Suspension

Everything that connects the Wheels to the Bodywork of your E30 is the Suspension. This arrangement of springs, shocks and arms is responsible for keeping the rubber of your tyres on the road at all times; without it, you'd be bounced around a pinball.

Suspension comes in two flavours; soft or hard. Soft suspension will give you a delightful wallowy feeling, like driving a mattress, and is the sort of ride big American cars are famous for. By absorbing all the knocks and shocks , the comfort of your ride is greatly increased. This is wonderful for the big flat German autobahns, but useless for aggressive driving, where body roll will have you lurching drunkenly round every corner.

Hard suspension tightens everything up, giving the car a much more rigid feel. Stiffened joints and tighter coils force the tyres back onto the road after every bump, allowing you to force the car into harder and faster corners. The downside is that every jarring bump will be felt throughout the car, and transmitted directly into your spine and teeth.

The E30 setup aims for a compromise between the two. The stock setup provides a good balance of comfort and performance, with many possibilities to upgrade the system if you need it. But as the cars age, it is important to keep on top of all the maintenance to make sure that at the car drives as well as it did when it left the factory.

For a better understanding, learn more about how suspension works.

Overview

The E30 employs a lightweight but efficient suspension setup, comprised of independent front struts and independent rear semi-trailing arms. This allows each wheel to react to the road surface without affecting the geometry of any of the other wheels. All E30s are equipped with this suspension layout, with small differences between each model depending on body style and and engine.

Sturdier components were fitted to the six-cylinder models (M20 and M21 engines), incorporating bigger front struts and sturdier springs to carry the heavier weights. The same struts were fitted to all Touring and Cabriolet models, as well as different rear springs to carry the heavier bodies of those cars.

Front and rear anti-roll bars were offered to various models to increase responsiveness.

Components

Front

Front suspension layout

The front suspension is comprised of two struts which each incorporate a shock absorber and a spring

Subframe

Not essentially a suspension component, the subframe is little more than a shaped metal tray to which everything in the engine bay is bolted. The subframe mounts to the chassis rails with four solid bolts. From there, the inner ball joints of the wishbones bolt through at the sides, to locate the suspension horizontally.

The subframe also carries the engine and steering rack.

Wishbones

Also known as control arms, these L-shaped curves of metal hold the bottom of the strut in place, relative to the chassis of the car and the subframe. Each wishbone has three flexible joints: the lollipop bush at one end, holding the wishbone to the chassis; a ball joint at the corner bolted to the subframe; and a final ball joint to the wheel hub.

The standard wishbones are made of steel. Lighter aluminium wishbones were fitted to the M3 and to the 325i Touring. While these may seem desirable for their lighter weight, it is impossible to replace the ball joints on them, and therefore very few cars still have them fitted. The cost of new parts definitely outweighs any advantage the aluminium wishbones may offer.

Lollipops

The lollipop bush is a strong circle of rubber, held in place with a circle of steel that directly bolts to the front chassis rail. The idea of the bush is to locate the wishbone to the car while allowing it to turn, based on the flexing of the rubber inside it.

The standard bush is a concentric design, meaning the hole for the wishbone is in the centre of the bush. M3 models were fitted with eccentric bushes, which pushed the end of the wishbone closer to the centre of the wheel arch, increasing the caster. This is considered a worthwhile upgrade for all E30s.

Ball Joints

The ball joints are special pivots that allow two joined parts to move around each other. E30 wishbones have two ball joints each, allowing the wishbone to rotate up and down around the subframe, therefore lifting the wheel hub without affecting the camber of the wheel.

Ball joints are service components, and will fail with age. They can be pressed in and out of steel wishbones (but not aluminium), but at current prices it makes sense to replace the whole wishbone.

The actual knuckle of the ball joint is covered with a rubber boot. These boots can tear over time, compromising the life of the joint as well as being an MOT failure. It is possible to replace this rubber boot without removing the ball joint; spare boots are available on popular online auction sites.

Rear

Rear suspension layout

Maintenance

Bush Renovation

Over time, the rubber suspension components will dry out, harden and perish. This inevitable deterioration means that all the bushes will need replacing at some point. Renovating the bushes with original rubber components will dramatically improve the ride quality.

Our list of bushes links to all the articles you need to replace every rubber part on your car.

Upgrades

The front end of each E30 is designed to carry the weight of its engine. If you've gone through the labour of an engine swap, you'll want to increase the front struts to cope with the heavier weight of the new engine, especially if you've upgraded from four to six cylinders.

The rear end can also get tired over time, after 20 years of tail-sliding abuse. Upgrading the rear suspension can yield a much tighter driving experience for these cars.