Anyone try the 6 Link rear suspension setup?

[macx]

After discovering the shortfalls with the rear suspension and looking for upgrades, I discovered this. It seems to be so much easier than adapting a C4 like some folks have done.

Just wondering about feedback from anyone that's tried it.

6-Link Rear Suspension (article about the original development)
Drag Vette 6 Link (It appears Drag Vette has bought the rights to make & sell it)
80 - 82 6-Link

For quite some time, they didn't have one available for the 80-82's, but now it seems they do - the main difference
being the bracket for the top of the differential.

 

[Vettehead Mikey]

I think the supposed 'shortfalls' are more than a little overstated- but that's what's usually required to flog a product like this. Each to his own though.

 

[macx]

Did you happen to read the original article where they did before and after handling tests? It seems it does correct the considerable amount of camber in the rear wheels under cornering.

Also, I really like reducing the stress on the differential carrier bearings and the stress on the 1/2 shaft joints from the side loads imposed from being the upper suspension link.

At least with this setup if one of the joints go out you aren't down on the pavement with a rear wheel messing up the fender opening.

 

[Vettehead Mikey]

Let's see here:

1) a before and after test showing that a product has worked 'miracles' despite hundreds of thousands of users that didn't know there was a 'problem' to start with.

2) solves 'issues' that were already very well engineered into non-existence during the original design

3) prevents bad things from happening - that wouldn't have happened in the first place.


Imagine that All the classic signs of marketing hype. Have you actually experienced any of the handling, durability or safety issues they're pushing?

 

[macx]

Somebody, incl Chevrolet, must have, else why so radically redesign
the rear susp in the C4?

And maybe the added stress on the half shaft U joints just might be
why NHRA requires shaft loops?

It sounds likeyou still haven't read that original article, written by
an engineer, BTW. Of coure, you must be, too, since you know all about it.

If some people knew half as much about something as they thought they did,
they'd know twice as much about it as they actually do.

 

[Vettehead Mikey]

If some people knew half as much about something as they thought they did,
they'd know twice as much about it as they actually do.

Yes, that's true. But that applies both ways.

I'm not going to argue- if you're convinced that a 4 link suspension is worth it and are going to bring all sorts of unrelated facts into the mix to support it, there's not much point in me or anyone else commenting. Your last post also seems to be taking on a personal note rather than dealing with the merits of the components in question.

Good luck!

 

[macx]

Well, I did start out asking for any experience with that, not opinions.
Opinions are cheap and often based on anything but fact. That's precisely why I asked for information on actual experience with it.

And, yes, BTW, I have experienced the problems mentioned in the original article, such as having to rebuild the diff, U joint problems, tire wear, etc.

 

[Peer81]

I've looked at it a couple of years ago.
When you go into the c3 suspension looking at the differend shortcommings it everything but perfect. But on the other hand the suspension didn't change much from when it was first put on a C2! And now about 40 years later yes we have other insides on suspension geometry.
On a C3 the halfshaft is used as a controlarm but that is still the case on a C4. The upper arm on a C4 is only there to control Toe. But I don't know it the upper arm on the C4 prevents the problems the late C3 diff's have.

As far as I can remember with a 6 link you have to remove the c-clips in the diff to let the halfshafts move more freely in and out. But I think the 6 link is only half the solution. Looking at a C4 it has 2 dogbones connected to the frame as a C3 trailingarm only has one with all its disadvantages. Of course where do you want to draw the line?
The shaft loops are there not for the stress on the half shafts but for high torque engines with dragradials that can torque the shalf shafts and brake them. There is alot more info on the net about C3 front and rear suspension maybe an idea to read them to.

To me it was to much work for the results I get with my drivingstyle. But if you want to get into trackraces it surely is something to look at.

Btw. Nice that Mikey is giving his idea's about this problem. But I don't see any technical things in his replies altho this is a technical question?

Greetings Peter

 

[macx]

Yes, AFAIK that is correct above removing the clips inside the diff with the 6 link.

