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OFFICIAL Suspension Theory and Modification Thread

G

Gurg

New member
What would you think about combining the eibach pro plus kit (kit has lowering springs .8in front and rear and 26mm front bar and 23mm rear bar) with the koni fsd shocks. Koni says they work best with stock springs so dont know if theyll wear out with .8in drop. Id like to avoid a huge drop and shocks that id have to tune. What i really want is nice stiff preformance a little low and dont want to be messing around with a bunch of different settings.
 
the bruce

the bruce

Go Kart Champion
Avoid FSDs with lowering springs if you want handling. Get Koni Yellows or Bilsteins,
best with DG springs. Feel free to mate them with you sway bars of choice.
 
kthor7031

kthor7031

Go Kart Champion
How do you calculate the roll center?
Moment of Roll (How hard you're vehicle rolls) = Roll Stiffness * Roll angle

Roll Stiffness = Front Roll Stiffness + Rear Roll Stiffness = FRS + RRS

FRS = 0.5 * Wheel Rate * Front Trackwidth^2 + Stiffness of Front Sway

RRS = 0.5 * Wheel Rate * Rear Trackwidth^2 + Stiffness of Rear Sway

*Sway thickness can be forund on the internet if you google Sway stiffness formula

*Assume your wheel rates are the same on each side

Moment of Roll = Sprung Mass * Gravity * (D) * Roll Angle + Sprung Mass * Laterall Acceleration * (D)

Lateral Acceleration = Speed into the turn / Radius of the Turn

(D) = Height of center of gravity above roll center (if roll center is above CG, d < 0 )
Click to expand...

Shouldn't the bold portion be squared? Would hate to see someone try calculations and mess up if so, considering how tedious it is :p. Love coming back to this thread.
 
imtimmy

imtimmy

Ready to race!
Thanks for all valuable info and input on this thread. Been driving 2012 gti for only 2 weeks now and still learning and loving the car. I do want to close gap in wheel wells but not if the ride is going to get harsh and tires uneven in 10k miles. I am following the dg vs. vwr spring thread now as well.
 
kthor7031

kthor7031

Go Kart Champion
After doing much research and reading this thread, I am still a little hazy on this concept. Is lowering enough to disrupt the geometry (ie: over an inch) bad for handling overall, including performance driving, or only for Daily driving?
 
thez99

thez99

Go Kart Champion
Funny, I see all this comparing of DG and neuspeed springs, but I see nothing of SPM's springs..First off their price kicks ass, they have built in bumpstops (perhaps negatable) and they look to drop front and rear an equal 1" which would be perfect to close the gap but def not cause rubbing on the fender or inside. Also, anybody know what the spring rates are on the SPM springs versus stock?

Also, Ive seen on here some bashing of the FSD's and also some bashing of the bilstein sport's "harshness", can anyone elaborate a bit more on how severe either of these situations are?
I dont track my car, but Ive been driving more than long enough to know what Im doing and I love to drive spiritedly and be able to feel the car and have it work well for me. Driving is not only just getting to work and back but also a hobby for me so.. Doing so I've been looking at the bilstien sports with the spm springs, looks like a great mate up, perfect height, set struts and dampers to much improve performance but not kill the ride. Was considering the FSD's but I had used them previously with my mk5 I had before, and honestly I didnt notice much of a performance improvement, Only drove em for about 4k miles before I sold the car though. That and also the fsd's are about $120 more than then Bil sports which honestly I feel are already better track tested and review better as Ive seen. Kinda just up in the air about what to do.

Also, about replacing the strut mounts/bearing/bolts front and rear for an aftermarket changeup, is this def necessary? Ive read plenty about it being more of a "put your mind to ease" mod when replacing shocks/springs, rather than a necessity but figured id ask. Ive seen the kits that replace the bushings, bearings, bolt, spindle bolts, nuts, etc. for the front and rear together at around $150 which isnt bad, but if not necessary than who knows :iono:

P.S. Forgot to ask if anyone has any dealings with the koni str.t struts/shocks? I mean you cant beat the price for sure, but are they really going to improve much in performance, etc. or are they pretty much just equal stock shock replacers?
 
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the bruce

the bruce

Go Kart Champion
thez99 said:
Funny, I see all this comparing of DG and neuspeed springs, but I see nothing of SPM's springs..First off their price kicks ass, they have built in bumpstops (perhaps negatable) and they look to drop front and rear an equal 1" which would be perfect to close the gap but def not cause rubbing on the fender or inside. Also, anybody know what the spring rates are on the SPM springs versus stock?
Click to expand...

