Help please - over sensitive brakes on RS Clio Cup

[Mrk]

Hello All

I’ve started running a Clio RS racer in the VLN championship at the Nurburgring and I am having an issue with the brakes being very over-sensitive.

It only takes a very light pressure to apply full braking force and ultimately its extremely difficult to modulate them and generally leads into locking wheels, especially if you apply to much pedal to quickly. Last of the late breakers is not in the cars vocab.


I was thinking of disconnecting the brake servo’s vacuum and I was hoping someone has had a similar issue and can lend some advice please?

Thank you

Mark

 

[mr.pink87]

What brake setup are you running? 4 pot calipers? How big is the master cylinder?

 

[Mrk]

Hi Mr.Pink, cheers for your reply.

The brakes are the standard RS 4pot Brembo's, the master cylinder is again the standard one fitted by Renault Sport.

And the pads are the excellent Performance Friction 01 Endurance pads. We did try the Ferodo pads the Clio Championship cars run here in the UK but they fell apart all to quickly with prolonged use and were importantly worse on the sensitivty issue. The shortest race in the VLN is 4hrs.

Mark

 

[Fred@BTM]

197/200 cup racer?

 

[Tony Hunter]

Mmmm,this sounds familiar to the problem we had on ours.

 

[Fred@BTM]

Drive faster

 

[Mrk]

Hi Tony

How did you cure the problem please?

Fred, would love to drive faster but dodgy brakes means you have to brake earlier, thus you go slower... Its a 197.

 

[Fred@BTM]

road car that's been converted for racing?

 

[Mrk]

No, its a bona fida Cup car built for racing from Renault Sport.

 

[Fred@BTM]

so no ABS and on board brake bias adjustment?

 

[Mrk]

Yes, thats correct Fred.

 

[Fred@BTM]

Hum, well The PF pads are normally quite "grabby" you do have to change your driving style to suit with them, i literally just use 1 toe on the brake pedal

how's the bias setup? Is the valve working ok?

 

[Tony Hunter]

Hi Tony

How did you cure the problem please?

Fred, would love to drive faster but dodgy brakes means you have to brake earlier, thus you go slower... Its a 197.

Had the car corner weighted by Fred and then changed the pads,they were just too grippy for us,and like you we were having to brake early to save locking up,no confidence under braking at all.

 

[Fred@BTM]

ie - not going quick enough

 

[Tony Hunter]

ie - not going quick enough

Your needle is stuck,you old fart.

 

[Mrk]

Hum, well The PF pads are normally quite "grabby" you do have to change your driving style to suit with them, i literally just use 1 toe on the brake pedal

how's the bias setup? Is the valve working ok?

Hi Fred, thats my point exactly - I don't want to use my big toe. I want to jump on the brakes in an instant with the whole of my foot and not for the wheels to lock up. If I have to carefully place my big toe on the pedal, then I've lost loads of time and have to start braking at the 100m board and not the 50m, for instance.

As for the PF's I would have to say that they are a vast improvement over the Clio Championship standard spec pad which are indeed grabby. I have also used the PF01's in different cars and they are not the issue as they have great modulation and feel.

Bias valve is working fine. This car is virtually new.

So have you disconnected the servo to any great effect?

 

[Mrk]

Had the car corner weighted by Fred and then changed the pads,they were just too grippy for us,and like you we were having to brake early to save locking up,no confidence under braking at all.

Hi Tony - so how did you solve your problem please?

 

[Tony Hunter]

As I said,get it corner weighted.We found we didn't have enough weight on the front,then we changed the pads.We now run EBC yellows,don't care what anybody say's about them,they suit us.Your car may be heavier and your races are longer,so these will not be any good for you(our races are 40 mins)I spoke to EBC and explained what we wanted,how heavy the car was,length of race etc,and they recommended yellows.Brakes are a very personal thing,and are a pain if not right.

 

[Mrk]

Arrh I see, I didn't realise the corner weighting and pads solved your problem. Of course our car has been corner weighted by our german team, twice now to find a good setup for the Ring. We have a good front/rear weight bias and unless your car has a stationary stance of doing an endo, you won't of moved much weight forward.

Next is to change the Cups bilstein coilovers for KW's as the billy's can't cope with the duration and intense use and overheat. And a 100l endurance tank will go in - which will put weight over the rear, so your method of shifting weight forward will not work for us. Its all a learning curve as we prep for the Ring 24hr next year.

So your servo is still connected, or are you running a pedal box now?

 

[Fred@BTM]

no they are not, they run a stock road car setup (based of the ragnotti RS) with no ABS


what are your weight figures per wheel?

are your front pads free in the calipers, VERY common people simply fit the pads without checking the pads are free to move/allow for expansion = the pads "stick"

 

[Tony Hunter]

All of the above.

 

[p@blo]

are your front pads free in the calipers, VERY common people simply fit the pads without checking the pads are free to move/allow for expansion = the pads "stick"

Inference of stupidity much? Bit harsh is it not? Lol.

 

[Fred@BTM]

Race cars > road cars = new set of rules

 

[p@blo]

Lol random. Was that response meant for anther thread?

 

[Tony Hunter]

Don't think so.
Earth and Mars comes to mind.

 

[Mrk]

Having trouble getting actual wheel figures from my German team, but front/rear weight is 63%/37%.