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Chrome Moly front K frame. 1/3rd weight. FULLY adjustable

7K views 52 replies 30 participants last post by  bondosgto  
#1 ·
Hows this look

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Off a top 10 V8 Supercar team car and will bolt into a GTO / Monaro with Zero mods other than the lower control arm to hub and Radius rod to hub will need to change but thats an easy fix.

If there is significant interest ill be shipping this to Gforce1320 to reproduce for the US Market.
 
#7 ·
Need some $$$ for that one. Nice piece.
 
#9 ·
No idea of pricing, thats upto Gforce. The lower control arms and radius rod use different links but connect to the stock hub/strut so they will bolt on no probs. This one i have has had the steering brackets added already to suit the Monaro/Holden rack. Shouldnt be any difference between the RHD and LHD types but im sure Gforce can measure it if required.
 
#26 ·
No idea of pricing, thats upto Gforce. The lower control arms and radius rod use different links but connect to the stock hub/strut so they will bolt on no probs.
How can this possibly be? The ball jioint in the picture is mounted to the knuckle with the stud going through the control arm. The stock kunckle is the other way around.

I also see 3 attachment points to the frame on each side. Stock is 2 per side. How/where does that 3rd bolt work with the stock framerails?

Control through single point lower control arms and radius rods has not been used on US cars since the 40s.
Ford used the design on about a dozen models in the 60s and into the 70s. Chevy used them on the Bel Air and Nova in the 60s. Buick and Cadillac used them in the 80s and 90s. Looking outside the US, Nissan used it in the 80s on the 240SX and 300ZX while Toyota used it on the MR2 starting in the 80s up to the late 90s. Are you talking about cars with straight axles that use radius rods from the 30s/40s?

But what is relevant, is that the structure is strong, light, and cheap (snip)
This is the holy trinity of engineering. Pick 2. That's generally all you're going to get at once. Light and cheap, cheap and strong, or light and strong.
 
#10 ·
I am very interested, so send it on over to Gforce. I have been hoping for something like this for the last 3 years. Looks really nice.
 
#11 ·
Do you know if the rack mounts are raised to reduce bumpsteer? I would buy one if produced!!
 
#14 ·
We (US) want to get away from the McPhearson pogo stick type suspension with single point contol arm and radius rod. Many of us are convinced the design has inherent flaws to control wheel shake. Control through single point lower control arms and radius rods has not been used on US cars since the 40s.

At a minimum, a two point lower control arm would eliminate the radius rods and their soft bushings. Better still, couple that with two point upper adjustable arms and you solve all the endless tweaking and camming of the upper strut mount to find the correct camber for a given racing situation.

Accordingly, many here are considering a newly designed K member using F Body control arms and coilovers. The stability advantages are apparent, while a plethora of various and cheap aftermarket control arms, springs and struts already exist.

The K member looked impressive and is no doubt constructed well. But, I did a double take when I saw the McPhearson pogo stick hanging there. Instead, use the strut tower as a coil over mount by cupping it with the appropriate steel mount to accept the spring and shock. Then bolt that to a lower two point arm and attach it to an upper two point arm with an F Body spindle. Add a set of Corvette brakes, and your good to go.

I would not speculate concerning what Gforce, a good suspension and driveline man, might be interested in. But, I can and did give you my as well as others thoughts on the matter. Its time to rethink the car's front suspension, and not only to save weight.
 
#16 ·
Agreed... mostly

I think a good compromise might be a mustang lower A arm (2 points) adapted to the factory spindle. Much less cost intensive.
 
#18 ·
From the pics provided, it appears that this subframe has provisions for a second arm, sort of a halfway point between a wishbone style and our radius rod set up. See the rod end not connected at the bottom of the spindle and the extra mounting holes in front of the single lower arm?
 
#22 ·
I reviewed the pics once again. Nice work, but this is a complete reworking of the GTO front suspension. It resembles a tubular Nascar frame: highly specialized for its particular use and expensive.

We are looking for a bolt up K member assembly which will allow us to use the OE shock tower, with modifications, and unequal length control arms with coil overs al la Corvette/ Fbody. The advantages are obvious. In particular, F body parts are cheap and yet durable. F body OE controls arms for instance, are more like a rectangular box and are not triangulated. This allows for wider, as in 11" rims, provided the rims fit over the spindle: 16" for LT1s and 17s for LS1s.

