Clio 172 cup braking.

[Gman]

Hi All,

The braking in my 172 cup isn't all that nice at the moment.

I've only owned the car for a few weeks so far and when i picked it up the front nearside under heavy braking locked up very easily and obviously pulls the car very hard under heavy braking.

I didn't really worry too much as i had a few bits i wanted to do, after new pads, discs, lines and fluid and checking both front pistons were moving freely it's still doing exactly the same.

I've got no plans for tomorrow so intend to have a further look into it, can anyone suggest anything else that can be causing this?
I'm thinking could it possibly be a rear piston that has seized and is causing this?

Cheers
Gman

 

[Henry]

sort of got this going on at the moment as well. i think it's likely to pull left anyway (..), as the brakes are hyper and you've road camber and weight distribution in the front end to factor in as well

think it's unlikely to be a rear (imo, which may be cobblers)

also interested in what's posted, anyway. assume you've already checked the sliders?

 

[Fred@BTM]

they generally always lock up the front left first, less weight over that wheel than the front right

 

[Gman]

It's not slightly noticeable though, even light braking from high speeds really pulls on the car. Yes the sliders are absolutely fine.

My thinking with the rear caliper causing the problem is that as it's a diagonal split could it be possible that the rear os is seized (mention of this in an old mot with work being carried out to 'free' the caliper) and is therefore sending all the force to the front ns. I'm no ezpert but could this be possible?

Gman

 

[Henry]

the hydraulic force is still sent to the ineffective piston, so it won't be that (the force isn't added to that operating on the other piston in the circuit)

 

[st3ve]

I'd check the rears.

Mine suffered the same thing you are pointing out but on the other side and it was really dangerous as it would cause the car to snake under heavy braking.

I sent it for a full service which included checking the brakes and low and behold the o/s rear was completely seized.

I personally couldn't detect it just by looking at it either, I'm no mechanic though.

 

[Gman]

I'm going to strip down the rear this afternoon, i took the car out this morning and it's just not right, I can appreciate that the nsf locks first due to the weight like Fred said but it just locks far far too easily.
Lets hope the problem shows itself as i hate not knowing when the problem lies....

 

[Henry]

don't actually know, but was assuming the rear compensator's likely to be fitted with non-return valves (?)

check the OSF piston as well

hope you can identify anyway

 

[Gman]

Well the rears move more freely than my 12k mile Trophy's rear calipers did so i don't think the problem is there.

 

[Gman]

Still no luck with this.

Could this be a issue with the front caliper? When i removed the old pads and fitted the new ones the pistons moved back with little force and all the sliders are free so i just assumed everything was fine here but now i'm wondering if there could be a problem that i just haven't found.

The car has recently had new wishbones, top mounts, dampers/springs fitted and all the geometry setup, it doesn't pull when off the brakes and neither does it pull under acceleration. It pulls left under braking from all speeds and on any camber of road.

Am i just going to have to try fitting new calipers or could it be a issue else where? brake bias valve? brake master cylinder?

Cheers
Gman

 

[Henry]

no expert, but i'd check the OSF caliper; also, bleed the brakes by pedal pumping, see if you're getting similar flow left-to-right (might suggest mc prob if not? my only experience of mc failure has been of the catastrophic 'wtf, no brakes' variety). assume you're not losing any fluid?