Porsche brakes at last

[Stick Insect]

Hi Dan,

Glad it wasn't anything nasty I was hoping to make new splash guards for mine, I will see how it goes and do a post.

The fronts splash guards can be fitted to the rear for big disk conversions.

DW

[dan_b]

Checked the bolt length too - they're just peeking through the backside of the thread in the disc, so they're ok. Shouldn't fall off just yet!

[Stick Insect]

as long as it's through the hub you are ok.

You don't want a length hanging out do you?


David

[dan_b]

Ok, so I've got rid of the splash guards so no grinding noises anymore, I've bled the brakes again and everythings bedding in nicely. Much firmer pedal feel, good bite, definitely more braking power, and I've still yet to give them any effort.

However, driving to Heathrow and back this morning, after about 20mins of urban traffic with lots of stop start stuff, 30-40mph sort of speed, I start to notice an occassional resonating noise from the front. This goes away if you press the brake pedal ever so lightly.

It feels to me as as if the pads are staying in contact with the disc a bit? Will that cure itself? Is this just because it's all new?
Is there anything I can do to prevent it happening? Will it go away? Am I doomed to have something wrong with my brakes?

[Beetie]

Are the discs grooved or drilled at all? They sometimes make a slight noise as the pads go past the grooves/holes.... If not are the pads free enough in the pad carrier?? If not then they may stick 'on' slightly.... could be a few things, just dont go touching them after a drive to find a 'loose' bit because you might have a 'loose' bit of skin hanging off your hands!!!

[s2avant]

My recently fitted porsche brakes where doing the same last night. I think it's because they got hot and expanded. I'll be seeing if it's the same later.

If so it's back to garage for a strip down to see whats touching.

Ben

[Alistair C]

Not sure if this is specific for the calipers you have there dan - but came across it on pistonheads

The beakes on the 993 are the same as on the 928, 964, 944 S2 and late 944 Turbo. Essentially they are aluminum calipers, with stainless steel plates on the top/bottom, to act as guides for the brake pade- so the pads will slide on the steel plates not the alloy. Apparently this is because the pads will corrode onto the aluminum calliper if not.


Unfortunantly moiusture can get in between the calipers and plates, corroding the calliper and lifting the plates slightly. This will restrict the movement of the pads, and prevent the excellent braking they should have.

Solution: remove the callipers, remove the plates (these need to heated), remove the corrosion and replace with new plates.

Or file down the brake pads slightly to make the clearence.

The latter is cheaper, but is it the RIGHT thing to do??

Not sure what the special paste is, but the plates do need loctite glue to keep the screws in place (its removing this which makes the heat necessary).

They are being truthful, and the difference in braking ability will be immense. Personally, if the price is £300 plus VAT for all four wheels its a very good price.

911 and Porsche world did an article about this problem, March 2003 p96-99

[dan_b]

When they say "plates" are these the "pad pusher" things that sit between the pistons and the back of the actual brake pad?

[Alistair C]

Dan - i've not actually seen the calipers they are talking about but I think they are on about some kind of guides which ensure the pads are held still & are only able to move in one plane (ie towards the disc).

However I'd guess that if this was the problem - you'd have noticed the pads sticking when you first got hold of them.....

[s2avant]

There is a plate at either end of the calliper that the pads sit on. My callipers where refurbished before fitting so had all the corrosion removed and new plates, screws etc.

The noise came back after some town driving today. I spoke to Jason about it and he says the clearance on the n/s calliper was very close. I gues it's back to the workshop for a bit.

Ben

[jubjub]

I get this problem on my motor. When you crawl along at slow speeds it makes an annoying noise, like someone blowing on the top of a milk bottle!!I had my callipers overhauled a few months ago and had the new plates fitted. Trouble is tho,noticed it starting to make that sound again

[Stick Insect]

Sorry to hear about the problems.

There are 2 distinct types of Porsce Calipers we are interested in.

1/ 968CS as fitted to RS2 as standard under this category fall 993 Carrera, 928S4 etc. These are aluminium 4 pot calipers and are made from 2 castings bolted together.

I picked up 1 x 993 carrera caliper ( black) from a scrapyard. The caliper pads were so stuck into the caliper that I had to use a 2 foot pry bar to lever the pads out. The problem comes from the caliper pad guides/holder. Each caliper has 2 x stainless steel plates against which the pads slide.
Water and dirt get behind the stainless steel plates and form electrolytic corrosion. This a white powdery stuff ( happens to your alloy wheels as well). This corrosion expands and forces the plates out of position. this then makes the pads stick ( usually on the disk, making a grinding noise!).

The fix is to remove the 2 hex screws holding the plate into position, clean and scrape the corrosion away ( or bead blast it if you have the facilities) and then refit the plates. Problems occur with the removal of the hex head screw, this is usually corroded and may need to be drilled out. Heating with oxyacetylene usually helps. when refitting the plate a neutral paste such as computer heatsink or thermal silicon grease.

2/ The 996 monobloc calipers (including Boxter S and all modern Porsche calipers) are aluminium 4 pot calipers ( Cayenne etc. are 6 pot) made from one casting. The pots fit in holes machined in this casting ( still haven't worked out quite how this is done!) Must be a pretty flash CNC Milling machine with a special head.

Porsche have dropped the split caliper system in favour of the Monobloc afaik. This is to reduce problems and the monobloc is more rigid. I think the pad location system has changed as well.

HTH
D.

[dan_b]

Just thought I'd report on my brakes again...
Having driven about another 300 miles since the above post, they seem to have stopped doing the slight sticking/resonating noises, which is good.

I also had to stamp on the anchors rather heavily last night - was on the M25 doing 70 in lane 4 when the whole thing just stopped, all 4 lanes jamming on the anchors at once. Was real emergency stop time. Let's just say they work bloody well.