As I have always been told by guys who race and get their cars set up on the alignment rack....that this is TRUE. On some for the cars I have seen being set-up the toe-in was rather significant...but that was due to the speeds the car was going to be running at and they knew that the front tires were going to splay outwards and thus...change the toe-in setting.

So it only makes sense that the toe will change under acceleration on the Corvettes with independent suspension in the rear. And this is where the million dollar question has been asked. Determining the amount of deflection and what the toe would need to be set at for the driving conditions. the Corvette was normally being put under.

DUB

 

The thread is about the rear suspension of a C3 Corvette, not a C5 Corvette.


I posted this,


And then you quoted my post, made the above part bold and then posted this under it.


Your post is rather clearly claiming that the inward force on the front of the torque arm that I posted about is cancelled out. If the force was cancelled then it can't affect the toe....

 

YES, the inward force of the LEFT rear tire, is, in essence, cancelled out by the inward force of the RIGHT rear tire, therefore the car goes relatively straight (hopefully). The toe changes, induced by acceleration, is generally a product of the "flexure" of the rubber bushings, which allow the nose of the trailing arm to move around, to a small (hopefully) degree.


Keep in mind, what the OP of this discussion implied (at least what I thought), is that his trailing arm bushings are more or less shot, allowing the trailing arms to move around quite a bit. He was saying that he "bubba-ed" a fix, by jamming shims in the t/a mounting pocket, hoping to minimize this movement.

 

This is what I was looking for....

 

Shifting fore and aft in the pocket is not a toe change.

 

OK, got it, you quoted my post, made it bold and then vaguely responded about a completely different force. Makes perfect sense now.

Now, even though you claimed it did, the video you're posting does not clearly show any toe changes....

 

When i was 16 i convinced my Dad to let me make a 1/4 mile dirt track in the corn field. Some neighbors donated old cars! What this has to do with this thread, is, i learned how to drive fast on old worn out cars.
One, a 56 ford had a rusted out frame, and had 1/2 to 1 turn of mystery play in the wheel! Another had no master cylinder!
So a less than perfect car does not worry me. it is just a test of your driving skill.
Just test drove my 72, and the only problem is the steering wheel is off center. So, a good bet the alignment is off.
So, when i get bored, i'll check the toe on the rear, and maybe the front too, as those stock bushings were new in 1989.
Thanks for all the comments; many good thought provoking points posted

 

In the video above...if the only thing that people feel is changing is the wheel base measurement due to clearly seeing the tire/wheel move...is kinda hard for me to agree with.

Assuming that the tire/wheel are still staying perfectly straight when this is happening....which I severely doubt. Because that is then assuming that the strut rod is not getting involved in this movement...which when the camber gets messed with enough.....it can effect the toe. And what are the odds that the trailing arm is perfectly going fore and aft 100% of the time?

Regardless of it is a new C5 or C6 Corvette with rear control arms that have rubber in them or if it is an older Corvette. Movement is going to occur thus changing the alignment specs when it was set sitting still on a rack.

So having every bushing in the car changed so all suspension components can move freely in their designed movement path is can more than likely be achieved...but thinking that that will fix everything is also kinda ridiculous due to frame flex and forces that change things when the car is in motion...depending on how aggressively it is being driven.

So where does a person stop worrying about it?

So...depending if the car is a 'parade' car or one being really driven with lot of 'spirit'. It is obviously up to the owner to do whatever they feel they need to to get what they want out of their Corvette.

So if Matt is happy with his 'mod' and he can live with it. I guess that is all that matters to him. I just hope it all goes well for him and that it does not cause him any problems in the future.

DUB

 

And that is why it's called suspension geometry. Things move in angles, which, in turn, causes other static settings to change.

 

You still can't see the toe changing in that video at all, let alone clearly....

I'm still waiting for an answer on why the rear toe on a C3 is set to toe-in so that it can transition to the "proper" toe-out when the car is cruising along down the road.

I guess maybe some video clearly showing the toe of a rear wheel changing might surface too????

 

My intention in posting that video wasn't to show actual toe change, but to demonstrate that the rear wheels will move fore/aft, as the power is applied/let off, during driving/racing. The camber/toe changes occur naturally, as the suspension goes through it's range of movement. The actual change, in toe, could be as little as 0.020", therefore you won't see it in a video that's primarily aimed at the sidewall of the tire.

 

The toe goes outwards the faster you go.

If you what to try this...so oyu do not need a video to see it......go get your car aligned and set the front toe to '0'...and then go down the interstate at high speed and see how hyper-sensitive your steering gets..

Give this a thought. From what I have been told by some of my friends who work on the high end German cars...and also alignment guys....that the alignment of them are so out of wack for local city driving.. That they are set-up for really high speeds due to the higher speed they do..the more the tires toe out. The reason i asked was I saw how the tires were wearing on Mercedes....and that was the response I got. I asked if it could be corrected and I was told that is how it was made and it is what it is. Whether if that is true or not....I do not know but I heard it from more than one source.