First, bump stops are not "built in". They come with their own (just 2?)
and this is what DG also come with. Bump stops sit on dampers, not on
the springs.

Spring rates, Google is your friend, mate:

http://www.drivespm.com/MK6-GTI-Spring-Kit-p/su10-600z-kn31-00.htm

They claim an increase of 42 % and this is why I say they are NOT a proper
match with stock dampers.


thez99 said:
Also, Ive seen on here some bashing of the FSD's and also some bashing of the bilstein sport's "harshness", can anyone elaborate a bit more on how severe either of these situations are?
Click to expand...

FSDs are fine with stock springs, at least on a Golf. They are NOT intended
to be run with lowering springs (which are almost always stiffer).

Mk.VI Bilsteins aren't harsh anyway. Some find the Mk.V Bilstein to be little
stiff - I don't.


I dont track my car, but Ive been driving more than long enough to know what Im doing and I love to drive spiritedly and be able to feel the car and have it work well for me. Driving is not only just getting to work and back but also a hobby for me so.. Doing so I've been looking at the bilstien sports with the spm springs, looks like a great mate up, perfect height, set struts and dampers to much improve performance but not kill the ride. Was considering the FSD's but I had used them previously with my mk5 I had before, and honestly I didnt notice much of a performance improvement, Only drove em for about 4k miles before I sold the car though. That and also the fsd's are about $120 more than then Bil sports which honestly I feel are already better track tested and review better as Ive seen. Kinda just up in the air about what to do.
Click to expand...

SPM with Mk.V Bilstein B8/Sport or DGs with Mk.VI Bilsteins for you.


Also, about replacing the strut mounts/bearing/bolts front and rear for an aftermarket changeup, is this def necessary?
Ive read plenty about it being more of a "put your mind to ease" mod when replacing shocks/springs, rather than a necessity but figured id ask. Ive seen the kits that replace the bushings, bearings, bolt, spindle bolts, nuts, etc. for the front and rear together at around $150 which isnt bad, but if not necessary than who knows :iono:
Click to expand...

Hard to say. I'd get at least new strut bearings, preferably SKF ones.


P.S. Forgot to ask if anyone has any dealings with the koni str.t struts/shocks? I mean you cant beat the price for sure, but are they really going to improve much in performance, etc. or are they pretty much just equal stock shock replacers?
Click to expand...

I've never driven them, but you'll certainly find 1st hand experience on the forum.
 
Stinger

Stinger

Ready to race!
See my sig for mods. I don't find my suspension to be harsh compared to stock. It's stiffer than stock but with better absorption, if that makes any sense. The only other sport cars experiences I've had is a stock suspension Porsche (stiffer) and Honda S2000 (stiffest -unbearable beyond 50 miles).
Because the sway bar mod was done at about the same time as the suspensions it's a bit hard to pinpoint what has had the most impact on the overall driveability of the car. But as a whole, the car is far more responsive and precise than stock and I don't regret the transformation. Only aesthetic wish it that it was a couple inches lower in the back and about 1" more in the front, for a truly compact look.
 
vrBilstein86

vrBilstein86

Ready to race!
Dave10781

Dave10781

Go Kart Champion
vrBilstein86 said:
I know you found his answer, but let me know if you have any further questions regarding the Bilsteins and ride performance.
Click to expand...


I ended up with VWR springs and B8s. When I rode in a car with stock dampers, the VWRs felt stiff and the car would also bounce at speed. With the setup I'm running, the ride compliance is great. I'd almost even say I would want stiffer springs, as the dampers seem to handle anything that's thrown at them.
 
the bruce

the bruce

Go Kart Champion
Pleased to hear you're happy with your current setup. ;)

Dave1078 said:
Would you say that DG springs + B8/Sport dampers would offer superior ride quality on the street over B14 coilovers?
Click to expand...

Oh yes, they do. :thumbsup:
 
VMRWheels

VMRWheels

Go Kart Champion
Dave1078 said:
I ended up with VWR springs and B8s. When I rode in a car with stock dampers, the VWRs felt stiff and the car would also bounce at speed. With the setup I'm running, the ride compliance is great. I'd almost even say I would want stiffer springs, as the dampers seem to handle anything that's thrown at them.
Click to expand...

I see the B8 is of monotube construction. Very good choice!
 
C

coachfoxta

Passed Driver's Ed
I've got DGs on the way and I'm looking to pair them with OEM shocks. My stock suspension has 61,000 miles though. What should I replace other than the stretch bolts? I want to do this right. Thanks.
 
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