voodoovette
Well-known member
Thanks to both STINGXRAY and STROKER-427, I appreciate your time and help very much, thanks again:yahoo:
Six Link Rear Suspension
- Thread starter Sky65
- Start date
pro-touring
Active member
Wow, you guys are incredible, way over my league!,really want to do this mod but dont have talent to fabricate and weld all thoose parts together.
Is there anyone who have one or can build me a complete giovanni 6-link set-up?.
Thanks...
Is there anyone who have one or can build me a complete giovanni 6-link set-up?.
Thanks...
pro-touring
Active member
Think i got it wrong, meant Stroker-427-6 link!.
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Stroker-427
Well-known member
:yahoo:
renevette
Member
Hi guys,
I am following this topic with more than average interest because i started a major body-off restomod of my '80 4 speed and would like to do some severe frame and suspension modifications, but looking at this six-link setup something seems to be not covered in this topic (or any other topic i read about the six link setup)
Can you guys help me out with my thoughts?
In this setup i see a lot of control rods with heim joints, which are proven technology i suppose. The main wheel hub is kept in place by two (upper and lower) control rods sideways, two rods in longitudinal direction replacing the trailing arm and one rod which controls toe.
All these rods were positioned to perform their job in the direction they were laid out, the upper/lower/toe control rods are almost parallel, so far no problem.
But what happens at heavy braking? It seems to me that under severe braking a huge torsional force is applied between the wheel and the caliper which is transferred to the chassis. This torsional force can only be transferred through the parallel upper and lower control rod and the toe control rod, and they are not in a position to cope with this torsional force in the direction they are positioned. (perpendicular to the circumferential braking force). The two longitudinal control rods replacing the trailing arm can do nothing (*) to withstand the braking torque being positioned in the same working plane as the braking torque.
(*) or can they? Do they act as a pulling rod to withstand the braking forces?
Why do the 3 control rods not twist as a pretzel under severe braking? (or perhaps they do but no one noticed?)
This situation occurs only under heavy braking and not under acceleration because slamming the gas does not introduce a heavy torque on the suspension as braking does (i assume because the brake caliper is mounted to the wheel hub). Just imagine a bar stool with 3 legs which are connected with heim joints to the floor and the seat. The floor is the chassis, the seat resembles the wheel and the 3 legs are your control rods. Now try to rotate the seat and imagine what happens with the three legs...
Just trying to understand suspension issues before i choose the setup which works for me, but this issue really botheres me because i am afraid this six link setup will soon starts to develope a lot of slack/slop as a result of the excessive forces on the control rods during braking. This really keeps me from choosing this setup for my car and for now i am considering either a custom offset trailing arm (offset as in moving the bearing hub outside) or maybe a full upper and lower A-arm construction (which is a lot more difficult). I am planning C6/Z06 wheels (19x12") at the rear with an increased track width and widened body.
Thanks for your input, Rene from The Netherlands/Europe
I am following this topic with more than average interest because i started a major body-off restomod of my '80 4 speed and would like to do some severe frame and suspension modifications, but looking at this six-link setup something seems to be not covered in this topic (or any other topic i read about the six link setup)
Can you guys help me out with my thoughts?
In this setup i see a lot of control rods with heim joints, which are proven technology i suppose. The main wheel hub is kept in place by two (upper and lower) control rods sideways, two rods in longitudinal direction replacing the trailing arm and one rod which controls toe.
All these rods were positioned to perform their job in the direction they were laid out, the upper/lower/toe control rods are almost parallel, so far no problem.
But what happens at heavy braking? It seems to me that under severe braking a huge torsional force is applied between the wheel and the caliper which is transferred to the chassis. This torsional force can only be transferred through the parallel upper and lower control rod and the toe control rod, and they are not in a position to cope with this torsional force in the direction they are positioned. (perpendicular to the circumferential braking force). The two longitudinal control rods replacing the trailing arm can do nothing (*) to withstand the braking torque being positioned in the same working plane as the braking torque.
(*) or can they? Do they act as a pulling rod to withstand the braking forces?
