Hi guys,i'm here with a question about an old story i heard and i want go deeper on this:
Does the C4 frame twist under heavy pull by engine torque?
Some guys talk about the asymmetrical wiev of the rear with left side highier than right ...

Was there something in the frame that was underestimate during C4 developement ?

I'm here to collect data so let me know as much infos as you have about this stuff,thanks guy

 

Highly doubt it they dont break wheels in half either.

 

Waiting for Wille to post another pic of his 84 doing a wheelie. .....

 

Not that I am aware of.

 

You have three questions there so...

1. TECHNICALLY, yes. It does twist because the frame is not made of a material that is absolutely resistant to flexing; steel can flex before it cracks so there is some flex/twist. How much does it twist? Not a meaningful amount.-less than .5* from front to rear. What causes the flex? The engine/trans output tq and the resr diff tq are resolved through the frame rails. In a stock ZR-1 in first gear, that could be as much as 1005 lb-ft of tq going through the frame, and not enough to create any meaningful twist. The frame will twist much more severely when traversing uneven terrain, such as crossing a deep gutter at an angle -when you are asking the suspension to articulate. That will impart way more twist than that which is imparted by motor tq.

The C5^ (in comparison) has zero tq imparted on the frame, because the engine/trans/diff are all connected rigidly by the tq tube. The tq tube resolves the tq between the engine and the diff and the frame "sees" none of it.

2. The car was designed w/a "T-Top" roof and that support bar was removed late in the design. This weakened the structure, however adjustments were made to the frame rails to compensate.

3. You son't get much hard, objective data here. What I posted above is about as close as any of us can get, I think.

 

Thanks guys ,all of you,i'm watching pics of twisted half shafts,like candies,cracked batwings,broken Dana case,underneath video showing differential case twists itself under heavy pull.This amount of torque (not that much in a stock engine) works on the batwings bushings,and in extreme case batwing cracks


I know the weakness of frame design,without targa top it is known to flex over bumps.Convertible frame was stiffed using a X-cross frame design...

What do you think about the frame itself ? Do you consider it a good project?what about the confort ?I'm discussing with my local forum members about reliability of our C4...they say it's crazy when you hit a bump the car seams to fly aside,and for a while you haven't controll,it litterally float over the bump...not to mention all of noises it produces from front end and inside ...every kind of squeeks a real concert of plastics things rubbing together...
I love my C4 but i wonder if somewhere a perfect C4 rolls over the street in mint condition witout noises and squeeks ,with a perfect front end...

 

My prior 35th Anni was very "tight" indeed. There was no "cowel shake" going over tracks nor any bump/jump steer over bumps or ruts. This condition lasted for >7yrs, >100k miles and MANY passes down the 1/4 mile with pulling mid 1.8s short time...

I haven't yet really "wrung out" my current 35th Anni but think it is not quite as "tight" as was the prior one.

 

My old Z was tight as a drum no squeaks rattles thumps not one ever had 140k on it at the time

89 had 120k and felt like it was going to fall apart and leave you sitting on the ground strapped to your seat every time you went over a bump.

Have driven an 88 that was gone through (bushings front/rear rebuild) and was solid and quiet as any new car inside.

they can ride stiff so the plastics vibrate loose making it sound not so pleasant

 

Mine is incredibly tight...less rattles than my brand new C6 had when I bought it.

AS for "loss of control" over bumps...those people need to do some suspension work. Mine did a little of that when I bought it, but some basic maintenance and good quality shocks eliminated that. That "symptom" is not caused by the frame.

AND as for what I think of the frame? It's not ideal but it's typical for a car designed in the early 80's...and it's twice as strong as a C2/3 frame...and you don't see those falling apart driving down the road. The frame is fine.

 

I had squeaks in my dash until I did this:

http://forums.corvetteforum.com/c4-t...sh-repair.html

I had cowel shake until I fixed the mounts where the dashboard bolts to the trans tunnel. Both were broken. It was REALLY bad with the console out. I took some pictures and have been meaning to add them to the above thread.

Years ago I had a Dodge mini motorhome with an engine problem. I was driving around with the engine cover off and I was absolutely amazed by how much the front suspension flexes while just driving down the road and hitting minor bumps.

