All about Classic Car Suspension

Suspension – How to make a classic handle without ruining the ride!

Before we start talking about upgrades it is important to understand what each part of your suspension is made up of and how replacing some, or all of it will change the road manners of your car.

What Components Make up Suspension?

Broadly there are 3 separate types of components in every vehicle’s suspension:

  • Firstly you have some kind of spring arrangement. These set the ride height of the car and to a certain extent how firm the ride is. The shorter or tighter wound the spring is the less deflection you will have and the lower the ride height.
  • The second is the damper. These oil filled tubes ‘control’ the deflection. The more they are allowed to move the more compliant the ride, but the more body roll you will have.
  • The third type of component are the rubber bushes that isolate these moving components from the chassis or body shell. They can have a huge effect on the car’s handling and comfort.

Most classics have relatively compliant suspension, which means that you can really improve the roadholding, body roll and feedback with some well chosen upgrades. However it is all too easy to ruin the ride quality and make the car bounce from one rut in the road to another.

Springs

There are three different types of spring that you will find on classic cars. A coiled spring, a leaf or ‘cart’ spring, and torsion bar. They need changing because like any spring they either lose their natural ability to ‘spring back into shape’ or they break in half! You will be amazed at the difference a new set can make to the drive of your car.

  • Coiled springs are what most of us instantly think of. These coils of high tensile steel either wrap around the outside of your damper and are called coilovers, or they are found between the top and bottom suspension arms, effectively holding them apart.
  • Leaf springs sit horizontally to the road and are attached to the axle. They are a little agricultural, but strong and simple. Despite being developed for the horse and cart, they are used on 50% of all classic cars and are still used on trucks today.
  • Torsion bars are long cylinders of spring steel that twist as the suspension rises and falls. Once fitted, they are easily adjustable. By ‘doing them up’ they get firmer and the ride height drops. You find them in the front of Jaguar E-Types, all rear engined VW’s as well as many others.

Consider keeping it standard

Springs don’t have a shelf life, like oil and often the originals are still on the car when it is 50 years old. Imagine if you had been compressed by a ton for half a century. You probably wouldn’t bounce back like Tigger! Replacing your worn out springs with OEM spec ones will often be the best solution. The ride height will normalise and the springs will be more compliant giving better handling and a better ride.

What benefits do ‘upgraded springs bring’

The most common spring upgrade is a lowering spring. These are shorter and firmer than those that came on your car from the factory. Lowering the ride height often improves the aesthetic, but crucially they dramatically reduce the body roll of the car and improve cornering stability. In modern vehicles we are use to this, so an upgrade can make a classic feel much more like your modern vehicle. There is little that can be done to ‘upgrade leaf springs’ and torsion bars are adjustable, so you can tune them to be softer/harder and therefore bring the ride height up or lower it. However, you have to understand what lowering the ride height does to the rest of your suspension geometry. It can change the way your car steers and how quickly your tyres wear out.

Shock Absorbers

Classics generally have two types of shock absorber. Lots of old British Cars such as MG’s and Bristols have ‘lever arm’ shocks. Your choice here is really either to get them rebuilt, or to modify the car to allow for coil-overs. All other classics have a more conventional gas or oil filled cylinder mounted between the top of the wheel arch and the lower arm.

Your cup overflows with options here. Koni, Bilstein, SPAX, GAZ amongst others are all great quality aftermarket options. Generally they have an adjustable range allowing you to firm/soften them up once they are fitted. Each manufacturer has different specialities, so it depends on your car and the characteristics you want to enhance as to what you choose. For example we would fit Koni’s to early 911’s, Bilsteins to 80’s BMW’s SPAX or GAZ shocks to a Lotus. If you are interested in changing or upgrading your suspension it is best to start with a conversation and a cup of tea with someone who knows what they are talking about.

Project Shop’s top tips for upgrading Springs and Shocks

  • Ask yourself is your suspension not to your liking because it is worn out or you actually want to change the road manners for a particular reason.
  • Upgraded springs are best bought with a matched set of shock absorbers where possible
  • Hader isn’t necessarily better and neither is lower when it comes to the road manners and safety of your car
  • Always have a 4-wheel alignment after refreshing suspension components. This will make sure you get the best out of any changes, keep the steering sharp and stop uneven or premature wear to you tyres

Bushes – What are bushes, and what do they do?

Rubber bushes sit amongst the joints of your suspension arms, in the top and bottom of your shock absorbers and where they mount to the body or chassis of your vehicle. They are also found where the engine, gearbox and rear axle mount and on cars with a separate chassis and body between where these two parts of your car bolt together.

The rubber bushes isolate all the moving components, stop jolts being transmitted through the car and help to dampen road and transmission noise. They are absolutely critical to the handling and ride quality of a car and they have a working life of 5 to 10 years depending on use and storage. Like all rubber components they are easily damaged by oil contamination and dry out or perish over time.

Generally if you renew a classic with good quality OEM rubber bushes you will be delighted! It will get rid of the squeaks and clunks, you will get better feedback through the steering and the ride quality will be much improved. The problem is that many rubber bushes – especially for British cars from the 50’s to 80’s are pretty bad reproductions that wear out quickly.

Polybush – The modern alternative and track car hero

Sold as a cure all product, you actually have to be very careful with polybushes for a classic car. Put simply they are often too hard. Body on frame classics, such as Triumph TR’s and Jaguar XK’s can be particularly affected because the shock is transmitted right through the chassis making it shudder over bumps. Unless you are racing, in which case comfort is well down the list of priorities, we would only ever use a heritage spec polybush on these cars, which are much softer.

In a unibody classic such as a 911, MGB or an E-type you can get away with a mid spec bush if you are looking for a fast road set up. Again there are a lot of aftermarket options, the best thing to do plenty of research before you take the plunge.

Project Shop’s top tips for upgrading bushes

  1. Check and see if there are good quality rubber bushes available first. Nine times out of ten these will be a better choice
  2. Only use heritage spec polybushes if at all possible
  3. You don’t have to replace all bushes with poly – We often only use them in ‘high wear or load’ situations, such as anti roll bar drop links, shock absorbers and in wishbones, but not in areas where you just want to isolate a component such as an engine mount
  4. Be aware of the difference they will make to how much judder and noise is transmitted into the cabin.

With a couple of lifetimes experience in upgrading classic car suspension for today’s roads, Project Shop can help you understand how to wisely spend your money on suspension upgrades that will improve your enjoyment of your classic car