964 C2 Front Callipers

[King Tiger]

Time to do my front brakes as I cannot get my vernier callipers to sit flat on the faces of the brake disc due to the outer edge burr but still, I measured them at under 26mm... The questions are these, is there any chance that the pad wear wire is reusable from the pads in place now, no light is illuminated on the dashboard, and secondly, the anti squeal shims. How do i find out if the size is 36 or 38 mm and can i buy these from euro car parts or should i buy Porsche only? Help gratefully received as otherwise it is strip them down and perhaps get stuck with immobile car!

 

[Dekker]

The front brake calipers have 4 pistons in 2 pairs. There sizes are 40mm & 36mm and there is no difference in the anti squeal shims wherever you buy them.

I've never been able to take the pad wear sensors off without them breaking into many parts.
I have been able to re-use the shims though.
There is a minimum thickness that the brake discs are serviceable but I can't find it at the moment.

Any burr on the disc edge can be removed with careful use of a grinder. This is useful to do as it helps with the fitting of new pads. Just remove enough for the length of the brake pad and then turn the disc around to line up within the caliper.
Sometimes the edges of the pads need a little judicious grinding because of corrosion underneath the spring plates that cause them to lift.

 

[Melv]

ORIGINAL: Dekker

There is a minimum thickness that the brake discs are serviceable but I can't find it at the moment.

Adrian's book says original 28mm/24mm F/R, so take 2mm off that.

 

[Steve Brookes]

If you're not bothered about having working wear indicators but don't want the light on the dash, you can use the old wear sensors as dummies. Just cut the wire about 4 cm from the plug, separate the two wires, bare them back, twist them together, tape up and plug them in.

 

[colin944]

You should really check your callipers for plate lift. This is a subject that has had a lot of discussion over on the 944 forum. Our Turbo's and S2's have the same callipers as the 964. If you search on the 944 forum you will find loads of posts and how to's on the subject.

 

[King Tiger]

Thank you. The discs are less than 26 mm thickness so will be replaced. I am removing(with heat as necessary) the 8 machine screws that hold the shims in place so that i can remove the shims and clean any build up of corrosion dust. The shims are going nowhere once the brake pads are in position and heaven knows why the bolts were loctited in place. i intend to replace the machine screws with non loctited ones so that they are easier to remove in future. Really there is nowhere for the shims to go even if both bolts drop out which i rate highly unlikely. I shall get a second new wear indicator wire and see whether i need any shim kits which at £26 per set i think, with 4 sets needed are not cheap!

 

[colin944]

I found it much easier to weld a bolt onto the screws to get them out.

 

[vitesse]

When I refurbished my front & rear brakes ,I cleaned & polished the wear plates(they are not really shims at all ) -they are also stainless steel-I also straightened them carefully & found there was no need to buy new ones -after all,all they do is provide a seating platform so that the pad backing plates don't wear the aluminium caliper bodies.

However I did use Loctite thread sealant -you wouldn't want a screw to work loose & interfere with braking performance for instance during an emergency stop.

I also use the welded nut removal method & used new SS domehead Allen setscrews bought for pennies at my local engineering merchants.

The main problem when removing the original setscrews is the fact that the head socket distorts because of corrosion fatigue--normally a good heatgun should allow removal of screws where the key is a good fit.

 

[colin944]

ORIGINAL: VITESSE

When I refurbished my front & rear brakes ,I cleaned & polished the wear plates(they are not really shims at all ) -they are also stainless steel-I also straightened them carefully & found there was no need to buy new ones -after all,all they do is provide a seating platform so that the pad backing plates don't wear the aluminium caliper bodies.

However I did use Loctite thread sealant -you wouldn't want a screw to work loose & interfere with braking performance for instance during an emergency stop.

I also use the welded nut removal method & used new SS domehead Allen setscrews bought for pennies at my local engineering merchants.

The main problem when removing the original setscrews is the fact that the head socket distorts because of corrosion fatigue--normally a good heatgun should allow removal of screws where the key is a good fit.

100% with you on that.

