Can't get the rear wheels to lock up.

[denkimi]

So i've build my clio rallycar a few years ago, but i can't get my handbrake to work on dry asphalt.
At first i tried the regular handbrake with cables, but couldn't get the rear wheel to lock up, no matter how tight the cables where.

So i fitted a hydraulic handbrake, but it still doesn't work when there's a lot of grip.
On gravel and on slippery wet asphalt it works, but in the dry i can pull so hard the bolts on the lever snap, but it still hardly locks the rear wheels.
I'm using regular brake discs with the abs still on, and ferodo ds2500 pads.

So, do clio's just have such bad rear brakes, or is there something wrong with mine? Are there rear calipers on the market with a bigger piston that just bolt on?

 

[JamesBryan]

Have you tried rebuilding the calipers with fresh seals?

 

[denkimi]

Not yet. I was thinking of getting new rear calipers as a last resort, but i don't know if it's worth the money since it might not fix anything.

It seems to brake fine, just a touch too little to make them lock up.

 

[PhillipM]

Smaller cylinder in the hydraulic handbrake
You do have it plumbed in after any prop valves, etc, yes?

 

[bloke]

Smaller cylinder in the hydraulic handbrake
You do have it plumbed in after any prop valves, etc, yes?

Made that mistake once!!!

Also did a full braided set up on a 106, all in nice black with red clips, looked spot on. Could I buggery get the rears to bleed properly. Went through fair bit of fluid and head scratching and was only when I was sat in the car crying and asking God why he was so bloody cruel to me that I pushed the brake pedal and had my hand resting on the hydraulic handbrake I realised I'd plumbed the sodding thing in the wrong bloody way round!!!!!

Half a bloody day to realise I was an idiot

 

[PhillipM]

It's surprisingly common, if I'd got paid for everyone I'd pointed out that was plumbed in before a prop valve or the wrong way around I wouldn't need to work again

The other fun one is people with bias bars adjusted 50:50 as they came from the manufacturer and then the prop valve cranked all the way down...

 

[denkimi]

Smaller cylinder in the hydraulic handbrake
You do have it plumbed in after any prop valves, etc, yes?

nope.
i've got the brake lines coming from the abs module, going to two parallel master cilinders, and then to the rear wheels. there's nothing in between.
i've thought about smaller cilinders too, but right now they're 0,625, and that seems to be the smallest diameter available. Perhaps somebody here knows if there are even smaller ones to be found somewhere?

 

[JB21]

Just pull the ABS fuse so the bias goes to 50/50, you don't even need the handbrake then it locks up that easily

 

[denkimi]

Just pull the ABS fuse so the bias goes to 50/50, you don't even need the handbrake then it locks up that easily

I have a button in my dash to turn abs off.
But that's not what i'm looking for. I like the rear nice and stable under heavy breaking on narrow roads.

 

[JB21]

I have a button in my dash to turn abs off.
But that's not what i'm looking for. I like the rear nice and stable under heavy breaking on narrow roads.

Rebuilding the callipers inc handbrake mech and fitting aggressive pads like CL RC8 will help.

 

[denkimi]

Rebuilding the callipers inc handbrake mech and fitting aggressive pads like CL RC8 will help.

Ok, will give it a try after the rally next week.

 

[PhillipM]

A 0.625 going to each rear caliper individually is the issue, they'll be much too large with the tiny calipers on the rear.
I use that size master cylinder on each rear wheel for the handbrake with Wilwood 4-pots and 320mm discs....


Edit - don't know if the Clio's have the common 30mm piston version of those calipers but if so the 306 gti6/rallye has a version with 32mm pistons.

 

[Usr117063]

Excuse my ignorance but its still running abs? How are they going to lock up with it?

 

[denkimi]

The Bosch Automotive Catalog is moving

The Bosch Automotive Catalog has moved

www.bosch-automotive-catalog.com

A 0.625 going to each rear caliper individually is the issue, they'll be much too large with the tiny calipers on the rear.
I use that size master cylinder on each rear wheel for the handbrake with Wilwood 4-pots and 320mm discs....
Edit - don't know if the Clio's have the common 30mm piston version of those calipers but if so the 306 gti6/rallye has a version with 32mm pistons.

that's was one of my first ideas. but 0.625 seems to be the smallest brake cilinders that are available.

Excuse my ignorance but its still running abs? How are they going to lock up with it?

the hydraulic handbrake is behind the abs module. So the moment i pull the handle, it closes the brake lines to the front, locking out the abs.
no matter how much effort the abs is trying to do to reduce brake pressure to the rear, i can't take away the pressure from the handbrake.

 

[PhillipM]

Then just put more leverage in the handle instead.

 

[Robbie Corbett]

I have a button in my dash to turn abs off.
But that's not what i'm looking for. I like the rear nice and stable under heavy breaking on narrow roads.

So fit a switch to your handbrake, when you pull the hand brake up it turns the abs off.

In all fairness, the rear brakes on the 182 don't seem to do anything, I've got new calipers, new Renault cables and it still barely does a thing.

I would also guess that the 2500 pads in the rear are a bit pointless, they won't be anywhere near up to temp so you may find the handbrake does more on standard/road pads?