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Suspension tuning 101 for the Genesis Coupe

49K views 97 replies 37 participants last post by  Bk1.Knny 
#1 · (Edited)
OK, I constantly see guys complaining and doing the wrong things to improve performance on their Genesis Coupe. There are also a few “generally” practiced theories that do not directly apply to the Genesis Coupe. So here are the basics of how to tune the Genesis Coupe suspension.

-First thing to improve are your driving skills. Any car can be driven “fast” without experiencing understeer or oversteer if you are capable of driving the car at its limit. Most drivers don't have the skill it takes to drive a car at its limit.
-The biggest no no I see people doing is reducing performance in the rear in order to “balance” the cars handling characteristics. Why oh why? The most common mistake is going to a stiff rear sway bar. I will get more into this further into the post.

-Air Pressures, Air Pressures, Air Pressures.
This is the cheapest and a very effective way to control the handling characteristics of your car. How to determine the best air pressures. Every track or diving condition will require slightly different air pressures. Even a couple of psi can make a huge difference. Start with the front tires. Record your cold psi. Chalk the sidewalls of your tires. Drive your car hard. Check the chalk to see how much has been worn off the sidewall. This will tell you how much air to add/remove to keep you contact patch on the tread and not on the sidewall. Record your hot psi. This method can also be used to give you an idea of how much to the adjust compression of your strut and/or spring rates if you are serious. Now that you have the fronts dialed in add or remove psi in the rear tires to control the amount of oversteer you would like in your car.
-Tires
The majority of you buy tires that best fit your wheels rather than buying tires that improve the performance of your car. Stretched tires will make part of the sidewall part of your contact patch. Our car is heavy and it is hard enough to keep the contact patch on the tread with properly sized and fitted tires. Sidewalls that are too small will decrease the consistency of maintaining contact with the road. If you are running 30 series and even 35 series tires, depending on the width, you do not have enough sidewall. One of the things properly sized sidewalls do is help with the compression and rebound. Sidewalls will soak up some of the imperfections in the road which translates into maintaining greater contact with the pavement. Small sidewalls transfer more of those roadway imperfections directly into the suspension and into the body of the car. In other words small sidewalls will make your car bounce more. Buy quality tires that will balance the handling of your car. If you buy cheap tires then you cannot complain about how your car handles. If you buy huge meats for the rear because you want to run 10.5s don’t complain about understeer. Buy tires and wheels for that matter, that are sized to improve the handling characteristics of your car not because they look good. HP always plays a part in traction so it is possible to that those meats are still not enough traction. There are things that can be done that are custom mods to increase rear grip but that involves some work. You can message me on it if you are serious.
-Coilovers/Springs
Springs only, don’t even bother. Waste of money. End of story. I’m not going to say one brand of coilover is better than another. I think you can get increased performance out of all brands of coilovers once they are set up properly. Obviously I have a preferences for Parts Shop Max coilovers because they offer great adjustability, quality, warranty and design. In setting up your coilovers I would start compression at 75% stiff in the front and 25% stiff in the rear and the same for rebound. Adjust as desired in 25% increments. This way you can really feel the change in performance and in what direction the performance is changing, for the worse or better. I would then adjust in smaller increments to really dial in your coils. The reason you will want to be stiffer in the front is because of weight. That’s where all the weight of the car is. The rear you want to set up looser than the front to allow for better traction while turning. You want some flex in the rear to maintain the largest contact patch. To stiff and the inside tire will lift thus reducing the amount of contact with the pavement. I believe most coilovers come with spring rates that are to soft. This is because if they build coilovers 100% for performance everyone would complain about ride quality. I am currently experimenting with 12kg, 10kg, 8kg and 6kg springs so I will have to get back to you guys on what provides the best performance.
-Sway bars
Contrary to popular belief you need a larger front sway and a smaller rear sway to optimize your cars handling. Why stiff in the front? Because you want to keep the front as flat as you can to maintain the largest contact patch. In the rear you actually need some flex to maintain the largest contact patch possible.
-Types of set ups
First you need to understand that at slower speeds like in autocross you will experience a greater degree of understeer and at higher speeds like in road racing you will experience a greater degree of oversteer. So understanding your end goal is important. I do not believe decreasing the performance of the rear in order to balance the car is the correct way to address a problem but I realize there is a limit to how much you can improve the handling of the front of the car. Personally, I would just add more air pressure to the rear than add a stiffer rear sway. I only recommend a stiffer rear sway for lower powered drift cars.
-Alignment
The optimum performance set up will cause a lot of tire wear on a DD so you need to decide what settings are worth the extra tire wear. You will not be able to dial in to much front camber. I have run as much as -3 up front and I think the front of the car would perform even better at -3.5. The reason is because of the McPherson front suspension design. There is so much positive camber gain under compression that you just can’t run to much negative camber. In the rear I believe running anything more than -1 is a waste. All you are doing is decreasing the contact patch in the rear. Toe out in the front about a 1/16” total. A little toe out will help your car turn in better and add high speed stability. In the rear I like zero because it’s a rwd. Our cars come with quite a lot of caster stock. I believe this is to improve the steering wheel return that is slowed by the dual knuckle design which does help with high speed straight driving stability but at a price. Reducing caster will help increase the size of the contact patch of the front wheels while turning. Basically as you increase your steering angle the more the car will rise. Park you car and turn the wheels and watch the front of your car go higher. That’ why I have reduced my caster.
-Ride Height and Weight transfer
Balancing the car significantly effects the handling performance of the car. I never weighed the car stock but I did have to raise the front when I had my car corner balanced just to get to a 55/45 front to rear weight ratio. I would say 99% of you including those of you who are at stock height have to much weight on the front. For all of you that are lowered. I will tell you right now 98% of you are to low. Our cars suspension geometry does not allow you to lower the car very much at all without increasing all the negative effects like body roll and positive camber gain. The lower you go the further away your roll center will be from your cars center of gravity. The effect of this is more body roll. This is a reason why so many of you love stiff sway bars. They reduce the increased amount of body roll you tuned into your car by slamming it. This is another example of reducing the performance of one aspect to make your car “feel” like it handles better.

