UrS4 Strut pinch bolt size & Bira brake bracket interference

Fri Jun 4 15:24:11 PDT 2010

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
>>>> ______________________________________________
>>>> uattro mailing list
>>>> ttp://www.audifans.com/mailman/listinfo/quattro
>>>> ttp://www.audifans.com/kb/List_information
>>>>
>>>> _______________________________________________
>>>> quattro mailing listhttp://
>>>>
>>>
>>> www.audifans.com/mailman/listinfo/quattrohttp://www.audifans.com/kb/List_information
>>>
>>>>
>>>>
>>>> _______________________________________________
>>> quattro mailing list
>>> http://www.audifans.com/mailman/listinfo/quattro
>>> http://www.audifans.com/kb/List_information
>>>
>>> _______________________________________________
>> quattro mailing list
>> http://www.audifans.com/mailman/listinfo/quattro
>> http://www.audifans.com/kb/List_information
>>
>