For handbrake auto-adjustment I've always assumed
Thinking about it, as you say, the actual cable adjuster is only required for cable stretch and has no bearing at all on thickness of pads (apart from perhaps the incremental turning of the piston)
General handbrake adjustment
- Thread starter bigeyun
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General handbrake adjustment
Thinking about it, as you say, the actual cable adjuster is only required for cable stretch and has no bearing at all on thickness of pads (apart from perhaps the incremental turning of the piston)
Argonaught said:
And that was exactly the point I made
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You obviously need to make sure the handbrake is OFF but I found that you could actually see the handbrake cable was very loose when winding back the pistons so there was no real need to slacken it (could be different for some Stilos I guess). Some people have mentioned that allowing brake fluid to escape via the bleed valve can make retracting the pistons a lot easier, which I suspect it will, but I found using the correct tool it was an easy job anyway. When done I just used the handbrake to wind the pistons back and the handbrake ended up in pretty much the same position as when I startedAnyway - when replacing rear disc pads on other FIATs (and I'm sure the Stilo is very similar) I've found it's ESSENTIAL to slacken off the handbrake cable! This helps the pistons wind back in and also ensures that the self-adjusters operate correctly. Once you've given the brake pedal ten prods or so, you can retighten the handbrake. Thanks PNL for showing us how to make the adjustment!
Given that this applied to my X1/9, my Croma, my Lancia Thema, my Uno Turbo, someone's Coupe, another X1/9, and of course the 164, I'm pretty confident it will apply to the Stilo as well, but correct me if not
The front pad calipers auto adjust so why do the rears need a thread? And why in different directions?
I'm not asking as a "I know something you don't" quiz, I genuinely haven't found a convincing answer
I'm not asking as a "I know something you don't" quiz, I genuinely haven't found a convincing answer
You're confusing me now Decks
Surely that's because you don't have a handbrake for the front wheels.
...or to put it another way. It allows the rear pads to be adjusted by BOTH the Foot AND Hand Brake.
What have I missed ?
No wish to confuse Argo, I confuse myself enough
But not really, you see the handbrake moves the whole caliper piston closer to the disc and back again when you release it. There's no self adjustment there which is why you need the cable length adjuster.
The pads will hydraulically self adjust when you apply the footbrake the same as the front pads
It's tempting to think the caliper pistons rotate down the thread in normal use but they don't. The thread just stops the piston retracting too far and to make life difficult for bozos like us replacing the pads. But why different handed threads?
But not really, you see the handbrake moves the whole caliper piston closer to the disc and back again when you release it. There's no self adjustment there which is why you need the cable length adjuster.
The pads will hydraulically self adjust when you apply the footbrake the same as the front pads
It's tempting to think the caliper pistons rotate down the thread in normal use but they don't. The thread just stops the piston retracting too far and to make life difficult for bozos like us replacing the pads. But why different handed threads?
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This is all immaterial as Argo is a self confessed Brake less driver any way :devil:
And a good philosophy too, use the eyeballs more and the brakes less
I follow from your diagram Decks but you don't show the internal mechanism.No wish to confuse Argo, I confuse myself enough
View attachment 27141
But not really, you see the handbrake moves the whole caliper piston closer to the disc and back again when you release it. There's no self adjustment there which is why you need the cable length adjuster.
The pads will hydraulically self adjust when you apply the footbrake the same as the front pads
It's tempting to think the caliper pistons rotate down the thread in normal use but they don't. The thread just stops the piston retracting too far and to make life difficult for bozos like us replacing the pads. But why different handed threads?
There has to be a rachet like mechanism which allows the handbrake to wind the piston in (I think this is mechanical rather than hydraulic). There's no question that it does this as I've done it myself. You can either pump the brake pedal or use the handbrake like a jack (i.e pump it). The piston obviously has to turn if using the handbrake but I'm not sure if it does when using the footbrake (I'd guess not).
