Brake information and ABS

Since the "what size brakes blah blah" question always comes up I thought I'd clarify it here.

1.4 and 1.6 litre petrol models, 1.9 litre diesel and turbo diesel models without ABS upto May 1997

Front brake type: solid disc, single piston sliding calliper
Front disc diameter: 247mm
Front disc thickness: 10mm

Rear brake type: drum
Rear drum diameter: 180mm
Rear shoe thickness: 4.85mm

1.4 and 1.6 litre petrol models, 1.9 litre diesel and turbo diesel models without ABS from May 1997 to June 1999

Front brake type: vented disc, single piston sliding calliper
Front disc diameter: 247mm
Front disc thickness: 20.4mm

Rear brake type: drum
Rear drum diameter: 228.6mm
Rear shoe thickness: 4.85mm


1.4 and 1.6 litre petrol models, 1.9 litre diesel and turbo diesel models with ABS

Front brake type: vented disc, single piston sliding calliper
Front disc diameter: 247mm
Front disc thickness: 20.4mm

Rear brake type: drum
Rear drum diameter: 228.6mm
Rear shoe thickness: 4.85mm


1.8 and 2.0 litre petrol models without ABS upto May 1997

Front brake type: solid disc, single piston sliding calliper
Front disc diameter: 266mm
Front disc thickness: 10mm

Rear brake type: solid disc, single piston sliding calliper
Rear disc diameter: 247mm
Rear disc thickness: 8mm

1.8 and 2.0 litre petrol models without ABS from May 1997 to June 1999

Front brake type: vented disc, single piston sliding calliper
Front disc diameter: 266mm
Front disc thickness: 20.4mm

Rear brake type: solid disc, single piston sliding calliper
Rear disc diameter: 247mm
Rear disc thickness: 8mm


1.8 and 2.0 litre petrol models with ABS (excluding Rallye and GTi-6), 2.0 litre HDi diesel models
Front brake type: vented disc, single piston sliding calliper
Front disc diameter: 266mm
Front disc thickness: 20.4mm

Rear brake type: solid disc, single piston sliding calliper
Rear disc diameter: 247mm
Rear disc thickness: 8mm


2.0 litre petrol Rallye and GTi-6 models

Front brake type: vented disc, single piston sliding calliper
Front disc diameter: 283mm
Front disc thickness: 20.4mm

Rear brake type: solid disc, single piston sliding calliper
Rear disc diameter: 247mm
Rear disc thickness: 8mm


ABS info
Very early models were fitted with Bendix 2-channel ABS. Only the front brakes are modulated by the ABS system. Later models used Bosch 4-channel ABS which modulates all four wheels. All models from June 1999 onwards were fitted with Bosch 4-channel ABS as standard equipment.
The Anti-lock Braking System is a vehicle safety system invented by the Germans many years ago. Its primary function is to prevent braked wheels from locking during hard braking. As well as reducing stopping distances on some surfaces, it allows the driver to main steering control under maximum braking.

Under aggressive braking, if the wheels lock, steering control is completely lost and the car is at risk of losing control and spinning. Before ABS, most cars had some sort of mechanical system which directed the majority of the braking power to the front wheels, in order to stop the rear wheels from locking. Although this allowed the driver to maintain directional stability, it did not allow them to maintain steering control.

ABS was introduced to stop all of the vehicles wheels from locking during heavy braking, in order to allow the driver to brake heavily and steer at the same time. It does this by using a sensor on the brake pedal, as well as on each wheel, to detect situations where braking could possibly lead to wheel lock (ABS registered that the driver has depressed brake pedal, wheel speed sensors observe the wheels decelerating at an impossible rate, therefore leading to possible lock-up). If ABS detects that a spinning wheel is decelerating faster than it possibly could without locking, it automatically opens valves to release pressure on the brakes, and then the hydraulic pump re-applies that pressure. This cycle occurs many times a second, and to the human eye it would just appear that the brake pedal is being pushed and released at a very high rate, because essentially that's all ABS is doing.

It is important to know when driving a car if it is equipped with ABS, so you know its limits if an emergency braking situation should ever arise.

From what I can tell, all 306's built in or after February 1999 have ABS fitted as standard equipment. Pre-1999 ABS was standard on a few models and optional on a lot of others. There are 3 main ways of checking whether your car has ABS. In order of easiest to hardest, they are:

1) Switch on the ignition. During the sequence where a load of warning lights flash up in their self-test, you should see a warning light with a logo resembling a car skidding from side to side. It's on the very far right of the instrument panel, and should illuminate for about 3 seconds before it goes out again. Click here for pic
2) Lift the bonnet and look in the bottom right corner of the engine bay. This is where the ABS brake pump is situated on cars equipped with ABS. It's a silver/black block with 4 metal pipes coming out of the top, and 2 coming out of the side and has "Bosch" written somewhere on it. If you don't have ABS, this space will be empty. Click here for pic
3) Find a long stretch of private land. Accelerate to about 30mph in a straight line and brake as hard as you can whilst trying to steer very slightly from side to side. If your wheels lock and you slide in a dead straight line, you do NOT have ABS. If you hear a strange noise, feel the car shaking and the brake pedal vibrating violently, and the car follows the path you are steering it in, you DO have ABS.

I also found this video on Youtube: