C5 Rear Calliper

[UVG]

Hi Guys
I’m looking for a second opinion...or a third or fourth opinion
I am replacing the rear calliper on my C5 (as I have nice wedge shaped brake pads)
I’ve read the different views on a couple of forums about the corrosion created by the different metals and the instructions in the Haynes Manual to use a Loctite sealant between the calliper and the swinging arm
I read that some people have used a thick plastic to keep the two metals apart and I thought that sounded like a good idea but the Haynes Manual says the sealant has to be able to cope with 200 Celsius that’s a bit toastie for a bit of polythene
So I bought a sheet of 0.8mm PTFE because I know its tough stuff its hard wearing and has a melting point in excess of 200 Celsius
So that’s the background here’s my problem and the bit I need some opinions on:
The calliper stops the car because it cannot move and it grabs hold of the disc which is going round at an alarming rate. The shear forces must be quite large so the calliper needs to be securely fastened to the swinging arm
So what does the holding? Is it just the shear strength of the bolts or does the friction (that is created by the tension in the bolts) between the calliper and the swinging arm play a major role because I’m about to put one of the slipperiest substance known to man in between them
So I still think the layer of PTFE will do a good job of reducing the corrosion but that’s not a lot of use if I rip the callipers off the swinging arms
So your opinions please....
Cheers
UVG

[Stickyfinger]

Hi

For what it's worth.........PTFE is not great under compression, under high pressures such as the caliper to swing arm joint I would not use it.
It breaks down (granulates) and then suffers flow, the joint will loosen.

Really a gas tight VITRON type would be best (225.Deg) but you have to isolate the bolts as well however or they will corrode at a faster rate. (Which is why Citroen advise coating the whole bolt with Lock-tight I think)

My advice would be, thickly zinc prime both surfaces. allow to dry and apply any high temp sealant with a spreader and bolt up. Keeping out moisture is the key, that and an clean up/re-apply at the yearly service.

[UVG]

Hi Stickyfinger

thanks for the info as you say if it breaks down then the joint will loosen which really isn't going to help

the sheet I have bought is only 0.8mm which sounds really thin but feels quite thick so if it breaks down that I be making things worse instead of better

I was planning to Loctite the bolts like Citroen recommends but to make sure they were tight not for corrosion protection as you suggest but I think you might have a point

all this trouble to avoid corrosion make you think it might have been a good idea to make it all out of the same stuff

Cheers UVG

[Bandit12]

I've been thinking on this same issue as i've just replaced the rear discs and pads for this reason. Seems to me all that is needed is a think layer of something that prevents corrosion wont shrink and can handle big and rapid temperature changes.

Would spraying caliper and swing arm joint faces with high temp engine paint, allowing to dry before assembly do the trick? Engines are alloy so the paint should stick.

I only ask cos as a biker i have a can or 2 in my possession

[KP]

Best option and cheapest is to really clean the surfaces and then cover them in copper slip. Then before you mate them up stick a piece of grease proof paper between them as this can handle the temps, it handles temps well over 200'c and if your rear brakes are getting that hot at the rear they are either fecked or you are towing or have your back axle at load capacity.

[darbuck]

the greaseproof is a good idea as im doing this job at the moment myself im going to add that modification to the list.

[Stickyfinger]

Copper will add to the corrosion as it will react with the alloy, the grease that carries it will help prevent it and it will not fully seal out moisture......I still think a paint/sealant/seal is better than an anode.

IF you really need to seal it up you should get some Tef-Gel
http://www.duogen.co.uk/page62.html" onclick="window.open(this.href);return false;

[MikeT]

Pagid Cera Tec brake grease, contains no copper.

[darbuck]

HI Sticky ,
didnt consider that 'have painted both calipers and arms'with metal paint used it before on a primera never any problems after.

[Stewart(oily)]

I made visqueen shims for mine, no problems in 10,000 miles, I greased the bolts too, the big lump of iron that is the rear arm ought to make a good heatsink, I reckon a chunk of milk carton would do the job.

[UVG]

well guys I did ask for your opinions
now I have a few different suggestions which all sound great
I've slowly been going off the idea of the PTFE since it arrived
so now I have to decide which of your many ideas I should use
because there wont be room for the wheel I use them all
I wont be doing anything till the weekend so keep those suggestions coming
I'll let you all know what I end up doing....

[Hell Razor5543]

Grease proof paper is probably the best choice, as it is very thin, and can manage the temperatures generated by the brakes (and is easy to do!).

[Stickyfinger]

The wax will go crystalline under temperature/time, it will crack and the paper will wick moisture. (You never use a wax/paper gasket on a high temp union/high pressure).

That's the rule of thumb anyway, would it work out that way....who knows ?, and anyway, its the bolts that are the real pain

[Hell Razor5543]

My cousin suggested baking parchment. I will see what that is made of, and post it up.

[wurlycorner]

I have to tackle this job someday soon.

I'm used to the similar problem on Xantia's, but it sounds to be worse on the C5???

I used silicone grease between the caliper and the arm when I 're-built my last one.

Reading these threads make me not look forward to it at all