Gencoupe Suspension Revealed - Page 2 - Hyundai Genesis Forum
Chassis, Brakes and Suspension Discussions about the platform, braking system or suspension components belong here.

Reply
 
LinkBack Thread Tools Display Modes
post #11 of 20 Old 04-15-2009, 09:34 AM
Moderator
 
dboz1's Avatar
 
Join Date: Jan 2009
Location: OHIO
Posts: 2,511
dboz1 is on a distinguished road
I was just thinking about the bump steer issue, it would be good for that to get corrected at the source to allow better aftermarket solutions. I don't want to deprive anyone of business opportunities, just want the car to be as good as it can be.
dboz1 is offline  
post #12 of 20 Old 04-15-2009, 11:14 AM
Member
 
Join Date: Feb 2009
Posts: 21
brads03zx3 is on a distinguished road
Pretty good writeup, but there are a few issues. The example of static vs dynamic camber is not quite correct. I assume it was simplified for those that don't have a great handle on suspension dynamics.

The example assumed no camber gain/loss in the suspension, only static camber minus body roll. This car sits very low and I'd imagine the control arms are nearly parallel with the ground already, so this may be close to accurate. For example, under cornering loads, the outside suspension may gain -.5 degrees of camber putting that example at -.5 static plus -.5 camber gain minus +3 body roll netting +2 total degrees of camber. Not good for cornering.

Another issue...no tire these days likes 0 degrees of dynamic camber. They all like negative camber, let's say -.5 degrees. That means we need to add -2.5 (-.5 minus +2 current dynamic) degrees of camber to have a happy tire in the corner for a total static of -3 degrees (-.5 current static + -2.5 adjustment). Most street cars will probably do well with -1.5 degrees of static camber. It should handle well and have pretty good wear. Track cars can ultimately dial in settings by using tire temperatures and will often have different camber settings for the right and left depending on primarily CW or CCW track configuration.

I 100% agree that this car has an issue with lack of bump travel. Previous gen miata owners can purchase modified top hats as lowering the car much at all will permanently set the suspension on the bump stops. This is a common problem with many McStrut cars these days.

I have an issue with the OP's spring tuning ideas, but every tuner/engineer has his/her own style. Motion ratio, front/rear weight distribution, etc is very important. "The number of oscillations is referred to as the frequency" this is incorrect. The rate of the oscillation is the frequency, the number of oscillations has to do with how close we are to critical damping. I will admit I don't have much suspension tuning advice for grandma's grocery getter. On track, however, it is very common to have much different spring rates at the front and rear of the car so that the frequencies at each end are also very different. Dampers control the movement of the unsprung mass (tire, wheel, brakes, some suspension - high frequency) and ultimately we want the tire in contact with the pavement at all times. Dampers also control movement of the sprung mass (chassis, etc - low frequency) and determine the rate at which weight moves front to rear, side to side.

This car will have a serious problem with camber curves. Once lowered, the front suspension will lose camber under cornering forces (very bad for handling...why the OP mentions good springs will be stock height or higher) and the rear will gain camber. Compromises can be made, but this will allow the rear of the car to have more grip than the front (read understeer). If any of you have watch Aussie V8 SuperCar Challenge, you will notice they dial in SERIOUS amounts of static negative camber up front. This is the reason. Those cars also have multilink rears and McStrut fronts.

We haven't discussed antiroll bars, I'll let somebody introduce that into the equation. I will advise you all, bars are the icing on the cake, and not the base itself. This is the last suspension component to be tuned. Remember, this car has independent suspension. Swaybars (especially large ones) remove that luxery.

Last edited by brads03zx3; 04-15-2009 at 11:17 AM.
brads03zx3 is offline  
post #13 of 20 Old 04-15-2009, 11:46 AM Thread Starter
Veteran
 
TurninConcepts's Avatar
 
Join Date: Jan 2009
Location: Cincinnati, OH
Posts: 185
TurninConcepts is on a distinguished road
(Thread Starter)
You make valid points and I agree with almost everything you said.

I was drastically simplifying the data and examples in order for the layman to gain understanding. I have read more books on suspension design than I care to remember and have spent countless hours on setup and didn't want to bring too much of the technical forward. Not trying to confuse anyone.

The control arms are parallel to the ground at stock ride height so there isn't really much to be gained as the loaded side compresses. This is normally the main concern with the height of a Macstrut based car, but int he case of the gencoupe suspension travel is overshadowing geometry for the time being.

I am very familiar with the Miata case and tophats. One of our shop cars is a 92 Miata with second gen tophats for more travel. We will figure something out for the Gencoupe in this regard. I didn't mention it, but the front tophat takes up 1" of suspension travel that could be converted to additional bump travel if the tophat is adequately redesigned.

You are correct on frequency. I didn't describe that correctly, but is what I was thinking. We have a spreadsheet that we used that was developed purely for calculating critical damping and frequency. I was trying to relate our findings from the spreadsheet into text everyone could understand.

