Fitted new discs and pads last week. Today I got thinking....

My assembly procedure involved cleaning the hub and very lightly copper greased the front mating surface, then put on the new disc. After fitting the caliper, I then lightly copper greased the mating surfaces of disc/wheel before fitting the wheel. All this was to ensure the wheel and disc could be removed easily next time I needed to

But now I'm thinking should I have greased the mating surfaces? I think I read somewhere that transmission of power and braking should rely on the clamped friction of those surfaces and not via the wheel bolts.

Comments please.

OK, I've just found the Fabia thread where it was discussed.

"....the joint face between the wheel and hub should also remain dry - this face is, effectively, a clutch face transmitting drive and braking torque between the hub and wheel. This torque should be transmitted by the friction, and not by shearing the bolts."

Also same thread has similar warning about dry assembly from vag.

So tomorrow it looks like a stripdown again.....dammn!!!

I've never had any issue getting the disc off without grease being applied, just make sure the surfaces are clean and free from debris. I would strip them down again and wipe the grease off just to put your mind at rest.

OK, I've just found the Fabia thread where it was discussed.

"....the joint face between the wheel and hub should also remain dry - this face is, effectively, a clutch face transmitting drive and braking torque between the hub and wheel. This torque should be transmitted by the friction, and not by shearing the bolts."

Also same thread has similar warning about dry assembly from vag.

So tomorrow it looks like a stripdown again.....dammn!!!

Don't forget to grease your pins, Like I did the first time I did my brakes.

 

I need to strip mine down again as I have used copper spray this time, and at the time did not think it felt great.

 

I now know that copper grease is not really great for the rubber, but even worse the spray has fast evaporating solvent, so even worse.

 

I happen to have some MTB Teflon grease - to 150 degrees - so will replace with this this weekend, weather permitting.

I've always put a thin coat of copper grease between the hub and wheel. Probably covered 100's 000miles and no issues with transmitting the power or braking.

 

On the other hand the wife had a Mini (BMW) Cooper S and before I got chance to have the wheels off she picked up a flat. As it was a bank holiday the RAC where snowed under and couldn't get to her quickly so I went to do the tyre repair complete with a winter tyre as a repair. Got there and the tyre was punctured through the tyre wall so no way was the sealant going to fix it so gets my jack out and change the wheel over. Would it chuff come off, kicking it to loosen it and still nothing. Put a couple of bolts in loosely and dropped the car back down to break the surface contact and nothing. Put the remaining bolts in again, still loose, and tried moving it back on forth. Still nothing but me swearing and the wife having kittens as she had vision of the wheel flying off.

Called the RAC again and told it would be a wait so sent the wife home in my car. RAC bloke turns up and explain to him the problem and what I'd already tried to which he says no problem I'll get it sorted. Tries lowering the car onto the wheel (I tried that already) then lifting from under the wheel with a pole then a jack and nothing. Calls his mate who suggest driving the car but they're not allowed to do that so I try again and still it's stuck fast. Car ends up getting recovered and nearly a full day is wasted. Local garage eventually gets the wheel off but is damaged in the process which I was warned about. This was on a 2 year old car.  Both the garage and RAC said a bit of copper slip prevents this which I already knew.

Wow!! Now I'm in two minds. I too now remember it was a bit of a struggle getting the wheels off the Octavia when it was a little over a year old due to tons of electrolytic corrosion. Same story with all the Fabias. No problem after a touch of grease. I guess its a question of using the minimum amount.

AFAIK the sliding pins should not be greased, just cleaned ( I used penetrating oil). The pins slide in nylon66 bushes (which I guess should be cleaned out too) and should not require lubrication. Grease will just mix with brake dust and cement them in place.

What to do? I think I'll sleep on it. In the meantime, some further comments would be welcome.

I always put a smear of copperslip on the hub face where the alloy wheel mounts onto it,i have done this for the last 26 years as a mechanic & ive never had a problem with any car that ive done this on,the amount of alloys ive come across siezed onto the hub is ridiculous. 

Sorry but I cannot see how an alloy can seize onto a hub. It doesn't rust. I'm not calling anyone a fibber though, but never have come across the issue myself either.

On the other hand I cannot see an issue with using a smear of copper grease, either. So long as it is just a smear.

 

AFAIK the pins should be greased, (or perhaps I should have said lubricated). But not with copper grease.

Edited 31 March, 201610 yr by Tilt

Sorry but I cannot see how an alloy can seize onto a hub. It doesn't rust. I'm not calling anyone a fibber though, but never have come across the issue myself either.

