Curious what you guys would expect with suspension setup Options

[peteinjp]

Narrow body 2.7 with 230ish hp. A052 195's on 6" wheels.


21mm hollow torsion bars in the front
Bilstein raised spindle RSR struts
Bilstien HD shocks
Tarett 22mm front bar and links
150 lb springs rear
Bilstein sport shocks
Factory rear sway bar
Patrick Motorsports adjustable tow link set for the rear

What would you expect in terms of handling with this setup? No autocross- just hard driving on mountain roads.

Pete

[mepstein]

Pretty miserable with the 21mm bars. Even mid 80’s Carrera’s only used 19mm and they weight 500lbs more than your car. 150lb springs, sport shocks and rear sway bar will build in a lot of oversteer. If you have low profile tires, then it will be even worse. Heavily lowered car, 3x worse.

I may be wrong about everything above but I think you are building a track setup and unless your roads are velvet smooth, it will become miserable to drive on the road. It will feel really cool for about five miles but once you realize there’s almost no suspension travel, it will become a chore to drive.

What I’ve discovered for myself is these cars have a lot of “built in handling” but if you try to radically ramp up the stiffness, they loose most of their suspension travel and become rigid buckboards.

[Superhawk996]

Always hard to tell based on specs alone and I’m not in the mood to do the math but that’s a lot of wheel rate in the front end between 21mm torsion bars and a 22mm anti roll bar.

I’ll put my bet in for plenty of understeer.

[mepstein]

Always hard to tell based on specs alone and I’m not in the mood to do the math but that’s a lot of wheel rate in the front end between 21mm torsion bars and a 22mm anti roll bar.

I’ll put my bet in for plenty of understeer.

I agree with the understeer but there’s also a lot going on with the rear. I’m certainly no suspension expert but I do know from experience that bigger isn’t always better on these cars. They are light and nimble but become a chore if you loose too much travel.

[peteinjp]

Thanks guys- yes it does understeer and I manage it by pinning the nose deep into corners- trail braking- on sharp corners. but it feels like I'm giving up momentum just to keep weight on the front tires. Even with the power I have on these small (but grippy) tires I have a hard time getting there rear loose. That coupled with the fact that the front sway bar is rubbing the gas tank is making me think I want a slightly smaller bar. I also have a pair of 18mm torsion bars.


When you talk about wheel rate what kind of balance are you looking for front vs rear and how do you calculate with torsion bars?

This is my first 914 and first mid engine car. I bought it after reading the build thread here- Snoopy. I think Doug had it set up for autocross at Rothsport.

Just out of curiosity what's working well for you guys?

Pete

[peteinjp]

Just to be clear- this is not a road trip type of car. It's just a backroad burner. That said the roads are not glass...

P

[Shivers]

I have 19 mm torsion bars and a 19mm sway bar in front. The rear has 140 lb springs and a 17mm sway bar. It rides like a go kart but handles well. The wife and I played on hwy 74, and did a few long trips, she never complained.

[Superhawk996]

When you talk about wheel rate what kind of balance are you looking for front vs rear and how do you calculate with torsion bars?

This is my first 914 and first mid engine car. I think . . . had it set up for autocross at Rothsport.

Just out of curiosity what's working well for you guys?

Pete

There is no one ideal setup. Clearly who ever set the car up wanted a LOT of understeer. Understeer is much safer and is what almost all OEM’s tune daily drivers to feel like. People get used to this feeling. Some people are afraid of a neutral car. It’s all up to personal preference and driving style.

The best advice I can give you is to get this book, read it, then decide what you want to do.

Here are the facts:

Torsion bar stiffness varies by the 4th power of diameter. In English: double the bar diameter and the stiffness increases by a factor of 16.

21mm torsion bars are about 1.8 times stiffer than the stock 18mm torsion bar

A 22mm front anti roll bar is 4.6 times stiffer than the stock 15mm anti roll bar. In turn, this increase in anti roll bar rate adds to the already increased torsion bar stiffness when cornering.