There are plenty more things I can add like figuring out a way to keep the suspension travel in the optimum range which results in the reduced change in suspension geometry but that requires custom modification which I plan to dig into once I finish up with my spring rate testing.
 
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#2 ·
Nice write-up. Lots of agreement here.

A lot of people do just take the 'feeling' at face value - but furthering that idea, just the feel alone gives confidence to get closer to the edge, even if the edge isn't what it potentially could be... I've had lowered GCs murder my stock suspension setup at the track just because they could push the limits better than I could. They could nose in better, but I could power out more predictably with the softer setup.... they would eventually spin where I would continue to carve the corners .... squishily :)

Switching to coils, I'm now in that boat of 'feeling' and getting confident at the limit - there's just more feedback with the springs, caster and alignment changes, even not properly tuned. I can't wait for a corner balance, height & alignment dial-in and hit the tracks to see what she'll do.

I'm finding a 2-3 finger gap fender-to-wheel well is about as low as I'd want to go - goal is to keep the Lower control arms parallel to the ground at rest as much as possible, or a teeny bit higher. Any lower and you just lose the front end camber dynamics like you said... static camber either wears tires bad on the street, or sucks at the track in the corners... can't have both when you're slammed.
 
#3 ·
Awesome write up. It's been about 10 years since I have done major suspension changes on a car, and this is my first that has been RWD. So I am learning and trying to take in all your wisdom :)

So far having the 27mm front sway bar up front with the stock one in the rear seems good. I should know by mid-week how I feel about it.

When it comes to the length of the front end links, how does it being shorter or longer play into things? And the inner hole on the sway bar would make it stiffer, correct?
 
