Front brakes not working

[Se7enBTCC]

Evening all,

13 month old car and it's gone through two sets of rear brake pads in 3000 miles on track. Local Caterham specialist has had a good look today and it's literally not touched the fronts, no wear at all. Anyone seen this before or know what it might be, he's looking further next week but never seen one like this?

thanks
Paul

[7 wonders of the world]

what brakes and pads are on the front.....?

Unless you've been regularly spinning off into the scenery its fair to sat they are working and its possible the material on the rears is out of balance with the fronts.

I suspect you have AP's 4pots with 1144 pads up front and standard pads on the rear.

[Se7enBTCC]

They were factory standard on all 4 but I wore through rears after two track days so had them replaced with next grade up on the rears only, got through another set of rears and the specialist has said there is even rust on the fronts, guessing on the disc. 

[7 wonders of the world]

It's unlikely you have both front caliper at fault, so possibly a rigid brake line that's been dinged at some point reduceing the line pressure to the fronts or even debris in the line up to the front T piece.

If they're that back I'm surprised you haven't spun on the track though.

How does the pedal feel..? any travel before it goes firm..?

 

 

 

[Se7enBTCC]

To be honest it's my first Caterham so it feels 'normal' to me, probably understeers at bit too much which may explain it.

[K7 VCT]

Who is the specialist? They should be able to tell you what the problem is.....

Get it tested at an Mot centre for proper brake readings ?

[ScottR400D]

Am I missing something?

It’s incredibly easy to run a cursory check, simply by jacking up, pressing the pedal and seeing if the wheel locks up. I know that doesn’t actually confirm they’re giving you full effort but it will give you a clue.

Re the rust, haven’t you got the car to see what’s rusty? 

Having said all that, if the front aren’t working you must have had very long braking distances on track days? Not to say a lot of rear locking up. 

[Tom_Arundel]

Dual circuit brakes.....air in front not bled?

[AnkerB-S]

My money is on the calipers. If there's rust on the front disks after a drive then the pads are making no contact. The pistons are probably seized because the brake fluid is full of water.

[aerobod - near CYYC]

A car that is only 1 year old with standard DOT 4 fluid shouldn't have a moisture or corroded caliper issue. More likely a faulty component such as a damaged caliper or proportioning valve (if fitted) not controlling line pressure to the back brakes correctly.

[Bricol]

As the split is front - rear, I can't imagine you wouldn't notice the terrible braking form having non-working fronts.

The rears are nicely tucked up in the rear arches and have next to no air flow over them - you can get them nice and hot and smelly with some spirited road driving, while the fronts stay pretty cold.  

[Richard Price]

Paul,

If you're driving hard enough to wear out rear pads, you'd certainly know if your front brakes were not working!!! (as stated above, if the fronts are not working, you'd spin whenever you braked hard!)

"replaced with next grade up on the rears only" - it would be useful to know exactly what pads you have both front and rear.

Your problem is likely to be that you're actually working the rears as hard as they should be. But, the rears actually contribute significantly to your overall stopping power. If you have vented four pots on the front (out in the open air with plenty of cooling), but standard solid discs at the back (which, as Bricol points out, are enclosed with poor air flow), its likely that the rears are getting pretty hot (and, pad wear accelerates significantly the hotter the pads get).  I'd suggest it is very unlikely that you have any significant mechanical problem, simply a mismatch of pad material for your use.

[Geoff Brown]

But the balance is more proportioned to the front so you should have felt the bite. You have probably been running almost entirely on the rear brakes. Trust me you know when  four pots are working as per spec.

So it could be anything forward of the master cylinder. Blockage, seized pistons you name it!

As suggested jack up car & do a physical check of front brake action with a helper.

[gulf 1]

I would crack a front bleed nipple get someone to gently press the brake pedal and see if any fluid is expelled. If both front discs are rusty suggests the calipers are receiving  no fluid pressure.

[MADMALC]

A cheap heat gun would be a good tool to get so you can check actual temperatures of the discs front and rear. If you have a brake bias valve check that is correctly adjusted. Can you lock all 4 wheels?

 

[Richard Price]

Paul,

When on track, does the car slow down without fear of the rear brakes locking and the car spinning?

If the car is stopping OK (if you're wearing out rear pads, you're obviously using your brakes reasonably hard!), then your problem is one of pad choice.

I can't see how you can possibly wear rear pads out if your fronts are not working. If the only indication that there is an issue with the front brakes is that there is some rust somewhere, then I'd bet they are working normally!

I have dual master cylinders with an adjustable bias bar. I can adjust it from locking rears first to locking fronts. I know that even a little too much rear bias makes the car very unstable on the brakes. If your fronts were not working, You'd know it!

I don't tend to do track days these days, but, when running standard Triumph brakes on the front, and standard Sierra calipers on the back, pad wear on the back was always far more significant than the front.

If you have AP 4 pots on the front, and standard rears, it is no surprise that you're wearing rear pads out fast if you're driving the car hard on track!

[aerobod - near CYYC]

I'd say 2,000km / 1,200 miles of track use (about 8 track days) is reasonable for a set of rear pads, based on my use. The rear pads on my R400D also wore unevenly until I replaced the solid brake pipe with the flex lines. I'm only about 30% through the life of my front pads on the 4-pot AP calipers, but 50% through the second set of rear pads, so about 5 times the wear in the rear compared with the front. I have over 30,000km on the car but only about 10 track days, the rear pad wear seems insignificant for just road use.

[ScottR400D]

I would agree with Aerobod. My pad wear sounds about the same. The fronts wear much less than the rear. 

[Se7enBTCC]

Morning all.

thank you for the messages. I wanted to wait until Pete @ GRS Caterham had had a good look before I replied. Pete is amazing and pretty much gotten to the bottom of it. He's also replaced the rear brake liners with flexis.

Essentially in 10 track days at Bedford I've gone through two sets of rears and done 2mm on the fronts. I've not necessarily noticed any braking issues but it's my first Caterham so can't compare. Petes come to the conclusion that it's most likely that the pads are too hard on the front, he's taking it to a rolling road tomorrow to prove that there is no other issue. There is no bias valve and brake pressure appears correct to the front.

I'll report back once I know more.

Cheers

Paul

[rj]

I found with uprated fronts and "blue" rear pads the bias was way out - when I had standard brakes with Mintex 1144 pads at the front I was able to brake a lot harder at the end of the long straigth.

Then I fitted CL brakes RC6 rears and had a Brown Trousers Moment following that and fitted a bias valve at the rears. Now the car stops as it should again.

If the car didn't brake on the fronts there'd be a lot of those BTMs.

If you undo one of the brake pipes it'll cause a mess with leaking fluid, but beleive me... you'll notice the lack of stopping power!

(Guess why I know)

 

[Se7enBTCC]

Good morning, firstly apologies for not posting this last month, life's been hectic since.

Just wanted to share the conclusion from a day on track at Bedford.... it was air in the front brakes, it took Pete Godfrey a couple of attempts to get it out but once he found it the front brakes started biting. We think it must have been like it from new as the front brakes were applying but no where near like they do now. After a day at Bedford in June I had noticeably more bite on the front and brake dust to match.

ironically it was slower to turn in so I must have got very used to the car with limited front brakes.

[andy_harries]

Interesting that it was biting enough to stop you spinning every time, but not to wear the brake pads much.

Your own version of a brake bias valve!