Does anyone have any idea why the primary brake circuit on a defender goes to the rear wheels and the secondary to the front?

My rear brakes wear out at 3 to 4 times the rate of the front on which the pads are all but original even after 70,000+miles. There is almost no wear on the discs. The dealer assures me that the brakes are working normally.

What would be the problem if the pipes were swapped around as presumably the primary will tend to come on first and then the secondary with higher pedal pressures. I am about to renew all the calipers so bleeding will not be an issue.

The two circuits of the brakes will always come on simultaneously.

You may have a very "hard" grade of pads in the front calipers, or the caliper pistons may be a bit stuck forcing the rear brakes to do more than they should. Whatever, if you are worried about this, check it out. Go to a MoT station and get brake readings taken.


SOME brake master cylinders do not have equal diameter bores, and by design these will create more pressure in the SMALLER diameter part which must be the FRONT part (furthest from the pedal). This is the end that would generally be connected to the FRONT brakes if the system is split between front and rear.

Thanks CharlesY

The brakes have been like this since new. They work and have passed MOT each time. The pedal pressures for an emergency stop are very high and I have never been able to lock up the fronts. The pistons won't retract properly but they do come out though this may well be causing a loss of efficiency. And the brakes pull the vehicle up square anyway, even with a large trailer on.


The pads are standard. But more worrying and this was posed to the dealer during the warranty is that there is no visible disc wear. But they assured me it was normal.

The diagram in the workshop manual (LR one) suggests that the bores are similar. However if there was a smaller bore in the secondary cct to generate higher pressure this would be countered by the greater volume of fluid for an equivalent movement, at least initially because of the 4 pot calipers compared to the rears. After this movement was taken up then the pressure maybe greater but also because of the greater surface area would be reduced in impact as well. Not easy. It is not something I've thought about or noticed before even after building rally cars and other vehicles. I am new to this forum but have been around LRs since 1969!

In any event the calipers and discs are being changed.

Thanks again.

Your analysis of hydraulics needs further study!

However, I think new calipers (or pistons and seals at a pinch) is a grand idea. and should make a difference.

The pistons in all disc brake system should periodically be pushed back to make sure they don't get sticky. Reminds me, I must do mine soon!

You should be able to lock the front wheels with a decent push. Is your servo working properly?

Another thing I suggest you check is that the bore of the master cylinder is correct - that it is the right diameter and that the rear wheel cylinders are the proper ones, and not some with much larger bores than should be.

It sounds a lot like you suspect sticky front caliper pistons, and I agree with that diagnosis.

But if that is not the cause, then the reason for the imbalance in the hydraulics needs to be identified and sorted.