Flexing 996

[bertman]

Some of you will be very aware of the problems that I have had with getting my brakes working as they should,without result
various people have looked at the car including some garages etc,and haven't been able to diagnose the problem.
The car is now in a specialist garage down in dunsfold park where Top gear is filmed where a very knowledgeble bloke called Steve pointed out to me that the 996 calipers are actually flexing apart.
The inner pistons on the bracket side remain still,tet the outer bank is physically moving out when the brakes are applied....by 2-3mm.Hence this might be causing my "spongy" pedal
According to the mechanic this could be due to the calipers being overheated.
remedies include:
a different master cylinder
strengthening the caliper itself

Any help or suggestions please let us know

[Rusty]

Interesting, the design of almost any calliper has to deal with the cleaving action of the pistons as they both exert a bending force on the centre section. If this is excessive then it indicates that either the calliper has been weakened in some way and thus the mateerial has been damaged or it's mproperties changed, or it indicates that one or more piston is not functioning correctly. I suppose you've just got to inspect the callipers as best you can. I've not seen the movement on my identical setup as I've not had someone put the brakes on whilst I've been specifically looking for that movement. Hope you get it resolved.

[twoqu]

Out of interest, what brackets are you using?

[bertman]

Out of interest, what brackets are you using?

Seat cupra brackets (machined down of course)

[s2driveruk]

that doesnt sound good at all....are the ones u have black or red? If red are they a dark red or the normal colour (if on original paint) Dark red would suggest they have been worked hard.

[bertman]

Interesting, the design of almost any calliper has to deal with the cleaving action of the pistons as they both exert a bending force on the centre section. If this is excessive then it indicates that either the calliper has been weakened in some way and thus the mateerial has been damaged or it's mproperties changed, or it indicates that one or more piston is not functioning correctly. I suppose you've just got to inspect the callipers as best you can. I've not seen the movement on my identical setup as I've not had someone put the brakes on whilst I've been specifically looking for that movement. Hope you get it resolved.

Andy if you had seen how much it did flex you would be very surprised if not a bit worried.
Because we are running different master cylinders to what was originally intented,there might be a case of our set ups running a higher load on the pistons.But no one has reported anything like this before
But I would deffo go would with the idea that the caliper has been weakend somehow.
He is going to call a mate of his at brembosport to find out some more info.

[bertman]

that doesnt sound good at all....are the ones u have black or red? If red are they a dark red or the normal colour (if on original paint) Dark red would suggest they have been worked hard.

They are black,so its diffucult to see if they have been cooked

[twoqu]

Well I guess its a possibility that removing that much from a bracket designed to be thicker might be a contributory factor. I doubt when it was designed it was massively over engineered.
Of course that flies in the face of all the collective experience on here!
I would try and eliminate the caliper first by a precautionary rebuild just in case those pistons are seized.
Can't see how you could strengthen the caliper. Wasn't the idea behind the monobloc that it was stiffer than a two piece bolted one. Think I have seen some arguments about this on the Stoptech site.

[bertman]

The side closest to the bracket doesn't move just the outer side,pistons etc were checked and deemed to be working ok.
but a rebuild could be a precautionary measure

[twoqu]

There you go:

http://www.stoptech.com/tech_info/wp_monobloc.shtml

Actually I have seen the larger 996TT monobloc used in a Movit conversion that used a 12.9 cap screw to hold the pads in rather than the usual pin!

[twoqu]

The side closest to the bracket doesn't move just the outer side,pistons etc were checked and deemed to be working ok.
but a rebuild could be a precautionary measure

So can those inner pistons be retracted? If they can then obviously they are not seized. Depends what you mean by not moving.

[bertman]

thanks mate will have a looksie at this

[bertman]

So can those inner pistons be retracted? If they can then obviously they are not seized. Depends what you mean by not moving.

Inner pistons can be retracted,two were a bit sticky but have been sorted.All I was saying was that the actual body of the caliper which the bracket is bolted to does not show any signs of flexing,just the outer bank physically moves,can be seen easily when foot pedal applied.
You'd expect to see a split or crack down the middle of the caliper the way it was moving

[denniselbows]

well i think you have just summed up what has just happened to me. with the engine off the pedal was rock solid started the engine and with the extra presure from the brake booster hydraulics the pedal went spongy i bet i have the same thing as you . have you had to replace many discs? as i am on the second set in 12 months of up grading and they are pretty much ****ed as well .

[twoqu]

Have you ever replaced the wheel bearings in your ownship of the vehicle?