SteveKozy

So....Seems i am having a few little niggly issues keep cropping up this winter. None more so annoying than a feeling my brakes aren't up to scratch.

Prior to the MOT i had done last month. I was noticing that my braking was/felt like it was getting worse, i.e. the pedal felt softer and the car was braking less sharply.

At first i thought it was tyres. They were Toyo's and a summer tyre and so i swapped them out for new Pilot Sport 4's. I run them at 33psi front and 31psi rear. The tyres feel very grippy, even in the torrential rain we have, so i dont feel its them causing the issue with braking and brake feel. As i know tyres can have a big effect.

I then noticed i was getting some binding/dragging noises from the rear and again noted the decreased braking efficiency, so i figured that as it was MOT time i would have my mechanic look at the brakes specifically. Turned out I needed two new rear calipers. They were shagged. So at the same time my mechanic, flushed the system of old fluid and replaced it with a good 5.1dot fluid. At the same time he replaced the rear brake discs and pads for standard OEM items.

The front pads and discs were left alone - aftermarket K-Sport 8 pot fronts, braided lines and yellowstuff pads. But the whole system was flushed and bled as stated.

Since having it done, i thought / felt for a week or two that things were improved. However, i think it was a placebo. Granted the rears are fine now and not binding but i certainly don't feel like i have a good pedal feel.

In fact it feels like in this cold weather and rain i've noted quite a lot of what i would describe normally as "fade", but after a very short time, distance and not very hard driving.

So describing the symptoms, braking from speed the pedal travels a fair bit, feels like about an inch, and i can then physically feel the pad bite the disc quite strongly, but, if i keep the same or increased pressure, almost immediately that bite seems to fade quite rapidly. To the point where it almost doesn't feel like the car is braking - like the weight is too nose heavy and it almost feels like its floating.

Around town i don't notice this. At low speed applying that same 1 inch of pressure can make the car jerk it bites so hard.

But my daily commute includes a nice 25mins of National Limit A-Road. And braking from a speed of 80mph, the pedal travel feels excessive at about an inch, and as stated i feel a good initial bite but then it begins to fade/float i would say within a handful of yards of that initial bite and certainly not on what i would call excessive/heat.

I'm a bit stumped to say the least.

I've searched and seen a lot of fade and brake issue posts but most around poor choice of pads or pad glazing, knackered calipers/discs etc. I've rectified all of those i feel. The rears are new and the fronts haven't been changed but have little to no real wear on the discs and the yellowstuff pads are about half way and have in the past felt much bitier (thats not a word). My parents live on the preseli mountains and roads are epicly good and in the summer the braking was phenomenally confidence inspiring and nothing has changed really. So i know it can brake really well it just doesn't feel like it right now. The only difference noted typing this out is the temperature.

I did read that it could be down to the fact that the brakes being bigger are just not warming enough to properly work in this temperature - but surely that shouldn't be the case? I've never known that on previous STI' Brembo set-ups i've had, granted they weren't as big, but that would mean i have to hammer them constantly to get the best from them during winter?? It is not a track car. It does run significantly(ish) over stock power (350hp) for standard wrx brakes, so i would have thought an upgrade seemed a sensible route to me?

I am questioning the front K-Sport calipers now and wondered if there was an issue with them. I had noticed this week the car pull under braking a wee bit, which it never has before, but it was very very windy and i had increased tyre pressure for a fully loaded trip so put it down to that and the fact the wind was that affecting the steering of the car under braking. Is that possible?

If not, that could suggest to me that one of the 8 pistons is sticking? I know you can't rebuild K-Sports so it would be a question of swapping them out. But i can't be sure they are the cause and swapping out to another brake set up is a costly method of finding out especially after spending just under £700 on the rear set up fix. I think the cheapest big brake upgrade is Ian @ Godspeeds AP set up of 6 pots and 2piece discs, but even that is £1700 before fitting.

So. Does anyone have any similar stories of braking issues like this and if so, what was the problem and what am i best doing to resolve it - i know this will end in mostly " get your mechanic to troubleshoot" but i like to get an idea myself first and i'm out of ideas almost on this one. I'd like to be able to go back and say it "feels like this and i've heard it can be this" to at least give us a fighting chance at reducing troubleshooting costs.

Thanks in advance guys.

John 37

It's difficult to advise at a distance.
Are you rear hoses braided? Hoses can fail with age and give strange symptoms.
Try checking your front calipers. Is a piston seized? I've no experience of K sport but frequently partially seized brakes can be freed by simply pushing the pistons in and out.
The other thing to check is that your front pads aren't seized in the calipers.

stonejedi

iTrader: (51)

My friend had a similar problem to you and he was running 8 pot Ksport callipers with EBC pads,he ask me for my advice first thing i told him to do was to bin the EBC pads and in all honesty His brake problem was cured,with a change in brake pad compound to carbone lorraine RC5+.SJ.

1509joe

iTrader: (2)

100% correct. Also check your wheel bearings.

stockcar

first job would be to strip and clean the front brakes and ensure that the pads are not jammed / trapped in the calipers
Ksports do get some bad press but are generally very reliable if maintained correctly we find

something like Z-rated PFC's would be a better fast road option

SteveKozy

Thats a great starting point guys. I'll get the brakes stripped and cleaned and as the pads are half way i will purchase a new set - certainly the cheapest and easiest avenue i guess.

In regards to the point about rear braided lines, the fronts were upgraded when the brakes were installed but i know the rears do need changing out. So that can be number two on the list.

Thanks alot. I'll report back when i have got it all done and back together.

stonejedi

iTrader: (51)

I should of stated my friends car is 480 bhp and his pad choice was based on the fact that his car is occasionally tracked and driven very hard day to day...plus he is not too bothered about noisy brake pads or dusting...As has been said above Performance Friction Z-Rated pads are a pad that works but with out the negative side effects.SJ.

SteveKozy

I had struggled previously to find somewhere stocking anything other than EBC for Ksport but managed to find a few different choices off the back of this thread.

I gave them a good clean and it doesn't pull as much now after a test but i think this may be caused by some lateral bush movement i've got somewhere in the rear/front. So i'm looking at that too whilst the pads are on order.

Will report back.

stockcar

plenty of options on the shelf if you know who to ask............