To me, preventing the accelerated wear inside the differential, and the additional stress on the U joints with the possibly rather severe body and other damage one would experience if a joint let go and the rear wheel tilted either in or out would be at least as big a reason for using it as would the handling. Also, if a joint let go it would hold the wheel in position which could easily help avoid loss of control and a resulting severe accident. Of less significance but also important would be the improved tire wear. Incidentally, I have to rebuild my diff because of that accelerated wear.

I know the loops are there for safety reasons on high power cars, but if they help contain a shaft in the event of an inner joint failure it could possibly help avoid a more serious situation or even an accident, as well as worse damage, and I would imagine that's why NHRA requires them.

By the time I get the car back on the road I'll be well into retirement and, I'm sure, even further removed from any heroics in the twisties, so the handling is unimportant to me for that reason. However, the better handling could also possibly be seen as a safety improvement in the case of emergency situations where a better handling car that's more responsive to extreme steering and braking input either to avoid a collision or on wet roads & curves, etc, could be of significance.

I'm hoping to take some longer trips esp in the mountains and better handling would make me feel more confident and secure on some of the roads I've already driven.

I agree it'll never improve to the point of a double forward arm setup, but if it can make a signicant improvement over the existing setup I feel it's as worthwhile as installing an OD transmission or converting to fuel injection.

It would be nice to hear some actual experiences with it.

 

[Vettehead Mikey]

Btw. Nice that Mikey is giving his idea's about this problem. But I don't see any technical things in his replies altho this is a technical question?

Greetings Peter

I didn't include much in the way of counter points in order to avoid aggravating the OP more than I've done already.

The stock suspension is not perfect- but neither is the aftermarket 6 link being considered. First, lets deal with the supposed durability and safety aspects. There was probably half a million C2s and C3s built and operated with stock suspension. I've never heard of a u-joint letting go from high lateral loads induced from the half shaft, a situation that would be unique to a four link suspension and eliminated by a six link. Yes, u-joints wear out over time but probably 99.9% of events are from lack of lubrication due to seal failure, or from sudden shock loads as experienced in drag racing. Neither of these issues are fixed by using a 6 link. Just for fun- the maximum lateral load on the u-joints is a mere 300 lbs, this being experienced when the car is going in a straight line. This load decreases during cornering and can actually go negative given use of aftermarket wheels with non-stock offset. Here's an example of such an installation with non-stock offset and a missing c-clip on the yoke

YouTube - Rear Camber Problem

Is there a genuine wear or failure issue on the u-joints from lateral loads? No. If you disagree, please show me from your own experience or testing.

Side yokes.

Restricting the discussion to issues induced by the 4 link set up, it is well known that the inner ends eventually wear out and without any doubt this is due to the lateral loads discussed above. It is also known that later C3s suffer from a higher wear rate than earlier cars due to a manufacturing process change at GM. 'Earlier' yokes usually last an average of 100,000 miles or so. Mine have approx 130K and are still within spec. Later diffs that have the wear issue can be addressed with better quality aftermarket yokes- and just be done with it.

Tire wear.

Assuming that the claim for a high rate of wear is from incorrect camber angles, again I have to refer to the half million stock 4 links that GM built. There is no known consistent unequal tread wear issue on cars that are properly aligned and in good mechanical condition. I've never seen a Corvette (or any IRS car) that had a tire wear issue not caused by improper set up.

Poor handling-

The 6 link claims that improved geometry (less camber change) will cure the 'unpredictable and dangerous' handling qualities of a stock set up. Do such cars actually handle as badly as they say? Mine sure doesn't. If you read the article, they mention that they also changed front and rear roll bars and shocks. That alone disqualifies the test if they want to claim that all benefits were due solely to the six link set up. I note that they make a big deal about toe in changes. How is this affected by using a six link? (It's not).

So- camber change. Let's use their figures and claims that such variations in angle are 'evil'. The cause of these changes are essentially due to the stock strut rod being of a different length and it being situated non-parallel to the half shaft. There's kits out there (smart struts) that lower the inner end of the rod greatly eliminating the camber change. This is at a fraction of the cost of a six link.

Have a look at this guy's web site

Mark’s Corvette Page

and compare his results in camber change from the smart struts vs. the claimed results from the six link. Is it worth it?

