Bad Brakes!

quattro

quattro

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Staff member
My lovely, rebuilt O/S caliper last July

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Is not so lovely any more :shock:

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The large piston has fluid in the dust seal, and the smaller ones are leaking so much fluid that BP are asking for suggestions :shock:

The disc has been soaked, pads are ruined (green stuff ones too), and I am a bit miffed.

They have only covered about 1,500 miles. I am a little concerned at the state of the pistons, they have a scoring around them

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And they also seem to be slightly ribbed :?:

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It's more the leaking I am worried about though, than what they look like. Has anyone else seen anything like this? or have I rebuilt them badly? Can you rebuild them badly? Bit confused here.

I bought these pistons and the new seal kit from a reputable supplier btw, so they aren't cheapies.

Any ideas?

Richard
 
Ribbed - for her pleasure .................

Serously ,I reckon you've been sold duff pistons , they should be smooth
Are they a loose fit in the calipers without rubbers fitted , if so maybe someone has been skimming old pistons and reselling them
What are the caliper bores like and the groove the seal sits in ?
 
Me too Dave :(

I'll take some pics of the bores tonight.

The supplier has agreed to send me a new set of seals FOC but claims never to have had a problem with the piston apart from someone sending one back last year because the chrome had a nick in it. (That was me as well :shock: )

I do feel that confidence in ones brakes is rather important so will be getting a set of stainless pistons made up.

As I have already fallen out with one large supplier and now we have lost Ian, I might just have to get the stainless ones, accept the seals and put it down to bad luck.

Anyone use stainless pistons here? any good?

Richard
 
If you ask me, it's using all this non-standard stuff.
Use what is engineered for the car and it will work. A bunch of hot rodders and green stuffers can not possibly know it better than Spen King did.
 
Junkman said:
If you ask me, it's using all this non-standard stuff.
Use what is engineered for the car and it will work. A bunch of hot rodders and green stuffers can not possibly know it better than Spen King did.
Click to expand...

Why would the pistons/seals leak if there are different brake pads?

Not quite sure what you mean

Richard

BTW - after looking through a box of bits that came with the car I found a set of green stuff pads which the car was originally advertise with, and after inspecting the pads on the car, they are standard ones.
 
It's a shame to have that problem after replacing the pistons, because I can't ever remember coming across a leaking front caliper, even after freeing off seized pistons they always remained leak free. They had to really, there way no way they could compete with the rears..... :LOL:
 
The marks look strange :shock: . I rebuilt both my front callipers around april/may last year, with what look to be the exact same pistons (and quite possibly from the same batch and have had no issues. In fact I took the car out yesterday for the first time in months and they worked nicely. When I fitted them they went in very smoothly and progressively. The marks appear to be approximately the width of the inner seals, and I would guess, are around the position they would fall. I take it you can't feel any edges in the bores? Strange that it should effect every piston!
Regards,
Dave
 
Looks to me like cr*p chrome, they don't look particularly good even on the good areas. Then it looks like the chrome is being attacked on the seal lines.

Go with the stainless pistons, should sort it out.
 
i'm afraid, Junkman, that there are lots of things that can be improved on the P6. It would be pretty tragic if there weren't after 50 years! The brakes are most certainly not imune from that. In any case, you can't buy some of the brake components - most notably the pads - to the same specifications as were used when the cars were new. Crushed horse bones and asbestos are not the most popular ingrediants these days. Oh and you can't buy petrol to the same spec as these cars were designed to run on either. So that's brakes and engine up the swannee!

Richard, your pistons are extremely disappointing. It is just possible to argue that the marking on the pistons could be due to "shimmer" eminating from the grooves and dimples on your Rossini discs. However, Lucky has not suffered from this and, as you know, he has microgrooved discs. They are definitely audible under heavy braking so ought to suffer similarely if that were the cause. Maybe I speak too soon? I think it is more likely to be significant that the seals have failed whilst the car has been standing for a while. Although I can't think of any particularely obvious mechanism.

Chris
 
3 pistons is to allow bigger discs / calipers to fit the wheels The side with 2 pistons is off a smaller radius (?) than the other side
But on that theory , why not have 4 pistons ?
 
Thanks all

I have measured the pistons at 40.32mm and 57.06mm.

Anyone know if these diameters are correct as I am going to get some stainless ones made up and want to make sure they are spot on

Cheers

Richard

I can't find the original ones :(
 
chrisyork said:
you can't buy some of the brake components - most notably the pads - to the same specifications as were used when the cars were new
Click to expand...

Not sure about the fronts, but you can buy the same spec (yes asbestos) rear pads as the original...I have them on old Alfred. :)
 
quattro said:
Thanks all

I have measured the pistons at 40.32mm and 57.06mm.

Anyone know if these diameters are correct as I am going to get some stainless ones made up and want to make sure they are spot on

Cheers

Richard

I can't find the original ones :(
Click to expand...

Hi, I bought a set off of Ebay quite a while ago but have yet to fit. I have measured them and
they come out at 41.40 and 57.21 the small ones are chrome finish and the box label says
Jag e type. The larger one are matt black finish. Both claim EU/UK manufacture.

Make of that what you will!!

Colin
 
Indeed, that would make a big difference.

I have ordered some stainless ones to fit and we'll see what size they are when they get here on Thursday.

Richard
 
quattro said:
Junkman said:
If you ask me, it's using all this non-standard stuff.
Use what is engineered for the car and it will work. A bunch of hot rodders and green stuffers can not possibly know it better than Spen King did.
Click to expand...

Why would the pistons/seals leak if there are different brake pads?

Not quite sure what you mean

Richard
Click to expand...

The higher friction coefficient could lead to resonance. That could score the pistons.
 
The original pistons, even though they were rusty, did not leak.

Even with the better braking of the Rossinnis, they should last more than 1,500 miles.
 
If these pistons were slightly undersize as it appears they were, then potential rocking within the bore could easily cause that leaking couldn't it.
 
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