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#6 · (Edited)
This is a great question. Swaping end links seems to be another one of those stiffer is better trends that has some negative effects. Starting with the front end links, longer is better. Hyundai went to the longer end links in 2011 because their design is flawed. The end link is connected to the strut/coilover so when you turn tension is applied to the sway bar. This is because the strut/coilover rotates as you turn. As the strut rotates it applies force to the end link by twisting it. Hyundai should have connected the sway bar end link to the lower control arm. The negative effect is experienced when one of the front wheels is forced to change its geometry more than the other, like when you hit a bump. The extra force that is applied to that wheel will transfer into the steering and make the steering wheel turn on you. The stiffer and the shorter the end link, the more force will be transferred back into the steering. The end links that reduce this steering wheel kick back the most are the factory 2011+ end links. Those are the ones to go with. Stiffness is best adjusted with the sway bar not the end links. To experience it yourself simply go over a speed bump with only one front tire or go up a drive way at an angle and see how much your steering wheel moves on its own. In a perfect world your suspension should soak up it up without effecting your steering. In regards to racing if you take a corner and hit the inside rumble strips with one tire and your steering changes, even a little, it's going to change your line. Physically your reactions are not fast enough to keep the steering wheel from moving. Now the rear end links. Some people have been bending their rear end links after going to the Whiteline rear sway bar. That's because that sway bar is so stiff that it applies enough force to lift your inside rear wheel off the ground. Your rear end links were not designed to take all that force. By going to a Whiteline rear sway, set on stiff, and stiffer rear end links you have just tuned your car to drive on 3 wheels around turns.

By the way, everything that I have posted is based on track experimentation. From different end links, tires, sway bars, alignments, on and on. I don't claim to know everything, just posting what I have learned from tuning my suspension.
 
#4 ·
Thank you for posting this! I highly value your opinion as you've spent more time with this platform's suspension than just about anyone, there's only a few other members that can speak to it like you can, so this is a great resource post and one that we can refer other users to!
 
#8 ·
So I have two questions:

1. Is there any amount of lowering the car on coils that is actually beneficial to handling with the rest of the suspension being stock?

2. Lateral locks on the sway bars yes or no? Sounds like no on the rear since you're conclusions are that the rear should stay completely stock.
 
#10 ·
Don't the factory bars have lateral locks? I know my front one did for sure.
 
#16 ·
great info!

any recommendations on front and rear sway bars for a base 2012 daily driver that is not raced or road coursed, with stock tires, rims, springs?

I've put bigger sway bars on my 2003 and 2004 honda civics, which made an improvement.
 
#19 ·
OP! so much right about this post
 
#20 ·
I was just informed about these end links. It's very interesting that Genracer points out that by adjusting the length of the end link you can position the sway bar neutrally with out any preload. Perhaps the preload is the problem when swaping to an adjustable sway bar. My front end links are connected to the lower control arms so I can't test this out but maybe one of you guys can. adjustable front sway bar end links
 
#23 ·
#21 ·
How do you feel about a rear sway bar delete on this car for more rear traction? I've been mulling the idea of a stiffer front and no rear sway.

I know quite a few Miatas that run minus the rear sway on the track. Since both are rear wheel drive, I was considering doing it but haven't yet. My tracking skills need much more improvement first :)

The way it was explained to me, was since the sway bar limits body roll by pulling on the other side, the inside tire would essentially "pull" the outside up.

Its late so my brain isn't working 100%. Pretty sure I got that right though. Anyhoo, I know its the rear sway delete with stiffer front I've been considering for autocross. What do you think? I'll probably do it either way if I get better tires by the end of the season and am able to get in at least two more track days.
 
#26 ·
Disconnecting the rear sway bar is usually a perfect "rain" setup.

We have found that disconnecting the rear bar really isn't ideal but if it suits you go for it. However no rear bar might also cause the front inside tire to lift off the ground. We have tested that and had to go with less front bar to compensate.
 
#27 ·
I think no sway bar in a miata works because it's a balanced car. Our car has a lot more weight transfer. Now if you want to do some custom work and some serious tuning I think there could be some advantages. I believe the main hurdle would be keeping the suspension travel in the optimum range. Rhys did not have a rear sway bar on his genesis coupe but he did have some straps connected between the lower control arms and the subframe that limited the rebound travel. The springs controlled the compression travel.
 
#28 ·
Thoughts on under car braces and anything to make things stiffer? It seems that our cars are pretty stiff to begin with.
 
#31 ·
The car needs to be on ramps to adjust front endlink preload. The suspension needs to be properly loaded up. Technically you only need to adjust one of the endlinks. Start out with one endlink installed completely, and the other endlink installed halfway ( one end on the bar, the other end hanging there disconnected ). Then put your wheel back on, drive the car up on some ramps, and adjust the second endlink so it now meets the sway bar. Presto, you now have no sway bar preload.

