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Stupid drum brake question...

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IanF

IanF

Jedi Trainee
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Greetings all...

I'm currently in the middle of replacin the rear shoes and wheel cylinder on a '79 Spitfire. Everythingseemed straightforward until it came to putting the drum back on. It simpy doesn't fit. For two days now I've tried everything I could think of:

Adjuster is completely backed out. Wheel cylinder is compressed. E-brake disconnected. Shoes are centered on the backing plate. But no matter what I do, the diameter of the shoes is simply too large. What am I missing??? /ubbthreads/images/graemlins/confused.gif

I have installed drum brakes before, but I'm at my wit's end with this one... /ubbthreads/images/graemlins/cryin.gif ...and we need to have the car back on the road ASAP.
 
Do both shoes interfere, or just one? Is the wheel cylinder free to slide back and forth, or is it "stuck" in one spot? It should slide, of course, and it would probably help to sparingly lubricate the sliding surfaces (I use white lithium grease).

If that's NOT the problem, 'bout the only other option is probably new shoes with slightly oversize linings, but I've yet to encounter that on a Spitfire.
 
[ QUOTE ]
Do both shoes interfere, or just one? Is the wheel cylinder free to slide back and forth, or is it "stuck" in one spot? It should slide, of course, and it would probably help to sparingly lubricate the sliding surfaces (I use white lithium grease).

If that's NOT the problem, 'bout the only other option is probably new shoes with slightly oversize linings, but I've yet to encounter that on a Spitfire.

[/ QUOTE ]

Nope... both sides... and all the parts in question are lubed at the suggested points.

I called the place where we got the shoes and he gave me a new trick to try... I'm heading home now to give it a shot. /ubbthreads/images/graemlins/hammer.gif
 
[ QUOTE ]
I called the place where we got the shoes and he gave me a new trick to try... I'm heading home now to give it a shot. /ubbthreads/images/graemlins/hammer.gif

[/ QUOTE ] And the new trick IS? Inquiring minds want to know.... /ubbthreads/images/graemlins/grin.gif
 
Just got home and apparently the trick worked and the drum is back on the car. I'll leave it up to him to explain it, though since I wasn't privy to instructions he received.
 
Okay... the "trick"... is pretty simple, really...

Unfortunately, it's also flame material akin to a placing bucket of gasoline next to a crackling camp fire...

If anyone runs into this problem and runs out of ideas, feel free to PM or e-mail me. But for now, I'd rather not post it until I get a better feel for the community's opinion on "hack-mechanic" techniques... as this would definitely fall under that definition... /ubbthreads/images/graemlins/square.gif
 
this is not that kind of place. "hack-mechanic" techniques are welcome. We are all capable of making judgements by ourselves and you'll find the flaming is so rare that in the last year I actually commented ONCE at how odd it was that a thread actually turned into a semi-flame war.

Just post it!
 
Ok then...

Apparently what makes some shoes not fit with drums still close to the OE diameter is the bonding agent used to adhere the friction material to the metal shoes. When installed, the overall diameter is a bit too big and the drum won't go on.

So, what to do... well, somehow the diameter has to get reduced. The easiest way is to grind off some of the metal where the shoes rest against the wheel cylinder and adjuster barrels. Grind... test fit... grind a bit more... test fit... and so on until it slides on easily while allowing a bit of play in the parking brake.

The down side to this is the shoe wear will be a tad "off" for awhile as the middle area of the shoe will wear before the edges touch the drum.

Considering we drove the car over 300 miles with basically <u>NO</u> rear brakes at all, it's gotta be better now. We shall see after we bleed the brakes tonight. If all else fails, she'll splurge for the rear disc conversion kit. /ubbthreads/images/graemlins/tongue.gif (j/k dear! /ubbthreads/images/graemlins/wink.gif )
 
It's interesting to read this thread, because on Sprites/Midgets I have found the opposite problem.
Even though my rear drums are in-spec, I've had to shim-out my last two sets of rear brake shoes in order to get decent adjustment. I put the shims on the slotted end of the wheel cylinder piston wher it bears against the shoe.
 
