Urgent advice required - 172 Cup rear brakes

[Donny_Dog]

My mate has a 172 cup.

It has developed a tendancy to lock the rear brakes. In particular the drivers side rear - wants to overtake you when stamping hard.
He checked to see if there is a brak compensator, but it looks like the cups don't have one.

When he took the wheels off, one of the rear discs was glowing. In fact it looked warped.

He greased the sliders and put a new disk on.

Same thing.

Options are needed.
I have said its a sticking caliper, but he said that it wound back in fine with a screwy and pushing.
He thinks it could be that the flexi has perished?
Could it just need a good bleeding?

Anything to try, would be appreciated.

Also - are 106 GTI and Saxo VTS rear calipers the same?!

 

[Bluebeard]

If it has a sticking caliper, then jacking the car up and trying to spin the wheel when its cold would establish this surely???

 

[The Fatty]

Also - are 106 GTI and Saxo VTS rear calipers the same?!

They were on the Mk1's, not sure about the Mk2's

 

[Donny_Dog]

If it has a sticking caliper, then jacking the car up and trying to spin the wheel when its cold would establish this surely???

Will try in the morning mate - times running out, track day on Sunday! Thanks for the idea.

 

[Donny_Dog]

Its obviously braking ok to the rears - as they both are somewhat effective. but just that one side is silly. Gotta be the caliper, surely....

 

[MG cup]

If its one side it points toward a seized caliper especially if its glowing red lol. Cups still have adjustment in the rear adjustment valve, there's an Allen keyed stud with a lock nut that needs undone and wound in or out to adjust, sounds like brakeing force needs wound forward if its locking rears.

 

[Donny_Dog]

If its one side it points toward a seized caliper especially if its glowing red lol. Cups still have adjustment in the rear adjustment valve, there's an Allen keyed stud with a lock nut that needs undone and wound in or out to adjust, sounds like brakeing force needs wound forward if its locking rears.

The arm is there, but there is no spring adjustment - it appears some cups are hit and miss if they have them.

He bought the parts and put them on anyway - but it has made absolutely no difference before and after - which to me says that is ok and its gotta be a sticky caliper.

 

[MG cup]

It's not a cup then If he has bought and fitted some parts then right? Cups definately have a small valve at the rear where a compensator would be, it dosent attach to axle to sense load like a 172/182, it is there purely for manual adjustment, like I said above, stud and lock nut to adjust.

 

[Donny_Dog]

It's not a cup then If he has bought and fitted some parts then right? Cups definately have a small valve at the rear where a compensator would be, it dosent attach to axle to sense load like a 172/182, it is there purely for manual adjustment, like I said above, stud and lock nut to adjust.

No, it's defo a cup.
He lowered it at the rear and coincidentally the rear is wanting to spin round.
He added the required parts from a normal clio, thinking it would sort it.

 

[MG cup]

Fix calliper and then fit new cup valve or bias adjuster( cup valves aren't cheap)

 

[Toastfrenzy]

Try the compensator valve, in front of the nearside rear wheel make sure that it's free to move up and down, mine was stuck and I had a bit off rear imbalance - freed it up and all's fine now. All the way up gives most braking to rear, all the way down least braking to rear.

 

[lesley]

As mentioned, if it is only on one side then its most likely a caliper fault, try removing the piston and cleaning it up, it is probably sticking.
The dust seals are normally damaged by this sort of age though, so bare in mind that if you do so the seal is unlikely to go back in again properly and hence you will need to replace it at a later date, but it will be fine to do your trackday without the seal (especially as its no doubt broken already anyway for the piston to seize in the first place)

 

[Donny_Dog]

Right,

New caliper - same thing.

Wound the Allen key thing on the compensator and same thing.

Track day is tomorrow.
How can we just turn off the rears?!

 

[Cupman29]

Is there anything wrong with the caliper or is it just the fact thatbyou have altered the rake of the suspension?

I would try raising the rear slightly as this seemed to only happen when you lowered it?

If he added the compensator from a non cup then the lower it is at the rear the more bias it will give as it thinks there is weight in the rear.

 

[Toastfrenzy]

Pull the compensator lever all the way down and tie down so it doesn't come up....

 

[Donny_Dog]

Tried it. It's as if the block/box thing is faulty. Using the Allen key or lever makes zero difference!

Is there a way of blanking or disabling the rear brakes? Even pikey style?

 

[Donny_Dog]

Is there anything wrong with the caliper or is it just the fact thatbyou have altered the rake of the suspension?

I would try raising the rear slightly as this seemed to only happen when you lowered it?

If he added the compensator from a non cup then the lower it is at the rear the more bias it will give as it thinks there is weight in the rear.

It's hardly any lower to be fair.

 

[Toastfrenzy]

Tried it. It's as if the block/box thing is faulty. Using the Allen key or lever makes zero difference!

Is there a way of blanking or disabling the rear brakes? Even pikey style?

So the lever -moves or doesn't move? It should move down when you press the foot brake pedal too.

Other than removing and getting it working and freeing off or replacing with a working one from scrappy or similar (mate with a cup who's not going?) is your only choice I think...

Mine is also a lot lower but made no difference to the rear braking.....being lower has nothing to do with your problem I think.

 

[Cupman29]

So the lever -moves or doesn't move? It should move down when you press the foot brake pedal too.

Other than removing and getting it working and freeing off or replacing with a working one from scrappy or similar (mate with a cup who's not going?) is your only choice I think...

Mine is also a lot lower but made no difference to the rear braking.....being lower has nothing to do with your problem I think.

It will if it's not a cup compensator with the arm attached.

 

[Donny_Dog]

So the lever -moves or doesn't move? It should move down when you press the foot brake pedal too.

Other than removing and getting it working and freeing off or replacing with a working one from scrappy or similar (mate with a cup who's not going?) is your only choice I think...

Mine is also a lot lower but made no difference to the rear braking.....being lower has nothing to do with your problem I think.

There's no lever. Cups don't have them. He added one, but removed it again after it did jack all.

As the Swedish man said there is a manual adjustment. The locking nut is solid yet the Allen key thing can move. Tried it fully up and fully out - no difference.
With the nut being stuck it has to be this thing at fault.

Looks like its a case of clamping the flexi's with mole grips!

 

[hilldawg172]

hand brake cable mate. unclip it from caliper at bottom and try again. Bet its rusted and sticking.

 

[Donny_Dog]

hand brake cable mate. unclip it from caliper at bottom and try again. Bet its rusted and sticking.

Tried.

No difference.

 

[Cupman29]

With a brake problem as bad as this, I would think twice about going on track till it is resolved.

 

[Donny_Dog]

With a brake problem as bad as this, I would think twice about going on track till it is resolved.

Barn yard Motorsport at its finest

 

[Mash.]

Really sorry to bring this up from far far ago, but did you have any luck sorting this?

 

[Crybert]

4 years later