Low Rear Brake Efficiency

[Ahl 4]

My car just had to be retested for the mot as it had low rear brake efficiency.

Both the handbrake and the footbrake werent good enough.

 

After fitting new rear discs and pads (it needed them!) the handbrake passed ok, but the footbrake still wasnt quite good enough - only just above 10% efficiency!

I dont really understand this though, as the mastercylinder and compensators were replaced before the last MOT and it passed that one fine. The brake fluid has all been bled properly, and the brake piston cylinders themselves seem to push out fine with no fluid leakage.

 

Has anyone else had this at all and knows why the rear brakes are so inefficient? Or is the MOT tester wrong, and the rear brakes are meant to be that crap?

 

thanks,

ahl

[Guest TB_205GTI]

can it be the pads that don´t make full contact?

 

what I mean is if they only touch the drum in the upper part, braking will be far from perfect.

 

I could be worth checking.

[pug_ham 244 3 Cars]

After fitting new rear discs and pads (it needed them!)

I'm guessing by this your have rear discs.

 

Take it out and when the car is nicely warmed through and there is nobody behind you really slam the brakes on a couple of times to get the pads in proper contact with the disc's.

 

It could be the calipers have become lazy because they do so little under normal circumstances.

 

IMO the rear brakes should have more than 10% efficency but I don't know the true amount. Take it to Kwikfit or somewhere that offers free brake checks as a last resort to have them tested again independently. There should be a chart in the MOt station telling you the brake reading's you need to have.

 

Graham.

[TT205 42]

Were the new compensators really new?

 

I am on my third set of rear compensators in 6 years!, they don't seem to last very long and poor braking efficiency has been the sign every time

 

Dave

[Guest dave364634]

ive got the same problem, and also have a fair bit of brake fade. ive bleed three (other nipple snapped), but my rear pads are f***ed. and the fromts may be to. im gonna work em at the weekend.

[fiji bob 0]

whereabouts does it tell you the rear brake efficiency? looking at my last mot checklist under brake readings it says

n/s o/s

355 267

50 59

132 105

 

is the rear brake efficiency the second pair of numbers?

[Ahl 4]

I think that means the amount of KG's that each wheel braked. (whatever that means exactly.)

 

My rear wheels braked about 50kg each, amounting to just over 100kg for the rear and that showed up as just over 10% efficiency on his rotatey-mot-efficiency-dial thing.

He reckoned that they should have been at least 50% efficient, but im beginning to believe more and more that he's in the wrong.

 

Your checklist is probably the amount braked on the front wheels, the back wheels, and the handbrake. That looks about the same as mine actually! The list weight for a 1.9 pug was 930kg, which would give you 67% efficiency on the front wheels and 12% on the back. That seems about right to me, providing we dont want the rear end overtaking the fronts under heavy braking!

[Ahl 4]

Just from working out fiji bob's figures, that would mean the 205 (1.9?) would have a front/rear braking split of 85/15.

Does that sound about right to anyone, or is it way out?

[Guest Bigj]

Just from working out fiji bob's figures, that would mean the 205 (1.9?) would have a front/rear braking split of 85/15.

Does that sound about right to anyone, or is it way out?

No it sounds about right to me

 

On a 205 the rear brakes do about 10% of the stopping

 

because the rear end is so light

 

If the hand brake works OK then its not pad related

 

Are you sure there's no air in the system ?

 

John

[cybernck 402 1 Cars]

yes, rear brakes should be doing only 10-20% (depending on how exactly you compare them to the fronts).

[Ahl 4]

Thats great. I was sure the MOT tester was wrong.

He went away and spoke to the other MOT tester after I had my 'discussion' with him, and he came back looking sort of sheepish. He mentioned that quite a few cars had given the same effects, but it was almost impossible to 'cure' them, and that he'd let it go and pass me anyway!

 

Anyway, im glad thats theres nothing wrong with it.

Bigj - the system was fully bled through and the brake pedal isnt spongy at all.

[Guest TB_205GTI]

After fitting new rear discs and pads (it needed them!)

 

I'm guessing by this your have rear discs.

 

TB, crawls back into the deep dark pit..

[Guest mbl]

If you find the braking OK, why not shove 4 25kg bags of sand in the boot & 2 on the back seat. This will provide more bias to the back & increase the reading if everything else is OK. Once the MOT is passed you can make a sand-pit & enjoy the holiday weather!!

[Ahl 4]

Ive done that, but now, as I drive around in the nude, I keep getting sand up my arse crack everytime I brake hard. Plus a small family of lobsters have moved into my boot and are slowly tearing up the parcel shelf and the seagulls that are following my car everywhere keep cacking through the sun roof!

 

I think I'll give up on this idea, and make the car into a mobile rock garden instead.

[Guest TB_205GTI]

*ROFL*

[C_W 3 1 Cars]

If you find the braking OK, why not shove 4 25kg bags of sand in the boot & 2 on the back seat. This will provide more bias to the back & increase the reading if everything else is OK. Once the MOT is passed you can make a sand-pit & enjoy the holiday weather!!

Ha ha, but that won't work on a 1.9!