548chevelle

Nice improvement on the C7. One eccentric for camber and the other one for caster. So what's the procedure for a C6 with only one eccentric?

ErnieD

Rear caster is not adjustable on the C6, just camber and toe -- camber via the eccentric and toe via the conventional threaded rod and jam nut.

Ernie

TCracingCA

All of the C6 and C7 Owners will actually know what they paid money for!!!!!!

Sorry I had to say it, and the ones that know what they had bought should get a good laugh from this post!

548chevelle

I got to this thread thru the C6 forum so I assumed that's what we're referring to. But then i found out this thread appears under other forums ie C5 C7 etc. So I can't tell which model people are talking about. Can you please specify what model you're talking about.

Apocolipse

C7....as stated above C5-C6 do not have adjustable rear suspension for caster.

C7Kevin

Looking at the "castor spec", as you say, will only tell part of the story.
Regardless of the static castor setting, either roll understeer or roll oversteer can override the static setting.

You said "Because you actually dont have steer control connected back there!!!!". This is incorrect for the reason that roll understeer and roll oversteer ARE forms of steering(albeit not connected to a steering wheel as at the front).

You said "Steer in the rear is a defect!!!!!!!! ".
This is also incorrect because rear wheel steer can be designed into a car to achieve handling effects.
Either roll understeer or roll oversteer can be designed into a car's suspension.
The following text is provided here via copy/paste from someone else's work.

Roll understeer is when a vehicle achieves a lower yaw rate and rotates into a turn less.

Roll oversteer is when a vehicle achieves a higher yaw rate and rotates into a turn more.

If you would like to learn much more about this, see:

TheSkunkWorks

I do hope viewers don't miss the point that utilizing the most cost effective production method is the priority in the General having adopted the eccentric rear camber adjustment as far back as 1963. There's nothing wrong with that decision, but many an enthusiast (not just the hardcore among us) could possibly benefit from something different. Not sure what all of the options are for later generations, but since the Global Announcement linking us to this thread is, well, global, IMHO it's worth noting there are a number of different systems for the C2/C3 which offer improved rear camber control and/or adjustability. YMMV






.

TCracingCA

He also covered things like corner weighting and cross weighting, and your yaw rates, etc other more advanced suspension designs or even tuning. I guess I will be forced out of the 1960/70s where I simply work to maintain footprint, and work in the conventional 3 dimensions of castor, camber, and toe buying the parts or setting up the suspension with the proven tricks learned. i would say my Corvettes handle in the upper 2% of my model years, and have outhandled the general mass of C4/C5 cars, because I have explored the C2/C3 truly "trick" suspensions. So like my statement somewhere above, i am studying the newest street enemies (competitors), so I think i have come to the conclusion that a further knowledge of the advanced is needed by me to run with these newer designs, or i take it to my brothers house and leave it because he has things like wheel scales, and other super fancy things. He to confess, has set up most of the family cars (the builds), but I have known enough to tune or adjust for a type of track and went after the foundational parts being smart with my wallet.

But to reply, so you don't think I am not semi knowledgable (but I also came on Ask Tadge to learn)-- but improper roll oversteer or understeer can be a defect (and can be a result of the suspension tune)!!!!!!!! Inducing incorrect yaw can mess things up!!!!!! (As per my recent attendance of advanced suspension designs )! So my statements should have had a qualifer added- ""unwanted/not designed in""! If the design or the setting/tunings are not right or you are experiencing ill handling from the rear end!! There fixed it!

Well almost because if you look at the pros of CART and NASCAR, F1- on any given weekend not everyone obtained a good handling setup, leading to only one winner! Therefore why we are here to ask or hear this of probably one of those 1% of the masses, that works in design/engineering! Therefore if 99% of the rest of us tried to design in yaw and roll OS/US, then we would probably get it wrong and that would be defect!!!!!! PS I did say guys that could set the characteristics of the end without the steer control, will probably win the races! I also myself asked specifically if these designs had some type of axis, torsional, etc steering assist above in one of my previous post! So far no one has put the answer down pertaining to these cars! Explained the theory of specific design engineered into these Corvettes! All that has happened is that we figured out which ones have the eccentric parts and where front and back, along with handling theory that is general or advanced, but not correlated or explained specific to these Corvette models!

But I am sure the designs from each subsequent generation have some of these advanced design features that is causing these modern handling gains! And my family member broke the bad news to me, that my cars are dinosaurs and anymore gains are limited! I kind of knew that, so i have been attempting to remove more weight targeting 2700lbs and more power to around 575hp!

So now i ask, that you or Tadge cover the specific yaw designs and roll oversteer/understeer and how/where it was designed into these modern Corvette suspensions specifically C6/C7 (with rear castor adjust)/C6 (with fixed castor/ or is it shims, just not eccentric adjust???)

C7Kevin

I don't want to speak for Tadge, but I also don't think there is any chance at all that Tadge will provide this information. To explain the C7's design, how it was chosen and how it works would be a very lengthy explanation. As for myself, I am still learning to drive my own 2015 C7 Z51 and have many higher priority items that I need to look into.

