OFFICIAL Suspension Theory and Modification Thread

[RacingManiac]

Just read through that thread, good stuff in there....I think from a pure performance perspective its hard to deviate from what was written. If you are an admitted riding "low and slow" crowd, your priority will likely be something that drops a lot, and maintain a tolerable ride. That requirement will obviously be different than someone who are looking for more grip when tracking or autocrossing a car. And if you are looking for handling gain, it is much more advisable to really experience the limit of the stock car first, before you do anything else. I am in the process of doing that, as I am trying to go out autocrossing at least twice a month to get some seat time and just to know where the limit for myself and my car is. Running also on stock all season, the limit is also lower and handling deficiency exaggerated. Without having this kind of baseline it'll be hard to make educated decision on where the car should go. I know for myself I am keeping the car stock suspension-wise for at least this and next year, as the main thing I plan to do next season is wheels and tire. Having adjustable coil-over and ride height will muddy the water easily and can add confusion....pretty much at this stage I blame all issue experienced squarely on myself....

I can also say first hand from experience that Teched's observation of the limit behavior of the GTI is pretty spot on. The car can be coerced willingly to rotate...which aids in negotiating the pylon courses....

On Koni's also, I was personally recommended against them by 3 engineers in my office who used them before in their own toy as well as one guy who used to work shock tuning at Nissan. One guy mentioned he blew up a set of Koni's on track, had them replaced by Koni under warranty, and same thing happened again. He went to Bilstein's and was fine after. I have no first hand knowledge of any so I am just keeping my ears open. If I ever were to go coil-over I might look at PSS10 or KW V2(whatever the PSS10 equivalent is). I am actually interested in retaining stock ride height for winter and slight drop to affect balance in the summer, and potential to actually make the ride softer when not tracking. And being in my line of work, I'd be able to properly corner weight my car also to retain stock balance after swap....

[Talguy]

Great read. Mods can we please sticky grambles technical discussion threads like this one

[jorgeecolina]

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.

[Mellow Dubmarine]

[grambles423]

Originally Posted by jorgeecolina

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.

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.

[Hilfloskind]

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]

Originally Posted by Hilfloskind

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.

[Djunited]

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]

Originally Posted by Hilfloskind

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]

Originally Posted by Djunited

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.

[grambles423]

Originally Posted by RacingManiac

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.

[Djunited]

Originally Posted by grambles423

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]

Originally Posted by Djunited

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.

[Djunited]

Originally Posted by grambles423

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