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OFFICIAL Suspension Theory and Modification Thread

Talguy

Go Kart Champion
Great read. Mods can we please sticky grambles technical discussion threads like this one
 
What you suggest for a guy like me that LOVE stock suspension BUT, wants to get rid of the GAP? I don't want to be "slammed" or either "tuck" any tire, just a nice sporty appearance. :iono:
 

Volkswagging

Don't Hate, Inseminate
 

grambles423

Automotive Engineer
What you suggest for a guy like me that LOVE stock suspension BUT, wants to get rid of the GAP? I don't want to be "slammed" or either "tuck" any tire, just a nice sporty appearance. :iono:

The moment you step outside those stock parameters, you're gonna have to adjust your damping values. Normally you can find good aftermarket kits that come close, but its hard to give you an exact answer.

I myself already have Neuspeed Sport springs with Bilstein Sport Shocks, and its a ROUGH ride. Nice on smooth surfaces, but in the city, its unbearable sometimes. I'm thinking Koni FSDs might be my answer.
 
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Hilfloskind

Go Kart Champion
I really believe after experiencing this process myself that, without being scientific about it, going from stock to coils and back gives you an appreciation for the fine tuning that goes into this car's suspension engineering. I just don't think anyone less than a perfectionist with solid understanding of mechanics would be able to maintain or extract true performance gains from a lowered setup on these cars. At minimum, having corner balancing done seems like a requirement for anyone looking for more than to "get rid of that gap".
 

grambles423

Automotive Engineer
I really believe after experiencing this process myself that, without being scientific about it, going from stock to coils and back gives you an appreciation for the fine tuning that goes into this car's suspension engineering. I just don't think anyone less than a perfectionist with solid understanding of mechanics would be able to maintain or extract true performance gains from a lowered setup on these cars. At minimum, having corner balancing done seems like a requirement for anyone looking for more than to "get rid of that gap".

Agreed, but there are some springs and shock combos that will get the job done. Granted, they're not tuned for the specific instance, but thats where some of these high profile systems come into play.

Corner balancing seems to be easily solved by a sway bar. I think the most conflicting deal is when people who want to "get rid of the gap" realize, oh shit....this doesnt ride like I wanted it too then they begin the long process of spring shock combos and coilovers. And end up underdamping the system and make for bouncy rides. Yes, it gets rid of the body roll, but daily driving sucks ass.

I hate how people think body roll is a characteristic of a "soft" suspension. It normally dissapates confidence, but if you know the limits of your suspension, it shouldnt be a big deal. I PERSONALLY like the stock suspension and might eventually make my way back, but I REALLY want to see if FSD's are everything they're made to be.
 

Djunited1

Go Kart Champion
how can i know if installing FK shocks and springs might ruin the car's handling?if that is possible in the first place?
 

RacingManiac

Drag Race Newbie
I really believe after experiencing this process myself that, without being scientific about it, going from stock to coils and back gives you an appreciation for the fine tuning that goes into this car's suspension engineering. I just don't think anyone less than a perfectionist with solid understanding of mechanics would be able to maintain or extract true performance gains from a lowered setup on these cars. At minimum, having corner balancing done seems like a requirement for anyone looking for more than to "get rid of that gap".

I am sure gramble knows this, but in the industry a lot of the ride and handling engineer, aside from looking at data and tuning on test stands, they also do subjective tuning with their "calibrated butt"....people who are good at stuff like that are really good at it. They can tell a shake or rattle in the suspension down to where it is happening and what to do about it....
 

grambles423

Automotive Engineer
how can i know if installing FK shocks and springs might ruin the car's handling?if that is possible in the first place?

Well, if you know:

-How much you're lowering the COG
-Where the center of gravity is
-Trackwidth
-Roll Center
-And other suspension characteristics listed in the OP

You should be able to find how much load transfer will change. The problem is the Tedious work of finding all of those variables.

I did a thread a while back about mass properties and finding you're center of gravity. Check through my threads and that should help you out there. I'll do my best one lonely afternoon to mock up something worthwhile for you gents.

As far as damping values and spring rates are concered, again, I will iterate that companies normally dont give that sort of information out, so deteremning you're ride quality will be a bit harder to quantify.
 
