Linksfahrer

I own a WRX MY05 , with standard Brake Master Cylinder and using Standard WRX Calipers.

Recently I have started to believe I some issues with my brakes.

During the summer I did a front caliper Refurb #26297 as the twin pots were starting to stick , so I did the front seal kit and polished the pistons and pot bores and used new DOT4 fluid
I dusted down my Ferrodo 2500 pads and refitted them.

before going in to the MOT I did have to swap my rear brake pads out ( my Carbon Lorain RC5's were 75% used )
all I could get at short notice were Brembo pads , but I thought this should not make a significant change on just the rear wheels.

The car went through the MOT fine , but I'm not certain that tells me the whole story.

Subsequently I have had couple of hairy situations when really have had to press extremely hard on the brakes , and have only just pulled up in time.
I can feel that I am losing a considerable amount of brake performance somewhere.

Now I could see again if I have still air in the pipe system , but I thought first I would just compared results from the Brake testing history,

The results from the 2015 and 2018 tests were interesting , as although no changes were made to the system in this period,
it seems the performance did drop considerably. I observe a drop of circa 100 daN on both axels




Unfortunately I don't have UK MOT measurement , actually I don't know if we even do them and protocol them , but IMHO it would be a good idea,
certainly the performance of the brakes has worsened since the MOT in Aug and is now unacceptable for me.

So the question to you all .

Does anyone have similar experience of such performance deterioration, and if so did a Master Cylinder seal replacement ( kit # 26471 ) resolve it ?

Note I am not looking to upgrade anything here ( no suggestions needed on that thanks) purely to restore the performance I once had.

1509joe

iTrader: (2)

Push your pistons back in and check your wheel bearings.

Linksfahrer

Well I expect you think the pistons are sticking , but actually testing with a screw driver they seem to move back in OK , actually pretty smooth.
that didn't surprise me really as that's been fine since I cleaned up the pistons did the new seals.
On wheel bearings, yes know what you mean and these were both renewed last year as I had probably overheated then following the binding issue caused by the sticking / stuck piston.

I just need to find the culprit , preferably before throwing more expensive parts eg master cylinder / brake booster etc etc at the problem.

Id be keen to hear from anyone who has resolved poor performance with new master cylinder / boost assembly or just with a relatively cheap new master seal kit #26471 ,
As I think perhaps a worn seal set might maybe flex and be a possible reason why the pedal feels woolly , the smoking gun here is that the brakes used to be fine , and clearly have deteriorated over time.

1509joe

iTrader: (2)

No the reason I said push the pistons in is they hold the wheel straight and if the bearings are suspect you can't feel the slack in the bearing. Is your pedal soft and if you release and re apply is it any better.
Have you excess travel in the pedal.