Any one using & also recommending a bump steer kit for their new C8?

 

What do you wish to achieve?

 

This hurts my brain. Should also look into the k&n filter and some thicker spark plug wires.

 

Checking to see if I'll need to consider getting a bump steer kit for the track alignment to be properly set-up. Don't know how much I'm going to lower the car.
But the lack of response to my original post questions means to me that there's probably enough adjustment available in the stock suspension. Frankly, starting the lowering / track alignment / corner balancing project only to find that I should change out some suspension parts is not fun.

 

Who says that the car has a bump steer issue? If you lower it just adjust your alignment.

 

This is my first Corvette and I'm coming from the track alignment set-up experience of a 911 Carrera. Lowering the 911's creates a need for special rear drop links, etc. in order to "just adjust your alignment". And I'd rather have the necessary parts in hand when starting the job - I like to be prepared - silly me.
But I may decide to not lower this C8 machine and instead get full range use of the factory installed magnetic ride shocks with the possible added benefit of a DSC Sport Controller (once they become available).
Still happily exploring my options... this is going to be a very fun car to drive / track & mod.

 

Completely understand your want of being prepared - especially being your first. You don’t need a bump steer kit for corvettes. They pretty well perfected them C6 and up in that regard. The engineering team has always been good with that.

 

Excellent question. This C8 is being tracked by a pretty good driver at Eagles Canyon who knows the track and drives around the shortcomings of the car. Under braking, I was alarmed at the amount of dive despite massive anti-dive geometry. He then has to cope with the front lifting in mid turn when he is done with braking. It lifts even more on turn exit. What happens in the geometry, I can't tell you but it ain't pretty. This is a Z51 without Magride. I've never seen anything like that since a Citroen 2CV.
https://www.youtube.com/watch?v=m72C...ature=youtu.be
I've mentioned before that some really inexperienced (incompetent) chassis and suspension engineers designed this car. Why design a car that handles like an early Porsche 911? The driver does what Porsche drivers do, he compensates for the design shortcomings with driver input. Porsche has been the absolute master at bump steer design since the 912 to address adverse chassis loading. (rear engine)
First, you must determine what the bump steer is. You will have to remove the spring at one of the front wheels to measure full droop and compression travel and the migration between the two extremes. You will also measure max travel with the spring in place. This requires locking the chassis in place and allowing the wheel to droop and trounce fully by jacking. You also have to perform this activity with full left and right turn also. This car has over 8' pos. caster so there is massive jacking on the outside wheel and massive camber gain. I don't know what the caster or pin trail or Ackerman are. Then there is the absurd 3' neg. camber for track days before turn in??? Holy moly.
Will tow have to be reset?
The Porsche tows in in droop and tows out for compression by design. The C7 has less than 100% Ackerman which caused tire chatter. You must know what the stock suspension does before you can modify or adjust it. Also, it all changes with downforce. I suspect the C8 has some Porsche Monkey Motion dialed into the geometry.
After this elaborate exercise, you can then determine the steer you will achieve at your new ride height. The Porsche has 9'+ caster. Generally, I design for tow in in droop and tow out for compression. Not so good for street. You can't change the location of the steering rack or change Ackerman in the C8.
Lowering 1" probably won't have any effect although with a stock C8 without downforce, I would prefer a fully compliant suspension. You will go faster.
About corner weighing. Note the weight at each corner. Jack the back up between the wheels to unload them. Note front weights. If they remain the same that's OK. If they don't, adjust the load to equal the original reading after you lower the car at the back. This assures no pre loading of the chassis. Unlike a Porsche, the C8 flexes like a bitch like all Vettes since the C5.
As far as the rear, beats me what to suggest. I don't know roll centers or roll couples so I'm in the dark about doing anything on a C8. My neighbor will receive his C8 soon, so I'll have all the answers soon enough.

The after market sell drop spindles. The customer has no clue what problems are introduced but it looks cool.



C8


No Ackerman an droop tow in.



No Ackerman



No Ackerman

 

Wow what a response!! Thx. Can't wait for your neighbor to receive his C8 and for you to post again after direct C8 knowledge. Did he order the magnetic ride control shocks?

 

Absolutely not. No e diff either. Did you watch the vid? It will give you some very valid pointers on how to drive and shift this car. That pitching in the front is pathetic.

