Brake help, Caliper shims

You really can't now but it's not hard to fix. They are used to keep the caliper parallel to the disc. Install the caliper w/o the shims and measure the distance between the disc and caliper on either side of the caliper at 4 points and see where the spacers are needed. Tedious work but easy.

 

http://www.ferrarichat.com/forum/showpost.php?p=141518448&postcount=11

 

Any time. Let me know if you get stuck. Pm me and I'll give you my number.

 

If it is too difficult to tell if the disc is not parallel most would say don't worry too much. What will result is uneven pad wear and perhaps shorter disc life but nothing catastrophic. By the looks of your photo it seems alright. What I can't tell is if you compressed the caliper piston all he way into the caliper body before you installed the new pads and measured.

 

I think the shims are there to corect the caliper piston perpendicularity to the disc face, so that the pressure is evenly applied to the pad/disc and even ware results, with no taper ware.

I will go out on a limb and prognosticate that, If it is close, no problem.

If it is out seriously, that is the perpendicularity of the pistons, then you could have pistons "cocked" in their bores, to the extent that they gaul or score the caliper/piston, because they are so misaligned, that they are binding. This is not a good situation, and frankly, I think not very likely to occurr.

I know of no manufacturer that goes to the trouble of shimming the calipers. We must also remember that ATE does almost all of porsche's brakes and many other manufacturers, as well. From this, i think we should expect a fairly high degree of manufacturing precision.

I will also confess, rather shamefacedly, that i did not measure the caliper alignment, when i put F-50 brakes on the front and 360 brakes on the rear. I have seen no adverse affects or inappropriate ware, even after tracking the car a couple of times, (where i could massively out brake the 360's - when they were hot).

I think Caliper shimming is a sign of Enzo's care and demand for precision. For sure, this is really necessary in high stakes racing, but, for our relatively modest demands, even occasional tracking, manufacturing tollerances are "close enough".

Having blathered on about "good enough", if you find a big handfull of shims when pulling the caliper to do a pad replacement, you might be well advised to put it back the way it came out or better yet actually measure the piston perpendicularity to the disc face, ( just in case the spindle/upright manufacterer slipped a crooked one over on good old Enzo.

Just to clairify an earlier post, it is not critical to have the caliper exactly centered on the disc, but it is improtant to have it fairly "normal", (perpendicular), to the face.

chris

 

I believe that the shims are more intended to correct centering than parallelism (as you'd really need wedge-shaped shims if you use unequal shims). One other point is that 308 and 328 use different brake designs and different wheel bearing designs. On Steve's 308, there are more (and larger) tolerances in the separate tapered roller bearings vs the monolithic ball bearing on Eric's 328, and the 308 being an opposed-piston, fixed caliper (vs the 328 single-piston, floating caliper) is maybe a little more important to have decent centering (i.e., a single-piston, floating caliper is self-centering), but, unless I'm seeing something wrong, your 328 photo shows the disc almost hitting the fixed bracket on one side (nor does the clearance to the OD of the disk to the fixed bracket look great, but maybe that's OK). Maybe the disk doesn't have to be perfectly centered relative to the fixed bracket, but IMO you should have at least a couple mm minimum clearance worst case:
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Yes, that's a much better relationship between the fixed bracket and the disk.