21 replies to this topic

[AeroNotix]

Hi,

 

I have a 1998 MPI. Discs up front, drums in rear.

 

The brake pedal is incredibly stiff and has a very short travel. The stopping power in the mini also feels quite bad for the speeds I am going at.

 

Now, I'm not expecting a mini to stop on a dime but it doesn't seem that good overall.

 

Which components can I check/adjust to play around with the brake pedal feel? I will adjust the brakes themselves with the adjustment screw but any ideas are welcome.

[Stiggytoo]

Regarding the short travel - Are you just used to modern cars? You may just have to press harder.
It could be that the servo does not work. This can be tested by holding the brake pedal down then starting the engine. (You should feel the servo assistance)
The only adjustment you have is on the rear brakes, but this would only make your pedal travel shorter.
If you suspect there are any issues with the brakes, a thorough check of the system is in order. Get the wheels off the ground and check the condition of pads and shoes etc as well as looking out for any fluid leaks.

Edited by Stiggytoo, 13 September 2016 - 06:29 PM.

[AeroNotix]

Hi Stiggytoo.

 

Perhaps I am. I suspected the servo because I definitely do not feel any difference in pedal feel when I start the car. I'll have a poke around with the servo to see if there are any immediate problems.

[Spider]

I would start by looking to see if there's any meat left on the Brake Pads in the front and the Shoes in the back.

[AlexMozza]

Mpi's are usually good under braking.
Is it standard calipers?

[Fast Ivan]

Have you changed or adjusted anything?

[AeroNotix]

I haven't adjusted anything myself. Standard calipers.  As an example, dropping down from 80kph to zero is a frightening experience and I'm braking much earlier than any car I've ever driven. There's no sensation of slowing down at all. Usually with heavy braking you get a good jolt, but the car just seems to take its damn time slowing down. For all those that will chime in and tell me I am being unsafe, I know this. I live out in the sticks and the car is not road legal yet any way (registering from a different country) so I am not out playing in traffic.

 

A dead battery is preventing me from confirming whether the brake pedal goes softer when turning the car on, but I definitely don't recall it happening before.

 

Was going to inspect the brake pads themselves when I get more time this weekend.

Thanks for the pointers guys/gals, will report back. 

Edited by AeroNotix, 13 September 2016 - 10:00 PM.

[tiger99]

Could the wrong master cylinder have been fitted? If the bore was too large you would get the brakes fully applied with a shorter than normal pedal travel, and a lot more effort.

 

A faulty servo would not give you noticeably shorter pedal travel, only increased force required.

[AeroNotix]

Could the wrong master cylinder have been fitted? If the bore was too large you would get the brakes fully applied with a shorter than normal pedal travel, and a lot more effort.

 

A faulty servo would not give you noticeably shorter pedal travel, only increased force required.

 

Good info on the faulty servo symptom! Thanks.

[AeroNotix]

OK So I've spent the weekend messing with the brakes to try to tweak them as best I can. 

 

What I've found is that the rear right drum seems out of round and there's a significantly different amount of wear around the shoe.

 

When I adjust the brakes such that they rotate relatively freely when the handbrake is off I find that there's an area in the turn where they bind up and become measurably harder to turn. This is on the wheel where the wear is uneven on the pads. 

 

The handbrake really doesn't work well either. I've adjusted everything as tight as it will go and the handbrake just will not hold, despite the adjustment being way too far to be reasonable.

 

The method I used is:

 

• Slacken handbrake cable all the way off
• Clean, degrease, remove shmoo from all surfaces
• Ensure handbrake quadrants are free of debris and actuate properly
• Adjust rear drums to where they turn freely by hand but stop within one rotation
• Tighten handbrake up such that turning the rears by hand is impossible

Despite this, I can still push the car when the handbrake is off and driving with the handbrake on is still possible. The car won't hold on something like a 15-20 degree incline on my driveway.

 

I've ordered a set of drums and shoes, thinking that the uneven wear is not gripping the drums well enough to hold. As for the on-road braking performance they seem to be a little bit better after the adjustment but I've not had chance to really chew into them. I know the new drums/shoes will need time to bed in and may perform worst in the short term.

 

Any other ideas? 

Edited by AeroNotix, 18 September 2016 - 10:53 PM.

[Stiggytoo]

It's your front brakes that do most of the work, so if there is a problem you should check this out too.

[tiger99]

If the handbrake is not holding, suspect the shoes and drums, as you do, but also the actuating mechanism, which consists of two levers joined by a pivot point, actuslly a rivet, which often siezes. You can buy the entire assembly or try to free it by using penetrating oil, with it removed from the car. But the end points where it engages with the shoes may be worn.

[AeroNotix]

How much ideally should the shoes be actuated (in distance) when the handbrake is enabled? I find that there's uneven actuation of the shoes. The bottom part of the shoe which is attached to the handbrake actuator moves much more freely than the top part. The top seems to only move a few millimetres.

 

I've drenched the stuff in penetrating fluid and wiped off as much shmoo as I can. Seems cleaner but it still isn't biting as well as I'd like.

[Ethel]

Shoes will wear unevenly, especially as on  the rear only one shoe is "leading"...

 

The shoe contacts the drum at the wheel cylinder end first, if it's leading the rotation of the drum pushes the whole  shoe into tighter contact with the drum.

 

I think I'd start by removing the pads from the front and checking the caliper pistons move freely.

[AeroNotix]

@Ethel -- is this in order to check on-road braking performance or handbrake?