Why do the 3 control rods not twist as a pretzel under severe braking? (or perhaps they do but no one noticed?)
This situation occurs only under heavy braking and not under acceleration because slamming the gas does not introduce a heavy torque on the suspension as braking does (i assume because the brake caliper is mounted to the wheel hub). Just imagine a bar stool with 3 legs which are connected with heim joints to the floor and the seat. The floor is the chassis, the seat resembles the wheel and the 3 legs are your control rods. Now try to rotate the seat and imagine what happens with the three legs...
Just trying to understand suspension issues before i choose the setup which works for me, but this issue really botheres me because i am afraid this six link setup will soon starts to develope a lot of slack/slop as a result of the excessive forces on the control rods during braking. This really keeps me from choosing this setup for my car and for now i am considering either a custom offset trailing arm (offset as in moving the bearing hub outside) or maybe a full upper and lower A-arm construction (which is a lot more difficult). I am planning C6/Z06 wheels (19x12") at the rear with an increased track width and widened body.
Thanks for your input, Rene from The Netherlands/Europe
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mfain
Well-known member
Renevette, I'll offer an opinion, and there will be others. First, as you noted, a six-link is really a 5-link (two longitudinal, two lateral, and a toe link). The axle shaft is not a suspension link. The major difference between it and the C-4 style suspension is that the axle shaft is replaced by the upper lateral link as a suspension member. The longitudinal (forward) links in either transmit the braking torque in a "push-pull" fashion with the instant center being the intersection of a forward projected line of the two links. This is the same way a 4-link works in a drag car. The instant center determines the anti-dive/anti-squat characteristics of the suspension. The acceleration torque is absorbed by the front mount of the differential (third member). A Corvette has between 60-70% of the braking force applied to the front suspension. Strength of the six-link to handle the braking forces is not really a problem.
The C-3 trailing arm has pretty strong bearings (a plus), but it has "roll steer" issues that can only be mitigated or dealt with - not cured.
I recently built a complete 6-link (discussed earlier in this thread), but I have not installed it. I can get the same geometry from a C-4 style suspension (roll center, camber gain, etc.) at the expense of having the axle shaft loaded as a suspension menber. I decided instead to spend time to upgrade my front suspension to a more effective system for large, modern front tires, each doing their fair share of the work. If you look at Danny Popp (72 Corvette) and Brian Hobough (66 Corvette), they are winning a lot of the Goodguys and Optima Challenge autocrosses and road course events, and they are doing it with very tricky (but somewhat stock appearing) front suspension and virtually stock C-3 rear suspension. Their approach is more dynamic caster, high suspension travel, and very low roll. They use balanced tire sizes (305s or 315s front and rear) and special shock valving that slows rebound. Then they balance the rear roll center and stiffness with the front suspension. The rear suspension has very little travel or roll. The trend in effective geometry is more toward that of a C6 than the old, conventional, low travel, high roll, lot's-of-camber-gain philosophy of days gone by. It's driven by tire technology and width.
Just my opinions and observations. There are a lot of smart guys on this forum, so stand by for their thoughts.
Pappy
The C-3 trailing arm has pretty strong bearings (a plus), but it has "roll steer" issues that can only be mitigated or dealt with - not cured.
I recently built a complete 6-link (discussed earlier in this thread), but I have not installed it. I can get the same geometry from a C-4 style suspension (roll center, camber gain, etc.) at the expense of having the axle shaft loaded as a suspension menber. I decided instead to spend time to upgrade my front suspension to a more effective system for large, modern front tires, each doing their fair share of the work. If you look at Danny Popp (72 Corvette) and Brian Hobough (66 Corvette), they are winning a lot of the Goodguys and Optima Challenge autocrosses and road course events, and they are doing it with very tricky (but somewhat stock appearing) front suspension and virtually stock C-3 rear suspension. Their approach is more dynamic caster, high suspension travel, and very low roll. They use balanced tire sizes (305s or 315s front and rear) and special shock valving that slows rebound. Then they balance the rear roll center and stiffness with the front suspension. The rear suspension has very little travel or roll. The trend in effective geometry is more toward that of a C6 than the old, conventional, low travel, high roll, lot's-of-camber-gain philosophy of days gone by. It's driven by tire technology and width.