[ QUOTE ]
... well, somehow the diameter has to get reduced. The easiest way is to grind off some of the metal where the shoes rest against the wheel cylinder and adjuster barrels. Grind... test fit... grind a bit more... test fit... and so on until it slides on easily while allowing a bit of play in the parking brake.

The down side to this is the shoe wear will be a tad "off" for awhile as the middle area of the shoe will wear before the edges touch the drum.

[/ QUOTE ]
Hmmm, perhaps this is what a previous owner did on the (same setup) rear brakes on my Herald. Took a 1250-mile road trip to fully bed in those rear shoes.

No "flame" here, but I'd worry that this approach might slightly change the geometry of the shoe. I think I'd rather remove a bit of lining and not part of the shoe.

[ QUOTE ]
Considering we drove the car over 300 miles with basically <u>NO</u> rear brakes at all, it's gotta be better now. We shall see after we bleed the brakes tonight. If all else fails, she'll splurge for the rear disc conversion kit.

[/ QUOTE ]I can't see any real point to spending that kind of money unless you've really "gone to town" with the rest of the drivetrain. Even then, I'd look first at upgrading the front brakes to the GT6 specification, and then possibly considering the 8" rear drum brakes from the early GT6. Perhaps before any of that even, you might consider Kevlar or other really upgraded linings front and rear (available from Ted Schumacher and probably from others).
 
[ QUOTE ]

So, what to do... well, somehow the diameter has to get reduced. The easiest way is to grind off some of the metal where the shoes rest against the wheel cylinder and adjuster barrels. Grind... test fit... grind a bit more... test fit...

[/ QUOTE ]

I don't see any huge problem with this. The linnings will wear out somewhat faster, but since the rear brake shoes last almost forever, this is no big deal.


[ QUOTE ]
If all else fails, she'll splurge for the rear disc conversion kit. /ubbthreads/images/graemlins/tongue.gif (j/k dear! /ubbthreads/images/graemlins/wink.gif )

[/ QUOTE ]

Unless you are planning on really aggressive racing, this is a big waste of money. Like Andy, I have a Herald ('70 13/60 Convertible) The Herald has basically the same mechanical parts as the spit (brakes are identical), and weighs significantly more. I regularly drive on rather steep mountains and have never had a problem with the brakes overheating. Make sure everything is working perfectly, and adjusted properly. You can also get EBC pads (front, and back). Note that in order to get the car to stop FASTER, you are not limited by the brakes. It is the point at which the tires lose their grip. Also keep in mind that these are not power brakes (I assume the Volvo has power brakes?) but you do have to press rather harder on the brake pedal! If this is the problem, you could upgrade to a power brake MC.

While you are playing with the rear axle, take a look at the back of the brake plate (diff side.) On the bottom, directly under the axle bearings, there is a little sloted hole, to let extra wheel bearing grease escape. MAKE SURE IT IS NOT PLUGED UP! I had a nice new set of brake pads ruined because of that. If it is plugged, when you start to grease the wheel bearings, excess grease can be forced right into the brake drum. Knock off any dried up crud. Since mine was really dried up, I also sprayed some degreaser in there, and then regreased the wheel bearings untill nice clean grease came out.
Yisrael
 
Good point about the grease port. We'll be sure to check that.

Yes, our Volvos all have 4-wheel power disc brakes. The braking system on these cars rivals modern cars in power and far surpasses them in mechanical complexity. Not just dual circuit, but redundant dual circuits. Each front caliper has two pairs of pistons fed from each circuit. So if one circuit fails, you still have pretty good braking power. And the parking brake is also a redundant system, completely seperate from the discs (drum shoes inside the rear rotors). Way ahead of it's time. Bleeding them is completely different than anything else.

The problem with reducing the friction material is how to do so evenly and without creating an incredible amount of rather dangerous dust. I suppose a disc/belt sander could do the job, but getting it even would have been tricky.

I was really just kidding about the disc brake conversion... /ubbthreads/images/graemlins/smirk.gif
 
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