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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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