S3 Front Brake Cams

[sllim1946]

Hi all,

Having just replaced the front brake shoes with ones with perfect cam following surfaces and with the shoes fitted with new linings I still find that I can only just lock the brakes without the adjustment cams going "over the top" - which they will do if I lean on the spanner a bit harder. This is making adjustment a tricky business and I can see that this will become impossible when the linings wear.

Has anybody replaced the adjustment cams and how easy is this to do?

Any ideas appreciated.

Brian

[lancianut666]

If memory serves me I think you drive a pin out of the cam pin on the backplate side and it will all come apart...the Consortium might have some used cams but I know different sizes are available, is it possible you have the wrong ones fitted? Table 35 in the parts book shows this in better detail.
Clarkey

[simonandjuliet]

The cams are the same for lots of sliding pillar Lancias and I would be very surprised that the cams were "worn", - they do very little work

On Aprilias the backplates can become distorted so the cams are twisted backwards (because they were seized and forced)  and then don't have the same effect. If this is the case, one option is to get a pair of grips and reposition the cam

Another thought is that the linings are a bit thin (better than too thick to my mind) so maybe add a shim/washer under the "cam follower" ??

The cam-followers are easily removed with a bit of heat - I then glue them in with loctite

Removing and changing the cams is possible , but a pain !

[nistri]

While repairing the brakes, it is helpful to carefully check that the drums are not slightly distorted (a frequent issue) so that their inner surface is not perfectly circular. Andrea.

[will]

I agree with Andrea may be worth trying to adjust the brakes in different positions on the drum or try another drum .Will

[williamcorke]

I have replaced an Aurelia 'snail' cam in the past, having not understood how it was assembled and broken it! A cloddhopping way to learn.

The adjusting nut and shaft are drilled through with a pin through the hole. Very hard to remove these pins and I'd suggest rather that if you need to remove them you might sacrifice the nut and save the rest of the assembly. Using a nut splitter is how I did it, then the pin could be removed and a new nut drilled.

[chriswgawne]

I cant imagine that the brake adjusting cam lobe is worn. Its more likely that the drums have been skimmed (or they are very worn) so much that thicker brake linings are needed. If too much has been taken out of the drums however, they will need to be replaced. From memory, if the i/d of front Aurelia drums is >2mm larger than when new, I bin them and look for better ones.
What i/d are the drums and how does this compare with the original i/d according to the manual?
Chris

[sllim1946]

Many thanks for all the useful suggestions,  will work on them starting with the ones that need less work!

Regards
Brian

[Appia 61]

Running out of adjustment with my Appia III front brakes has been a perennial problem for the 48 years I have had it.  There is only 3mm adjustment on the cam so a couple of brake drum skims leaves it short.  I have seen pieces of aluminium glued to the pads on the shoes but they fall off.  I have tried screwing on pads but they came loose.  At one stage these screws came loose and moved with brake applications so the brakes stayed on and dragged.  Then I drilled and tapped the pad to take a flat headed screw which could be adjusted for height and secured it with a small grub screw against its thread.  Recently a grub screw fell out, got trapped between the drum and back plate and caused a loud graunching noise.  Finally i drilled out the threaded hole and machined up aluminium pads to be a light press fit in the holes.  I drilled the grub screw holes and fitted 1/8" roll pins through the arm of the pad.  If this fails I will cry!  If anyone would like details and photos email me: prenou@bigpond.net.au.  Peter.

[lancianut666]

Hi all
Reading through the comments it seems the problem comes when either wear or re skimming of the drum creates a gap the 3mm of adjustment as mentioned by Peter is not sufficient to ensure the shoe is making a good contact with the drum. A solution I can suggest but have not tried is to either replace the drum with a better one or skim the drum and replace the linings with thicker ones to allow for the metal removed from the drum. The thickness of the standard linings is 5mm with 5.5mm and 6mm oversize linings available these will correspond to a 231mm and 232mm internal diameter of the drums after skimming. These oversize thicknesses do not seem to be very large so perhaps re metalling the drum might be a better way? A question that might be asked is what is the internal diameter of a new drum?
Clarkey

[sllim1946]

Thanks, Peter and Jim for your comments.

