Re: Front Brake Pads

["JOHN CLAYTON" <john.h.clayton@domain.elided>]

Glenn A. Merrell wrote:-

> Hello John,
>     Please thank Mr. Allen for allowing me to hold his toes to the
> fire.  I appreciate his timely research and  providing his verified
> information.  I believe that Mike Wattam is away on business this past
> week on the continent, not allowing comment on the list until he returns
> this week.  I'm sure he will respond though.
> 
> A bit longer with the toes in the fire, if you please ...
>     The ROM section 10.00.16 (56) shows a completely different type of
> pad similar to TR250/5/6 pads, depicted by Triumph Drawing # MT 2718,
> having holes and solid pins to hold the pads in place.  Any comment as
> to possible caliper change?  I know that when the Stag was originally
> designed with the 2.5 litre, smaller calipers and pads may have been
> planned, but thelatest ROM is in Revision "D" and published 8-10 year
> after this original design.  Agreed, the ROM is not perfect.
> 
>     There is also a comment in Autobook 808 page 106 section 11:3
> states:  "Make sure the pad assemblies are able to move freely in their
> recesses, using a fine file to ease any high spots if necessary."  I'll
> bet that some machanics took this literally, filed or ground off  the
> positioning tab in order to get the split pins to fit.  With the tabs
> gone, the pads are no longer handed and can be easily reversed.  I'm not
> saying this was right,  just probable, as I've a set removed from my car
> that were ground off, intalled by DPO or garage.
> 
> Now, here is another odd occurence, something that I believe may be a
> potential safety issue.  The pad handed "tabs", what are their purpose?
> Is it to keep the pad from rotating out of the caliper on hard front
> braking, or reverse braking?  I've spent many hours looking at this on
> my calipers and pads, but I'd like to have some observations from the
> professionals as to specifically why the tabs are there. If you say hard
> front braking, please check again the orientation of the pad and tab in
> the caliper carefully, and tell be how it stops against the caliper body
> with the forces applied.  If you say reverse braking, please explain why
> this would be needed with the forces in play?  Maybe the calipers on my
> Stag are incorrect??
> 
> Food for thought, In My Humble Opinion, some simple observations.
> 
> Regards,
> Glenn  Merrell, VTR Webmaster ProTem
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Here is Mike Allen's reply:-

"The ROM drawing MT2718 on page 10.00.16 is an odd one, as I 
believe it to show Spitfire pads.  They certainly are not Triumph
2000 MK1, which prototype Stags may have had.  Incidentally other 
drawings on these pages do not appear to be Stag either!

The 2000 MK1 parts book, Plate no. AW (between pages 101 & 102)
shows pads the same as Stag, numbered AW 513080, with 2 PAIRS
needed up to Comm. no. MB1129. and then AW 513083, one SET
needed, after.

As regards the 'handedness' of the pads, I have been in touch with
Lockheed Technical dept. for this one.   They tell me that it is to
ensure that the offset of the pad material is correctly sited.  This
offset is apparently common on this shape of pad, and is done to 
reduce squeal, and increase braking efficiency.  They did NOT
approve of them being ground off to assist fitting, as this could
result in uneven braking if the offsets were fitted differently on
either side of the car.

I have to agree, on further inspection, that this offset does not 
actually locate the pads, or resist any turning motion.  If the pads
are correctly installed there is no strain on the fixing pins. 
However, I think we should ensure they are installed as Lockheed
and Triumph intended.  (And Ford - Rover - Reliant etc.)

Mike Allen.