 

Well, the OEM C8 has an understeer problem, for instance, at cornering limits on a skid pad. The problem might be due to suspension bushings or might be due to bump stops. If so then simply a stiffer suspension that doesn't allow as much suspension movement could fix the problem.

Or this link says, "No more deflection under loading,":

https://www.lgmotorsports.com/c8-monoball.html

Here is another link:

https://gspeed.myshopify.com/product...suspension-kit
.
.

 

 

its not a problem all base model vettes understeer. If anything it’s a problem with general public not knowing how to fix oversteer.

 

Many thx for the link B Stead... This is a monoball kit that is available (pre-order) for the 2020 C8. Designed for the suspension for better car control.
LG MOTORSPORTS C8 Monoball Control Arm Kit.
I'm not familiar with the company or their products. Has anyone dealt with them? On the surface, the kit looks to be well machined.

Complete kit for 8 control arms.

 

No.

 

Honestly before you start making major changes to the car I'd suggest the following; lower the rear two rounds, -2.2/-1.8 camber F/R, stock caster, 1 mm toe-in each wheel, and get some better tires like the Goodyear 3R. I really did not like the stock tires on track but even with the stock alignment (-0.5 camber all around) the car didn't understeer as badly as everyone says. The GM recommended track alignment was loose at turn-in which was not fun - that was at stock ride height. With what I listed at the beginning the car was pretty well balanced and you could finesse it with trail brake or throttle - it might need a touch more rear toe-in.

Since you're coming from Porsche's and are already familiar with DSC Sport you might want to reach out to Mike Levitas. He's been tracking his C8 as well and we've been comparing notes. I know he had it back at Summit Point last week.

If it's one thing I learned the hard way it's to wait and see your experience before you start making changes and that some people will be unhappy no matter what GM does.

 

I would like to see the suspension analyzed in a "dynamic" state, I.e. compressed with nominal wheel turn. If the car has 8 degrees of static caster (at ride height), it probably has caster gain with compression - perhaps a significant amount. Extreme caster results in significantly increased negative camber on the outside tire when the wheels are turned, and decreased negative camber on the inside tire. Starting with 3 degrees static camber could result in a lot of negative camber (on the outside) and 3 degrees of initial negative camber on the inside could be hard to overcome. The inside tire needs positive or near positive camber while cornering to be truly effective. If the inside tire is not doing any work (too low roll stiffness in most cases), then the outside tire is exerting most of the cornering force. Bear with me on this as I express an opinion. Watching numerous C8 track videos, I often see a quick/abrupt push that has to be corrected when the throttle is applied off an apex and the nose starts to rise due to acceleration. Most attribute this to a throttle loose condition. This could, however, be caused by a reduction in caster as the nose rises which in turn will reduce negative camber on the outside tire if the wheels are still turned in the least. This will be especially apparent if there was a push at mid corner and the slip angle is high in correction (oversteer). I don't have a C8, but I designed my track car suspension with high caster gain with compression, soft springs, and a stiff sway bar. That way I can run less static camber which keeps my tires flatter on the track for straight ahead braking, and the caster causes good camber changes (increased negative on the outside/decreased negative on the inside) when the wheels are turned. By pinning the nose down through the apex/initial acceleration with good shock calibration, you then prevent camber being reduced too early. FWIW and JMHO.

Pappy

 

 

Out of curiosity, what are your thoughts? You obviously have a difference in opinion. Do you know if anyone has measured/calculated the dynamic caster at full compression (where you would likely be under heavy braking just prior to turn in)? It would be interesting to see what the outside tire's camber is when the tire is turned with the suspension under full compression. Starting with 1.75 degrees of static negative camber, I gain 2.1 degrees of negative camber (outside tire) and lose 2.8 degrees of negative camber (inside tire) with 10 degrees of turn and 3.2 inches of compression (splitter on the ground). My point (respectful opinion) was that if the nose rises from the condition I just described (due to acceleration squat), it will take out 2+ degrees of camber. If you are still in the turn, that is bad. If you have all of the C8 suspension pick-up point measurements, you could use a suspension analyzer program to get the data. I remove the coilovers and use sort-of a poor man's pull down rig, degreed turn plates, camber/caster gauge, and a bump steer gage to get my data. As an aside, the angle (in or out) of the steering arms is not the only thing that defines Ackermann. Moving the rack forward or back also produces changes. I run my rack on slugs so I can move it for adjustment - probably not possible with the C8 however.

 

You are all way overthinking a base model car.