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Author: Subject: binding rear sierra callipers
AlexXtreme

posted on 27/3/16 at 03:00 PM Reply With Quote
binding rear sierra callipers

I think I have managed to get the brakes bleed - just had to take off the calipers and bleed them whilst rotating them...

However I have not clear part of the problem I had in the first place of a binding rear disc :-(. I can just about turn the wheel by hand.

The near side runs fine
The hand brake cable has some slack in it - though not much but I have no more adjustment
The caliper is a refurbish unit so this is not the issue and seems to be running smoothly on the mounting bolts

Any ideas?

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britishtrident

posted on 27/3/16 at 05:06 PM Reply With Quote
Work logically
(1) Try disconnecting the handbrake cable.

If that dosen't work

(2) Try cracking open the bleed nipple.





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AlexXtreme

posted on 27/3/16 at 09:48 PM Reply With Quote
Sorted.... there is a run on the disk (for some reason - they are worn with at an angle) and swapped the pads over and the brakes not longer bind :-)

Thought I had fixed the bleeding though but not chance - just as bad a before

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AlexXtreme

posted on 4/9/17 at 11:46 AM Reply With Quote
Bring up an old thread and looking for suggestions on how to fix it..

Fitted new discs and pads thinking that this might sort the problem - except it did not - obviously! In fact it made it worse as the Mintex 1144 pads are noisy and due to the slight binding the car squeals at low speed all the time!

Anyway it looks as though the adaptor plates and not holding the calipers true to the disc ... in fact they are quite some way off and there a considerable run on the pads and at the moment after some bedding in only 1/2 the pad is in contact on the outer surface and 1/2 on the inner surface. Both sides of the car are the same.

Ideas so far are

- to bend the adaptor plates until it looks better...

- use some shimming washers on the adaptor plate mounts to get it to run true.

Has anyone else had this problem before and sorted it before I jump in and start experimenting? I have a solid rear axle with std sierra calipers

Alex

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obfripper

posted on 4/9/17 at 01:24 PM Reply With Quote
I had similar problems with my original live axle caliper mountings.
They were too thin (iirc3-4mm) and went out of shape as i used the car, juddering under load and leaving the caliper at an angle to the disc after a summers use.
I replaced them with some thicker ones (1/4"/6mm) like these:

ESCORT MK1 MK2 REAR DISC CALIPER BRACKET ENGLISH AXLE FOR 13" FORD BRAKES

Unfortunately they appear to be sold out atm, but it give a fair idea of whats needed.

Dave

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AlexXtreme

posted on 4/9/17 at 03:33 PM Reply With Quote
Hi Dave,
That is very useful info - thanks!
Will have a look and see what I have fitted... I must admit I do feel a judder under load but thought it was my imagination!

Alex

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AlexXtreme

posted on 4/9/17 at 03:53 PM Reply With Quote
do these look like the same

http://www.ebay.ie/itm/271427554189?ssPageName=STRK%3AMEBIDX%3AIT&fromMakeTrack=true

Alex

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obfripper

posted on 4/9/17 at 06:05 PM Reply With Quote
They look similar, you may want to get some installation diagrams from them to check your flexible hoses and handbrake cables will work with the caliper position these brackets give. The other thing to consider is the total bolted area is only 2x 5/16" unc bolts, the other 3 bolt fixing ones are going to be 50% stronger and spread the load over a larger area, it is probably ok using high tensile bolts.
I had to change the flexible hoses when i changed to the thicker brackets as it located the caliper differently but the handbrake cables were ok.

On my setup i have fiesta front discs and have to use a 1mm thick washer on each lug to centralise the caliper on the disc, depending upon which discs you have this may be different.

I'll snap a couple pics later that will show the caliper position, and check where i got the replacement brackets from - iirc it was mk2 mania as per the link.
They may still sell the brackets on their website or if you contact them, they just don't seem to sell on ebay anymore.

Dave

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obfripper

posted on 4/9/17 at 10:35 PM Reply With Quote
I had a look, they came from shorttrack motorsport who no longer exist, but are the same as mk2mania ones.
Here's a couple pics with my current setup and the original thin brackets.

https://www.dropbox.com/sh/kh5pi05usxv1i6t/AADgwfs_bDFZ4QC-1z6x1WQMa?dl=0

Dave

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AlexXtreme

posted on 5/9/17 at 07:51 AM Reply With Quote
Hi Dave,

Really useful info and pics! I will have a look at the weekend.. I will call mk2mania and see if they still sell them.

My set up sounds the same with fiesta front disks ... hopefully I will not need to replace the flexible hoses! Do the brackets located the calipers in a total different position? From the pics it looks like it rotated the position by around 45 degrees.

Alex

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AlexXtreme

posted on 7/9/17 at 12:27 PM Reply With Quote
Hi Dave,

They still sell them :-) and I have a couple in the post to me for this weekends "job" and will let you know how I get on.

Alex

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AlexXtreme

posted on 12/9/17 at 09:11 PM Reply With Quote
Latest update... stupid thing "in my head" the mounts were bolted but after I brought the new brackets - I looked at what was actually on the car and saw as shown on the pics - the very thick plates are welded to the rear axle. Is this usual?? Anyway I now have 20 of mounting plates I do not need - need to buy parts before I know exactly what I need!

Anyway as you can see from the side picture due to the misalignment, only outer part of the pads are in contact with the discs and the discs do not fully lie flat against the axle mount - there is probably a couple of mm out over the dia of the disc.

https://photos.app.goo.gl/fbaaqwLtuMdqsi1j1

Looks like the only choice is the hammer - but there is not much room to get much of a swing. Hopefully nothing cracks when I bend the plate

Alex

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obfripper

posted on 12/9/17 at 10:18 PM Reply With Quote
That's a bummer, they look like they may have been welded on misaligned, and they look thick enough that you're going to need a fair effort to bend them.
I can't think of any means of shimming the brackets to counteract the misalignment you have.

I would be tempted to cut the brackets off and start again, however your mounting offset is different to the bolt on brackets (looks like 25mm further inboard requiring different discs) and there is a massive amount of weld holding them in place that is going to take a serious effort to remove. Also to fit the bolt on bracket there needs to be clearance to the axle casing to screw in the bolts from the diff side, so the weld would have to be removed for clearance in those areas.

Have you got something sturdy that you could bolt to the mounting lugs and then bend them into alignment? - Something like 4ft of scaffold pole with a 10mm thick plate welded on the end that can bolt to the lugs would give you sufficent leverage and control to get as straight as possible.

Dave

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AlexXtreme

posted on 13/9/17 at 07:48 AM Reply With Quote
Unfortunately I do not access to welding kit etc to make a something strong enough to make a controlled bend. There is also so much weld that I expect starting afresh or machining back what is there would be easier.

I think that it was not a misaligned plate but the weld was asymmetric due to poor access on one side and when the weld cools the plate distorts.. I am guessing.

For now I will try a gentle tap with a lump hammer to see if it moves... :-)

Alex

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AlexXtreme

posted on 16/9/17 at 04:46 PM Reply With Quote
fixed in the short term anyway and the car now rolls like a dream with no binding brakes....

a couple of "taps" with the lump hammer and the brackets were straight! Isn't mild steel rubbish (as a structural engineer I am allowed to say that)!
Even with the thickness I have, I expect the strength of the bracket is just not up to the offset loads from the braking and the plates yield... well I will find out if this is the case.

Alex

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