Front Brake Caliper Adjustment

OK, so my ongoing project to bring a long stored 308 back to its best..... need some more advice.

There was a slight squeal on the front left caliper, so I thought I'd strip and clean the front brakes and throw some fresh pads in there as well in case the existing ones had gotten rust embedded into them.

I pulled the pads first, and the outer pad brought a shim with it. Stuck between the pad and the disc, no doubt the squealing. I'm guessing its a caliper shim, although at this point I've not removed the calipers yet. I'm going to do this week if I can get some shims in the post from Superformance.

So 2 questions.

1. I can't find the procedure for aligning the caliper. (i'll admit I struggle with the search on this forum, I usually try google and then pick a result from this forum from there but even this failed me! Perhaps I'm doings something wrong)

2. The disc is running extremely close to the caliper. As part of adding shims/alignment, are you meant to centre up the disc? Either way I'm sure its not meant to run as close as it is.

Sorry, I forgot to take a pic.

 

Many models intentionally have a thin metal shim between the piston face and the pad backing plate to reduce noises (with a little brake grease applied on the interfaces), and sometimes the "shim" is bonded to the back of the pad (and models that do have them have them on both sides). Don't see such shims in the 308 SPC, and having an asymmetric shimming has to be some outside fiddling.

There should be other shims, item 3 here:

https://www.ferrariparts.co.uk/diagram/ferrari/308-gtb-gts-usa/033-calipers-for-front-and-rear-brakes

between the caliper and the spindle upright, to center the rotor in the caliper opening by selecting the proper thickness. Maybe someone forgot to install them, or put them under the bolt head instead of between the caliper and the upright (although that is where extra shims can be stored if ever changed, and often manufacturers have a standard shim "set" for every car and the Assembler puts the needed one(s) between the caliper and the upright, and puts any extras under the bolt head). They are a bit of a bugger to keep in place when installing the caliper mounting bolts.

 

Hi Steve

Thanks for that. It was definitely a caliper shim rather than a large pad backing shim. Basically like a thin M8 flat washer, and it was between the pad and rotor, not the pad and the piston!

OK, so you do set the rotor centrally within the caliper, you don't just ensure there is a suitable gap rotor to caliper? In my car that's going to need (I'm guessing a little here as the car is back together) but around 2-3mm of spacers. The rotor is a hairs breadth from touching the caliper as it stands.

 

OK -- We'll put that in the TOTALLY BIZARRE file .

Can't say that I've ever seen a specific tolerance for how well-centered the rotor needs to be in the caliper opening in the F documentation -- they tend to just say "centered". You can see in the SPC parts list that the quantity for the spacer 3 is four for both front and rear, and the max thickness is 1mm, so a 2mm adjustment (using two spacer 3 on each bolt) is not crazy. The whole "centered" thing is to: 1) ensure the rotor doesn't rub the caliper (so having some gap on each side is required), but the other goal 2) is to ensure the pistons on each side extend about the same amount out of their bores as the pads wear. It sounds like you are in an obvious "not right" situation, so any improvement in the rotor centering would be a plus. Do you have no spacers presently between the caliper and the spindle upright, and having some there would improve the rotor centering? If so, I'd say someone just (wrongly) left them out the last time it was taken apart and reassembled.

 

Steve, when I had my front calipers rebuilt by PMB Perfomance, I struggled a bit putting that #3 washer/shims in place. I didn’t know the purpose of them before (I do now) but I know it’s there for a reason that’s why I put them back on.

 

My 78 308 brake shims… used superglue to attach shims to caliper.


Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login

 

On Gt4 there is a washer behind the caliper on the fronts.

 

Perfect, thanks all. It just seemed a bit odd having such a large stack of shims as I'm going to need to centre up the rotor in the caliper but I guess that's a Ferrari for you. Nothing is usual. I've ordered a load of shims from Superformance. I'll swap out the bearings and refit the calipers properly. Will get some images whilst I am it it.

I've found a few areas now where maintenance on this car has clearly been carried out by someone with no Ferrari experience, so a shim dropped into the brakes isn't out of character!

I've read about aligning the pistons to the correct angle to prevent squealing? Another new one on me. Never done that on any other car I've worked on!

 

I believe it’s caliper shield plate then bolt then washer. It’s pretty tricky. When tight check to be sure the washer is still there. Or find away to hold the washer there. I sued a drop of CA. From memory I think the washer is 2mm.
BUT I’m not positive

 

Not sure i worded the order correctly. But the washer is between inner side of caliper and mount

 

If you need a bunch of shims to get the caliper centered I'd be looking for something amiss. Maybe it's just a bunch of tolerances adding up for that result or maybe something is wrong. Since the car is sort of unknown and with a random washer in a weird place I'd not rule anything out.

That said, the only thing I can think of to look at is the inner bearing race not being seated all the way. This would move the disk outboard relative to the caliper. Is that the direction of you alignment issue?

 

My initial eyeball measurements were rather out! The total gap across both sides was around 3.5mm. New wheel bearing did move things a fraction, it took a single 1mm shim
In the end to centralise it.

Image shows after.
Image Unavailable, Please Login

 

That's normalish -- because there is no such thing as a "negative spacer", the nominal design will include having a spacer there so adjustment can be made in both directions.

 

And before
Image Unavailable, Please Login