I certainly have had problems with the pads on the shoes wearing away. The original shoes (just replaced),  had quite deep scouring. I tried filling the depressions with epoxy metal but that wore as well.

When I put in a replacement set of shoes with seemingly perfect shoe pads I still could only just a full lock of the wheels. Have checked and measured as follows:-

 - drums have not been skimmed. One is 230mm, i.e.no wear, the other 230.2mm, so the standard 5mm linings should be fine

 - cylinders are firmly attached to backplates.

 - cams  are not bent and move through 360deg

 - cams rise 5mm over 360 deg which as Peter says gives 3mm of  lining movement  at centre of shoe arc

 - from locked brake position to 30 deg adjust on cam nut gives 0.3mm movement on shoe arc centre

So nothing appears wrong there.

However I was surprised that after just 60 miles of running the shoe pads already show distinct wear!

So my solution at present is to epoxy steel bond 2mm thick 11mm x12mm steel plates onto shoe pads. I can see from Peter's experience I will need a close eye on this! If it fails then it looks like I will follow Peter's latest mod.

p.s. - will let you know how this works once I have cured a persistent wheel cylinder leak even with ss sleeve and new seals!

Enjoy Lancia!

Brian
 

[will]

I found this brake problem hard to understand as Lancia cars of that period
were so well engineered.  So to break down the problem is why and how to fix it.
I believe there are two adjustments on Lancia cars with twin leading shoes the snail
 cams and the eccentric cams. As the Appia workshop manual does not mention the
eccentric cam. I assume both Brian and Peter are not aware of eccentric cams and may be the reason for
the pads wearing on the brake shoe. See Brian Longs ‘Late Series Brake Aurelia Brake Adjustment. 
The 3rd series brake shoes are made of a different alloy than the 2nd series shoes which could be another
factor in the wear of the pads on the brake shoes. On my 2nd series Appia I have never seen any wear on the brake shoes pads or on the 4th series B20 which is the same design but larger. A possible way to repair the shoe is to tig weld new brake pads to the shoes.

[lancianut666]

The plot thickens...I must confess I can lock up my front brake shoes to the drum with the adjuster but these are later twin leading shoe types on a S1 car....sounds like these braking systems have too much of what my grandfather would have called slogger in them and all the wear has added up to a distance not adjustable by the cams. I will try and check the thickness of my linings as I had to file a lot off to get the drums on.
Clarkey

[sllim1946]

I found this brake problem hard to understand as Lancia cars of that period
were so well engineered.  So to break down the problem is why and how to fix it.
I believe there are two adjustments on Lancia cars with twin leading shoes the snail
 cams and the eccentric cams. As the Appia workshop manual does not mention the
eccentric cam. I assume both Brian and Peter are not aware of eccentric cams and may be the reason for
the pads wearing on the brake shoe. See Brian Longs ‘Late Series Brake Aurelia Brake Adjustment. 
The 3rd series brake shoes are made of a different alloy than the 2nd series shoes which could be another
factor in the wear of the pads on the brake shoes. On my 2nd series Appia I have never seen any wear on the brake shoes pads or on the 4th series B20 which is the same design but larger. A possible way to repair the shoe is to tig weld new brake pads to the shoes.

The S3 twin leading shoes, do not have eccentric pivot cams as the pivot points are floating so that the shoe aligns itself to the drum.

I think your point about the S3 shoe alloy being inferior to S2 is probably correct or there is a design error on the original shoe pad height.I say this as the rears on mine(Same as S2 I think) have considerable wear on the shoes where they contact  the cams but there is still plenty of adjustment left.

Regards
Brian