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Old 18-05-2019   #1
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Brake pedal movement

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
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Old 18-05-2019   #2
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Re: Brake pedal movement

Firstly it will not feel the same as your VW.
VWs have for most of my time had a quite hard feel to the pedal, especially before servos. Most other makes have a softer feel, with Renault and Peugeot often feeling like treading on a sponge.

If after you've trodden on the pedal a few times, it is then better, with less travel, until allowed to relax for a few minutes, this suggests excess movement of calipers or shoes.
If the longer travel returns immediately, this is air, swelling hoses, or the master cylinder.

Excess travel on small Fiats is usually down to the rear adjusters not operating properly, causing the shoes to retract further than necessary, so needing pushing a long way to contact the drum every time.

The rear shoes use little friction discs on pegs to hold the shoes out after application. A loose fit onto the pegs allows just enough to clear when released.
Usually new shoes come with new adjusters already attached. If the old ones have been reused, they may be letting go too much. There used to be a trick for the first adjutment after fitting new shoes. Drive backwards and brake firmly several times. This is supposed to make the shoes sit out as far as possible. Seen it done on a 126, never needed to do it on my Pandas. This can also help centre the new shoes.

At the front end, if the pads retract too far, a longer pedal travel will result.
The sliding calipers have a tendency to stick a bit on their wedge sliders. Those need to be smooth and free of rust, and lubricated only lightly, as too much lubricant attracts dust, which then makes them tight. (Catch22)

New discs need to be fitted to clean hubs. Any dirt on the mating faces will cause the disc to run out of true, which will push the caliper piston back further. New Brembo discs should be fine for trueness in themselves.
If the sliders are tight, the system mayneed a lot of pressure before it moves the caliper. In some cases, if the caliper will not move, it bends the disc. (We're talking small amounts here) This will give longer pedal travel.

If you can isolate the rears, clamping the hoses, then see if the pedal is better, this will show if the problem is at the front or rear.
Isolating the fronts can be done, but needs a lot of care, as stopping power will be frighteningly poor using just the back brakes, so best not.

Hoses can swell, so with help, check them all as someone pushes hard on the pedal.

This needs a lot of very careful inspection, to check movement and clearances.
Ensure calipers move freely, but without too much clearance, as escess clearance on its mountings can allow tilting and seizure.
Ensure pads are able to move in their carrier, and on their pins.

At the rear, removing the drums should show the shoes to be quite close to the drum, if not, they can be levered out to make the adjusters work, getting them to a point where the drum will just go back on.
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Old 18-05-2019   #3
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Re: Brake pedal movement

Thank you for such a comprehensive answer. I will systematically work through all the points raised but I think the front end should be in good order, the calipers were cleaned and lubricated and checked they would slide without too much force. The new rear shoes were fitted by a previous owner and as they looked like new I didn't touch them. I like the idea of restricting the brake fluid to the rear as a check.....knowing where the problem lies is halfway to fixing it.

Thanks again.....…...Graham
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Old 18-05-2019   #4
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Re: Brake pedal movement

i have been riding around for years with this.. both Talon and Ratchet have this issue. will have to try the stopping in reverse to see if that helps! do you get the same results if you use the hand brake to stop (as that only brakes the rear wheels)?

i will say though, i have been that fed up with the pedal travel recently that i just kept bouncing my foot off the brake pedal (i naturally jiggle my leg when i sit down anyway) with the engine idling while i was eating my lunch at work. since i have done that the pedal has gone way more firm and raised its brake position a little higher. i even connected a vacuum pump up to one of the rear brakes bleed nipples to make sure i had no air bubbles when i injected brake fluid into the reservoir.

like i said, i tried everything to get my pandas brakes good but they are still not great. cant lock up the wheels which is pretty poor for any disc brake. assisted or not.
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Old 18-05-2019   #5
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Re: Brake pedal movement

Quote Originally Posted by GEH View Post
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
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Old 19-05-2019   #6
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Re: Brake pedal movement

