PBC query rear brake union - pre IVA

[Mucus72]

Hi all,

I am just looking at making a change to the rear brake union where the rear flexible hose goes through the chassis hole and then into the make brake pipe attached to the chassis.

My PBC comment from the guys at BookATrack was: " too many washers on rear flexible brake hose (union tightening up on lock nut)"

P132 of the assembly guide states "Place a plain washer over hte male union on the other end of the braided hose then pass the union forwards through the vertical aluminum panel, apply a further plain washer then the shake proof washer and secure in place with the locknut provided. Finally, attach the rigid brake pipe from the transmission tunnel."

I have just had a look, and if I read the instructions correctly, then the two photos attached show that I have followed this. I'm therefore questioning the PBC notice, and am looking for POBC advice please.

Photos:

[ScottR400D]

The union you refer to doesn't have any washers. On my kit it was already fitted as such. 

The instructions you quote seem to refer to the front brake hose connections, through the alloy panel. 

[Ian Mackenzie]

The issue that I can see is that the union is closed up onto the nut, I would want to see a bit of a gap so the clamping force is all on the pipe and not onto the nut. Yes this has either been caused be over tightening the union, the extra washers, or a combination of both.

I'd refit with less washers to ensure a gap between the union and the nut.

cheers

Ian

[Mucus72]

Hmmm. Both of you agree with each other and the PBC advisory. So I must be wrong, based on count of data points ;) however I've double checked the assembly guide and the instructions on p132 and the washers described are from the rear, not the instructions regarding fronts through the side skin. 

[Jonathan Kay]

Previous versions of the Assembly Guide had:

8 Attach the other end of the braided hose to the solid brake pipe coming from the transmission tunnel through the vertical aluminium panel. A plain washer should be placed between the solid brake pipe fitting and the aluminium panel and a shakeproof washer between the aluminium panel and the braided hose fitting. 

Jonathan

PS:

If you check the preceding paragraph of your Guide (concerning the other end of the flexible hose) does it have:

"The rear braided hose can now be fitted. Thread the locknut onto the male union on one end of the hose then attach the braided hose to the three way union on the De Dion tube and tighten to 10 Nm. Lock into place using the locknut. The locknut supplied should not restrict the union from tightening fully."

In 1998 that used to read:

"If the locknut is too big and overfills the threaded space it should be replaced with a smaller one, otherwise the hose fitting will be pulled from its taper seat."

 

[ScottR400D]

Forget my earlier post  

After looking at my manual again I found the OP's instructions on P140. Looking at my car again maybe I did assemble that part in that way but not with all the washers. In all honesty I have no recollection of that part of the assembly but it appears I have one washer under the nut on the rigid side, that's the nut that is rotated to clamp the joint.

Plenty of clear thread ensuring by the union locks up properly.  

One thought. Are you sure the washers you've used are the right ones? They look quite thick. Looking at the various hose kits available from CC they seem to come with lighter, thinner ones, if any.   

 

[Mucus72]

In the end I removed one on the solid brake pipe side simply because that's where it was and fluid was dripping out pretty quickly when I was doing it. I can confirm that the locking nut definitely has a gap between it and the union nut, which is the aim. I can also confirm that my end result is exactly opposite to what Jonathan has posted above! So one plain washer on the flexi hose side, and a shake proof one on the solid pipe side. At the end of the day, and with all of your help, I can see what the aim is, and I've achieved that! It will probably pass IVA on Wednesday. ;)

[griffchris]

This thread rang a bell from my build last year, so i fished out my email to Derek H, and his reply:

Hi Derek

Just a quick one - attaching the rear flexible brake hose  to the rigid pipe, through the vertical aluminium panel.  If I add plain washer/aluminium panel/plain washer/shakeproof washer/locknut then attach to the female rigid pipe union as suggested in the manual, the female union strikes the locknut before it has actually tightened on the threads.  i suspect this might be because the plain washers I'm using are too thick - which washers should I be using for this?

Ta

Chris

Reply:

Hello Chris,

Leave the second plain washer off as long as the shack proof is still there it will be ok.

Kind regards 

[Mucus72]

That confirms that my removal of one plain on the shake proof washer side is accurate, the PBC advisory was correct, you guys all helped. Oh and finally, yet again the assembly guide is rubbish! 

I feel satisfied now, and my IVA is this Wednesday. Thank you all!

[John Vine]

...yet again the assembly guide is rubbish! 

When I assembled my current 7 in 2008, I followed the AG precisely (it was worded exactly like yours).  I had no trouble tightening the fixed-pipe union correctly, so I suspect your difficulty is not so much down to the AG but rather the thickness of the plain washers supplied.

Well spotted, BookaTrack.  And good luck with the IVA.

JV

[Garry7]

I had the same issue with my 2012 build and fed it back to CC with the front hose / washer issue too. Sadly they decided they know best and have left the manual as it was

[ScottR400D]

Thing is, it's said to be bad practice to put a shake proof and plain washer together. The plain washer reduces the effectiveness of the shake proof and can render it useless. IIRC the use of them is quite common in the CC manual. 

As is often the case it doesn't matter either way most of the time but there may come a time when it will!

maybe loctite's the way to go!

 

[Jonathan Kay]

Thing is, it's said to be bad practice to put a shake proof and plain washer together. The plain washer reduces the effectiveness of the shake proof and can render it useless.

I think it's necessary to distinguish between split ring washers and star washers, and for the latter the types of surfaces that are engaged. The relevant Wikipedia article has links to guidance from NASA and others, but note the uncertainty about who asserts what.

Jonathan