Getting the drums off your Z

[Ron Earp]

I'm making a list of items I have to accomplish to get the old Z ready for track. One thing I'd like to do is replace my drums, or at least inspect them.

Last year when this maintenance item came up it was hell. The shoes were fine and had pad material, but had worn the drum a bit so that the drum could not be removed. Jeffrey ended up cutting the drum off the car.

I'd like to not repeat that episode.

So what tricks are there for getting the drum off? My car still has the parking brake and I use it regularly to hold the car in place. We had it disengaged last year.

We have been successful with a slide hammer before and I've considered heating them up in order to help a bit. But I don't ever remember drums being this hard to remove before.

[pballance]

Ron, FWIW I had this problem "back in the day" with my street Z. About the only thing you can do is adjust the shoes in so you know they are clearing the drum and heat the hub area with a torch. then apply a dead blow hammer to the edges of the drum to try and knock it loose.

I am not a metallurgist but I think the problem is corrosion between the steel of the hub and the aluminum of the drum. I think the "corrosion" is a direct result of the amount of heating that takes place between the hub and drum under race conditions. I have put thin layer of anti sieze on mine and so far (knock on wood) I have neither contaminated brake linings and the drums remove fairly easily. I forgot to add that if your backing plate is ventilated you can use a punch and hammer to apply some direct pressure to the drum to help break it loose.

YMMV,
Paul

[x-ring]

Depends on why you can't get the drum off. There's two common reasons.

The aluminum drum can galvanically (sp?) bond to the steel hub. When I was younger I had a chum that drove a Fiat coupe. Back then we called the effect Italian LocTite. If this is your problem, and it commonly happens on Zs frequently driven in the rain, the best thing to do is whack the face of the drum a few times with a 5 lb dead-head hammer, try a little heat, more whacks, more heat, etc. Eventually it will come off.

The other common problem is that the shoe can wear a ridge in the edge of the drum, and then the shoe won't let the drum come off. Will the drum wiggle in relation to the hub, even a little bit? If so, here’s what you do:

Use a hole saw to drill a 0.75” hole in the face of the drum. On the drum face there should be a lead plug blocking off a ~0.25” hole. Knock the lead plug out and locate the new hole centered there. Pull the pilot drill back as far as you can so it doesn’t hit anything inside.

Once you have the drum drilled, spin the drum around until your new hole lines up with the adjuster mechanism. Poke a smallish screwdriver in and gently pry back the ratchet so you can spin the adjuster wheel backwards with a second screwdriver. A couple of turns and the shoes should be retracted enough to pull the drum off.

Once you get them off, you can grind (or machine) he ridge off, and maybe even leave a little chamfer so it doesn’t happen again.

[Ron Earp]

Hey Ty,

What you wrote essentially describes what we had to do last year, except, it got a lot uglier than that. The drum is is sticking due to the lip on the drum, not the hub bonding to the drum in the center.

I think I'll take to drilling a hole in my new drums before installation, and, doing as Paul suggests and put some ventilation holes in the rear to help knock it off from that direction. It is definitely a pain in the ass.

Ron

[pballance]

Ron, FWIW, my OEM Brembo drums already have a hole that I can block the ratchet and back the shoe away from the drum. You should be able to use it as a pilot for a larger hole. I was using a small screw driver to do like Ty says and backing the shoe away. Hope that helps. I think that is the "accepted" method from the Service Manual anyway.

[Parrish57]

I've had to do exactly as Ty said in years past. It's a pain but you can save the components by doing it his way. It's my belief that having the parking brake active leads to this condition. I've started loosening my drums after every race weekend to prevent having to drill them, especially when storing the car for the winter.

[Ron Earp]

I thought the parking brake was an integral part of getting the Z shoes to work worth a darn under racing conditions? That is, the adjuster kept the shoes near the drum so that you'd get some rear action.

R

[x-ring]

I thought the parking brake was an integral part of getting the Z shoes to work worth a darn under racing conditions? That is, the adjuster kept the shoes near the drum so that you'd get some rear action.

R

That's how I do it.

[x-ring]

Hey Ty,

What you wrote essentially describes what we had to do last year, except, it got a lot uglier than that. The drum is is sticking due to the lip on the drum, not the hub bonding to the drum in the center.

Yeah, I've never had the drum galvanically bond to the hub on the race car, but I have had it happen on a street car, more than once. A little anti-seize, as pb suggested, may be just the thing on my DD.

I think I'll take to drilling a hole in my new drums before installation, and, doing as Paul suggests and put some ventilation holes in the rear to help knock it off from that direction.

Hmm, where does it say in the ITCS that you can drill your drum face? LOL

That would be right on par with a 'no washer bottle' protest. <_<

It is definitely a pain in the ass.

