UrS4 Strut pinch bolt size & Bira brake bracket interference

Cody Forbes cody at 5000tq.com
Fri Jun 4 19:34:01 PDT 2010 

I'm fairly certain that the friction between the OD of the ball joint  
pin and the ID of the strut housing is what holds the ball joint, not  
the notch in the pin vs the bolt. This is why and how the joint  
previously mentioned was able to come undone even with the bolt tight  
due to the housing ID being damaged.

Anyways I do agree with using the proper bolt and nut.

-Cody (mobile)

On Jun 4, 2010, at 6:24 PM, Mark Rosenkrantz  
<speedracer.mark at gmail.com> wrote:

> The tension is minor and even a low grade, fully threaded fastener  
> would suffice for that aspect (if that was the only aspect). The  
> critical function is to secure the ball joint from leaving the wheel  
> bearing assembly and that is in double shear.  And this is why I  
> commented on the need for the correct length of unthreaded area.  If  
> the fastener's only role was tension, I'd submit that those other  
> issues don't matter and even some elongation (torque to yeild) would  
> be acceptable.  Because of this, the correct material is a  
> requirement to avoid a number of issues, including galling with the  
> ball joint as well as any deformation which would compromise the  
> surface area of the ball-joint to fastener interface.  I also think  
> that surface area is critical to the design... that relying purely  
> on the small lip would lead to failure, even under normal useage  
> (especially considering road debris could create wear and/or a ramp  
> effect).
>
> But again, the factory nut and bold are just a few dollars and work  
> fine.  It's a good idea to just replace them any time they are  
> apart.  On this, I'm sure Cody would agree!  =)
>
> Cheers!
> Mark Rosenkrantz
>
> On Fri, Jun 4, 2010 at 6:05 PM, Cody Forbes <cody at 5000tq.com> wrote:
> Actually it's not in double shear, it's not in shear at all in  
> normal use. The bolt is used to clamp the pinch area to hold the  
> ball joint pin. That means it's purely under tension. I suppose that  
> if/when it comes loose the relief in the ball joint could be  
> considered to be putting it in shear, but it shouldn't be loose.
>
> -Cody (mobile)
>
>
> On Jun 4, 2010, at 5:34 PM, Mark Rosenkrantz <speedracer.mark at gmail.com 
> > wrote:
>
> Proper fit is the key.  Having the correct thread length is critical  
> to
> maximize the contact area.  The bolt is in double-shear so I doubt the
> forces would require any exotic steel.
>
> ARP makes excellent fasteners, but having a custom fabricated  
> mechanical
> fastener for this application does seem overkill when the only  
> failure mode
> of the factory (inexpensive) bolt is due to corrosion.  And that only
> manifests itself during removal.  Personally, I reinstall the new  
> fastener
> with anti-sieze on the wheel bearing housing contact areas.
>
> Mark Rosenkrantz
>
> On Thu, Jun 3, 2010 at 7:35 PM, Chris Talley <talleycm at gmail.com>  
> wrote:
>
> I ordered the parts from the deal for  $ 2 a piece.
>
> As far as outsourcing I thought there might be a better/higher
> quality choice for the application, there are aerospace and other  
> ultra
> high
> quality automotive fasteners like ARP that offer the same  
> specifications,
> and usually have very good technical support and a premium price.
>
> The design on the URS4 ball joint incorporates a groove to retain  
> the ball
> joint in case the fastener loosens.
>
> Chris
> .
> On Thu, Jun 3, 2010 at 9:25 AM, <dgraber460 at aol.com> wrote:
>
> My reason for "qualifying" my remarks is evident.
> My experience is with the URQ struts, and the ball joint for them is
> grooved in such a way that if the bolt is the correct diameter and
> present,
> the joint cannot come out.
> I have seen a 928 loose a BJ while moving and agree it is _not_ an  
> area
> to
> try to substitute or save money.
>
> Dennis
> Denver
>
>  -----Original Message-----
> From: Fred Munro <munrof at sympatico.ca>
> To: dgraber460 at aol.com; talleycm at gmail.com; quattro at audifans.com
> Sent: Thu, Jun 3, 2010 7:09 am
> Subject: RE: UrS4 Strut pinch bolt size & Bira brake bracket  
> interference
>
> There have been a couple UrS listers who have had the ball joint  
> drop out
> while the car has been in motion - one that I recall was at highway  
> speed
> on
> an Interstate. This is guaranteed to ruin your entire day. From what I
> recall, in one case the improper bolt had been used. In the other case
> someone at the shop had pried open the slot in the strut housing to
> release
> the old ball joint when they were changing the control arm. The tool
> marks
> were still in the slot. This deforms the strut housing and it will  
> never
> hold the ball joint again - the strut housing has to be replaced.
> This is not an area to fool around with if you don't know the  
> engineering
> reasons for some of the design choices. The Bentley states an  
> orientation
> for that bolt and there is a reason for that. They don't mention
> orientation
> for many other bolts. Retention of the bolt if the nut falls off is a
> good
> guess, but just having the bolt in the hole won't keep the ball  
> joint in
> place. If that bolt loosens off the ball joint will pop out. My guess
> would
> be it has something to do with the way the clamping pressure is put on
> the
> strut housing. In any case, I'd recommend using the correct new bolt  
> and
> nut
> each time it is loosened and orient it per the Bentley.
> Chris, removing the BIRA bracket is a PITA, but I'll guarantee it  
> will be
> more of a PITA if the ball joint drops out while you are driving the  
> car!
>
> JMHO
>
> Fred Munro
> '97 S6
>
> -----Original Message-----
> From: quattro-bounces at audifans.com [mailto:quattro- 
> bounces at audifans.com<
> quattro-bounces at audifans.com?>] On
> Behalf Of dgraber460 at aol.com
> Sent: June 2, 2010 11:25 PM
> To: talleycm at gmail.com; quattro at audifans.com
> Subject: Re: UrS4 Strut pinch bolt size & Bira brake bracket  
> interference
>
>
> My understanding (which is only hearsay, and my own assumptions) is  
> that
> a
> grade 8 would be more than sufficient, and easily sourced.
> My other assumption is that it is head forward so that in the rare  
> case
> the
> nut vibrates off, the bolt will be more likely to stay in place.
> Anyone with the true engineering "facts", feel free to chime in.
>
> Dennis
> Denver
>
>
>
> -----Original Message-----
> From: Chris Talley <talleycm at gmail.com>
> To: quattro at audifans.com
> Sent: Wed, Jun 2, 2010 9:35 am
> Subject: UrS4 Strut pinch bolt size & Bira brake bracket interference
>
>
> Hello All
> Is the strut/ball joint pinch bolt a off the shelf or a dealer only  
> part.
> ither way does someone have a spec or a part number.
> I had to grind the head off to remove thebolt and strut, because the  
> Bira
> racket for the BBK prevent easy extraction,  the Bentley indicates  
> that
> the
> ead should point forward, with the brake bracket it the way that  
> will be
> mpossible without removal of the bracket which I am relunctant to  
> do. Why
> oes the bolt need to be instalelled in this direction and will it be a
> bad
> dea to install backwards to aid future removal.
> TIA,
> Chris
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