On the other hand I cannot see an issue with using a smear of copper grease, either. So long as it is just a smear.

 

AFAIK the pins should be greased, (or perhaps I should have said lubricated). But not with copper grease.

 

When you get 2 dissimilar metals together the corrosion rate increases, I have taken quite a few wheels off and finding one that is stuck in isn't very common but it does happen. I've also seen copper grease applied and although its not technically right, I agree that it would be big surprise for it to cause any issues.

 

Its like re-using stretch bolts, its not right, but i have done it many times and the dealers do it all the time as well but you never hear of any snapping

SuperbTWM, on 31 Mar 2016 - 21:14, said:

When you get 2 dissimilar metals together the corrosion rate increases

 

Quite right, SuperbTWM: it's galvanic corrosion arising from dissimilar metals in contact, as anyone who has worked on motorcycles will know, where steel fasteners will seize solid into alloy engine cases over time.  Here's why: https://en.wikipedia.org/wiki/Galvanic_corrosion

Sorry but I cannot see how an alloy can seize onto a hub. It doesn't rust. I'm not calling anyone a fibber though, but never have come across the issue myself either.

On the other hand I cannot see an issue with using a smear of copper grease, either. So long as it is just a smear.

Aluminium oxide...white powdery stuff that bonds pretty well to steel. I now recall several years ago on our first fabia watching the tyre fitter belting the rear alloys with a sledgehammer and block of wood, took him a few minutes to get them off. I've used grease of some form ever since without problem and have always been shocked at the corrosion present when stripping the wheels for the first time on all the new skodas we've bought, in one case only a month out of the factory.

The quotation in my first post seems to have actually originated from a certain self declared engineering expert on hj's forum. Im familiar with him on that forum and he is somewhat convinced of his superiority in engineering matters and does not accept anyone but his own opinion and thats enough for me to downgrade the importance of his opinion.

Consensus on the internet seems to favour the antisieze approach and there doesn't seem to be any reports of damaged or sheared wheel bolts due to its use on mating faces that I can find.

So I think I'm overreacting and although VAG may disagree, I'm going to stick to the seasoned mechanics lightly greased approach (strictly speaking its more anti seize compound than grease - every time I strip off the wheels the grease bit seems to have disappeared leaving only the copper powder deposit.)

Edited 31 March, 201610 yr by xman

To the OP:  If you worked on the normal male theory of "Xis good, therefore 2X is better then you probably need to clean it off.  If you put the thinnest smear I would worry too much.

Several years ago a good friend of mine arrived at work with a flat tyre on his car (astra ragtop) we had a hell of a job trying to get the wheel off - all due to oxidation, steel hub / alloy wheel. the wheel came off in the end - copper hammer, piece of wood  & a crow bar, car nearly fell off the jack. Since this I have always applied copper grease between the two matting faces with no issues.

 

paul

Edited 1 April, 201610 yr by Flyfisherman

After a night reading all about electrolytic corrosion and how aluminium/zinc/steel could rot when paired with copper, and then realising the JURID disks I fitted had a "NONOX" coating (zinc or similar plated), next day I stripped the calipers and discs off and cleaned all the copper grease off except for the carrier slide/pad interface and the centres on which the wheels locate (not the face).

Incidentally I found one of the alloys had copper grease splattered on the inner edges so even my "light application" was in fact too much!

I intend to remove the wheels every diy service (6-8 months), unlike skoda dealers, who never remove them, I'll soon see if the NONOX coating is effective.

I had the back wheels of the Octavia for the first time last weekend and they needed a block of wood and a lump hammer to shift them. Not sure when last off, but plenty of white crud particularly around the central hole. I have no qualms about having put a thin smear of grease on the inner face of the wheel after cleaning up. It is absolutely correct that torque should be transmitted by the friction between hub and disc and disc and wheel, but the clamping forces are sufficient even with a bit of grease in there - don't forget the surfaces are not perfectly flat so the high and low spots will interlock. There is only so much that grease can do!

As a follow up I can report....

A week or so later I still noticed brake drag along with excessive brake dust. After a bit more googling, Ive decided that Yes, I do need to lubricate the caliper slide pins. So another partial stripdown! Used the Cer-tec brake grease for this.

I also noticed that even after just a week, when I cleaned the copper grease off the alloy wheel centres, there appeared to be pitting in the alloy. Electrolytic corrosion!! So now I am of the opinion that copper grease causes more problems than it prevents with alloys, so Cer-tec non metallic grease is what Im going to use from now on.