It is, and predrilling may be just the cure.

[JeffYoung]

Ty -- "Brakes may be ventilated" or some such. It's what in my view allows the drilling of the backing plates as well. Not that I have done that, cause I haven't....lol

[pballance]

Here ya' go Jeff,

b. Backing plates and dirt shields may be ventilated or removed.
Air ducts may be fitted to the brakes, provided that they extend
in a forward direction only, and that no changes are made in
the body/structure for their use. Brake rotors and drums shall
not be modified other than for truing within manufacturer’s

specifications

Sec 9.1.3.6 (b)

Washer bottle time..........

[JeffYoung]

Got it. So, can ventilate the backs, but can't cut the fronts.

I need to cut some holes in teh backing plates on teh TR then -- I imagine I could even duct up some air in there.....

[x-ring]

Not that I have done that, cause I haven't....lol

Naw, me either. That's why I don't know exactly where to drill the hole. And to be careful when the hole saw breaks through. And that holding a shop vac nozzle up next to the hole saw keeps the metal chips out of your drum. :cool:

Let the scribbling begin...

Seriously, though, you can do the same thing through "ventilation" holes in the backing plates, it's just a PITA. Especially if you have to drill the backing plate from the back, with the drum on.

EDIT: I just had another thought. There is a hole in the drum face as delivered from the manufacturer. I just checked the FSM and there is no dimension or specification for that hole, much less a +/- tolerance. FWIW...

[JeffYoung]

Oh, I HAVE taken a hole saw to that front hole, but that was only to get to the star wheel to take the drum off. I didn't drill holes to ventilate/lighten it -- I through that drum away when done. It was shot after I Jeffed it up.

The TR drum mechanism is very different. Self-adjusting, and usually the drums just come right off. The Z is much more difficult, but then again, it has way better pedal feel.

[pballance]

It was shot after I Jeffed it up.

Now that is a classic. FWIW In my cars previous life on the left coast, it had some type of ducting fitted to the lower control arm. I still have evidence of the sheet metal and rivets. I have seen one other ITS Z fitted with ducting for the rears. After school this month, I will be fitting some NACA ducts to the lower arm and a short piece of ducting toward the backing plates.

[x-ring]

Oh, I HAVE taken a hole saw to that front hole, but that was only to get to the star wheel to take the drum off. I didn't drill holes to ventilate/lighten it -- I through that drum away when done. It was shot after I Jeffed it up.

OK, confession time. I have drilled them when I couldn't get them off. I also have continued to use them after that until they're worn out. As I said, let the paper fly.

I'm too broke, or maybe just too cheap, to toss a >$100 drum because I had to enlarge that hole. They don't last that long, so the drum will be headed for the garbage soon anyway.

The TR drum mechanism is very different. Self-adjusting, and usually the drums just come right off. The Z is much more difficult, but then again, it has way better pedal feel.

Damn, you have worse brakes than I do? How do you drive that thing? :eek:

FWIW In my cars previous life on the left coast, it had some typ of ducting fitted to the lower control arm. I still have evidence of the sheet metal and rivets. I have seen one other ITS Z fitted with ducting for the rears. After school this moth, I will be fitting some NACA ducts to the lower arm and a short piece of ducting toward the backing plates.

NACA ducts, hmm. I was thinking of using a couple of defroster nozzles scavanged from one of my wrecks. You know, the thingies that attach to the underside of the dash to distribute warm air to the defroster vents on top of the dash. NACA ducts might work better. 'Course defroster nozzles are free...

[Parrish57]

I thought the parking brake was an integral part of getting the Z shoes to work worth a darn under racing conditions? That is, the adjuster kept the shoes near the drum so that you'd get some rear action.

R

Oh, absolutly! I use the brake to adjust mine as well. But the byproduct of that is that they are adjusted tight when you get home from the racetrack. If you use the brake when you get to impound, again when you unload the car from the trailer, then again when you park the car and then let it sit for the winter it can be tough to get the drum off.

As for the legality of drilling a hole, I justify it as "necessary repairs". Venting works for me too!

[JeffYoung]

Uh oh! Next time Steve, you are PROTEST TOAST.

Yes Ty, TR8 brakes are significantly worse than Z brakes. Significantly. On the other hand, I have a magnificently sculpted right quad from all the pedal pumping I have to do at CMP.

[pballance]

Sounds to me like it is modification to perform a function that would otherwise be prohibited!

Just kidding, I agree that it is a necessary mod for normal repair and like Ty said, the hole is in the Brembo's I have on mine and there is not a spec for the hole so write away Jeff.

[Parrish57]

Uh oh! Next time Steve, you are PROTEST TOAST.

.

Yeah you go ahead and write that paper and consider yourself Jeffed Up for the rest of the year!