Simon's new Xantia V6 and Leaf blog

[RichardW]

Hope it doesn't need new drums... I can't see them anywhere else, and they are £75 each from PSA....

[bobins]

It's all a bit uncharted territory for us hydrocarbon burners I've no idea of the rear braking characteristics for a battery car. In theory they'd use less rear braking effort than a conventional car for most of the time as they use regen braking, so are the rear brakes spec'd to match this ? i.e. softer material ? harder material ? or 'thinner' drums ? Or have they just grabbed something that fits from the parts bin ? Are they more susceptible to a build up of brake dust ? It'll be interesting to see what Simon finds.

[Mandrake]

Simon, I've sent you the PSA docs for the rear brakes - but I see you have another source .

Thanks for that PDF - it's far better and more detailed than the Mitsubishi version I have! That will be very helpful.

Amusingly the PSA docs say to remove the drum "remove wheel. Remove Drum" No mention of any screws, and I can't see any on the diagram, so it would appear to just 'lift' off. Might need some persuading over the studs if it's never been off.

Strangely though if you look carefully at the pictures all the later pictures show the stub axle nut removed! Hopefully that's not actually necessary and was just done for photo clarity as I don't see any steps saying to remove it... I'm not sure that I'm equipped to remove and refit a stub axle nut - when we did the Xantia I used your tools for that!

I wonder if you might find a debonded lining....

As soon as you wrote that I had one of those "Ohhhhhhhhh...." moments of realisation... I think a partially de-laminated lining would explain the symptoms perfectly, especially if it was the self-applying side that tends to try to dig in if not controlled properly... It would explain the intermittent sticking on, and the squealing/scraping I hear when applying the handbrake while moving, which goes away after a few applications - the lining is probably moving around sideways with each application and scraping on the outer drum sometimes.

I think you may well be proven right and I think when I take the drum off the very first thing I'll do is check for de-lamination and if I find it I'll stop right there and put it back together until I can get a set of new linings, as stripping it down will be pointless and probably just lead to the car being off the road completely until new linings are sourced. Let's hope it's not that but I think it may well be!

I dislike rear drum brakes nearly as much as I dislike exhausts! My worst effort was on our first ZX - failure of a wheel cylinder was caused by some nugget being there before me and making a bog of assembling it which had resulting in a shoe twisting till it let the piston pop out. This had ruined the cylinder, shoe and the drum. They had also made a bog of fitting the adjuster, and broken it. Removing the pipe from the cylinder resulted in its failure - and same on the other side. So this resulted in new drums, bearings (in the drums), shoes, adjusters, cylinders and pipes - and finding someone on Saturday morning to make the pipes and press the bearings in. To cap it all, said nugget had also managed to mash the thread on the (M20!!) axle thread, so I was luck to get the hub nut back on Here's hoping yours is more straightforward!!

Here's hoping!

One thing I'm a little worried about is the special tools listed - in particular the one for the "brake shoe retention cups" - there is no picture of the tool and not a clear picture of the cups so its hard to visualise what kind of tool it is and whether I can improvise. I'm also hoping that I don't have to remove the stub axle nut!!

I'm also not sure what kind of grease I should be using - for the "contact points of the brake shows on the brake backplate" - is copper grease likely to be suitable as long as its kept away from the cylinder, or should I be using something else ? It just says to grease the in the document, it doesn't specify the kind of grease as far as I can see...

[Mandrake]

Hope it doesn't need new drums... I can't see them anywhere else, and they are £75 each from PSA....

Drums are probably ok (he says hopefully) but I wonder about the linings ?

[Mandrake]

It's all a bit uncharted territory for us hydrocarbon burners I've no idea of the rear braking characteristics for a battery car. In theory they'd use less rear braking effort than a conventional car for most of the time as they use regen braking, so are the rear brakes spec'd to match this ? i.e. softer material ? harder material ? or 'thinner' drums ? Or have they just grabbed something that fits from the parts bin ? Are they more susceptible to a build up of brake dust ? It'll be interesting to see what Simon finds.

The rear drums will do bugger all during most driving, light to medium braking is all done by regeneration on the rear wheels. Harder braking adds the rear and front friction brakes but I suspect the rear drums aren't particularly sensitive or powerful compared to the front discs, which are quite sensitive. (Or were when I first got the car!)

I suspect they're out of the parts bin though as the i-Miev is based on the petrol Mitsubishi i-Car, so I strongly suspect that aside from adding an electric vacuum pump that the mechanics of the brakes are identical to the petrol version!

[bobins]

One thing I'm a little worried about is the special tools listed - in particular the one for the "brake shoe retention cups" - there is no picture of the tool and not a clear picture of the cups so its hard to visualise what kind of tool it is and whether I can improvise.

You'll like this The brake shoes are held against the brake back plate via a pin, spring, and cup to hold the spring under tension.

