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How do the RV8 and the Hoyle front suspensions
compare?
A recent thread on the V8BB launched by
Peter Taylor reached a point where Robin Gell was seeking views
on how two suspension upgrade systems for an MGBGTV8 or V8 Roadster
compare. (Nov 08)
The
query from Robin Gell was "it seems then that the
suggestion is that it is better to use the original crossmember
with Hoyle upgrades than a standard RV8 one? Or are we saying
that the RV8 set up can be improved "satisfactorily"
with a change of spring / shock combination to an aftermarket
one with no further changes in geometry etc? It all sounds very
interesting Bryan, thank you. I shall have to delve a bit deeper
into it methinks."
Geoff King provided a useful summary of how the two set
ups compare based on his experience of fitting Hoyle front and
rear suspension kits to the V8 Roadster. The remainder of this
note is his summary.
The Hoyle suspension uses a modified standard crossmember.
The very end of the cross member is cut out and a curved section
welded in to allow a coilover damper to be installed outboard
of the original spring position - as there is more mechanical
advantage this allows a softer spring and damper to be employed.
The lower wishbone uses the original inner attachment points
and the upper wishbone uses the lever arm damper mounts. The
crossmember bolts to the MGB, MGBGTV8 and RV8 chassis rails
as normal.
Unfortunately the RV8 front suspension retains most of
the geometry used on the MGB, MGA, ZA, TD and Y type and dates
back more than 50 years. It might have been good in 1950s but
it leaves a lot to be desired today - as it did in the early
'90s when MG fitted it to a then 'new' sports car; unbelievably
they also fitted a heavy live rear axle with leaf springs to
the same car. At least the RV8 has less caster angle and telescopic
dampers through the spring - like the ZA Magnette.
When I was building my V8 Roadster I considered the RV8 suspension
but rejected it in favour of the Hoyle; not due to cost - although
the RV8 suspension was ludicrously expensive - but because the
Hoyle offered an adjustable system with revised geometry and
better brakes. I liked the RV8 ball joints, replacing the MGB
king pins but I didn't like the smaller diameter discs. In my
opinion, apart from the ball joints, the RV8 has no advantages
over the Hoyle double wishbone and coilover damper suspension.
The Frontline Costello rear coil conversion uses the
original live axle; that has the advantage in that it is significantly
cheaper than IRS. Five link suspension does locate the axle
very well but it will never be comparable to IRS due to the
massive unsprung weight of the axle. I considered composite
springs and the various axle location systems; Panhard rod,
anti-tramp bars etc, but chose the Hoyle IRS as the only real
rear suspension for a MGB/RV8. In fact I built the car with
a live axle but drove it less than 500 miles before accepting
that it had to be changed.
Incidentally, my objective was to build a car that had the traditional
look but with modern features, performance and handling, hence
my decisions regarding the suspension; costs certainly weren't
ignored but they were a secondary consideration. I can thoroughly
recommend the Hoyle front and rear suspension.
Mike Howlett added "as a footnote to Geoff's comments,
he took me for a ride in his car shortly after he had finished
it. As a long-standing MGB owner, I was so impressed, particularly
with the ride, that the V8 I am building is virtually a GT clone
of Geoff's car, with Hoyle front and rear suspension and an
injected motor. I hope to have it finished for the Spring." |
Matt
Jones then noted that "having seen the Hoyle IRS, that
is the way I'll be going on the rear. The front I am not so
sure about. Can anyone confirm if the Hoyle front is better
than the RV8 set up and how it differs? Can you adjust the camber,
castor and
toe settings on the Hoyle and if so, does anyone have any baseline
settings for this?
Geoff King returned with more useful information. "The
Hoyle is fully adjustable for height, camber and toe. The front
has some caster adjustment and the rear also has limited track
width adjustment, the dampers are adjustable with a thumb wheel.
I have the front with just under 1 deg negative camber and slight
toe-in (set with a Trakrite); the rear has ½ deg negative
camber and slight toe out. I have a 7/8 inch front anti-roll
bar; the car is lower than a RV8 and about the same or slightly
lower than a chrome bumper MGB.
The wishbones are tubular on the Hoyle and pressed on the RV8
but the inner attachment points on the crossmember are the same.
The RV8 has the spring in the same place as the MGB with a telescopic
damper through the spring; it's really too far inboard and consequently
has to have a high rating and a stiff damper. The Hoyle has
the coilover damper mounted much further outboard and has a
softer spring and damper.
The Hoyle uses a standard MGB stub axle and king pin, the RV8
has a bespoke axle with ball joints - the only area that the
RV8 has an advantage over the Hoyle. RV8 brake disc is from
the Rover 800 and is more than 10mm smaller in diameter compared
to the MGB/Hoyle. The Hoyle can use standard MGB brakes or GTV8
or vented using re-drilled Peugeot 505 discs and Austin Princess
or Rover SD1 calipers (I have solid GTV8 discs and non-vented
SD1 calipers).
Replacement parts for the RV8 are priced to kick start the British
economy; wear parts for the Hoyle are standard MGB and available
from dozens of suppliers competing with each other."
Geoff King later provided additional information on the
Frontline Costello rear coil rear suspension conversion saying
"the Frontline Costello five link suspension is very good
but no matter how well the axle is located the unsprung weight
cannot be reduced. The total weight of the MGB axle assembly,
springs and dampers is approximately 100 kgs, the unsprung weight
is 85 kgs. The total weight of the Hoyle is 105 Kgs, unsprung
is 45.5 kgs. The
design compromises are shorter wishbones than would be ideal
and relatively short suspension travel because of the chassis
rail limiting the movement of the wishbone but there is still
comparable travel to the live axle. But how many sports cars,
or any car for that matter, are made today with a live axle?"
See
V8NOTE302, Geoff King's detailed note on installing the
Hoyle suspension kits. More
You can see the Hoyle independent rear and front end kits,
plus his new lightweight front end kit, on the V8 website
at:
Hoyle suspension
Hoyle engineering
There is also a link on that webpage to John Hoyle's
website too.
For
members considering a Hoyle upgrade there is one thing
you need to bear in mind and that is the Hoyle rear IRS
kit, which uses Ford back axle and disc brakes (and an
LSD too if you want), needs 15 inch wheels rather than
the standard 14 inch on the Factory MGBGTV8.
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