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grambles423

Automotive Engineer
I am sure gramble knows this, but in the industry a lot of the ride and handling engineer, aside from looking at data and tuning on test stands, they also do subjective tuning with their "calibrated butt"....people who are good at stuff like that are really good at it. They can tell a shake or rattle in the suspension down to where it is happening and what to do about it....

From personal experience, I've done NVH, BSR (Bump Squeak Rattle), Windnoise and Driving Experience evaluation for JD Power IQS activities. Its nothing more than sitting in a car and going with your instincts on what rides good and what sounds are annoying. It can be very subjective sometimes, thats why we use a lot of transducers, microphones, and frequency modulators to accurately quantify those characteristics, so its not totally based off someone's opinion. However, experience starts to trump the doubt.
 

Djunited1

Go Kart Champion
Well, if you know:

-How much you're lowering the COG
-Where the center of gravity is
-Trackwidth
-Roll Center
-And other suspension characteristics listed in the OP

You should be able to find how much load transfer will change. The problem is the Tedious work of finding all of those variables.

I did a thread a while back about mass properties and finding you're center of gravity. Check through my threads and that should help you out there. I'll do my best one lonely afternoon to mock up something worthwhile for you gents.

As far as dampening values and spring rates are concered, again, I will iterate that companies normally dont give that sort of information out, so deteremning you're ride quality will be a bit harder to quantify.

don't all the major suspension companies out there do these calculations before they release their products? i don't care much about the ride comfort. i want to enjoy twisty mountain roads so firmer is better for me. they probably lower the car by 1" all around.

edit: posted right after you did so did not see your post
 

grambles423

Automotive Engineer
don't all the major suspension companies out there do these calculations before they release their products? i don't care much about the ride comfort. i want to enjoy twisty mountain roads so firmer is better for me. they probably lower the car by 1" all around.

Then there you go. You've answered you're own question. If you dont car about ride comfort, I'd definitely say get coilovers.
 

Djunited1

Go Kart Champion
Then there you go. You've answered you're own question. If you dont car about ride comfort, I'd definitely say get coilovers.

i see. the fks are not coilovers however.they cannot be adjusted,and i feel like i have no use for the added adjustability of coilovers.price is a factor as well. only thing i have to check is if i can fit 245s with them
 

RacingManiac

Drag Race Newbie
From personal experience, I've done NVH, BSR (Bump Squeak Rattle), Windnoise and Driving Experience evaluation for JD Power IQS activities. Its nothing more than sitting in a car and going with your instincts on what rides good and what sounds are annoying. It can be very subjective sometimes, thats why we use a lot of transducers, microphones, and frequency modulators to accurately quantify those characteristics, so its not totally based off someone's opinion. However, experience starts to trump the doubt.


Ah, but thats not ride work. Ride engineer although speaking of rattling and sound, is mostly concerned with ride. Its hard to talk to them sometimes, as you build your shock, you hand it to them and have it installed on the car. They go out and drive around some ride loop, come back and they tell you what is wrong with it. A lot of it is just a feel thing. It can be how the sharpness in a bump is tuned out or not, or how the body settles after a whoop or a dip. The car at this point usually will be fully instrumented with string pots, accelerometers to try to find some data to correlate to the event they describe but at the end of the day their butts are the key....

OEMs keep these guys around for a long time....and I often hear when some OEs changed their ride engineer that the next batch of products don't ride the same as before because of it...

IMO unlike objective handling and balance, which coming from a racing background is easier to fathom and deduce as the data are easily correlate-able, ride work is an art in itself....
 

Erwan1

Go Kart Champion
Thanks for the info, I'll def have to spend some time and try to do some calculations.

However I do have one comment for anyone reading this, learn to drive your car and push its limits before you start playing with suspension....I don't know how many times I've heard people tell me they want coils or suspension upgrades to improve handling when all they do is drive on the street and barely push the car. Trust me the car's stock suspension is very capable, I've been tracking my car a fair amount this summer and I can tell you that my suspension has not been a limitation. My driving and learning to drive a car to its limits is the first issue....I'm now looking into getting a rear sway bar but again I'm just now pushing the car to the point where I will be able to make use of this sway bar.

All in all just take a step back and think about what you're going to be doing and how much you've actually pushed the car, is the suspension REALLY limiting you and your driving? Ignore this rant if you're lowering your car for looks haha :D
 
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