 

[Dekker]

ORIGINAL: VITESSE

When I refurbished my front & rear brakes ,I cleaned & polished the wear plates(they are not really shims at all ) -they are also stainless steel-I also straightened them carefully & found there was no need to buy new ones -after all,all they do is provide a seating platform so that the pad backing plates don't wear the aluminium caliper bodies.

However I did use Loctite thread sealant -you wouldn't want a screw to work loose & interfere with braking performance for instance during an emergency stop.

I also use the welded nut removal method & used new SS domehead Allen setscrews bought for pennies at my local engineering merchants.

The main problem when removing the original setscrews is the fact that the head socket distorts because of corrosion fatigue--normally a good heatgun should allow removal of screws where the key is a good fit.

I re-used the original spring plates too Colin, after buffing them clean with wire disc.
I found heat and a good tap with a centre punch, at the right angle, broke the thread and allowed me to use a 1/4 drive socket to get them out.

 

[vitesse]

David--I salute you -despite your wealth ,you have a go yourself[]-because of the "corrosion between dissimilar metals"-periodic table & the location of the screws,I also carefully cleaned both the screws & the female threaded socket ,coated the screws with copper ease thinly except the very tip,then applied the Loctite (can't remember the code but it's gel like blue).

Please don't besiege me with the fact that one should use the correct Aluminium paste because it isn't necessarily valid in this case-the idea here is to make the screws much easier to remove next time so that plate lift can be quickly dealt with.( note to lookers on)

 

[Dekker]

ORIGINAL: VITESSE

David--I salute you -despite your wealth ,you have a go yourself[]-because of the "corrosion between dissimilar metals"-periodic table & the location of the screws,I also carefully cleaned both the screws & the female threaded socket ,coated the screws with copper ease thinly except the very tip,then applied the Loctite (can't remember the code but it's gel like blue).

Please don't besiege me with the fact that one should use the correct Aluminium paste because it isn't necessarily valid in this case-the idea here is to make the screws much easier to remove next time so that plate lift can be quickly dealt with.( note to lookers on)

I can't remember what I did with the screws but I remember using some high temp paint on the inside, several coats, so hopefully the corrosion won't return for my lifetime.
What wealth? it all goes on cars and women, well cars in anycase.

 

[King Tiger]

Thank you everyone for the advice given. The job is scheduled to start at 8.10 a.m. on Wednesday February 19. There is double sided tape on the back of the new anti squeal shims. This presumably, is to pull the brake pad ever so slightly off the disc , to prevent squealing,once the brake pedal is no longer being pressed. Does any one have any recommendations of tape to replace that on the antisqueal shims that I do not wish to renew, or should i replace all eight anyway?

 

[mcgc0]

Uh, isn't any tape going to become a gooey melting mess the first sight of hard or continuous breaking??

 

[Dekker]

ORIGINAL: mcgc0

Uh, isn't any tape going to become a gooey melting mess the first sight of hard or continuous breaking??

I don't think he's talking about Poundland foam double sided tape Marcus

 

[Dekker]

ORIGINAL: King Tiger

Thank you everyone for the advice given. The job is scheduled to start at 8.10 a.m. on Wednesday February 19. There is double sided tape on the back of the new anti squeal shims. This presumably, is to pull the brake pad ever so slightly off the disc , to prevent squealing,once the brake pedal is no longer being pressed. Does any one have any recommendations of tape to replace that on the antisqueal shims that I do not wish to renew, or should i replace all eight anyway?

I didn't need to use anything the last time I replaced the pads because the shims were still tacky.
However I do have some high temp silicone sealant which I would have used very sparingly. I would also have done a test on it 1st to see what happened when it got very hot as I wouldn't use anything that might melt and run around the calipers. Ask around the brake specialists and see what they recommend.
3m's Double-Coated Tape 96042 is the stuff but no idea where to buy it in small quantities.

 

[King Tiger]

On dismantling, the stainless steel plates top and bottom were lying flat against the Callipers, with minimal corrosion distortion. The brake pads were entirely free to move laterally[], once we had eased the pistons back with a lever. The wear on the pads was minimal compared with the new pads which I had purchased. The discs were in good condition with small burr on the outer and inner edges. Result: we put everything back together and will have another look in six months time.