The rear brake corrector is designed to limit the brake pressure applied to the rear brakes, and to prevent the rear wheels from locking up during braking when the rear axle has a light load.  

Consider a truck configured with a tray on the back for commercial use and its wide range of load variations: i.e. fully loaded when delivering something and then unloaded on the return journey.  However, with a motorhome the load variation is quite small; the majority of the mass is the actual motorhome and there is minimal variation in its loading.  With the ABS turned on (the ABS is automatically turned off when the centre differential lock is engaged), if either of the rear wheels starts to lock up, the ABS will intervene and reduce the brake pressure going to that wheel, even if the brake corrector has failed to do so.

The brake corrector valve is calibrated by Iveco to vary the restriction of pressure to the rear axle up to a rear axle of 2665 kg; at that point the full brake pressure is allowed to pass without restriction.  When Cuthbert as fitted-out as a motor-home is completely empty, the rear axle is just over 2700 kg.  This means that Cuthbert’s rear axle is always above the mass at which the rear brake corrector limits the rear brake pressure. The corrector is never actually limiting the brake pressure and is therefore not required.

I have also seen that a number of Daily 4×4 owners have suffered from partial brake failure due to the failure of one of the pipes that connects the brake corrector to the rear brake flexible pipe joint.  It seems that this particular pipe is prone to a vibration which is causing it to shear at the corrector connection.  There have also been cases where the brake corrector has restricted the pressure to the rear brakes regardless of the weight on the rear axle and so reducing the braking efficiency.  It is also worth noting that the new Euro 6 Iveco Daily 4×4 has an upgraded ABS and no longer has the rear brake corrector.

So given all of the above, I have decided to remove Cuthbert’s rear brake corrector.  For the T3 service I now need to replace the brake fluid, so it is an ideal time to also make a change to the braking system.

Luckily, the brake pipes leading to the brake corrector are long enough that they can be removed from the corrector and connected directly to the flexible pipe fittings that lead to the rear axle.  However, one of the fittings for the corrector uses an M12 fitting which needs to be replaced with an M10 fitting so that it can be fitted into the flexible pipe’s fitting.  The brake corrector and its associated brackets and linkages were then removed, which weigh 4 kg.  Finally, the brake fluid was replaced and the whole brake system bleed as part of the T3 service.

To test the modification, I reduced Cuthbert’s rear axle weight as low as I could given the motor-home configuration (i.e. with minimal fuel and water in the tanks) and tried doing emergency stops on gravel and tarmac surfaces, both with and without the ABS selected. In all cases there was no evidence of rear wheels locking up and the truck remained directionally stable.

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