I have 1990 Panda CL1000 which had rather poor brakes, (non servo). The rear shoes have been changed, new Brembo discs and pads fitted, brake fluid changed and well bled. The car will stop but the brake pedal seems to travel an awfully long way before any serious stopping happens...…..is this normal or should I be looking to also replace the master cylinder? should the pedal feel hard as on my VW?
………..Graham
Hello Graham. Our L plate Panda Parade (so mechanically virtually identical to yours) had exactly this problem. I became very familiar with these back brakes over the several months, or was it years? of experimenting to get the best result. Fiat used this type of self adjuster for many years - I remember seeing them on the 128 - and they were never brilliant.
So here's my take on this problem. Lets think of how this hand brake works. When you pull the handbrake lever the cable pulls on a lever which pivots on the cylinder end of the rear most shoe (usually the trailing shoe - not that it really matters) there is then a balance bar running from near the pivot point of this lever through to the cylinder end of the other (leading) brake shoe. So when you pull on the handbrake the cable pulls the bottom of the lever on the trailing shoe which in turn levers out the cylinder end of this shoe and pushes against the balance bar so forcing the cylinder end of the leading shoe out too. So both shoes are now forced out and so grip the drum. You will have noticed that both shoes have friction fittings about half way along them which fit over pegs in the back plates? There is a very small amount of clearance between the bore of these adjusters and the pegs. In operation when the shoes move out to touch the drum - whether being moved by the hand brake or hydraulic cylinder (foot brake) - This very small amount of clearance is taken up almost as soon as the shoe moves and then the shoe moves through the friction pads until the drum stops movement. When the applying force (foot or hand brake) is released the shoes will now be held in their new position in relation to the adjusters, by the clamping action of the friction rings and their strong springs so the shoes can only retract (under the influence of the normal retracting springs between the shoes) by the very small amount of clearance between the adjusters and the pegs. That's what's supposed to happen anyway but often the friction pads just don't hold so the shoes retract much further than they should and you end up with long pedal travel because the linings just have to travel too far before they contact the drums.
I got to thinking about this. Other manufacturers use a self adjuster on the balance bar which works using either a screw or cam type arrangement to lengthen the bar to keep the shoes, and their linings, just "kissing" the drums. This arrangement means that the hand brake cable pretty much stays in adjustment too once it has been initially set up correctly. Our early Pandas (later ones use the screw idea) don't do this as the balance bar stays a fixed length. You will have noticed that as the rear linings slowly wear the handbrake travel gets longer and the "slack" has to be periodically taken up by adjusting the cables. I noticed that the pedal got considerably better after adjusting the handbrake cable! Why? well tightening the cable is, of course, pulling on the lever acting on the rear most (trailing) shoe which in turn is pushing the balance bar against the front (leading) shoe. The result is to move the shoes nearer to the drums so the cylinders will not retract so much when the pedal is released so next time the pedal is pushed it doesn't need to travel so far. I found I could achieve a really good pedal by keeping the handbrake adjusted as tightly as possible - without causing the linings to drag against the drums of course! Adjustment was than manually performed whenever excessive play became apparent. This only works with this type of adjuster. If you over tighten a handbrake which works with an adjustable balance bar in this way (so just about every modern car you can think of - including those with disc rear brakes, although they don't have a balance bar) the self adjuster will stop working as it requires free play for the lever/cam to return far enough to engage the self adjusting action.
Having discovered how well this works (remember this is only going to work on this particular type of friction type self "non adjuster") I started thinking about another problem which our Pandas suffer from - poor handbrake figures on the MOT brake test. My MOT guy tells me the "old" Pandas are well known for only just scraping through on the handbrake. Well actually it's obvious when you engage the "little grey cells" More modern setups, with the adjustment on the balance bar, will keep the lever which the cable engages with on the shoe in a more or less static resting position. Because the bar lengthens as the linings wear. But on our cars, with the fixed length balance bar, as the linings wear down the lever has to be pulled further and further forward to compensate for the thinner linings. This happens whether the "silly" friction adjusters are working or not. So you have to periodically tighten the cable. The problem this creates is that the lever/balance bar now operates "over centre" (poor choice of word maybe) but what the effect is that the mechanical advantage of the lever/balance bar system is reduced as the lever is pulled further forward so the clamping effort of the lining against the drum is reduced and the MOT figures get worse.
The situation is often exacerbated (cor, not sure what that means) by wear of the pivot pin and bearing faces (lever to shoe) on the lever/balance bar assembly. Simply renewing this component on a well worn car can give a noticeable improvement in hand brake grip. I dismantled "Felicity's" and drilled out the old rivet to take a slightly bigger diameter one so eliminating the wear (and the old rivet was quite worn as was the hole) I also built up, by welding and filing to shape, the worn ends where they bear against the shoes such that the lever was in a fully retracted resting position when refitted (thus virtually eliminating any "over centre" action on the lever).
The result of this - modifying the lever/balance bar and keeping the cable adjustment tight, but not tight enough to make the linings bind - gave me a very good pedal feel and praise from the garage every year (had the car for many many years) for the best Panda handbrake they'd ever tested.
I have to qualify this all by saying that unauthorised, non standard, modifications to any part of your car and brakes are probably a particularly dodgy area, may well land you in trouble with insurance and the authorities. So if you want to try any of this don't unless you are experienced and know what you're doing around cars. Understanding just how differently these rear brakes work helps greatly in getting the most out of them though.
Hope you found that entertaining folks? The votes are just coming in on the Eurovision and Mrs Jock is getting a little too excited so I'd better go and calm her down!
Night all!
Jock