I'll not indulge myself in repeating the details of discussions I've had with guys with real, documented experience in road racing C2 and C3 Corvettes. Their dismissal of six links set up was quite convincing but would be only hearsay in this discussion, no different than putting full faith in what the vendors that are flogging these set ups claim.

I'll refer back to my first post above instead and the comment regarding the overstatement of shortfalls in the stock set up.

Again, use it if you want but don't expect miracles.

 

[Peer81]

Thanks for the reply Mikey!

I also don't know where the concern about the failing U joints comes from? I almost never seen or heard about a failing U joint.
And about the rest of the problems. Are you now running your 81 with new rubber or poly bushings and you're saying handeling could be better or are you running around with the original 30 year old bushings?

Greetings Peter

 

[1320]

Thanks for the reply Mikey!

I also don't know where the concern about the failing U joints comes from? I almost never seen or heard about a failing U joint.
And about the rest of the problems. Are you now running your 81 with new rubber or poly bushings and you're saying handeling could be better or are you running around with the original 30 year old bushings?

Greetings Peter

This is old I know, but in several places people say where this fictitious half shaft failure or u joint myths come from.....well I wish I had a 6 link....because with my 66 427 coupe it broke on thesstarting line, cracking the fender, my car has a fairly stock ls1' dynoed several times and put 294 to the wheels the day before it broke. It runs 11.70's with 1.65 60 ft times the way I drive it daily.know I have halfshafts to replace, a fender to repair and I need a solution to protect it in the future. No myth here.

 

[Vettehead Mikey]

The discussion above revolves around road racing or autocross situations, not drag racing. The proposed 6 link will not address u-joint or half shaft failure induced by drag racing.

 

[1320]

Thanks for the reply Mikey!

I also don't know where the concern about the failing U joints comes from? I almost never seen or heard about a failing U joint.
And about the rest of the problems. Are you now running your 81 with new rubber or poly bushings and you're saying handeling could be better or are you running around with the original 30 year old bushings?

Greetings Peter

The discussion above revolves around road racing or autocross situations, not drag racing. The proposed 6 link will not address u-joint or half shaft failure induced by drag racing.

Im baffled, I wouldnt think it would matter at all, but I believe that drag racing was the cause of the 6link. It most definitely DOES adress the issues. First and formost, make the car legal (nhra) and keep the wgeel control so in the event of a break, loss od cobtrol and fender damage is virtually eliminated. The small benefit by keeping the tire flat to the road is also a plus in this case, were not in road racing or autocross, so if anything its more pertinent to drag racing.

 

[Vettehead Mikey]

You mentioned that 'it' broke on your car. I assume you mean the stock u-joint or half shaft.

The proposed 6 link suspensions retain the stock u-joints and half shaft, so you're no further ahead.

 

[1320]

Thats a pretty ridiculous statement. As the stock half shaft is 2 1/2 and some with 1330 u joints. Obviously there is a difference, with 3 inch or 3 1/2 with 1350 or in some cases the 1480 u joint. The point being that they do break, they due cause damage. And the 6 link would have caused no damge to the body in the event of a break.

 

[Vettehead Mikey]

Good luck then.

 

[Peer81]

Alright, does this 6 link change half shaft length? No! For that matter, does the idea behind a 6 link make your u joints break less then stock? No! In theorie there is even more danger because the (crappy) stock system has less tire contact so power makes the tires spin sooner even before the u joints should break. With the 6 link your tires have more road contact so when applying power there is more stress on the u joints before you can make the tires spin.

If you do want the bigger stronger u joints just buy '82 half shafts and change the yokes in the diff and your done!

If you don't want broken u joints with half shafts spinning freely buy some drag loops that you can weld or bolt to the suspension or diff.

A 6 link is a nice system but only addresses the part of the rear suspensions problem. You do need a upper control arm above the half shafts but you want the half shafts only for power not for suspension purposes so you need shaft shafts that move in and out (like a viper half shafts). Then you dont want a single point trailingarm but a suspension with two links at front like a c4 has. I think its called an 8 link or something (mix between the 6 link and the guldstrand suspension) So please read a book before you talk boy!

Greetings Peter