 

thanks Cliff very helpfull thread.
My friends come from exotic germans car (they live in Europe) and when they put the car on the road they are scared...i've adviced them to do this :

front suspension:
hub bearing
tie rods
ball joint upper and lower
polybushing
bilstein shocks
new tires
allignement
the same for the rear...

Is this the perfect cure to restore original front end design?And for the interior squeeks?I'm taking apart all plastic consolle and putting neoprene strips in between,it's a tedious job but may be it make a little quiet my interiors

 

Some question about the monospring.I've heard opposite opinions on this part:
it's a fact that it's a must to change for a coil over set up,specially in sport aplication.
There's a limit in the monospring design?Is this set up a good compromise for comfort and sport ride?Do you ever feel a floating sensations over bump?we know the 84 spring rate Z51 was the stiffer monospring ever fitted with a rear rate of 87 N/mn versus the standard 39,9.If your country road aren't the best your back is litterally under attack.softer spring rate and a different shocks brand like KYB may be the cure?

 

softer springs will solve that one
dont see anything wrong with the monospring
some of the autox and track guys like coilovers to fine tune their handling to different tracks

 

Probably most of symptoms i've described are typical of early C4,from 84 to 89,we are talking about aged car,with many miles,and when these come overseas...probably they are at the end of their life...
Coil over set up give you the ability to change to even softer ride,some shocks have dual valve set up for compression and rebound,improving sport and tour rides.
Talking about monospring some reputable vendor say that monopring has a bad "cross talk" from side to side,this is what i feel,it's like when you hit a bump with left wheel even right wheel jump over the same time, exactly the cross talk Exotic Muscle claim on his site:

"Coil Over Springs provide true independent suspension on all four corners by eliminating the Transverse Leaf Spring. This eliminates cross talk from one side of the leaf spring to the other. Cornering weight and ride height can also be adjusted."


http://emracingcorp.com/scripts/prod...?idproduct=291

 

Ok, no twist here. Hope you're not too tired of these.

 

I should write a tech thread about monoleaf springs. Geeze....

You can't change the spring rate w/a coil-over by "screwing the pre-load nuts" -that only changes ride height or "stagger" which is way beyond the scope of street driven cars. To change coil overs to a "softer ride" one must do the same thing as with the monoleaf; change the spring(s). This IS easier to do with the coil-overs, but still, spendy, and arduous.

The shocks with more adjustability can help ride, but those same shocks can be used with the stock monoleaf spring with the same benefits.




^That is nothing but a bunch of marketing BULL ****, scripted to trick people into buying that which they do not need. Why?
1. NO independent suspension is "true independent", and that is because of the...swaybar! That's right...regardless of spring design, the two sides of the suspension are linked together w/a sway bar ANYWAY. The monoleaf spring, when mounted as in the front, on a C4 does have "crosstalk" (nice marketing term), but that is deliberate and reduces the requirements for the sway bar. In other words, if you convert to coil-overs in front on a C4, you'll need to increase your sway bar stiffness to keep the same degree of roll stiffness or...(ahem) "cross talk". The mounting of the rear spring on a C4 is such that there is no "cross talk" so that term applied there is bogus. Each side of the rear springs acts just like a coil-over or any single-sided spring design. Anyway, as a consequence, the rear sway bar is larger (than otherwise would be necessary) to compensate...so the rear suspension also has this..."cross talk" due to the swaybar.

2. Ride height can also be adjusted w/the stock springs. In the rear, it's as easy as turning a nut. Front requires shimming/shim removal, or building an adjusting bolt system. About the same level of complexity as installing a coil over system, IMO.

3. Your issue with the suspension "jump" when you hit bumps has nothing to do with they type of spring. It MAY have to do with your spring RATE...but much more likely it is due to shock valving/condition, as I stated earlier in this thread.

4. The only true/accurate statement in that Exotic Muscle propaganda is the part about cornering weight; that is easier to adjust w/coil-overs, however, cornering weights have nothing to do with the symptoms that you are discussing here, and are also way beyond the scope of what street driven cars are concerned with.

 

thanks Tom...foods for mind

 

Never tired of them, but I want to see the dash cam video

 

I mounted one up once but all I could see was sky!

 

I don't think it would happen in a Vette, but when I was a kid, my brother's buddy had a 71 Vega w/ a 350. Put on slicks at the track and the torque popped the windshield out.