Hi Listers,
this following info was cut and pasted from the MGCC Club mag pages.
Mr Parker has struck a few chords here - I am modding my GT6 brakes - and I
found it immensly useful. Hope you do, too. I am going the Vit 1600
caliper bracket with Ambassador callipers route. I am also trying to have a
go at getting the brackets machined up. The TSSC couldn't supply them (I
was surprised), but pointed me in the right direction. I found mine at Chic
Doig, Scotland. I already have another club member interested in a set so
perhaps these could become a RM best-seller!!!!!!!!
Here it is:
PARKER'S PEARLS
In the second of this series of technical notes by Roger Parker, the V8
Register's V8 Conversions Representative, (and M.G.C.C. FWD Register
scribe!), Roger carries on from where he left off in March's Safety Fast!
Roger writes 'The brakes on my car are being subjected to much work to drag
the system in to the 90s, starting with the body mods to take the post '77
dual circuit master cylinder and servo for both safety and performance
enhancements. I very seriously considered the inclusion of one of the latest
ABS systems, but on this occasion costs and time have consigned this to the
back burner. If I did go with ABS, then an electronic traction control
system could also be employed, which with 200+ bhp (and torque), is not such
a bad idea! To date the brakes have advanced most and here there are many
areas that can be considered for improvements, not just for the V8 owner,
but for the owner of any MGB. The front brakes of the V8 may be specific to
just that model, but manufacturer's will always use off the shelf parts to
keep costs down. The V8 calliper illustrates this with it being a mix of AP
standard parts (the inner half being specified for the Triumph 2000/2500
with the other outer half being MGB). This was to allow for the increase of
disc width to 12.8mm (1/2"), a fairly common thickness for solid disc on
many models. Pads also fall into this multiple application field with
smaller Transits fitted with twin-piston callipers using the same pattern
pads as the V8. (Use Transit 100L, from 1986 as the current
cross-reference). This should make sourcing pads from your High St. Factors
quite easy (and probably cheaper), along with the fact that the pad material
will be suitable for the V8 performance. Even a small Transit when laden,
and stopping from slower speeds, will generate more heat in the brakes than
a V8 stopping from high speed, and the V8 has the advantage of greater
airflow to dissipate the heat.
Seven years on my V8 hasen't shown up any problems. Moving on one stage, we
know that V8 callipers are expensive and in short supply. Triumph's large
saloons are no longer a common site in scrapyards, so constructing V8
callipers from this source is no longer a common site in scrapyards, so
constructing V8 callipers from this source is no longer the easy route it
once was. All is not lost though, and this is due to parts rationalisation.
I mentioned that 12.8mm disc thickness was a common size, and with other
common factors in mind, there will be alternative callipers which can be
used instead of the V8 type.
The Princess/Ambassador range of cars did not exactly create a cult
following, but they were made in reasonable numbers. I certainly have no
fond memories of driving these things, especially at speed, with their
see-saw ride, tendencies to go off at tangents when one whell hits puddles
etc., but they say all things do have a use! In this case we have what can
only be described as a very advanced braking system for the time, with a
calliper with 4 pistons, usually termed '4 pot'. The benefit to us is that
it has commonised dimensions which means that it will bolt straight onto the
MGB hub with shouldered bolts. What is more it was originally used with a
12.8mm disc, so the bridge is of the correct width to accept a standard V8
disc. The only difficulty is that you have to cater for two hydraulic inlets
per calliper, so you have to fit a double feed to each. I have numerous AP
callipers including Princess items, and I have used my hub to test the
theory. Yes, they will bolt straight up to the MGB hub and the spacing is
such that the V8 solid disc sits perfectly within the calliper. There is a
slight difference though, and that is with the bolt hole size. It has the
same centres as the MGB hub, but they are bigger holes to cater for larger
bolts, with a different thread. The MGB bolts are too small and will have to
be replaced with either a shouldered bolt, or cut a new thread in the hub to
take a Princess bolt. The same Princess hole spacing also applies to Rover
V8 Vitesse 4 pot callipers, and the Police version of the same calliper.
Incidentally the difference between the Vitesse have two hydraulic feeds,
whereas the Police have just one. The Police versions has been used on
several conversions that I know of, and are easy to plumb in.
Also of interest is that this calliper can probably be found on some earlier
Sherpa 200 vans, if one I examined in a scap yard is representative. I have
both these types as well, and once again they can bolt to the MGB hub,
although brodge dimensions are too wide for the solid disc. However, if
vented discs are the desired route, then the Vitesse uses a vented disc so
this provides a possible solution, howver sourcing a vented disc to fit then
presents a problem unless you want to throw large amounts of money in-to
specialised kits. One thing that I am wary of with these kits is the use of
a vented disc will then be used to make up for the loss, before any benefits
over the original are seen. I see this as a "Peter to rob Paul" scenario.'
And that is where we must leave it for this month. Needless to say more
about brakes and other mods from the Pen of Roger Parker soon! (GB).
Hope this was of some help. Rimmers do the Vitesse callipers new for
about 120GBP for the single line vented. Could be a way to really beef up
the stopping power of some of those tuned PIs out there!
Best wishes.
Jon Clancy
1970 GT6 Mk2
2.5 PI lump awaiting!
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