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Rear brake caliper question


Chris King - Webmaster

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Chris King - Webmaster

Being a biker and not really a car tinkerer prior to Westy ownership, the only time I have meddled with rear calipers that have a handbrake is when I built the car and they were new. 
 

So now I’m swapping bits on the rear and wondered why you need to use some special tool to wind in the pistons?

 

Can’t you just push them back in when you come to fit the pads?

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Dave Eastwood (Gadgetman) - Club Secretary

Not for Sierra or Golf, no.

 

its down to the difficulty, (compared to drum brakes) of making a self adjusting handbrake mechanism for Calipers and discs. The piston has to be kept within a certain distance of the disc, or once the pads have worn past a certain amount, there wouldn’t be sufficient travel on the handbrake lever to sufficiently apply them.

 

In the hydro-mechanical handbrake Calipers, they have for want of a better description, a sort of one way screw arrangement behind the piston, that lets it push out as normal when you operate them with the pedal, but limits how far back they can release to, when you take your foot off the brake.

 

The only way to reset the piston when changing pads etc is to wind it back down the thread.

 

Of note, when fitting these sort of Calipers, YOU SHOULD NOT apply the handbrake untill the hydraulic system has been bled properly, as moving the piston out with the handbrake, rather than foot brake, before bleeding, can leave the pedal feeling permanently a wee bit soft, and it’s really difficult to sort out just by bleeding the rears.

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Steve (sdh2903)

The golf ones can be an A*** to push back aswell.

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Dave Eastwood (Gadgetman) - Club Secretary

I bought a wind back tool set years ago, fortunately with the right adaptor on, my Golf calipers seem reasonable to wind back, maybe I’ve just been lucky?

 

(I’ve upgraded the S2000 to Golf rear callipers as I’d rather toast my testicles in hell, than have those piece of **** Hi Specs on there any longer :laugh: )

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Chris King - Webmaster

I think I’m going to use the Sierra calipers. They are a few 100g heavier but it all just fits without any bodges. 
 

Will get a rewind tool then - thanks for the info @Dave Eastwood (Gadgetman) - Club Secretary 👍

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  • 8 months later...
IainCameron
On 18/01/2020 at 13:20, Dave Eastwood (Gadgetman) - Club Secretary said:

Not for Sierra or Golf, no.

 

its down to the difficulty, (compared to drum brakes) of making a self adjusting handbrake mechanism for Calipers and discs. The piston has to be kept within a certain distance of the disc, or once the pads have worn past a certain amount, there wouldn’t be sufficient travel on the handbrake lever to sufficiently apply them.

 

In the hydro-mechanical handbrake Calipers, they have for want of a better description, a sort of one way screw arrangement behind the piston, that lets it push out as normal when you operate them with the pedal, but limits how far back they can release to, when you take your foot off the brake.

 

The only way to reset the piston when changing pads etc is to wind it back down the thread.

 

Of note, when fitting these sort of Calipers, YOU SHOULD NOT apply the handbrake untill the hydraulic system has been bled properly, as moving the piston out with the handbrake, rather than foot brake, before bleeding, can leave the pedal feeling permanently a wee bit soft, and it’s really difficult to sort out just by bleeding the rears.

Hi Dave, I was doing some research on brake bleeding before posting a question.... then I found this post of yours from earlier in the year which has posed another question.  My original question was about the new brake fluid coming out of previously unused brake pipes and newly refurbished callipers; it's filthy.  Could the WSC brake pipes be full of dirt, despite the ends having been taped over since I bought the kit?

I filled the system yesterday, and did a one-man-and-a-long-stick bleed of the system, which got the brakes 'sort of' working, but I ran out of time and didn't keep flushing until the fluid ran clear in all four corners.  Today, the brakes still 'sort of' work, but they are very far from being firm, let alone hard.

 

Your post from January rang an alarm bell or two... when I was fitting the handbrake, I operated it to check its movement etc, but there wasn't any fluid in the system; I haven't operated it since, but I'm wondering if your caution about not using it until the system is fully bled will apply to me?  I've got Sierra rears, BTW, and have no idea if they have the 'one way screw' arrangement which you described above.

 

Many thanks, Iain

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Chris King - Webmaster
28 minutes ago, IainCameron said:

Sierra rears,

are a swine to bleed!

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IainCameron
45 minutes ago, Chris King - Webmaster said:

are a swine to bleed!

The process seemed to go ok, even if the fluid came out a bit murky.  And I've swapped the nipples round, so the bleed is at the top.... is the 'swinishness'  due to residual air getting trapped, or some other problem?

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Chris King - Webmaster

You need to pretty much take the calipers off in order to truly get the bleed nipple to the “top” of the system. 
 

I did that and still not properly bled. Then took a second person to do it properly. You really can’t use any “one man” technique or cool tool. 
 

edit: I guess I meant that I couldn’t manage single handed with either a Gunson or a vacuum pump thing - only really got a decent result with someone else pushing the pedal while I manually opened and closed the bleed...

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The tools come as a kit..loads of different sizes and left and right hand thread..in nice plastic case..around fifteen quid on well known auction sites..

You can use a pair of pliers or similar but so much easier with the tools..

 

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Steve20

Sierra rears on my SDV are hard work to bleed, Gunson Easy Bleed worked but was difficult to get a decent seal on the master cylinder.

 

Took a couple of attempts.

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CosKev
16 hours ago, IainCameron said:

when I was fitting the handbrake, I operated it to check its movement etc, but there wasn't any fluid in the system; I haven't operated it since, but I'm wondering if your caution about not using it until the system is fully bled will apply to me? 

 

Yeah it will,you need to wind the caliper pistons back in now and bleed again.

Then once they are bled you press the foot brake down a few times to push the pistons out to their natural position against the pads.

Then you can lift the handbrake lever to set the auto adjuster in the caliper.

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Dave Eastwood (Gadgetman) - Club Secretary

— Yep, you’ll need to follow the process Kev explained. (Everything will sort of work if you don’t, but it won’t be right, and you’ll tend to find random issues like a long brake pedal, pumping up, etc)

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CosKev

Yeah that looks to be fully in🤔

 

Strange as you've bled them and pressed the pedal.

 

Must be loads of air in the rear calipers still I suppose🤷🏾‍♂️

 

Did you position the rear calipers so the bleed nipple was at the highest point?

 

 

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