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> V8 conversions: Torsion bar size and rear spring rates?, What do you run?
tygaboy
post May 6 2020, 04:00 PM
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Hi V8 folks -
I'm looking for recommendations to size my torsion bars and rear spring rates.

Component-wise, it's an LS3 with Boxster 6-speed. The total drive train weight is around 575 lbs.

I'm running Koni yellows (helper springs on the rear), 17mm raised front spindles and the 2" Tangerine rear suspension points and tall shock tower kit.

I'd like the ride to be sporty but tolerable. if that means anything! The use case is "spirited street driving" I'm not worried about ultimate track performance - at least not yet.

So, wha'cha running?
Thanks,
Chris


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ValcoOscar
post May 6 2020, 04:10 PM
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This is my LS Car with 901. Boxster S trans is stored for now. Ride is very tolerable, not uncomfortable at all. No twisties yet. (IMG:style_emoticons/default/headbang.gif)


190 lb Springs...Let me check torsion bars.

Oscar

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tygaboy
post May 6 2020, 04:30 PM
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@ValcoOscar - Looks great! But what rate rear springs and what size front torsion bars are you running?
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FL000
post May 6 2020, 05:20 PM
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Chris,

I don't have a baseline for comparison, but for what it's worth I am running stock torsion bars and 200# springs. I have only used mine for spirited driving (IMG:style_emoticons/default/driving-girl.gif)
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roblav1
post May 6 2020, 06:15 PM
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On my performance based build, I have 21mm Sway Away bars on the front. Have not driven yet but bounce feels about right for performance street.
Rear springs are aftermarket blue... no idea of make or rate but feels around 250 lb per inch. I don't like those rear springs because they go loose at full rebound droop extension at a ride height that isn't low enough for what I want. The rear spring rste feels about right though. I may take them out and measure the rate in a drill press.

I'm thinking the rear coils should be progressive rate to prevent looseness at full droop.

On edit, my rear setup is exact same as Valco Oscar except springs are blue. The real solution is shorter rear dampers.
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tygaboy
post May 6 2020, 06:38 PM
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QUOTE(roblav1 @ May 6 2020, 05:15 PM) *

On my performance based build, I have 21mm Sway Away bars on the front. Have not driven yet but bounce feels about right for performance street.
Rear springs are aftermarket blue... no idea of make or rate but feels around 250 lb per inch. I don't like those rear springs because they go loose at full rebound droop extension at a ride height that isn't low enough for what I want. The rear spring rste feels about right though. I may take them out and measure the rate in a drill press.

I'm thinking the rear coils should be progressive rate to prevent looseness at full droop.

On edit, my rear setup is exact same as Valco Oscar except springs are blue. The real solution is shorter rear dampers.


@roblav1 - You can solve for the "loose spring at full droop" via adjustable coil overs with helper springs. I got this set up from Elephant Racing. Works like a charm.
The helper springs (the flat coil spring at the bottom) fully compress as soon as the car is set on the ground but keep the spring seated at full droop.


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roblav1
post May 6 2020, 08:24 PM
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Ahhh! Helper springs. I have the yellow Koni adjustable coilovers. Just need those helpers. Thank you much.
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Chris914n6
post May 6 2020, 08:55 PM
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Stock 911 front and 180-200lbs in back.
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Andyrew
post May 7 2020, 01:59 AM
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Your running a big bar up front.

You also have good free flowing bushings.

I would say 19mm T bars and 225lb springs. Dial the setup in with the front sway bar and enjoy.

You can easily back the 225lb springs down to 200 or 180 if you want, But my 225lb springs feel pretty compliant with my light 1.8t and I have only slightly better bushings than you (ball bearing bushing replacements, the ones Mueller made), I would expect they perform the same as the elephant in the real world. I know for a fact that this drops the effective spring rate down.

I would say its probably a similar ride firmness to your taildragger. Koni shocks help make it livable.



For full reference I run 22mm T bars up front, 225lb springs, koni yellows, ball bearing bushings, and no sways. I plan to finish up my nascar sway to plant the front a bit more, but it feels pretty good as is.
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tygaboy
post May 7 2020, 07:35 AM
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@ValcoOscar @FL 000 @roblav1 @Chris914n6 @Andyrew

Thanks, gents! That helps greatly. (IMG:style_emoticons/default/smilie_pokal.gif) I'm off to get new rear springs...
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Krieger
post May 7 2020, 08:14 AM
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I don't know what size springs you have now, but I have a set of almost new 225# springs you can try on for size/have. I don't know if you saw my post in your other thread, but with my Koni Sports I had to have a machinist cut new grooves in the body of the shock to get my rear end down. I will be in Petaluma this afternoon. I can drop them off.
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Krieger
post May 7 2020, 08:27 AM
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I had the same problem as you. You can ditch the helper springs for an extra 1/4 inch. Zip tie the shock to the top perch. It will seat perfect on the lower no problem. This is exactly what I have done to my track car. Many thousands of miles and those dang zip ties are still there!
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tygaboy
post May 7 2020, 08:32 AM
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QUOTE(Krieger @ May 7 2020, 07:14 AM) *

I don't know what size springs you have now, but I have a set of almost new 225# springs you can try on for size/have. I don't know if you saw my post in your other thread, but with my Koni Sports I had to have a machinist cut new grooves in the body of the shock to get my rear end down. I will be in Petaluma this afternoon. I can drop them off.

@Krieger Andy, I'd love to give those springs a try. That'd be great! I'm home all day and any time is fine. Thanks!
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andys
post May 7 2020, 09:01 AM
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Stock '89 Carrera 18.8 front T bars, and 200# rears with spring tenders (they're not really "helper" springs) over Koni DA yellows. I have 250# springs, but got too lazy to install them before taking car to the track. For the street, the car has surprisingly good ride quality (confirmed by knowlegeable friends that rode with me).
LS1/Audi 01e 6 speed.
Cheers,
Andys
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MidshipMadness
post May 7 2020, 09:08 AM
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QUOTE(ValcoOscar @ May 6 2020, 05:10 PM) *

This is my LS Car with 901. Boxster S trans is stored for now. Ride is very tolerable, not uncomfortable at all. No twisties yet. (IMG:style_emoticons/default/headbang.gif)


190 lb Springs...Let me check torsion bars.

Oscar

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How is the 901 holding up to the torque? I didn't have any luck with a 915.
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dan10101
post May 10 2020, 05:06 PM
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Hey Chris,
A little late to the game.
I'm at 22 and 250#
I'm 2550# if that makes a difference.
Tolerable ride with good handling.
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tygaboy
post May 10 2020, 06:23 PM
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QUOTE(dan10101 @ May 10 2020, 04:06 PM) *

Hey Chris,
A little late to the game.
I'm at 22 and 250#
I'm 2550# if that makes a difference.
Tolerable ride with good handling.


@dan10101 Dan - No worries, thanks for the input. With the 930 box, your car is a good match for mine, weight-wise.
I'm going to start with 21 and 225 and adjust as needed. Thanks again!
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