Topic: Your experience with Poly bushings?

[Yps]

Hey,
i had a look into the poly bushings from energy suspension parts - link.
In the forum i found the Poly bushings update from snaponbob but really not much more info at all. 

Can you share your experience with the poly bushings regarding:

• Does it fit to all Kappas without the probs snaponbob reported in the beginning?
• improvement in handling?
• any other experience?

Thank you all!

[snaponbob]

If you are not racing the car, the effort and aggravation is not worth it. The likelihood of getting a COMPLETE package of ALL the CORRECT parts seems .... ummmm .... challenging.   

[spicy3480]

If you decide to upgrade your sway bars to the ZOK style ones, it is recommended to get the upgraded bushings specifically for those.  I got mine at Summit racing. 

[snaponbob]

Be VERY aware that the picture on that link is NOT what is in the kit. The kit bushings for the Kappas are single piece rather than the multi-piece as seen in the picture.

[Yps]

OUCH!

... The likelihood of getting a COMPLETE package of ALL the CORRECT parts seems .... ummmm .... challenging.   

This sounds like there might be a lot of frustration involved in case it doesn't fit. Imagine the parts beeing shipped to germany and i start the installation and recognize it doesn't fit.   

I'm on the race track app. 2-3 per month. I made already some modifications to make the chassis stiffer but it still isn't as precise like it should feel.

Can you tell me a bit more about the ZOK style sway bars?
Maybe an url to see the design? It sounds interesting 

If you decide to upgrade your sway bars to the ZOK style ones, it is recommended to get the upgraded bushings specifically for those.  I got mine at Summit racing. 

[TomatoSoup]

Can you tell me a bit more about the ZOK style sway bars?
Maybe an url to see the design? It sounds interesting 

It's just a stiffer version of the swaybar you already have.  Loads of info on this thread (read though all of it!): http://www.kappaperformance.com/forum/index.php/topic,2017.0.html

[snaponbob]

OUCH!
This sounds like there might be a lot of frustration involved in case it doesn't fit. Imagine the parts beeing shipped to germany and i start the installation and recognize it doesn't fit.   

I'm on the race track app. 2-3 per month. I made already some modifications to make the chassis stiffer but it still isn't as precise like it should feel.

Can you tell me a bit more about the ZOK style sway bars?
Maybe an url to see the design? It sounds interesting 

What have you done to your car so far?
What sort of track speeds to you see?
What tires do you run on the tracks?

[Carbon Sky]

I've tried polyurethane bushings in control arms, tie-rods, anti-roll bar ends, anti-roll bar clamps, etc.  In general, all have "sharpened" steering feel, as in everything feels more rigid, and there's less "flex" between the steering input, and the wheel.  This also meant less isolation, as in, high frequency vibrations itched their ways through the bushings, and a "grainy" vibration was more present, where it used to be a silky feel before.

Also, they tend to be more prone to squeeking.

Would I do it again?  On a very performance oriented car where you're willing to give up some civility for some added sharpness, then yes.  If it's your daily driver, and you're past loud exhausts, peaky power bands, suspension harshness, etc, then no.

I can't quite explain it, but Porsche just has a way of giving you scalpel sharp steering feel, without the harshness getting through.  Boxsters/Caymans have such an amazing feel yet still being very sharp in steering response.

Just my 2 cents.

[Yps]

1. What have you done to your car so far?
2. What sort of track speeds to you see?
3. What tires do you run on the tracks?

1.

• modified "Wiechers" rear brace to fit Magna exhaust
• front brace will be self-made,
• replaced the stock rubber sway bar bushings with self-made teflon bushings
• KW V3 suspension with harder spring on the rear

2. that's hard to explain 
in quick left/right corners the steering seems laggy and the rear feels too soft. Hard to say at which speed. I tried several coilover settings but couldn't improve the feeling to fit my expectation. In the beginning i tried to eliminate any possible influence by chassis torsion. The next step is simply to reduce any flexible bushings to improve steering feel.
Adjustable sway bars would be neat - need to be custom-build tho 

3. 19" Semi-slicks on the track, 20" on the road

The kappa isn't my daily driver. It's my car for having fun on the road and on the track which i drive only during summer (April-October). I'm willing to sacrifice comfort in order to achive a higher performance.

[Gentleman Jack]

Have you looked in to the following:

DDM backbone brace (tunnel brace) either race or extreme versions
Any of the engine bay braces
DDM probeam rear brace


These have made wonderful differences in most vehicles.  They will all work together to make your new coil overs work better.

For DDM: www.ddmworks.com
Search this forum for: LV front chassis brace, many threads about it


Good luck!

GJ

[snaponbob]

1.