You can also start with both installed, and then adjust each one to zero preload, but why double the work?
 
#32 · (Edited)
We have ran these endlinks for a full race season with no issues and have ran every bar on the market. Heims are 1/2inch that has Ultimate Static Load Rating: 8,386 lbs
 
#33 ·
We have ran these endlinks for a full race season with no issues and have ran every bar on the market. Heims are 1/2inch that has Ultimate Static Load Rating: 14,580 lbs
But how much daily driving time did you put on those endlinks? That's where the heim joints start to show their weaknesses. After 6 months of pot holes, road grime, and rough city roads.

Send me a set to test:)

I would need 2010 style though.
 
#43 ·
#44 ·
The chassis is the base of your suspension so stiffening the chassis definitely improves the handling performance as it would help keep the suspension components in the optimum position or at least the positions you set them to. Basically the more the chassis flexes the further away the suspension geometry/alignment is from optimum.

As far as the braces I believe the ones that bolt to the subframe would provide the greatest improvement since the subframe is what all your suspension arms are attached to. Also, examine where the braces bolt to. If the mounting points can not be torqued to a decent number I would think the brace has less of a chance to be effective. For example, I have the rear strut tower brace but I discovered during installation that the mount points have inserts that can not handle much torque at all. So no matter how stiff the bar is it will be only as strong as its weakest point which were the mount points. I did not notice any improvement after installing that brace.

I only have the stock front tower brace and the rear strut tower brace because I plan on getting a full cage so I think the other braces would be redundant for me but I think all the braces that have solid connections would provide a subtle improvement.

On a side note why hasn't anyone made solid bushings or rigid collars for the front subframe?
 
#47 ·
:eek: :shock: :eek: :)
WOW..What a write up and discussion concerning suspension. I been around cars for while lowering modding and all that stuff but its great to see such in depth information and knowledge on this new car. ...101 <---you are not kidding. I feel like I just took a semester course in college! Thanks 1320drift and other contributors. This helps majorly when impulse buys get close after doing light reading and research. I am going to continue to examine more.
 
#51 ·
1320 - can you ask Dan when he expects to have the steering angle kit in stock? I don't have facebook and last I heard was August
 
#55 ·
Ok so I am a total noob here and have just ordered Eibach Pro-Kit springs, I was wondering if I just use these and install them, then take them to get the car aligned will it mess with my shocks/struts? Also I was thinking about returning them to get the Sportline series, although I know this will probably put more stress on the shocks/struts being that they put the car at a lower center of gravity. More or less will I have to do anything besides putting these springs in and then drive to my shop to get it realigned? Will it destroy my shocks/struts? Total noob just in need of some advice, and I don't have the money to invest in coilovers at the moment, but it is something I have thought about for the future. Thanks in advance!
 
#56 ·
Springs will lower your car and kill your ride quality. But other than an alignment, keep this in mind. (Taken from the QM Files)

A.) By installing higher-spring rate and shorter-stroke springs onto your OEM dampers, you are now forcing them to operate outside their acceptable life stress levels, and as such they will die much sooner than they normally would. How hard you abuse the car will determine how much shorter their lives will be.

B.) You will lose ride quality. Bumps will hit harder. With most spring kits (per their instructions) you may need to cut down your OEM bump stops, meaning hits will hurt. Springs take a short while to settle, and once they do, your ride height is fixed, so deal with it.
 
#57 · (Edited)
great feedback on this car! When I went to a squared setup of stock rear rims and 245 re-11's, it lifted the front to level and became a totally different car with -1.2 front camber. Its compliance is its best asset. My driving style in autox is to power out anyway, so I still have the power oversteer to control. I also run some crowned road rally. The car performs best in these events.
OK- Im getting a set of Kontrol coilovers, and plan to keep the squared setup. My initial instinct was to lower the car by only .5 in (maintaining level), and run the middle setting on the rear shock, and forget it. Then- max out the front camber-reduce the rear to -1, and go from there...only dialing in the front damper/rebound.
I hate to break something that's not broken. The car is neutral and free the way it is now. Its just needs more (off-throttle) front grip w/out having to rotate it with the loud pedal, or trail braking.
???????Am I on the right page with my strategy??
380 track 8spd with solid brake upgrade.
Thanks for any feedback
 
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