Talk torsions and springs. Options

[gnomefabtech]

Hello all-

So, I'm finally able to turn my attention to the suspension on my car now that it's running.

The car was hacked for a v8 when I got it and I have instead done my Hayabusa engine swap. I'll have to make a separate thread on the adaptor setup, but it's mounted north south and uses the original 901 trans. Dynos at about 300whp with turbo. 2k lbs overall weight. Narrow body.

The PO added some crazy stiff rear springs on coilover sleeves and they need to go. Also the front is way too stiff. It's all 911 front suspension and brake parts.

Questions:

I'm thinking about 140# springs in the back, but how long a spring should I use. 14"? 12"? Helper springs?

In the front I think it might have like 21mm bars, and that's way too stiff. Are normal 19mm 911 bars soft enough for a street driven 914? Or are there thinner 911 compatible bars?

Thanks!

[Superhawk996]

Here is a question to think about

If you are running a 2000 lb car and doing so on the street why would you need rear springs that are 55% stiffer than the GT ran?

There is no right or wrong answer it all depends what you’re trying to achieve with the car (which you haven’t stated).

[Root_Werks]

I went down to 110lb springs in the rear of my six conversion. As far as I know, front are stock 914-4 torsion bars. I like this combo for street use. The 914 will actually take some bumps and potholes in stride instead of bouncing and skipping across the road.

I think it really depends on your intended use for the 914. Drive it or race it?

I ditched beating the crap out of myself, passenger and car a long time ago.

(IMG:style_emoticons/default/driving.gif)

[Shivers]

@gnomefabtech

Hey dude, I’m from LA and know there are some great roads in the county.
If your are an enthusiastic driver, and prefer your car remains flat under
any situation then the 140 rear and 19 mm front is a capable setup.A 19mm and 17mm sway bars work well with that. If you prefer to motor under more comfortable conditions Root Werks setup sounds nice.

[mlindner]

@gnomefabtech

Hey dude, I’m from LA and know there are some great roads in the county.
If your are an enthusiastic driver, and prefer your car remains flat under
any situation then the 140 rear and 19 mm front is a capable setup.A 19mm and 17mm sway bars work well with that. If you prefer to motor under more comfortable conditions Root Werks setup sounds nice.

Ive go what Shivers mentions. works well at auto-cross/hill climbs but is still street compliant. Love it. Mark

[mepstein]

Make sure you identify your A-arms before buying torsion bars. 911 have a different spline count than 914 and are not interchangeable

[gnomefabtech]

Great replies.

I am one to set stuff up pretty soft and get the most out of the suspension that way.

I had no idea that the stock rates were so soft! Sounds like even 100# springs would be pretty firm. Also, my engine is much lighter than even a stock 4 cyl 914. My dream is to have the springs work all the way to full droop, because I've found that having active droop spring rate really helps with corner exit grip on an open diff..

I'm pretty sure it's all 911 stuff up front so I'll need 911 torsions. Are the thinnest 911 torsions 19mm? Or are there thinner ones?

Has anyone tried progressive rear springs?

[mskala]

Note that the torsion bars on both the 914 and 914-6 were 17.9mm (914-6 has
the splines for the 911 front end). I haven't seen anyone making < 19mm new parts, but you could find some used ones.

[Geezer914]

I have 140 lb. springs in the rear and 19mm torsion bars up front. Nice firm set up and not too stiff.

[Front yard mechanic]

I like soft suspension with sway front and rear it’s much easier on my L3 L4

[mepstein]

Great replies.

I am one to set stuff up pretty soft and get the most out of the suspension that way.

I had no idea that the stock rates were so soft! Sounds like even 100# springs would be pretty firm. Also, my engine is much lighter than even a stock 4 cyl 914. My dream is to have the springs work all the way to full droop, because I've found that having active droop spring rate really helps with corner exit grip on an open diff..

I'm pretty sure it's all 911 stuff up front so I'll need 911 torsions. Are the thinnest 911 torsions 19mm? Or are there thinner ones?

Has anyone tried progressive rear springs?

The smallest 911 torsions are ~18.9 while the standard 914’s are ~ 17.9

[gnomefabtech]

What did those 18.9 bars come in? Short wheelbase 911?

[gnomefabtech]

Do any of you know roughly what a type 4 weighs fully dressed? Might help me guess at my rear springs. Hayabusa weighs around 220# with turbo, pumps, oil tank, and stuff.

[brant]

The common answer is 250. With close to 50/50
Any weight moved forward in a 4 helps the handling

And a six close to 400
Messes with the ratio of F/R significantly

[gnomefabtech]

Does anyone know the motion ratio of the rear suspension? Seems close to 1:1.

[JamesM]

Here is a question to think about

If you are running a 2000 lb car and doing so on the street why would you need rear springs that are 55% stiffer than the GT ran?

(IMG:style_emoticons/default/agree.gif) That! 100%

in the 90s people over sprung the crap out of these things in addition to using the dog (IMG:style_emoticons/default/stromberg.gif) poly bushings that just caused control arms to bind up. It "feels" like it handles better because its more responsive but both your grip and your ride quality suffer. Unless you are regularly taking corners at 100+ MPH you are probably better off keeping it on the softer side.

[JamesM]

Do any of you know roughly what a type 4 weighs fully dressed? Might help me guess at my rear springs. Hayabusa weighs around 220# with turbo, pumps, oil tank, and stuff.

My flared 4 weighs 1950 (44% Front / 56% Rear), but i've done some things (IMG:style_emoticons/default/smile.gif)

Stock 2200-2450 depending on the year and options.


I wouldn't go over 140lb in the rear. I have that on my autocross car currently and am thinking about dropping even lower. Stock front torsion bars, 19mm Tarret sway bar set full soft.

[captain awesome]

Are most of the softer 100 lb recommendations with the caveat that you are running a rear sway bar? I was considering 140lb to start since I don't have one but this thread is making me reconsider. Also interested in the spring length as I too would like plenty of droop travel.

[slivel]

Does anyone know the motion ratio of the rear suspension? Seems close to 1:1.

This is what I came up with:

MR = Motion Ratio Rear MR(SQ) = 1.68 MR*MR
d1 = spring to arm pivot
d2 = hub to inner pivot 1.296296296 Rear Trailing Arm Motion Ratio
d1 = 17.5
d2 = 13.5
914 trailing arm

[flxzcat]

My new to me 914-4 is 1825lbs weighed last week on Longacre scales and a 44%-56% balance (I like adding lightness)

Somehow, I got talked into 21mm hollow bars up front and 250lb coils in back.

The car is way too stiff on the street and I consider myself a hard-core racer canyon carver type.

I will soon be changing to 19mm front and 180lb rear.