Imbalance in front braking efficiency

[markcarlile]

Hello
We have just had our car MOTed (Ford Fiesta Reg: 04).
The documentation states that there is an imbalance in front braking
efficiency, and this should be further investigated.
So my questions are:
- What exactly does this mean - what is an imbalance in front braking
efficiency and what consequences does it have.
- Related to the first question is it something that needs to be fixed
asap, since the garage let us take the car away, I would think no, but
need some clarification.
Cheers
Mark

 

[naebothernoo]

imbalance means that one side of your brakes is less efficient than the other. It should be fixed as it may cause the car to pull to one side when you brake, the harder you have to brake the more violent the pull will be It may be caused by one side of the brake caliper sticking and not pushing the brake pads onto the disc

 

[Ron Gamma]

Start with the simple stuff and then work your way up.

1. Tyre pressures - are they correct, are they the same and are the tread depths roughly the same on both front tyres?
2. Check the brake pad thickness, quality and condition. Are they both displaying the same amount of wear on both sides. You might have some oil contamination on one side caused by a leaky bearing oil seal or hydraulic cylinder.
3. Assuming that brake fluid is not leaking and the pads are ok then bleed the brakes all round.
4. If none of the above work then you may have a sticking cylinder in one of the brake calipers. (could be evidenced by one of the pads on a particular side not being as worn as the other - should be checked in point 2 above anyway but if the disc is 'warping' then it might not show up)
On some brake calipers the whole unit slides on the mounting bolts and if even one of these is corroded or sticking then it will reduce the efficiency of the single acting cylinder.

N.B.
Brake balance valve: Under braking the weight of the car shifts forwards and causes the rear wheels to 'go light' so they stop turning before the fronts and thereby skid. A skidding wheel is travelling faster in relation to a slowing wheel, which in turn causes the back to try to overtake the front. (spinning) To reduce this risk of spinning there will be valve in the braking system to reduce the hydraulic pressure to the rear of the car - this can go wrong but generally only affects the rear brakes and would show up as a front/rear imbalance, not side-to-side as you have.

Get it sorted asap - don't take chances with tyres and brakes.

 

[ratm]

I take it it passed the MOT?
If so it means that the brakes both reached the required standard for a pass. This does not however mean that they're working efficiently and as the previous contributors have stated the problem should be investigated as soon as possible.
Having experience of this type of system I would suggest the sticking caliper slides every time they're a total pain in the ass. I've found the only cure is to ream them out slightly to give a little more tolerance/clearance between the piston, sleeve and bolt/mounting and the caliper body and pack it with Molly Grease NOT Copperslip. Copper and Steel do not a good combination make and any moisture entering into the mix will start a highly corrosive reaction called electrolysis. Also bear in mind that there is a lot of heat generated by the brakes and light oils and lubricants are as good as useless.

This process can be carried out successfully on lots of makes and models and although not all systems are identical most are based around a fairly universal principle.