TCracingCA

I see/have all of these suspension theory books in my house, but they all tell you what all of these terms and definitions are plus show you all kinds of diagrams, but kind of don't get into the specifics related to any particular car model's engineering, and they are boring as hell to read. I understand suspension arcs, bump steer, etc. etc but how is that frame and those particular parts in these new cars designed to induce stable and wanted steering benefits from the rear end of the car. My brother is busy also like you, but he was going to look at the modern Corvette chassis in general, because a friend (Owner)and him were playing with a Katech car at the autocrosses back some months back to see if he can tell with the limited dimensions and engineering drawings available where they have went with the design. Unlike me, he loves this stuff, but he doesn't work at GM and just plays with 5 on 5 race trucks mostly!

To show that very few actually know what they are talking about, I could even take a known Corvette great and post up alot of embarrassment from reviewing this type of stuff that is surprising poorly wrong in his catalog. In other words, there are only so many truly smart guys on the topic of engineering this stuff. I am not one of those! Even certain manufacturers don't have truly talented engineers on car handling, but some do! Out of the Japanese cars, i think Honda, Mazda, and actually Mitsubishi do-- with the second tier being Nissan, Toyota, etc. For American cars- i don't think Dodge has it down yet, Ford more so, and Chevy only primsrily on their flagship models- like the Corvette and Camaro and a few others in their line-up! I would say all of the German marques have this stuff figured out- all of them (Porsche, BMW, Audi, Mercedes, GM Opel, etc.) but can tend to compromise on their lessor models.

TCracingCA

I have chatted with Doug quite a number of years ago (in excess of 10 years ago)on a bunch of his stuff! Those are the delrin/aluminum bushings (non eccentrical thou). My a-arms are all reinforced gusseted welded with the Global West bushings, I did the conversation just as he instructed (maybe my welding/gusseting is more than needed) but the bolts were changed to studs as recommended, added Moog HD offset shafts with the square pad areas (upgrade), I cotter pinned the studs to keep them from loosening up so I get close to zero deflection and bearing like movement on the arms which are mated to Superior spindle coil-over adapters for my double adjust race shock coil-overs and I heat shielded the delrin/aluminum bushings closest to my headers. I haven't gotten the spring rates down yet and the shock setting yet. My back end is far better than any of the sphericals or camber bracket that they offer running the old Trans Am race 5 link CVC-Apex unit! But I don't run a good tire and wider rims on this car, as it is more my street car! I like the nostalgic look, with some surprises if i was to run someone. I can embarrass you if i run into you or at least hold my own! But my C2 is my real toy!! And i am throwing all of the bells and whistles at it and it is an engineering project, but I am not an engineer! It is all apart currently getting worked on, with a future thread planned when all done.

So because we have had Eccentrically drilled bushings in our father's C3 since 1976 and my C2 since 1984, and threw out those cams 100 years ago in favor of heim sphericals, so it sure took Corvette long enough to put these types of parts in them stock at the factory! i have went thru changing them out for newer replacements at least twice now and i am switching to SPC performance race pieces and a modified guldstrand 5 link in the a$$, with extra top link i am designing if my brother gets to helping me with that and Jeep retractable or telescoping halfshafts!

Ps there are only two heim suspension cars built in the modern (one Porsche and one Ferrari!)

TCracingCA

because he would be giving away trade secrets!!!!

But any of these other manufacturers could buy a C7 Z06 and disassemble it for analysis! Basically evaluate and test and measure things like chassis rigidity, torsional force on the chassis's capability, spring rates, suspension geometry, etc etc.

Therefore say the car is diving hard into a right turn under hard braking, what is happening to all four tires and my footprint of all tires, especially the two rear ones, and especially the rear opposite one???? Well most think the two inside or the two outside, but the trick is what is happening to the unweighted one on the back left rear (opposite side and diagonally to the front right tire and where the suspension based on castor, camber natural or function of the steering, along with toe is doing! So is the chassis flexing in the back, is it spring rate causing the maintaining of footprint, is it toe or castor, camber or suspension travel that is causing that rear tire to stay effective or planted?? So since everything is integrated together in the design, naturally the engineers would have to kill me if they shared their secrets, but a car handling on four tires is a better handling car than if effectively a tire or two were taken out of the equation by bad engineering! Plus easy to drop the center of gravity and ride height lowering the weight, but you lose suspension travel which could cause lifting or leverage to unweight a tire or tires (like in our Family Porsche 911 with the 935 suspension and the short wheelbase that we own- always have a tire doing something that we would prefer it not to do). So drop weight overall or strategically within the chassis to cause these effects (benefits) is a another handling trick employed.

I do see the C7 base and Z-06 are employing different birdcages/chassis and the weight are different, more than likely very strategically so!!!!!

OK brain is tired now!

VADanno

I had a machine shop make up some brackets for the rear caster measurement. They allow a magnetic digital angle gauge to give you the caster measurement. However, to get a precisely machined bracket was a lot more than $5. It was $200, but I ended up with enough material to make six brackets. Anyone interested in buying one at cost?

Dan