Caliper/rotor alignment?

[BrokeMyCar]

I replaced my front brake-pads today and was surprised to find that my front right caliper was off-center from the rotor. So much so that I couldn't fit in a new brake pad there!



Caliper spacing - YouTube

Does anyone else have this problem? Any adjustments for it?

I ended up leaving one of the old pads on the tight side, and after the new one wears down a bit I'll swap it in.

Thanks,

Babak

[ivangene]

want a tool... I will send you one for free...

PM me your address...
Ed

I have to warn you .... my tool needs a little adjustment on the size.. I will trim it off before sending...I need to re-do this one....learned AFTER sending a bunch out.

[Brown747]

Trade you a coupler for a brake tool!



Thor

[ivangene]

LOL..you are welcome to one Thor....remind me when we get together!

[timmy2]

You can mail me one too. I'll trim it myself if you point out what needs removing.
I'd trade you a coupler but I plan on using the one you sent for a long time!

[ivangene]

OK Dennis, i will send you one...your address is still on file from the coupler.....

from the best info i have they are about a 1/4 inch proud on the thickness...I will toss a handful of them in the mill tomorrow and trim of a bit....please let me know if they work....I feel bad I send these out to a lot of people before finding out they had an issue....

With my calipers I aligned them off the car so didnt notice they didnt fit right

E

[Walt Fricke]

If I am doping out that video properly (stills might have been better), the "tight" side is the inner side of the caliper. You can move the caliper itself farther in by putting washers as spacers between the caliper and the steel ears of the axle spindle housing to which the caliper attaches. Experiment a bit until you get it centered. If you don't have to move it much, you can use the existing caliper mounting bolts. Or you can get new, longer bolts.

But before I'd do that, I'd want to hunt around some more. Stock calipers on cars in stock spec accept the A caliper pads at full thickness. The only pads which would be too thick would be the old S caliper pads - S calipers were wider, and so could accept thicker pads. A mismatched set of pads would be low on my list of suspects, and I suppose you measured what you got when this came up, and they were all the same thickness. So something is wrong here, as this is not normal. That is, new pads not fitting is not normal. I don't know if Porsche carefully centered the rotor - as long as the pads slide in that does not really matter.

The fact that it is only on one side also suggests there is some other issue. What could that be?

If the brake rotor bolts (the ones which hold it to the aluminum hub) were loose, the rotor could move inward. But I'd think the rotor would also be and feel loose.

If somehow the races of the inner wheel bearing were very worn, the rotor could move inward. Or if the balls got ground up? But I'd think you'd notice a very loose wheel, or hear noises, or something. Mushy brake pedal, also, from wobble kickback of the pistons.

You don't say what car this is. If an SC, if you replaced the rotor with the thicker ones for a 3.2, that could cause a problem. But this is a brake pad change, so you'd have found that out at once, I'd think. And you'd have the same problem on both sides.

But my suggestion would be to pull the rotor and hub off and look for what might have changed dimensionally due to wear. At least tug and pull on them.

And I assume you got the piston fully retracted? You ought to be able to push it back flush or very close to that, I think, so nothing sticks out.

Alas, I don't think this has anything to do with the clocking of the cutouts on the ends of the pistons, which is what those tools are for.

[BrokeMyCar]

Hi folks,

Thanks for the suggestions!

@Walt: The caliper wasn't loose when I was working under it, the car is an SC, I was able to get the piston retracted, but it was a little proud of the surface.

I wonder if one of the pistons was stuck, and so the rotor was being pushed the whole time. The brake-pad on the too-wide side was more worn than the other ones. When I go in to swap the brake pads around I'll play with washers to get it centered.

Thanks all!

Babak

[Walt Fricke]

You don't need much clearance with fresh pads. Tight squeeze plus a hair. They will wear soon enough.

Now might be a good time to pull the calipers, and clean and inspect them. Not much to them, not too hard to do, and plenty of write-ups here on how to do it. Maybe it's in Wayne's 101 Projects too?

I've been working on my cars long enough now that I know what works for me and don't have to think much, so I have lost the mental picture of just how far in an A caliper piston can go. I know that when I use titanium backing plates (thin plates cut to the outline of a pad between the pad and piston) on my SC for racing, I can't get a fresh pad to fit. I have to wait for a little wear.

[hcoles]

if they don't easily push back to I think flush or close or at least the same as the other side, I also suggest as Walt to pull'em out and disassemble/clean/re-seal/etc. If you decide to do this you can use the pedal to get the pistons almost all the way out before pulling the calipers, keep the spacing even and one will blowout but not before they are both almost out

[911pcars]

Same situation on both calipers?

Do both pistons move? If only one pad wears, that's a sign the opposite piston isn't moving under hydraulic pressure.

Using the worn pads (or equivalent) as a spacer, insert a lever between the rotor and the pad and force each piston inward. With pads still in place, press on pedal and see how the pistons react.

Sherwood

[Andy911sc]

Is that the tool for piston alignment. If so, I am going to be rebuilding my calipers here in the next month and would love one of those tools.

[hcoles]

you can make a tool out of almost any material, I cut up some plastic sheet I had, the key is to get the angle and orientation correct, it is nice if the gauge slides in on the flat ledge on the caliper as reference for the angle.
What bothers me is why the pistons move around even with the booties on them.

[eastbay]

bearing spacer missing?

[Walt Fricke]

Eastbay - there is an interesting thought!

But he says he hadn't had this problem before.

Though if this is his first pad replacement since purchasing the car, that would be worth checking out.

But I don't know if things will go together and work if that piece is missing. And is it a spacer? I have always thought of it as the surface for the seal lip to seal on. For sure the grease would escape if that were missing.

I'm looking at a spindle I pulled off of a bent strut, but whose innermost piece I pried off back when. It's been long enough since I pulled a front bearing apart I'm unsure what limits the inward motion.

[911pcars]

The answer could lie in a recent thread on upgrading calipers.

Rotor Clearance

Sherwood