Just my opinions and observations. There are a lot of smart guys on this forum, so stand by for their thoughts.
Pappy
renevette
Member
I will absolutely do, thank you for your explanation.
I was struggeling with the idea that the forward control arm can somehow be the only connection to withstand the braking force but could not quite visualize it properly.
Although i have a technical background i found out the subject of suspension is so widely expanded i can probably read and learn for a year and still not know everything.
That is probably what makes it so interesting..
Belgian1979vette
Well-known member
I will absolutely do, thank you for your explanation.
I was struggeling with the idea that the forward control arm can somehow be the only connection to withstand the braking force but could not quite visualize it properly.
Although i have a technical background i found out the subject of suspension is so widely expanded i can probably read and learn for a year and still not know everything.
That is probably what makes it so interesting..
Can you change that much to the suspension in The Netherlands ? Over here you can have a serious issue with tech inspection.
renevette
Member
In the Netherlands we have an annual technical inspection which every car has to pass but this inspection only looks at safety issues, not if the car is completely original.
A few issues such as tires which cannot stick out of the fenders are important but it is allowed to put some "performance upgrades" to your car and pass inspection without any trouble. Hell, i know people with a Weiand blower and air intake sticking 2 feet through the bonnet which passed annual inspection in Holland with only one comment added: "you should cover that rotating part of the blower belt and pulley so it is safer..."
And most inspectors are of an age they have never seen a C3 up close before and so they don't even know the difference between original and upgraded unless you pointed it out to them.
As long as you deliver good craftsmanship you still can do a lot on your car in Holland. It's crappy and amateuristic work that attracts the wrong kind of attention from an inspector. If the work looks OK and is of good quality it will pass because the inspector assumes it is original. You don't want to give hime a reason to investigate deeper....
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Stroker-427
Well-known member
I agree with Pappy !!
The suspension system is like any other component of a sport car...... a short blanket !
Regarding the forces to the longitudinal rods.... the rod-ends are much more strong than necessary.... the forces you are talking about are applyed to the hub via two bolts (the ones holding the caliper).... so don't be afraid of that !!!
The suspension system is like any other component of a sport car...... a short blanket !
Regarding the forces to the longitudinal rods.... the rod-ends are much more strong than necessary.... the forces you are talking about are applyed to the hub via two bolts (the ones holding the caliper).... so don't be afraid of that !!!
denpo
Carburated Nihilist
LOL, the welds on an original frame would be considered an amateur hack job from today's standards.
renevette
Member
Well, you could not be more right on that one.
I started a complete body off restomod and i am looking at my frame this afternoon to inspect it...
Man i have never seen such awfull welds on a car (or anything for all it matters...).
I am going to box-weld the entire frame to start.
Belgian1979vette
Well-known member
Over here we have to be carefull with mods. Anything suspect/deviating from original might be a problem if the inspector is a little too much awake. I for one will have to cover up my stack manifold and put an old round filter on the cover to make it look like a cold air box for a carb...
Heaven help us, a blower sticking out of the hood...totally forbidden.
I hear that not even the TUV in Germany is that bad.
Heaven help us, a blower sticking out of the hood...totally forbidden.
I hear that not even the TUV in Germany is that bad.
That is an interesting observation. But, something to consider, the two forward control arms are not parallel (on a C4).
Bad Bird
Well-known member
I have a question regarding the trailing links in this suspension design. If you were to use the stock length half-shafts as a suspension member (instead of running the top link), are the trailing links parallel to the car centreline in plan view? Or will the trailing links converge towards the centreline?
voodoovette
Well-known member
Hello all,
I would like the measurements of the forward link attach points on the hub upright. Specifically, the distance above and below the hub centerline and the distance between the holes as indicated on drawing. Thank you!!
Attachments
Stroker-427
Well-known member
Hope this help....
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voodoovette
Well-known member
Bad Bird
Well-known member
This photo shows what I mean:
Does the 5 bar design presented in this thread look like this C4 conversion in plan view (with converging links)?