• modified "Wiechers" rear brace to fit Magna exhaust
• front brace will be self-made,
• replaced the stock rubber sway bar bushings with self-made teflon bushings
• KW V3 suspension with harder spring on the rear

2. that's hard to explain 
in quick left/right corners the steering seems laggy and the rear feels too soft. Hard to say at which speed. I tried several coilover settings but couldn't improve the feeling to fit my expectation. In the beginning i tried to eliminate any possible influence by chassis torsion. The next step is simply to reduce any flexible bushings to improve steering feel.
Adjustable sway bars would be neat - need to be custom-build tho 

3. 19" Semi-slicks on the track, 20" on the road

The kappa isn't my daily driver. It's my car for having fun on the road and on the track which i drive only during summer (April-October). I'm willing to sacrifice comfort in order to achive a higher performance.

1) Good start. Since you are not restricted by some of the rules some of us are, the front brace can be anything you want. a) If you can create something to triangulate the spring towers back to the firewall there would be a usable increase in stiffness. b) Make sure those bushings do not bind the sway bars. c) KW V3 come with a ridiculous combination of rates, and stiffening the rear was a good move. KW builds their V3 with WEAKER rear springs and that is backwards on out platform. Hopefully your rears are about 1K above the fronts. (What rates do you have?)
2) There are stiffer (18-20%) bars available for your car, but shipping could be expensive. In total, they could be cheaper than custom made. (I have a "calculator" that can be used to work out bar rates, so when you are ready, I can run some figures. BTW, solid bars are SOFTER than hollow bars, so must be much bigger and heavier provide an increase.) When I started chassis tuning, EVERY bit of (correct) advice was based on creating the basic handling with springs, tune with bars, fine tune with shock rates, and finish with tire pressures. Some of the very quickest cars in autocross don't use bars at all, but the result is undriveable on the street.
3) The slow response may be partly due to the 19". The rotating mass is quite a bit greater than 18". A few years ago somebody posted a formula for calculating those numbers, and the results were amazing just for heavier 18" TIRES, and the 19" wheel/tire combos were jaw dropping !!!!!

Just a few thoughts. HTH.

[Yps]

I forgot that i have a tunnel brace installed. 
A member of the GT-Forum designed a pretty nice one and it's well engineered.


The KW V3 came with 40N/mm(200mm) spring for the rear and 50N/mm(250mm) on the front. That was really ridiculous for a car which has almost 50:50 weight balance 
For the rear i'm using now the same spring rate as for the front -> 50N/mm(250mm). This requires 2 adapter plates.


Do you know another supplier for a harder spring which would fit?
Which spring rates have you installed?

18"/19" or 20"
That was a tragedy for me. I started with original 18" then went to 20" to reduce the tire height which reduced the instability. Then myself because of the unsprung masses of the 20" weight. Even that i had "light"(31.3lb) 20" rims it felt to heavy. Then i bought another set of "really light"(18.6lb) 19" rims with semi-slicks -> This was an excellent improvement on the track.

[snaponbob]

If you can afford it, a set of 18x9 or 18x10 wheels would improve things further, but that is a lot of money.

Springs - it would be a good idea to try some 6K rear springs. The Opel GT comes with 180 lbs/in front springs (about 3.4k) and 220 rear (about 4K). Going to 6K rear springs will restore that balance. The GT has about a 52/48 f/r balance so the heavier rear springs will allow the car to be more neutral. Another VERY effect change is to re-align the suspension to achieve more negative camber, and if you not done this yet, it will wake up your car in a big way. The GXP/Z0K sway bars are about 18-20 stiffer than the bars that come on the GT. If, as mentioned earlier, then go to 8K front and 9K rear springs (which is probably a better road course solution than bars, and certainly cheaper). If that combination make the car to loose (in the back) either go UP to 9s in the front or down to 8s in the rear. The stock bushings really are quite effective, enough so that given the work involved, they should be considered only after alignment and springs are tried. 

[Gentleman Jack]

If you can afford it, a set of 18x9 or 18x10 wheels would improve things further, but that is a lot of money.

Springs - it would be a good idea to try some 6K rear springs. The Opel GT comes with 180 lbs/in front springs (about 3.4k) and 220 rear (about 4K). Going to 6K rear springs will restore that balance. The GT has about a 52/48 f/r balance so the heavier rear springs will allow the car to be more neutral. Another VERY effect change is to re-align the suspension to achieve more negative camber, and if you not done this yet, it will wake up your car in a big way. The GXP/Z0K sway bars are about 18-20 stiffer than the bars that come on the GT. If, as mentioned earlier, then go to 8K front and 9K rear springs (which is probably a better road course solution than bars, and certainly cheaper). If that combination make the car to loose (in the back) either go UP to 9s in the front or down to 8s in the rear. The stock bushings really are quite effective, enough so that given the work involved, they should be considered only after alignment and springs are tried. 

Sometimes your genius amazes me.

[snaponbob]

Thanks (I think!!). School of Hard Knocks at the Bloody Knuckle University.