Anti roll bars/sway bars are coming and will be talked about in detail. I think though that they should be thrown into the equation sooner than at the end as when combined with the rest of the suspension will determine the overall wheel rate. The suspension is a system of parts that all have to work together. Considering some components without others will result in unneeded money spent and more setup time to dial in a great setup.

Keep the ideas coming though. Perfecting this suspension for track use will definitely be a joint effort.

The TiC Staff

Turninconcepts.com
Designers of Performance Suspension Components
TurninConcepts is offline  
 
post #14 of 20 Old 04-15-2009, 01:27 PM
Member
 
Join Date: Feb 2009
Posts: 21
brads03zx3 is on a distinguished road
Something also to consider (and I don't know if this is the case for the GenCoupe) oftentimes, the manufacturers are using the 'bumpstop' as an active suspension member, unlike bumpstops of the '70's and '80's. The better term for the 'bumpstop' that you posted is Microcellular Jounce Bumper and acts as a secondary progressive spring. As I found out a couple weeks ago, there are very few NASCAR fans here but there are some great engineers in that industry. Especially now with the COT, the suspension is designed to use the bumpstop. Static ride height is determined by the spring, dynamic ride height is determined by the bumpstop. I would imagine the GenCoupe was designed this way so a soft cushy spring will be comfortable, but the higher rate bumpstop will control ride height in the corners. You mentioned it seems these rates aren't fastastic for anything but understeer and understeer is slow.

This is the main reason manufacturers use swaybars on road cars. We can use nice cushy springs for comfort, but the bars increase roll rate and better control body roll/camber loss. This doesn't help one bit with brake dive. Proper rate springs are necessary for balance and response. It is the driver's/owner's opinion how to weight these compromises with comfort.
brads03zx3 is offline  
post #15 of 20 Old 04-15-2009, 03:44 PM
Moderator
 
Tufast's Avatar
 
Join Date: Sep 2008
Location: Columbus, GA
Posts: 10,780
Tufast is on a distinguished road
Excellent comments Brad & Tony. I don't know a lot about suspension, but really want to learn. I also want my car set up more for track than DD. So, keep it coming, great stuff.

Sponsored By: Columbus Body Works / ARK Performance / Modern Automotive Performance / Forged Performance
Tufast is offline  
post #16 of 20 Old 04-16-2009, 09:45 AM
Veteran
 
Split's Avatar
 
Join Date: Feb 2009
Location: Wisconsin
Posts: 220
Split is on a distinguished road
I don't presume to know too much about all this suspension technology...

but wouldn't it save money if instead of trying to fix the stock setup, if we just dropped some good coilovers in there that replaced the stock setup?
Split is offline  
post #17 of 20 Old 04-16-2009, 12:12 PM Thread Starter
Veteran
 
TurninConcepts's Avatar
 
Join Date: Jan 2009
Location: Cincinnati, OH
Posts: 185
TurninConcepts is on a distinguished road
(Thread Starter)
Quote:
Originally Posted by Split View Post
I don't presume to know too much about all this suspension technology...

but wouldn't it save money if instead of trying to fix the stock setup, if we just dropped some good coilovers in there that replaced the stock setup?
Coilovers are a whole other can of worms. We like to start with a common denominator which is the stock car. We then work with it within normal mortal bounds to see what we can do. Then we start to go nuts on the higher end stuff (properly engineered coilovers for example).

What this helps is covering a wide array of knowledge, budgets, and capabilities.

The TiC Staff

Turninconcepts.com
Designers of Performance Suspension Components
TurninConcepts is offline  
post #18 of 20 Old 04-16-2009, 10:20 PM
Moderator
 
Tufast's Avatar
 
Join Date: Sep 2008
Location: Columbus, GA
Posts: 10,780
Tufast is on a distinguished road
I want to have a good foundation on which to build on. If all the busings are too soft, coil overs alone will not correct the issuse. I would want to get the factory suspension operating the way is was designed to, then improve on that if & where needed. I plan on doing coil overs as well, but want everything else right 1st.

Sponsored By: Columbus Body Works / ARK Performance / Modern Automotive Performance / Forged Performance

Last edited by Tufast; 04-16-2009 at 10:21 PM. Reason: grammar
Tufast is offline  
post #19 of 20 Old 10-07-2013, 09:31 PM
Junior Member
 
Join Date: Aug 2013
Posts: 2
ben_art is on a distinguished road
any news, TiC, on parts for the front suspension geometry issues? tophats? bumpstops? bushings? ect..... ?
ben_art is offline  
post #20 of 20 Old 10-07-2013, 09:33 PM
Junior Member
 
Join Date: Aug 2013
Posts: 2
ben_art is on a distinguished road
i assume this thread is long since dead...... given the last post date. oops.
ben_art is offline  
Reply

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome