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Measuring Parking Brake efficiency?


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Old 17-09-2009, 15:40
AgentBauer
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I had never used the parking brake on my car, until it failed its MOT today with only 13% efficiency!

I think i managed to get that efficiency up today by just gently pulling the handbrake up whilst the car was moving, several times. Although some smoke was emitted whilst doing this. The effect the parking brake has now seems to be far greater than it did before...

But before I take it back for the retest how can I ensure the efficency is above the requirement leve (16% i am led to believe?)

Is there a simple test I can do such as driving at 20mph and then pulling the handbrake up to see how long it takes to stop (or the distance it takes to stop)?

The garage said they didnt know what was wrong with it, and were going to charge me for labour and parts if needed, saying they were going to take the drums off and everything.

But I knew there was some rust on the drums at the back, but after using the handbrake whilst the car was moving, that rust seems to have dissapeared..

I just need to know if there is a test I can do at home to find out if it will pass the retest (16%) ?

Any help, thanks!
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Old 17-09-2009, 16:19
skunkboy69
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You'd never used the handbrake ? Ever ? It might just be seized or something.
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Old 17-09-2009, 16:47
Mystic Eddy
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I'd love to know how you've got on during day to day life without using it?
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Old 17-09-2009, 17:01
skunkboy69
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By going through 20 clutches I reckon.
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Old 17-09-2009, 17:58
AgentBauer
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Well I ment occassional use...

I'd still like to know how to obtain the efficiency rating?

I've just been out in the car

- The Handbrake takes 6 clicks to reach maximum
- on a 45 degree incline slope, the car does not move
- on a 45 degree decline slope, the car does not move
- With the Handbrake applied fully, the car does not begin to move until the biting point is around 90-95%. Even after very slowly removing my foot from the clutch then it struggles and gerks whilst moving as if it is fighting a stall.

My question is what is the formula to work out the efficiency? because I dont want to have to take the car back to the garage tomorrow and be ripped off.
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Old 17-09-2009, 18:04
richard cranium
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Erm, simples really.

If you live in hilly town like me then a good handbrake is essential.

Find a steep hill, sit at the top, apply the handbrake, put in neutral, cross your arms, if the car stays still, then it will pass the MOT.
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Old 17-09-2009, 18:06
AgentBauer
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Erm, simples really.

If you live in hilly town like me then a good handbrake is essential.

Find a steep hill, sit at the top, apply the handbrake, put in neutral, cross your arms, if the car stays still, then it will pass the MOT.
I've just been out and done that, I did it with the car facing upwards, and downwards, it never moved an inch. It took 6 clicks for the handbrake to be fully applied, so I dont know if that is the problem.

I used the steepest hill in town which is around 45-55 degrees incline/decline.
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Old 17-09-2009, 18:08
susie-4964
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I think that in most modern cars (i.e. up to about 15 years old at least), the handbrake is at least to some extent self-adjusting. So the number of clicks is irrelevant, so long as the car doesn't move on a hill when the handbrake is applied.
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Old 17-09-2009, 18:11
AgentBauer
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The handbrake worked fine on the hill... both ways.... It didnt move an inch...

I still dont understand how I got a failure and only 13% efficiency...

I did another test as well, I travelled at 30km/h (20mph), pulled up the handbrake, and it took 6-7 metres to stop... Is this right?

Can someone tell me if my handbrake is fine, cause if it is i'm going back to the garage tomorrow to complain... Am I in the right here?
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Old 17-09-2009, 18:16
susie-4964
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The handbrake worked fine on the hill... both ways.... It didnt move an inch...

I still dont understand how I got a failure and only 13% efficiency...

I did another test as well, I travelled at 30km/h (20mph), pulled up the handbrake, and it took 6-7 metres to stop... Is this right?

Can someone tell me if my handbrake is fine, cause if it is i'm going back to the garage tomorrow to complain... Am I in the right here?
Personally, I'd get another garage to check it for you (they'll probably do it for free if you're nice to them). You might get an answer on here, but it won't hold water with the first garage, whereas if you can tell them that Joe Bloggs down the road is willing to sign away his children's inheritance that the handbrake is fine, they're more likely to pay attention.
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Old 17-09-2009, 18:31
ianradioian
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Youve probably got it working at a better efficiency now youve started to use it--it only needs to be 16% to pass, so try the mot again.
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Old 17-09-2009, 18:44
Cruachan
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The handbrake worked fine on the hill... both ways.... It didnt move an inch...

I still dont understand how I got a failure and only 13% efficiency...

I did another test as well, I travelled at 30km/h (20mph), pulled up the handbrake, and it took 6-7 metres to stop... Is this right?
As well as the speed, you need to know the weight of the car and, I think, the co-efficient of friction between the tyres and the particular road surface, to do a proper calculation. The formula is probably on the web somewhere.

The other option is to get hold of a decelerometer - Tapley is a brand name - used by the police and MOT stations years ago to conduct braking efficiency tests.

From what you've described about how the handbrake held on a 45 degree slope, you seem to have unseized, or unrusted, whatever was seized or rusted.

What kind of car is it (hope I did not miss mention of that). A "discs all round" car nowadays usually has the handbrake act on a small drum on the hub carying the rear disc whereas in years gone by the handbrake on such cars operated on the discs themselves. Lack of use in the former could result in rust build-up on the operating face of the drum which you may by now have removed.
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Old 17-09-2009, 19:18
richard cranium
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The tester will measure the handbrake holding power
of BOTH wheels and they must be roughly equal.

Maybe the handbrake works better on one wheel than the other.

Also, if the handbrake is binding when the handbrake is released it may be failed.

But, generally your handbrake has to be pretty useless to fail.

Is the retest free ?

If not try another [ less persnickety ] MOT Centre.
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Old 17-09-2009, 19:40
paulyoung666
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What kind of car is it (hope I did not miss mention of that). A "discs all round" car nowadays usually has the handbrake act on a small drum on the hub carying the rear disc whereas in years gone by the handbrake on such cars operated on the discs themselves. Lack of use in the former could result in rust build-up on the operating face of the drum which you may by now have removed.

do they , mk3 mondeo's handbrake operated mechanically onto the discs , and early on were notorious for sticking on and causing issues , been there
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Old 17-09-2009, 19:56
r_mitchell85
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how can you only occasionaly use the h/brake?

do you just leave the car in gear whenever you park? (I DO do that... but I put the h/b on also)
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Old 17-09-2009, 20:01
_ben
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- on a 45 degree incline slope, the car does not move
- on a 45 degree decline slope, the car does not move
Well that's better than any car I've ever owned and none of them failed their MOTs

Find a steep hill, sit at the top, apply the handbrake, put in neutral, cross your arms, if the car stays still, then it will pass the MOT.
A mathematician would tell you that the top of a hill is defined as the point of zero gradient
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Old 17-09-2009, 21:11
Cruachan
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do they , mk3 mondeo's handbrake operated mechanically onto the discs , and early on were notorious for sticking on and causing issues , been there
That's my experience of Vauxhalls Cavalier (1989) then Omega, Zafira and Nissans X-Trail.

My 1978 FIAT132 handbrake acted on the disc brake caliper and mechanically applied the disc brake. I'd no problems, but there were some reports of such mechanisms, after having been applied on hot discs, letting the car roll free after the discs cooled and contracted leaving the disc pads firmly applied against fresh air.
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Old 17-09-2009, 21:57
Bedsit Bob
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The other option is to get hold of a decelerometer -....................- used by the police and MOT stations years ago to conduct braking efficiency tests.
MOT stations still use them, when testing permanent 4-wheel-drive vehicles.
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Old 17-09-2009, 23:38
John Robinson
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My 1978 FIAT132 handbrake acted on the disc brake caliper and mechanically applied the disc brake. I'd no problems, but there were some reports of such mechanisms, after having been applied on hot discs, letting the car roll free after the discs cooled and contracted leaving the disc pads firmly applied against fresh air.
I'm glad you said that. My (brilliant) Skoda Fabia has discs on the back as well as the front. The handbrake acts, presumably, on the rear discs.

Although I have never encountered any such problems, I wonder whether this may happen one day, especially when parked on a steep hill. Fortunately, I usually remember to leave it in gear in these situations.

Do cars with rear discs have some sort of mechanism that ensures continued pressure on the discs, even when they have cooled?
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Old 18-09-2009, 15:28
Cruachan
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I'm glad you said that. My (brilliant) Skoda Fabia has discs on the back as well as the front. The handbrake acts, presumably, on the rear discs.

Although I have never encountered any such problems, I wonder whether this may happen one day, especially when parked on a steep hill. Fortunately, I usually remember to leave it in gear in these situations.

Do cars with rear discs have some sort of mechanism that ensures continued pressure on the discs, even when they have cooled?
I don't know - all my rear disc cars since my FIAT 132 have had handbrakes which operated on drums built into the rear hub.
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Old 18-09-2009, 15:39
COAX
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I'm glad you said that. My (brilliant) Skoda Fabia has discs on the back as well as the front. The handbrake acts, presumably, on the rear discs.

Although I have never encountered any such problems, I wonder whether this may happen one day, especially when parked on a steep hill. Fortunately, I usually remember to leave it in gear in these situations.

Do cars with rear discs have some sort of mechanism that ensures continued pressure on the discs, even when they have cooled?
I remember when citroen first released the xantia, there was stuff on tv saying that they were susceptible to rolling down the hill due to presumably the disc cooling down. I have worked on my mums 1993 citroen xantia and a peugeot 206, both of which have discs all round and the handbrake operates on the front not the rear. Not sure about a fail-safe mechanism though- didn't see anything there when i was working on it. The handbrake cable hooks onto a lever on the brake caliper and pushes the piston out independantly of the hydraulic system that is operated by the brake pedal. Maybe its designed in such a way that the tension on the handbrake cable will be enough to allow the caliper to adjust itself when the disc cools down.
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Old 19-09-2009, 10:23
David (2)
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Still no answer - how does the OP manage not using the handbrake?? This is simply not an option in this part the country (too many hills - lots of hill starts).

.....unless its an automatic car.
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Old 19-09-2009, 10:32
abarthman
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Still no answer - how does the OP manage not using the handbrake?? This is simply not an option in this part the country (too many hills - lots of hill starts).

.....unless its an automatic car.
Handbrakes are for women and pensioners!

Real men only use their foot brake and ride the clutch!

I'm more concerned about these 45 and 55 degree hills in the OP's town! That's a 1:1 and steeper. I've never driven up or down anything that steep!

His town must double as a 4X4 course!
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Old 19-09-2009, 13:20
Aspartame
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I'm more concerned about these 45 and 55 degree hills in the OP's town! That's a 1:1 and steeper. I've never driven up or down anything that steep!

His town must double as a 4X4 course!
I only just spotted that. His estimation skills must be a little out. There's no public roads as steep as 1:1, and nothing much short of a Land Rover Defender will handle that sort of slope As for 55 degrees, well I just checked out the info on the web, and 45 degrees is the maximum gradient Land Rover quote for the Defender

1:3 is about as steep as you're likely to see.
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