The fact that the pistons are left and right handed must be the biggest clue as that allows the handbrake cable to pull uniformly from the top on both sides (otherwise it would need to pull from top on one side and bottom on the other - a bit cock handed but at least Fiat could have made their wind-back tool a bit cheaper as you'd only need the one
)
I think it's the other way around Argo, the "ratchet mechanism" is purely the hydraulics, exactly the same as the front pads, pushing the pad out to the disc and the disc pushes the pad back so it's just skimming the surface again. The handbrake lever rotates the caliper innards which moves the piston internally just a little along the thread, not much but enough for the handbrake mechanism to push the pad up to the disc. That would explain the left and right hand threads. That makes sense to me now
Thanks for talking that through
Thanks for talking that through
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Yes, the mechanism is there because the handbrake IS auto-adjusting. It has to be, because the amount the pads wear down is significant compared with the pad travel from brakes-off to brakes-on.
On the older FIATs/Lancias/Alfa Romeos that I mentioned before, both pistons wound back in clockwise. I'm not sure why FIAT would have changed that to one clockwise, one anticlockwise.
-Alex
On the older FIATs/Lancias/Alfa Romeos that I mentioned before, both pistons wound back in clockwise. I'm not sure why FIAT would have changed that to one clockwise, one anticlockwise.
-Alex
Alex, interesting you should say that as my comment was purely theory
Argonought said:
Never realized Fiat actually made cars like that
Don't get the chance to see the internals of the Budweg calipers as most people understandably change the whole unit without delving in but as they're very expensive here's some piccies which show the internals and how it works
This is off an MR2 which is very similar to the Stilo
Exploded view apart from handbrake mechanism
New piston
Internal shot showing handbrake adjuster screw thread
Very coarse screw thead
Internals of piston, fitting new securing nut plate and finally the securing circlip
Assembled unit.
The screw threads don't need to be handed on these as the lever pulls inboard
Whereas on the Stilo the lever pulls forward which is good for a straighter cable run but needs handed threads internally
This is off an MR2 which is very similar to the Stilo
Exploded view apart from handbrake mechanism
New piston
Internal shot showing handbrake adjuster screw thread
Very coarse screw thead
Internals of piston, fitting new securing nut plate and finally the securing circlip
Assembled unit.
The screw threads don't need to be handed on these as the lever pulls inboard
Whereas on the Stilo the lever pulls forward which is good for a straighter cable run but needs handed threads internally
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Super information there Decks
Is it your MR2?
-Alex
Is it your MR2?
-Alex
So how does that work then ("lever pulls inboard") ?
You mean the cable pulls toward the middle of the rear axle instead of towards the front ?
Not my Mr2 unfortunately
By inboard i mean the handbrake lever on the MR2 moves in the same plane as the caliper piston
On the Stilo the lever moves at right angles to the piston travel so needs to be handed with left or right hand threads. Better for cable runs and efficiency but slightly more complicated handbake mechanism
Now we can see what's inside we can imagine more of what we're doing when winding back the pistons!
By inboard i mean the handbrake lever on the MR2 moves in the same plane as the caliper piston
On the Stilo the lever moves at right angles to the piston travel so needs to be handed with left or right hand threads. Better for cable runs and efficiency but slightly more complicated handbake mechanism
Now we can see what's inside we can imagine more of what we're doing when winding back the pistons!
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Very true
Makes you cringe though when you hear you about some peeps getting the hammer out
You can see why it's a good idea when winding back the piston to clamp the brake hose and open the caliper bleed valve so the hydraulic fluid is just pushed out of the cylinder rather than back uphill into the system. The fluid is usually contaminated too from sitting in the caliper all that time, not good shoving that back into the system. Wonder why your ABS valve doesn't work afterwards.
The piston should rotate quite easily in the bore but pushing the hydraulics back uphill as well would make it much harder which is why people struggle so much to reset the pistons often, we hear, resorting to hammer blows of frustration
The piston should rotate quite easily in the bore but pushing the hydraulics back uphill as well would make it much harder which is why people struggle so much to reset the pistons often, we hear, resorting to hammer blows of frustration
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Is this what you've actually done or is it just theory as I've often wondered how much easier winding back the pistons would be without the resistance of the brake fluid. Of course it's a two edged sword as careless opening of the bleed valves could allow dirt into the system so you could end up even worse off.
You can always go for a complete fluid change anyway
