Robski, this was basically the same issue I had with my brakes. I too drive on a stretch that has a few r'bouts with long straights in between. The first sign of fading was a louder rubbing noise followed by subsequent drop in performance. My DIY ducts seemed to have sured this. Is yours a 99MY 4pot?

 

Sunday I was taking the scoob out for a drive (got to keep th battery topped up in the cold weather ).

I decided to test the brakes out a little, so used a few mile stretch of road thats basically 4 dual roundabouts fairly evenly spaced out (i.e. approx 1/2 mile sprints in between).

I was progressively braking later and later at each one, until I got to one where I wanted to brake a bit harder so I pushed harder than I had previously, the resistance from the pedal was much much greater, but it didnt increase the braking effect, as it was I stopped in time, but it was closer than I was expecting (no ABS kicked in).

Thing is, I thought brake fade meant you could push the pedal to the floor, this was the opposite, like the system had pressured more than normal.

robski

 

Robski

Brake fade is when no matter how hard you press, you do not generate any more retardation. Pedal pressure is not affected.

When the pedal unexpectedly drops to the floor, the most common cause is pad knock off. This is caused by excessive heat melting the hub grease, causing excess hub play, allowing the disc to push against the padfs, which in turn push the pistons back into the caliper. Its a fault with sliding calipers and when you press the brake pedal, you are re-flooding the caliper pistons, not pressing the pads against the discs.

 

Yep MY99 4 pot, spot on!

is this what you have then?

I was very surprised by this. Im now wondering if its partially heat soak, but Im not 100% convinced there isnt something at least a little wrong. Why did the pedal get much harder, but with no noticeable increase in braking?

Im going to have to test it again I see.

robski

 

There are two types of heat-related brake fade.

Pad fade, where the pads get too hot:
The pedal still feels normal, but nothing happens when you press it as the pad no longer applies much friction to the disc.

Fluid fade, where the brake fluid gets too hot:
The fluid boils (usually in the calipers) creating bubbles. These bubbles are compressible, so the pedal goes to the floor and nothing happens.

There are other effects, such as those described by Pete above. Also, on some older cars, where the servo-assistance isn't very good, it is possible to briefly "empty" the brake servo by repeatedly pressing & releasing the brakes. Symptoms are the same as pad fade. You can get the same effect by switching off the engine and pressing the brakes a few times.

robski: When you say "the pedal got harder" is it possible you were pressing it harder in an attempt to apply more braking?

IMHO, it sounds like your pads are getting too hot. How old are they? They might be on the way out.

 

DavidRB,

I braked the same amount as normal, but it wasnt going to be enough, so I pushed a bit harder, but it needed to be a lot harder!

On the way out, hope not, 6000 easy miles is all they have done!

robski

 

Robski

I had a severe case of brake fade once in my MX5 coming up to a Give-way, I had to use my 1st gear to stop!!!

The pedal feels harder than normal but its a mental thing, you're automatically pushing harder because they are having no effect and therefore your foot is feeling more pressure.

My problem was that I installed cheepo pads, a mistake I'll NEVER make again. When it comes to brakes it's worth getting the very best, especially on the Scooby.

Dave.

 

I dont think age of the brakes has much to do with brake fade. I experienced fade in my Cossy with 3k miles old Taorx discs and pads shortly after an engine rebuild taking power from 250/260bhp to 320/330. I was blasting down an open country road, braking hard for the various bends before accelerating off again. There were a few cars dotted about so id accelerate hard past them and then brake hard when approaching the rear of the next one (in plenty of time, not last minute up the bum braking). When i came up to a roundabout i found that the effectiveness of the brakes had gone through the floor, although i managed to stop in time easily enough.

Suprising how much difference an extra 70bhp can make to the speed at which you accelerate Quiet alarming really as i didnt think we were going THAT much faster than before the conversion (when id NEVER exeprienced fade).

bren

 

I've also got a MY99 on four pots, with Mintex pads and Silkolene fluid. I did these mods to reduce the break fade.

Iain P - What is this mod you speak of?

 

Robski, I experienced the issues you descibed from new. I did have the disks changed at 14k miles 'cos they had tiny cracks in. It's just a basic heat retention issue. When fade occurs, the pedal pressure is still maintained but obviously not converted to friction as the pads must be glazing over. When it dores occur it takes a few minutes to recover before they work properly again. Try the ducting mod that I posted over xmas. There isn't a lot you can do if you want to maintain your warranty.
Mr B, go back a week or so and check out the post that Puff started for me (in the general section).