they can absorb friction better throughout their working life and last six times longer than normal rubber bushes, for many classics undergoing a restoration, they are a fit and forget job.

JUST DON’T TRY SO HARD THOUGH…

Before you go putting on poly, speak to your marque specialist first. Not everybody approves, reckoning polyurethane spoils the authentic feel and can make the ride harsher and only worth fitting as part of a suspension upgrade.

Most reckon competition quality bushes are far too unyielding for road use plus their more vivid colours can spoil the look of a restoration; normal ‘touring’ bushes are usually a very dark blue/purple that passes as black. Powerflex actually manufactures them in black if required although these are some 25 per cent stiffer than Powerflex’s performance ranges and a massive 80 per cent harder than standard and so are really aimed at dedicated competition use.

It may not be wise to change every bush, even if they’re available. For example, Alfa expert Richard Norris of Classic Alfas advocates leaving the rear standard as the car will be too harsh for road use otherwise, but Powerflex says its bushes complement each other and ideally should be fitted as a complete set although sells bushes individually so customers can pick and choose which bushes to fit and not limit them to buying a full set.

As we said, consult a specialist first and decide what you want to use the car for but where there’s a bush – wishbones, spring shackles, anti-roll bars, tie rods even engine, subframe and axles, they can be uprated. If you turn to our product pages in this issue you’ll find that Powerflex has launched a harder bush for the front anti roll bar on the MX-5, a worthy mod we reckon.

FITTING TIPS

We fitted a selection of Powerflex bushes to a BMW, having previously used Superflex types on a Viva and a Golf. You may need to check out the respective web sites and catalogues as not all classics are catered for.

It’s a straightforward if tough job as the old bushes may be seized in solid and demand brute force and even heat to remove. But if you’re lucky they can be drifted out or pulled out with a special tool; take care not to damage the component (anti-roll bar wishbone and so on).

RESULT: A nice taut feel is returned to the car and handling feels crisper. Using the mid-range hardness hasn’t really affected the refinement as it was always set up on the low and firm side anyway.

JOYS OF SPRING

Penny to a pound that the first suspension component that receives uprating isn’t the spring but the damper which controls it. That’s fair enough as they work harder and have a shorter service life but, whereas you can test a damper, a spring is only given a visual check.

Not only do they settle with age but they also rust and break, the latter becoming more common thanks to the poor state of our roads.

Their renewal is generally straightforward – it is choosing the right spring which can cause problems. Let’s start with used ones found at autojumbles. Apart from checking their condition you need to ascertain that they are the correct one for the model and year of your car as they may have been uprated or changed during production. This means that buying and fitting a singular one will cause a mismatch. If you can, it’s far better to buy them in matched in pairs and preferably new so you gain maximum benefit.

CAR MAKER OR AFTERMARKET?

Even though suspension manufacturers produce original equipment parts for factory fitment, these products differ to an aftermarket alternative, says Spax. This is because aftermarket ones may be designed to fit a variety of other makes and models as well to reduce part numbers required. This means that an aftermarket damper, for example, will be of a dissimilar performance standard to the type fitted when new; not necessarily better or worse, just different.

Also, most aftermarket dampers are, by design, stiffer to counteract the relaxation of an old body and chassis. So if you want your classic to perform exactly how it should then you’ll probably need to seek out dampers and springs from a main dealer, if they are still obtainable.
Most folks won’t be so picky and opt for new or reconditioned aftermarket types which are cheaper and widely available. There’s a wide variety of types on the market and at varying prices, but there again so can their performance capabilities. Our advice is to stick to a known name or at least one with original equipment accreditations.

STANDARD OR UPRATED

Going the aftermarket route also means you have a choice of opting for standard types or uprated alternatives of varying stiffness for a sportier feel. We’re not talking being a boy racer here; many old saloons and even sports cars now feel decidedly wallowy and roll prone which is uncomfortable and sometimes upsetting for passengers and as a result, a slightly firmer feel can be beneficial.

Lowered springs are a matter of taste but it’s the current fad with the max power brigade as it ‘slams’ the car down, sometimes right on its bump stops! Don’t go that mad…

But a slight clip of the car’s ride height can improve both the car’s looks and handling.
It depends how low you go.

A typical aftermarket coil spring will lower a suspension by around 40-60mm which is an ideal compromise; too low and the car may ground with a full load on board. Also, any lower and you probably need to consider uprated dampers says Spax, who produces a massive range of dampers and springs, including a dedicated Classic series. It is currently offering 10 per cent off its wares.

The ultimate, if you don’t mind deviating from originality, are ‘coil overs’; these are dampers with a dedicated coil spring integrated. Gaz Shocks Ltd (Tel: 01268 724585, http://www.gazshocks.com ) is one of the best known specialists in this area and has just released an adjustable front damper for the four-cylinder TR sports cars – see our product pages for fuller details.

FITTING TIPS

Always raise and support the car carefully when carrying out a spring change using stout axle stands and jacks. Similarly, douse all bolts and nuts in penetrating fluid days beforehand so it soaks in to aid removal – they may be extremely rusty and leaf springs in particular can be messy to remove.

Never attempt to replace springs without proper compressors and make sure they are heavy duty as uprated springs are tougher to compress. The tracking and steering alignment may need readjusting RESULT: Overall pretty positive with our Spax Ssx springs. Although they are lowered and uprated, the ride on the Fiesta we fitted them to, it did not significantly suffer and the car certainly felt sportier. Was this because we retained the original (Ford) dampers?
Interestingly, a similar conversion we carried out on an Audi a few years back also retained the standard ride quality but a Spax Sports Suspension kit, featuring uprated dampers, resulted in a much firmer ride but the car’s handling was transformed so it rather depends whether you want show or go!

LEAF SPRINGS AND WHY YOU SHOULD GO PARABOLIC

Leaf springs are normally uprated by the number of leaves they contain and as a result you can normally uprate a saloon by substituting those from an estate or commercial version before looking to aftermarket types. Parabolic springs are becoming more popular as they also help the ride quality thanks to their ability to absorb the rough stuff better than a conventional spring type. This makes them ideal for hard riding classics like MGs, Triumph TRs and Land Rovers.