Brake Bias

[Smiffy69]

I am confused which to be honest is not difficult.

 

I have a R300 (2010) and was wondering just how much brake bias goes to the rear brakes as from what I can see by rust patterns on the disks that after 6K miles the rear pads do not yet wear evenly across the whole of the braking area. The fronts are fine.

 

There is fluid flow to all callipers after recent ezee bleed

 

There are no obvious leaks.

 

Therefore on the standard master cylinder is it very heavily front biased to the point of hardly using the rears?

 

or am I not driving hard enough and therefore not braking hard enough ?

 

Very puzzled

[garybee]

If the pads/discs are not wearing evenly across the whole of the braking surface I would suggest that you disassemble the rear brakes and make sure that they are free to move and not seized. Seized pistons, caliper/carrier, sliders and pads (not able to move relative to caliper) can all cause uneven wear. This will affect the brake balance as some of the 'effort' is just pushing against the seized components.

 

This is where I would look first.

 

Edit: missed a bracket

 

Edited by - garybee on 15 Jun 2014 22:42:17

[CharlesElliott]

Also check that the rear calipers were set correctly with an indent in the piston at the 6 o'clock position

[Smiffy69]

Thanks I'll check as suggested

 

[TomB]

Have you got flexible hoses at the rear of the car? ISTR that solid pipes can restrict the movement of the inside of the caliper.

[Richard Price]

Smiffy69,

 

is it that you have rust on the outer 6-8mm or so of the disk, and then a rusty line towards the centre of the disk with just a strip of around 35-40mm that shows signs of being cleaned by the pads 🤔

If so, that is quite normal. The Ford Sierra pad was not really designed (by Ford) to be used with a Triumph Spitfire disk, however, its a compromise that works reasonably well.

It is quite common for this strip of rust to grow, and wear the edges off the the pads is the car is often used in the wet and not dry when stored, and if the breaks are not used very hard or very often.

 

To answer your original question, in a standard system, the hydraulic pressure is identical front and rear.

 

 

[7 wonders of the world]

As pointed out piston size in the M/C are the same so line pressure will be equal, age and disc quality can effect rear brake efficiency as can pad material and caliper set up, condition and operation, also getting a good bleed and ridding the rear calipers of all trapped air which often requires caliper removal to allow the nipple to be placed uppermost - not easy with rigid lines !

 

Also worth checking the rear brake lines from the M/C for their entire run length have been correctly routed and not damaged, seen a few with nipped kunifer lines on the DD and one in the tunnel, I assume someone had being trying to centralise the gearbox with a lever and inadvertently caught the brake line, both effectively squashed flat leaving little of no brake to the caliper, also seen incorrectly routed flexy's that foul to the trailing arms and get partially nipped on full bump, naturally this eventually results I a fractured line with loss of the rear brakes.

[Smiffy69]

Thanks for the top tips and places to go and look.

 

Had the wheels off this evening and the probelm was with the lug on the pad not sitting in the indent position at the 6 oclock position. This was causing the uneven pressure on the pad.

 

All sorted now with the use of the angle grinder spanner to twist the the piston into position.... a quick bleed as it's a doddle with an ezeebleed kit.

 

A quick blat has removed all suspect rust 😬

 

Once again many thanks POBC