If you have a problem with the rear brakes locking up before the fronts on your SE5A then this mod could be for you.
Buy a mini rear brake pressure-limiting valve (also called a brake proportioning valve). The best one to have, apparently is the early cast. You can either get one from a scrap mini or you can buy a new one for about £20.
If the valve is from a
scrap mini dismantle by unscrewing the large end cover.
Then carefully remove all the internal parts and clean
them thoroughly. Make sure you remove the plunger and
The limiting valve needs
to be fitted to the rear brake circuit. It should be
firmly mounted somewhere near the master cylinder so
adjustments to be made easily. The main feed pipe from
the master cylinder to the rear brakes needs to be cut
and connected to the feed into the valve as shown in the
diagram. The other part of the pipe that goes to the rear
brakes should be fitted to either of the outlet
connections. The other outlet should be blanked off with
a UNF bleed nipple. Note that the ends to be flared on
the brake pipes are different, one is a single convex
flare and connects to the inlet that has a concave
facing, the other is a double concave flare and connects
to the outlet that has a convex facing. Make sure that
you get this the right way round.
To adjust the front/rear balance you need to find an open space with little or no traffic and unscrew the adjustment bolt. Drive gently at around 20-30mph and while turning declutch and then brake gently. You should feel the front of the car run wide (understeer). Turn in the adjusting bolt around half a turn and repeat, not forgetting to declutch. Repeat this process until you feel the back of the car stepping out (oversteer). When this happens, lock up the adjusting bolt. Now drive in a straight line and make an emergency stop. The front wheels should lock up just before the rears.
Note: This was taken from a article given to me by a colleague from an unknown author.