Clio 172 cup rear bias

[krys_short]

I know this has been talked about many times but just want to clear up some confusion.

First of all I have a 172 cup that failed MOT because of the rear brake issue but when I asked if they knew about the special note that the cup should have poor rear pressures, he was aware of this and had been in contact with Renault to confirm and was told by them that the rear bias thing should be connected. the only part that was missing was the rod but as this is not available separately, I had to have a full new rear bias valve fitted.
All passed now so I am happy and brakes are fine, but...

1. Is it true that some should have it connected?
2. Would I notice any difference on track days? (I guess I could disconnect if needed)

 

[JamieG]

No, its not connected, its there, but its not connected. It does regulate the fluid, but its a predetermined value.

 

[mark123]

No, its not connected, its there, but its not connected. It does regulate the fluid, but its a predetermined value.

This 100%

 

[krys_short]

So the info from renault is wrong, according to them some of them do have it connected.
I dont notice any difference under normal driving but you can tell by just looking at the rear discs that there is more pressure being applied as they used to be quite rusty but cleaned up now.
Is it possible to disconnect for track days, and does anyone have any experience in difference it makes?

 

[JamieG]

No cup has it connected - it's the misinformed that don't know the product that are telling you it should be connected.

It will be clearing the discs up, because it will be working properly - the issue they have is, because there not actively connected, they seize up and eventually stop working. I haven't had effective rear brakes on mine for the last 2/3 years.

How do you mean disconnect? Take it away from the rear axle or remove the compensator completely?

You can disconnect from axle (as that's how it should be)

You can't disconnect it from the system completely, as you'll have brake fluid everywhere.

 

[mark123]

When I took my 172 cup for its first MoT when it was 3 years old, Renault were just as useless.

Firstly they said it needed new calipers. Then a new compensator as the bar was missing. In the end when they'd had another in with the same issue. They realised that was how they were supposed to be.

You can rig the compensator for maximum rear effort all the time with some cable ties and some people do this without issue.

I do it for the MoT but then remove it as I once locked the rears with it in the max position under moderate braking for some traffic lights.

Personally I'd go and get my money back. But if you want an easy life I'd look at removing the bar and just reattaching it for MoTs.

Edit: Have you seen the pdf about it? I'm sure that says the bar should not be present.

 

[mark123]

Here is the info

http://webarchive.nationalarchives....k/vosa/repository/MoT Issue 31 - Apr 2006.pdf

Clearly says no bar should be fitted.

 

[MicKPM]

Basically the valve is there and plumbed in to the system but the rod that connects it to the rear beam (which alters the bias based on rear ride height) is not there or connected so it's constantly at MAX flow. What does tend to happen on the 172 Cup though is this bias valve seizes up, usually in the wrong position, which does cause the rear bias to be even worse than normal which is (technically/actually/insert other word) an MOT failure as despite the VOSA note they do still need to record some form of balanced effort at the rear for both conventional brakes and parking brake.

Get under the rear of the car and locate the valve. Then use loads of penetrating spray on the valves pivot arm, spring and... well just drown the mo-fekker and walk away for a coffee. Come back and gently start to actuate the pivot and the pull it all the way down. Go back to MOT station and this *should* rectify the problem. If not replace the valve.

Mick

 

[krys_short]

I just ment disconnect the rod from the axle.

Thanks for all the info, finally got me head round it and think I figured it out.
Arm up- low rear brake effort
Arm down- high rear brake effort

From factory the arm should be up in a fixed position.

What I don't get is, if Renault wanted the rear brake pressure fixed why use an adjustable valve. It would have been less faff and cheaper to fit a fixed restrictor.

 

[MicKPM]

Because they had them? (probably)