Parking Brake efficiency??

[cps13]

My car just failed it's MOT, one of the points was the parking brake efficiency was down to 15%. Apparently the lowest it can be is 16%.

What does this actually mean? i.e. what bits need replacing?

Cheers

[Alex@POD]

Just an amateur's opinion, but if it was me I'd try tightening the handbrake cable, and if that doesn't solve it, replacing the pads/shoes as well... How high does your handbrake come when you pull it up as high as you can (how many clicks)?

[cps13]

Thats the thing... it only comes up two clicks!

I'm at a loss!

[leorest]

This is off the top of my head but I don't think it's too far from the truth
100% = The weight of the vehicle or more accurately the weight stated on the MOT testers chart.
For the sake of easy maths let's say your car weighs 1000kg
That means at 15% efficiency your handbrake is able to resist a force equivalent to 150kg

cps13 said:

...What does this actually mean?...

It means if you fully engage the handbrake and push the car really hard it will most likely move.

cps13 said:

...what bits need replacing?...

You can only find out by inspecting for maladjustment or wear.

[cps13]

Thanks for your help.

When you say it needs inspecting, what parts need to be inspected? i.e. calipers, cables etc.

If it makes any difference it had new brake pads on the rear about 2 months ago.

Cheers,

[leorest]

cps13 said:

Thanks for your help.

When you say it needs inspecting, what parts need to be inspected? i.e. calipers, cables etc.

If it makes any difference it had new brake pads on the rear about 2 months ago.

Cheers,

It's a bit difficult to diagnose through the power of qwerty especially when equipped with such scant information... Some cars have separate callipers/drums for the handbrake so your new pads wont necessarily make a difference. I suggest you start at the lever by the drivers seat move on to the cable and finish up at the wheels They are normally quite a simple system so it should be relatively easy to see where the problem lies.
It's time to step away from the keyboard and get some oil under your nails.
All the best

[LeightonBuzzard]

If it's drums on the rear might have leaking/seized wheel cylinder it was only 1 wheel.

[Bobupndown]

Really old thread revival......
Son's girlfriend has a Fiat 500. Failed mot on parking brake low efficiency. Asked me to take a look at it. Handbrake was coming up about 6 clicks but locking drums solid when applied. Took both rear wheels off it. Rear drums looking crusty but turning freely with brake off. Adjusted handbrake cable so it's fully on at 4 clicks. Put two wheel bolts in each drum and tried turning them using a 3' length of angle iron levering against the bolts. Not turning at all. Pretty sure handbrake is now effective. Retest today and it failed, parking brake low efficiency again, now worse % than last time. I'm somewhat at a loss. Next step would be drums off and checking all internal components.
I suppose I'm wondering, does 'low parking brake efficiency' only relate to the handbrake operation or is it the rear brake operation, including by applying the brakes with the pedal? Are they describing the failure wrongly? Could be that it has seized wheel cylinders effecting normal braking but this would have no bearing on the handbrake?

[GreenV8S]

Bobupndown said:

Put two wheel bolts in each drum and tried turning them using a 3' length of angle iron levering against the bolts. Not turning at all. Pretty sure handbrake is now effective.

That is not an accurate way to test the parking brake effectiveness.

While driving along (slowly in a safe place) you should be able to lock the rear wheels by applying the hand brake firmly. If you can achieve that then it should easily pass the MOT. If you can't, you have a problem that needs fixing.

[Belle427]

Following the manufacturer's adjustment procedure is key too, most just tighten the handbrake thinking that's fine but can lead to incorrect operation.

[E-bmw]

Both good bits of advice there.

TBH if I were lifting the car & adjusting the handbrake I would also have gone the extra mile & had a look at the actual brakes while I was there.

[tapkaJohnD]

To work on the handbrake at the wheels, did you have the rear of the car up on a jack or stands?
Some cars - can't speak of Fiats - will loosen/tighten their handbrake cable as the wheel go into full droop.
If you tested the brake by levering on the hub I presume they were so drooped, so maybe the brake wasn't correctly adjust when the weight went back onto the wheels.

John

[paintman]

Take the drums off & have a look.

Although I would expect it to show up on the service brake test as well a leaking wheel brake cylinder can lubricate the shoes with brake fluid & that will affect the efficiency.
Been there done that!

[stevieturbo]

Bobupndown said:

Really old thread revival......
Son's girlfriend has a Fiat 500. Failed mot on parking brake low efficiency. Asked me to take a look at it. Handbrake was coming up about 6 clicks but locking drums solid when applied. Took both rear wheels off it. Rear drums looking crusty but turning freely with brake off. Adjusted handbrake cable so it's fully on at 4 clicks. Put two wheel bolts in each drum and tried turning them using a 3' length of angle iron levering against the bolts. Not turning at all. Pretty sure handbrake is now effective. Retest today and it failed, parking brake low efficiency again, now worse % than last time. I'm somewhat at a loss. Next step would be drums off and checking all internal components.
I suppose I'm wondering, does 'low parking brake efficiency' only relate to the handbrake operation or is it the rear brake operation, including by applying the brakes with the pedal? Are they describing the failure wrongly? Could be that it has seized wheel cylinders effecting normal braking but this would have no bearing on the handbrake?

At least offer the full test results which should indicate left/right readings and balance.

But you seem to suggest it is working fine ?

[Bobupndown]

Thanks all, a few interesting pointers there.
Agree full brake examination is the only way to be sure, have had failed wheel cylinders before. Was asked to have a 'quick look', seemed fine after adjustment, easily holding the car letting the clutch out in gear.
I'd suggested a full brake rebuild before next year's mot was going to be required given the look of the drums but apparently needed sooner