It is not uncommon to find F body vehicles with 275 to 305 tires on the front without fender, wheel housing or suspension modifications. These dimensions are needed for oval track/circuit track racing. Drag racers can use skinnies instead and benefit from significant weight reduction with the redesigned K members. The McPhearson suspension makes it difficult to add wider wheels due to strut location.

What is needed is a cost effective multipurpose front suspension which reduces weight, allows for larger front tires, and is strong enough for street driving. Whether it incorporates F body or Fox body parts, or both, is irrelevant. But what is relevant, is that the structure is strong, light, and cheap allowing for a variety of tire sizes and spring rates.

The McPhearson strut must go, if we are ever going to get some rubber under the car, and to end wheel shake by eliminating radius rods in any form. Porche has putzed around with the 911 McPhearson front end for 40 years and still finds it has short comings which can only be corrected through unequal length control arms with coil overs.
 
#23 · (Edited)
If the K-frame alone saves 1/3 the weight, I am interested. But, it appears that other parts of the sub-frame and engine bay were changed for less metal weight and accessibility.
Any other known benefits besides adjustability?
 
#27 ·
This is for 24UGTOinFl. No, Ford in the 40s was attempting to improve the Hotchkiss (leafspring and straight axle) set up commonly found in that era. A 40 Ford uses radius rods to stabilize the lower control arm and spindle. It was developed before the McPhearson strut system.

Todays GTO, while of course not identical to cars from the 40s, uses a two point contol arm and radius rod for stabilization. The control arm resembles a dogbone and is attached at two points: one at the K member; and the second at the strut. The entire assembly would flex back and forth under acceleration and braking without it, such that it would be impossible to drive the car.

Additonally, any type of radius rod set up relies on flexible bushings to allow the lower control arm to travel up and down. The bushings and radius rod movement causes instability. The solution, at a minimum, is to have the lower control arm attach to the frame or K member at two points and then attach the strut to it on the outer end. This will eliminate the radius rod.

I have have not done a study on which cars use this system. It is fundamentally flawed for racing regardless of wether Toyota, GM or someother manufacturer uses the system. There is a lengthy (30 page) thread concerning GTO front wheel shake which was recently started. Search my name and you will see extensive postings regarding McPhearson strut systems in general and ours in the particular.

The system was desiged to eliminate expensive ball joint and spindle machining, and to provide suitable ride control over the European cobblestone streets of that era. But, the system is not well suited for racing or stability. That why in the 50s US manufactures went to upper and lower two point connected control arms for stability and durability. McPhearson struts are found on all low cost cars. But, the system is not well suited for a car capable in excess of 150 MPH, such as our GTOs.

See the other postings regarding same.
 
#28 ·
It appears that a rear sump oil pan could be used.
Maybe VooDoo can comment on this.
 
#35 ·
Is the trunk large enough to hold a battery??? Ha Ha!! This what I like to see, some levity, concerning an otherwise serious discussion.

The following is for sbca96. You are thinking correctly and maybe closer to our mutual goal than you think and without searching the junkyards for parts.

Gforce is in discussions with his suspension people concerning a new K member which will accept either F or Fox body control arms and spindles. But, he stated in the Driveline Forum that completing the modified rear control arm project is the first priority for the shop. So, alas, we must wait.

No doubt the economy is also a factor. But, he only needs to provide a suitable K member and not the entire system. Again, there is a plethora of either aftermarket parts or junkyards with F bodies where we can source the necessary spindles, arms, and perhaps steering racks as well. I would like to see an LS1 rack bolt to the new K member. The ratio is on the order of: 13.8 or 14 to 1 and can be easily sourced for about $100 in good condition. A fully reconditoned rack with warranty can be purchased in the $200-300 range.

In any event, nice work VooDoo. What size tires will fit on the race car??
 
#41 ·
Gforce is in discussions with his suspension people concerning a new K member which will accept either F or Fox body control arms and spindles.
I was looking into using a set of 4th Gen spindles, but the problem
is the rack on the 4th Gen is in FRONT of the wheels, and the GTO
is BEHIND the wheels. This will make the angle of the arms bend
the wrong direction with the designed in caster. I wouldnt want to
move the rack on the GTO, one of the benefits is an amazing turning
circle. Sometimes I think it will turn so sharp I might touch the front
and rear bumpers.

Tom