Front brake backplate corrosion.

[maccy]

A question here for the team.My 6Y5 is coming up for MOT shortly, everything looks OK except for both front brake backplates are quite corroded now.The backplates are easy to get but when I ask about the mounting bolts I have drawn a blank.Does anyone know what size the bolts are so I can buy them before I strip it down to replace the backplates ?

       Thanks in anticipation.

 

[sepulchrave]

You don't even need backplates for the MOT, so they won't fail as long as they're not flapping about.

 

As for bolts, M6 x 13 if memory serves, just take one out and have a look.

[Breezy_Pete]

MOT isn't interested in the backplates, they can be completely absent from that point of view.

Retaining screws are an M6 thread, 10 or 12mm long will be plenty I think.

[StevesTruck]

Expect the bolts to be very seized, very seized indeed, and accessible only by spanner with the hub in place. 

[AnnoyingPentium]

If it makes you feel any better, one of my backplates was scattered along a main road when it decided to let go at 60mph.

[Lofty]

15 hours ago, sepulchrave said:

You don't even need backplates for the MOT, so they won't fail as long as they're not flapping about.

 

As for bolts, M6 x 13 if memory serves, just take one out and have a look.

 

Assuming they come out! They'll be as corroded as the back plates.

M6 x 13mm is bang on though. 

 

Best bet would be if they are hanging off to tear them off and forget about them, unless you're going down a rebuild worm hole. Not many have the original backplates anyway now (on vRS models at least) as most have fitted bigger front discs so would have been discarded long ago.

[Breezy_Pete]

10mm length on the parts diagrams, could well be tapped deep enough for longer though.

The heads usually corrode to buggery and might need chiselling round, but the threads are usually clean within the bearing carrier, in my limited experience.

[KeithCheetham]

2 hours ago, Breezy_Pete said:

The heads usually corrode to buggery and might need chiselling round, but the threads are usually clean within the bearing carrier, in my limited experience.

 Having done them on my Mk2 last year, agree with Pete's comments as I had to chisel mine around, but once started to move they came out easy. Looking back, they were £9.02 each side, and replaced the screws with copper greased stainless steel capscrews. It will be a balance between leaving as is and possibly rustproofing with a product such as Vactan which rust convers and primes in one to tidy up, replacing with no problems or chancing bolts heads shearing off causing more work. As with all these corroded fastener issues, I always try to heat bolts with a pen type gas torch (giving small controllable heat area) and then spraying with Plusgas - won't use WD40 which I consider a do everything badly product - with the heat plus rapid cooling/contraction plus the possibility of Plusgas being drawn into the threads tending to aid removal.

 The change out was basically driven by a requirement to swap out an ABS sensor which is not really possible with the dust covers in situ.

[KenONeill]

22 minutes ago, KeithCheetham said:

won't use WD40 which I consider a do everything badly product

Water dispersion!? I totally agree that WD40 is not, and never was, a dismantling lubricant.

[nta16]

Please note - I am not a mechanic or expert in anything.

 

1 hour ago, KeithCheetham said:

spraying with Plusgas - won't use WD40

Totally agree with not using WD-40 (but it can be a useful jack-of-all-master-of-none spray if nothing better is available for emergency use).

 

PlusGas I don't find to be as good now it's brewed by someone else (black cans) as it used to be but that might be false nostalgia (Rapideze was my go to decades back).

 

My current favourite as a penetrating releasing fluid and lubricant (smells nice too) is something I first used in the 1980s (along with LPS) as a lubricant - GT85.

 

(Again sadly GT85, as with PlusGas, is no longer a British company.)

 

Whether using GT85, PlusGas, WD-40 or other, reading and following the instructions is need along with often two items in short supply or out of stock with many, time and patience, waiting to allow the fluid to soak well in, possibly overnight, then if the first application and waiting doesn't work applying a second and leaving to soak in.  This is why many resort to using heat which is fine if it's sufficiently available and suitable but it isn't always available for some/many.

 

Edited 7 October, 2022 by nta16
ETA:

[maccy]

21 hours ago, maccy said:

brake

 Thanks for all of the replies,I will see what happens at the MOT next week.

[TMB]

I used to have a MK2 Fiesta 950cc that had no disc backplates from the factory. Interesting bit of penny-pinching.

[KeithCheetham]

6 hours ago, nta16 said:

Please note - I am not a mechanic or expert in anything.

 

 PlusGas I don't find to be as good now

 

allow the fluid to soak well in, possibly overnight, then if the first application and waiting doesn't work applying a second and leaving to soak in.  This is why many resort to using heat which is fine if it's sufficiently available and suitable but it isn't always available for some/many.

 Plusgas was the go to product in our factory, most refineries and oil rigs I visited. The problem with just spraying is that the rust may form a barrier between the male and female threads that liquid cannot penetrate, and the initial tightening pulls the thread pitch faces tight onto each other again stopping any penetration of liquid. What it may do is bleed under the fastener head to component interface, changing the co-efficient of friction requiring less break away torque.

[KenONeill]

2 hours ago, TMB said:

I used to have a MK2 Fiesta 950cc that had no disc backplates from the factory. Interesting bit of penny-pinching.

Similarly with a Citroen ZX (and some of those definitely had disc backplates).

[nta16]

Please note - I am not a mechanic or expert in anything.

 

13 hours ago, KeithCheetham said:

 Plusgas was the go to product in our factory, most refineries and oil rigs I visited. The problem with just spraying is that the rust may form a barrier between the male and female threads that liquid cannot penetrate, and the initial tightening pulls the thread pitch faces tight onto each other again stopping any penetration of liquid. What it may do is bleed under the fastener head to component interface, changing the co-efficient of friction requiring less break away torque.

Yes a good soaking is best and approached from all angles possible, I often preferred the use of the drip can as it could be more direct to an area.  Also you can prepare the area to help with the success by cleaning off layers of whatever crud, grease, paint, etc. so that the penetrating releasing fluid has more opportunity to soak into where it's needed, but often that's far too much effort and thought for some.

 

After the fluid has been left to soak in for as long as possible I also like to try to tighten before loosening, many say that's a waste of time but I think that can sometimes be the bit that can crack the crud seal of 'whatever' that even if it doesn't loosen the fitting may allow the second soaking, and leave as long as possible, to work.  Let the chemical and tools do the hard work.  Professionals are often in a rush so have to use strength of arm, for those not being paid that's often more about vanity and ego, no problem as long as they don't bust your fitting.

  

[KenONeill]

5 hours ago, nta16 said:

After the fluid has been left to soak in for as long as possible

Or "at least one tea break"...

[nta16]

Please note - I am not a mechanic or expert in anything.

 

I was thinking at least one mug of tea and at least two pees, but for us old uns that'd be nowhere near long enough.  It's a car so leave it whilst you do anything more interesting and better (that's almost everything to me) but then you'd never come back to it so limit it perhaps to overnight just to be practical.

 

[StevesTruck]

On 07/10/2022 at 10:37, Breezy_Pete said:

10mm length on the parts diagrams, could well be tapped deep enough for longer though.

The heads usually corrode to buggery and might need chiselling round, but the threads are usually clean within the bearing carrier, in my limited experience.

 

The holes go all the way through the carrier so it doesn't matter if the new bolts are a bit over. 

[J.R.]

It does if they are not tapped all the way through or are done with a taper tap, both accepted practice to minimise machining costs.

[sepulchrave]

5 minutes ago, J.R. said:

It does if they are not tapped all the way through or are done with a taper tap, both accepted practice to minimise machining costs.

 

CNC milling machines don't use taper taps, they use a helical machine tap that does the entire operation in one pass and it would definitely go the whole way through rather than stop and risk jamming.

[Breezy_Pete]

I think they are blind holes, and that's why the threads don't get corroded (no water access in from far end).

Aftermarket versions, but a couple of examples in ebay listings: NEW SEAT IBIZA MK3/MK4 FRONT LEFT STEERING KNUCKLE WHEEL BEARING HUB (W/CARRIER) 5060952960659 | eBay  (256mm type)

 

NEW SEAT IBIZA MK3/MK4 FRONT PASSENGER SIDE HUB STEERING KNUCKLE (288MM DISC) 5060952963810 | eBay

 

 

Bit harder to see on this one, but a genuine one i'd've thought judging by condition:

2010 SKODA FABIA 1.2L Petrol PASSENGER FRONT HUB 6Q0407255S | eBay

 

Edited 11 October, 2022 by Breezy_Pete

[sepulchrave]

14 minutes ago, Breezy_Pete said:

I think they are blind holes, and that's why the threads don't get corroded (no water access in from far end).

Aftermarket versions, but a couple of examples in ebay listings: NEW SEAT IBIZA MK3/MK4 FRONT LEFT STEERING KNUCKLE WHEEL BEARING HUB (W/CARRIER) 5060952960659 | eBay  (256mm type)

 

NEW SEAT IBIZA MK3/MK4 FRONT PASSENGER SIDE HUB STEERING KNUCKLE (288MM DISC) 5060952963810 | eBay

 

 

Bit harder to see on this one, but a genuine one i'd've thought judging by condition:

2010 SKODA FABIA 1.2L Petrol PASSENGER FRONT HUB 6Q0407255S | eBay

 

 

If they're blind holes then the machining is different but; none of this is really relevant since the OP doesn't even need to bother doing them for the MOT so this thread is meandering into irrelevance somewhat.

[Breezy_Pete]

People will post whatever they wish to.  Has battery charging come up yet, I don't read everyone's posts? 😁

[KenONeill]

1 hour ago, Breezy_Pete said:

I think they are blind holes, and that's why

... the length of the bolts/ set screws matters.

[sepulchrave]

Just now, KenONeill said:

... the length of the bolts/ set screws matters.

 

Not if the OP doesn't even need to fix the stupid thing at all.