ION brake shoe fixing, modified PSA image - fair use

There is one pin per shoe. The pin (circled blue) passes through the back plate and loosely through the metal frame of the shoe. A small spring holds the shoe in tension against the back plate to stop it wobbling / vibrating around. The spring is held onto the pin via a piddly little cup (circled red) - it'll be a case of pushing the cup onto the pin against the spring pressure and a quarter turn to lock it onto the pin. You can try and source the specialist tool if you want.... but a pair of needle nose pliers will work nicely Be careful though - the cup and spring is a junior version of the original pingf*cket, it's not capable of such a violent trajectory as most pingf*ckets, but it can still go a fair way to the uninitiated

[bobins]

I'm also not sure what kind of grease I should be using - for the "contact points of the brake shows on the brake backplate" - is copper grease likely to be suitable as long as its kept away from the cylinder, or should I be using something else ? It just says to grease the in the document, it doesn't specify the kind of grease as far as I can see...

Personally, I'd use copper grease as it'll be metal against metal and only a couple of 5mm contact points per shoe. In use, each shoe is only going to move a matter of (under 10) millimetres from rest to fully applied, so you don't need to go overboard on the grease. The end goal is to make sure the shoes move smoothly over their very short distance of travel.

[xantia_v6]

I was told by more than one well qualified person that copper grease should only be used as an anti seize compound in situations where there is no relative movement between the components, as copper grease is actually slightly abrasive and will cause steel components to wear if it is used as a lubricant.

Also see https://textar-professional.com/textar- ... rn-brakes/ for another point of view.

Be aware that if you see a fault after dismantling your brakes, then reassemble and use the car without properly repairing, you could be on sticky ground if you have an accident (driving a vehicle in unsafe condition).

[RichardW]

If a picture is worth a thousand words...



Interesting that the drum appears to have threaded holes to act as a puller. Looks like new shoes are available not too dear - you may well be able to get a set at a local factors if necessary - there's a big one over the back of Hamilton, or TMS has several branches locally, but they close at lunch time today!

[Mandrake]

I was told by more than one well qualified person that copper grease should only be used as an anti seize compound in situations where there is no relative movement between the components, as copper grease is actually slightly abrasive and will cause steel components to wear if it is used as a lubricant.

Also see https://textar-professional.com/textar- ... rn-brakes/ for another point of view.

So much conflicting advice about grease. That article basically rules out the use of copper grease on brake systems at all, and the one application that everyone seems to claim it is good for - "preventing" corrosion between the caliper and rear arm on a Xantia, according to this article doing that will make the corrosion far worse!

So just use standard lithium grease then to lubricate the pins and shoe slide points ? That's the only other grease I have on hand at the moment. I've ordered a small tube of silicone based grease for the front brake slide pins but that hasn't arrived yet. My only worry is I'm not sure standard lithium grease is sticky enough to stay in place in a large open environment like the inside of a drum assembly, especially if water could get in, and I'm not sure it's temperature rating is high enough.

[bobins]

The amount of movement that takes place, and the forces involved in keeping the shoes snug against the contact points, your car will have rusted away and long been recycled before any appreciable wear takes place between the brake shoe and backplate contact point !

[myglaren]

I only ever used Castrol High Melting Point grease on drum brakes and never had any problems with it.
Drum brakes in general were no fun though.

Molyslip grease should be OK too.

I noticed when in Homebase last week that they have small tubes of silicone grease on sale.

[white exec]

Looks like an utterly conventional/traditional brake drum set-up. An arrangement that's been in use for 50+ years!
The threaded holes in the drum face allow bolts to be inserted, which push against the hub flange, and help the drum to come off.
The shoe steadies can be released by pressing the washer at the outboard end with the ends of some point-nose pliers, and then rotating, so the pin is released from the washer - push, turn, release.
Copper grease on shoe ends and the backside steady post (where it rests on the shoes) and other not-much-movement parts will be fine. It does transmit (damp) vibration rather well.
With the new shoes, it could be worth gently chamfering the very ends of the lining (ie slope off the square end a bit, say 3-4mm; this can help prevent squeal).

[Mandrake]

Thanks guys. I’ve started on the job and just got the drum off. There is loads of built up lining dust that you can see in the pictures below in the drum and elsewhere.

Initial impressions - inside surface of the drum looks and feels perfect. Linings both have 3.5mm material left and are not delaminated. They actually look fine.

No obvious problems yet except the build up of dust so I’m hoping a strip, clean, lube adjust and reassemble may do the trick!

[Mandrake]

Just looked up the lining thicknesses in the service data I have - new linings are 4mm and the minimum allowed is 1mm, so at 3.5mm they're hardly worn!

The maximum inside diameter of the drum is specified too, I went to measure it with my digital vernier until I realised it only goes to 150mm... So I'll just have to take it on faith that the drum diameter is OK.

I do notice a bit of a rust lip on the edge of the drum on the other side of the car which might potentially brush against the edge of the lining so I'll see if I can sand that back.

And yes I'll give the end of the linings a slight chamfer as well as they are square at the ends...

One thing I have noticed is that when I try to rock the linings they don't slide across the backplate very smoothly they seem to be grabbing quite a bit, so I wonder if them not moving freely on the backplate due to lack of lubrication and build up of dust is the main issue. Still undecided whether to use copper grease or normal lithium grease on the backing plate slides.

With the linings held away by the hand brake, both pistons seem to slide in and out freely and smoothly on both sides of the piston so I'm not going to touch the cylinders - I forgot to buy any dot4 fluid anyway.

Right, tea cup down and back to work.