So regardless if it is the front suspension or rear...the dynamics and forces are still doing the same thing. I am sure you can agree with that. Or hopefully you do.

So...ask an alignment tech who knows their stuff because I am sure that they can confirm that the tires toe out the faster you go.

DUB

 

leadfoot4 - why did you post that the toe change is clearly visible then?

DUB - No, I don't agree with the front vs rear forces being the same. The front wheels on a rear wheel drive car are being pulled along by the spindle. The rear tires of a RWD car are pushing forwards on the spindle.

 

I didn't post that "the toe change was clearly visible".......I posted that the WHEEL'S MOVEMENT is clearly visible!!

That movement, IN TURN, causes the initial alignment settings to change.

 

You didn't post this then?

 

I apologize for the lack of clarity.....what I was referring to, was the original video(s) that LG posted, a couple of years ago. I'm pretty sure that they showed the wheel movement from both the side, and the back. And the video that was shot from the rear, showed some slight change in toe, as the wheel moved forward, in reaction to acceleration. I was able to find only one of the videos, not both, so I posted only the one......

 

We are not talking about a front wheel drive. I thought you knew that we are talking about a Corvette. Becasue that is what I am talking about.

And even if the car is front wheel drive...the effects of the toe at high speed will change. Because a front wheel drive car still has to have the ability to turn the car. How much it will change may or may not be attributed to how good the rack and pinion is.

And with the video that was shown...do not not think that the front wheel cars can have this type of movement??? Becasue if a person only thinks that this movement is only going to happen to a rear wheel drive car still does not understand the forces in motion.

Then explain to me why you can not consider....that the four wheels are attached the same to the suspension components. Regardless if they are hub bearing assemblies or wheel bearing on a pre-1984.

And that when driving down the road...even in a straight line....the tires are going to be experiencing same forces. Actually the rear may be more due to weight transfer and being the drive wheels...thus causing more deflection.

One of the 'blessings' I have experienced in my life was working on a Nitro funny car team for a while. Being a part of that team and seeing what goes on into having car in one of the most extreme motorsports gave me an insight into how stresses and forces can effect how the car goes down the track STRAIGHT. Yes this is taking it to the extreme...but nonetheless...it opened my eyes to taking things into consideration. Becasue there would be times that the chassis builder was at the track and they placed load sensors in key areas and the car would make a pass and then they would download that information.
Then make some MINOR changes and run it again I could CLEARLY see the information that these load sensors were giving the crew chief had changed due not the previous minor changes that were made.

I feel you will not even go and talk to people at an alignment shop like I suggested. Your choice obviously But you come back with this response which is fine also. So any further discussion from me to you in this matter is pointless. I tried to do what I can. And I will bet that even if you do go and find out that what I mentioned is confirmed...you more than likely will not come back and confirm any of it. And if you come back saying that it is all B.S. That is fine also because I do know what is going on here and do not need to see videos ( which was cool to actually see) or ask questions about this stuff..

Have great holiday.

DUB

 

I seriously doubt you could visibly see toe changing on the rear of a C6 when switching between accelerating and coasting. They'd be pretty nasty cars to drive if the toe was changing a visible amount.

 

Apparently you can't even read other peoples posts. I NEVER posted anything about a front wheel drive. You're the only one going on about what happens with the front wheels on completely different cars.

You are claiming that at high speeds the front wheels on a DOUBLE A-ARM front suspension REAR DRIVE car get pulled backwards or pushed inwards by a force, which causes the toe to change to toe-out.

Then, you are further claiming the same thing happens on the rear of a C3, even though it's not a double a-arm suspension and those wheels are being driven, two things different then your example.

Trying to claim the same forces happen between the two suspensions is ridiculous since they are different suspension designs and one has driving forces being applied to the wheels while the other does not. You long rant still had no data directly related to the C3 rear suspension...

Still, since you want to go on about different cars and what happens, it's recommended to set the REAR suspension of a C5/C6 to toe out so it is closer to no toe on the track. This IS the same double a-arm suspension as you have been going on about as always having more toe-out at speed.

 

OOPS.....MAJOR SCREW UP-----SORRY for me being human and after having a hard day...I READ what you wrote incorrectly.

MY APOLOGIES!!!!!!!!!!!!!!!!!!!!!!!! (BOY...I f''d that up royally)

Ask people who align cars.. YES..the wheels?tires will splay outwards...thus toe out the faster you go.

How do I know this....because I have had an alignment set at '0' toe in the front and rear and drive it at interstate speeds and the car is really scary and very light in the steering. Put teh toe setting to what it suppose do be and the car reacts completely different. Then playing around with the other variables in the front to compensate for the peaking of the road also so the owner does not have to constantly correct the steering wheel.

Due to the suspension are rubber bushed....it does not matter if it is a trailing arm on C3...or the 'dog bones' for a C4...or if it is control arms on new Corvette. Movement of some degree is going to take place. And the previous video proves it.

DUB