Eurovison can't have been all that thrilling! Thank you for your write up, that, and some old pictures from the forum have enabled me to at last understand how the rear brakes are supposed to work. Must say I'm not impressed by the design but I'm sure one way or another I will be able to fix the long travel issue now. …….....Graham
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Old 19-05-2019   #7
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Re: Brake pedal movement

interesting! see i thought about this very same thing.. only i was going to completely remake the lever/balance bar.. but change the pivot point creating it to be "longer" when the handbrake is pulled up.

sadly my lazyness got the better of me and it never got done.... but i do have a few brake balance bars/levers around now to "play" with.

one thing i also heard was someone had the brake shoes relined with much thicker material which helped too. pretty much the same effect i guess.
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Old 19-05-2019   #8
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Re: Brake pedal movement

Oooooowh! thicker linings! now that is "thinking outside the box"! I'm sure that would have the same effect but probably cost a fair bit for a custom job like that? I did think about changing the leverage ratio by moving the rivet hole but it occurred to me that making the lever "quicker" would reduce the mechanical advantage of the system so I went for trying to "cock" the lever further back and get a slight advantage that way. It worked so I never tried anything else.

How I just love this Forum. There's always someone with a different "take" on problems.
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Old 21-05-2019   #9
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Re: Brake pedal movement

I carefully adjusted the handbrake to a maximum (3 notches) and the long brake pedal is much improved, not ideal, but much better!...…..Graham
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Old 21-05-2019   #10
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Re: Brake pedal movement

Quote Originally Posted by GEH View Post
I carefully adjusted the handbrake to a maximum (3 notches) and the long brake pedal is much improved, not ideal, but much better!...…..Graham
I'm pleased for you that things have improved - pretty much proves your problem is with these darned silly adjusters! When you get the time jack both back wheels off the ground and tighten the handbrake cable until the linings are rubbing on the drums. Then slacken off until the drums/wheels turn freely without binding. What you are trying to do is get the linings as near to the drums as possible without them actually gripping. Yank the brake lever up and down and drive the car around for a bit to settle the linings then see if you can get just a little more tightening on the cable - but with no binding. You will now probably find that the hand brake is firmly applied by the second click and the pedal is even better. Forget the conventional 3 clicks "thingy" in this case - you're being unconventional here anyway, might as well go the whole hog?
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Old 31-05-2019   #11
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Re: Brake pedal movement

Ok if you want excellent panda brakes up grade to discs all round then Lexus servo

My force was 148 front

131 rear

Hand brake 124.
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Old 31-05-2019   #12
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Re: Brake pedal movement

'Upgrade to discs all round', sounds good but do could you give a little guidance on where to start with such an upgrade?
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Old 01-06-2019   #13
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Re: Brake pedal movement

Well do the servo up grade first if that’s not good enough , then I will post a how to for all. The servo up grade can be achieved in a few hours. Discs all round will need a few days to plan and make parts.
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Old 4 Weeks Ago   #14
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Re: Brake pedal movement

Almost everything has been replaced in the brake system so to be complete I have fitted a new master cylinder. So whilst doing that I thought I would adjust the brake pedal position......only to find there is no adjustment possible. The brake pedal pushes a fixed rod which pushes on the master cylinder. The brakes should feel better if the pedal did not go so close to the floor and some of the clearance is taken out of the system. So I made a new fixed rod, (it helps to have a lathe etc). The new rod was made longer and trimmed down by trial and error until it fitted nicely. It turned out to be 4mm longer than the standard rod which when multiplied by the mechanical advantage of the pedal works out to about 16mm movement at the pedal.

I also tightened the handbrake cable again to what I think is the maximum without the brakes binding. The result of the work is the brakes are still poor but the brake pedal feels much, much better. So until I look at a servo I just need to keep a prudent distance from other traffic.

As I didn't change the brake shoes myself and was wondering if the friction adjusters work better on any particular brand of brake shoe? or are they all as bad?


Graham
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