Brake Disc Removal

[Gsbx1220]

Hello.

I need to change the brake discs on my 1978 GS.

Can the discs be removed without removing the callipers. I had a swearing session with the car trying to remove the callipers. It seems an impossible task as one of the calliper retaining bolts is under the subframe!

Haynes manual etc says to unbolt and remove caliper and withdraw the disc upwards.

But how? Is there a special trick to this?

Cheers

[myglaren]

I don't recall any difficulty removing the caliper but the disc was difficult to shift, or at least the hub nut.
Searched a long time for a suitable ring spanner until I heard that the way to remove it and the 'C' nut was to drill the periphery and break it off with a cold chisel, throw them away and buy new ones, they were 34p when I did it but that would have been in 1983.
The disc was easy to fit, bought a huge box spanner to fit the new hub nut. Still have it and it has never been used since to the best of my recollection.

The really hard part was that the brake pipes crumbled into dust with the caliper removal, as did the next part when the first part was removed, and so on until every brake and suspension pipe bar the ones from the accumulator to the pump and doseur were replaced.
I was impressed with the way that all the pipes came in sealed plastic bags with plastic end stops in them to keep muck out, and they all seemed to be £17.
That said, it is unlikely that they would still be available.

Just realised that you meant the front discs Never needed to touch them apart from pad change which was simple, and handbrake pad change, which wasn't.
I expect that it is necessary to remove the driveshaft, which you don't mention.

Welcome to the FCF and I hope someone sensible can give you the right advice.

[Gsbx1220]

Hello,

Realised I did not say which discs

Yes, you need to undo the fasteners between the driveshaft and disc. I haven’t got that far yet as the callipers issue stopped play and never went any further.

[myglaren]

The rear discs were the first job on my GS, which was my first French car and quite baffling, the disc sheared off, there were no pads on the backing, that was clamped and rusted onto the disc, so I recall that vividly.

Had the driveshafts off a few times but don't remember any useful details.

[Stonehopper]

It is absolutely necessary to remove the caliper to remove the disc. But you do not need to remove the parking brake cable. You cannot remove the disc leaving the caliper in situ, it's a physical impossibility.

I can't remember if the trick used on the 2cv is applicable, if so, to save splitting the caliper, one retaining bolt can be removed allowing the caliper to 'rotate' on the remaining retaining bolt (slightly slackened). Then when able, re-insert the removed bolt and tighten. Now remove the other bolt allowing the caliper to be lifted off. Best to release the pressure on the suspension/braking system by cracking the relief valve before starting.

The drive shaft must also be unbolted from the disc.

It's a pig to work on. 'Course, you could whip the whole unit out . . . . Coat.

[Gsbx1220]

Hi yes,

Those are basically the steps outlined in the manual.
The real issue is getting access to the mounting bolt which is under the subframe which is at the bell housing end of the gearbox.
It has been suggested to me to undo the engine mount bolts and push engine to one side for better access.

Surely replacing service items shouldn’t be as difficult.

All tips and tricks on this are greatly appreciated

[darbuck]

I still don't understand the logic of manufacturers of that era putting the brakes in there.

[Stickyfinger]

Best place for disks....reduces "sprung wheel weight" thus improving ride comfort and handling.

[Stonehopper]

Best place for disks....reduces "sprung wheel weight" thus improving ride comfort and handling.

It's unsprung wheel weight, but hey - message understood.

The wheel assembly, including wishbones and the outer part of the drive shaft, are reduced in overall weight (the unsprung weight), and so the said assembly will rise and fall over bumps and undulations easier, causing less transmission of the unsprung weight to the car body This was especially important on the lightweight 2cv allowing the body to be less affected by pitch and the vertical mode.

[Stickyfinger]

OK....as the disk spins and the caliper is attached to the wheel hub.....that is the "sprung wheel weight" part ....is my thinking

[Stonehopper]

Except in the case of the 2cv, GS/A, the disc and caliper (front brakes) are not attached to the wheel. They are attached to the gearbox - inboard. Hence they are part of the 'sprung' weight, being of the car, engine, gearbox etc. The wheels of themselves are not of the 'sprung' weight, as they are directly in contact with the road - the 'unspung' part of the vehicle.

[Rp0thejester]

I never knew this, I'm intrigued about how it worked

[Stonehopper]

It is simple. Instead of braking the wheel directly, the transmission shaft to which the wheel is attached, is braked at its innermost end. Less weight to be bounced up and down at the wheel. The downside is less access, as Richard is finding out!

[Gsbx1220]

Indeed so

I’m now leaning towards pulling the engine out!

[Stonehopper]

Yes. Spot the drive shafts/inboard brakes!





A rats nest. Necessitating disconnection of hydraulics, exhaust, cabling etc. Once it's out (and the bumper, front vallance come off easily. The four engine bolts are easy to get at from beneath, but it's so long ago since I did that job - I've forgotten how to access the rear gearbox mount!

Back in, and Tea!