The rear stiffness is a little tougher to discuss because it depends on what we consider a “stock” baseline. There is some data that showed the 914/4 stock rear at about 50 lbs/in. Let’s use this.

Your rear spring rate is 3 times stiffer. You have the stock rear bar.

So using vague generalities and excluding motion ratios and actual effectiveness of the front & rear anti-roll bars, your front end stiffness in a corner is about 7x stiffer in the front vs 3x stiffer in the rear.

The front stiffness has increased way more than the rear. Lots of understeer shouldn’t be too surprising.



If you want a more neutral and better steering vehicle, soften the front. Doing that will also give you better ride quality as Mark has already referred to in addition to better handling.

[Jack Standz]

Thanks guys- yes it does understeer and I manage it by pinning the nose deep into corners- trail braking- on sharp corners. but it feels like I'm giving up momentum just to keep weight on the front tires. Even with the power I have on these small (but grippy) tires I have a hard time getting there rear loose. That coupled with the fact that the front sway bar is rubbing the gas tank is making me think I want a slightly smaller bar. I also have a pair of 18mm torsion bars.


When you talk about wheel rate what kind of balance are you looking for front vs rear and how do you calculate with torsion bars?

This is my first 914 and first mid engine car. I bought it after reading the build thread here- Snoopy. I think Doug had it set up for autocross at Rothsport.

Just out of curiosity what's working well for you guys?

Pete

Currently not enjoying our '74 as much after replacing entire front suspension with 911 parts and heavier rear springs. Way too stiff.

Are you sure those 18mm torsion bars will work with your arms? Aren't the spline counts different?

[Chris914n6]

That's really out of balance.

The stock suspension is nicely tuned.

3.0L V6. I installed a 87 Carrera front end- 19mm bars and 22mm sway. Rear 180 lb springs for the added weight which actually wasn't much heavier. Tires 205F 225R and I can break the rear end out fairly easy.

I downsized to 20mm front sway, and 140 lb progressive springs I had on hand. Going to weld in the rear sway mounts next time drivetrain is out. Upsized wheels and went 225/225. My car is essentially stock f/r weight balance so heading back to stockish setup.

[flxzcat]

Soften the front sway bar and run it.

I have a canyon carver too, with virtually the same set up in my car which weighs 1835Lbs.

I run a 19mm low mount modified 911 front sway bar with 3/8" rod ends. 21mm Hollows, RSR Bilstein's with the mods, 150lb rear springs, no rear sway bar yet...

My tires are Firestone 500's 195/60-16, so a little cush there (these tires are highly rated on Tire Rack) The car reacts fast enough that I basically drive around any potholes I do see, but I live in SoCal in an area where most of the roads are relatively nice.

I am nearly 70 years old and not really a glutton for punishment these days. If you have any endurance at all, you will love it.

Cheers,
Paul VDL

[Geezer914]

19mm torsion bars, 19mm front sway bar, 140lb. rear springs, Bilstein shocks, Rebel Racing RSR bushings front and rear. Turbo tierods. No rear sway bar. Handles like a go kart!

[TRP]

Hello Pete,

I'm not sure I understand the question. What is it that you are trying to fix with the current setup? Are you trying to plan a suspension upgrade for canyon carving and this is what you are leaning towards? Are we bench racing? What's wrong with the suspension setup on the car today?

Ted

[mepstein]

19mm torsion bars, 19mm front sway bar, 140lb. rear springs, Bilstein shocks, Rebel Racing RSR bushings front and rear. Turbo tierods. No rear sway bar. Handles like a go kart!

Simple and effective. (IMG:style_emoticons/default/beerchug.gif)

[peteinjp]

Thanks a ton guys- I feel like I know what direction to go now. Not bench racing- not racing at all just having fun experimenting with the car and wanted to get an idea of the range of setups that are working for people that drive hard.

I have Phun's book- just looking for more information specifically from 914 users. But ya- you're right- there is no one correct setup and ultimately I'll have to do my homework. I get lost at spring frequencies......

I wish I could find a skid pad near by- that would be a great start. But in Japan it's not so easy and all the large business parking lots I'd get kicked out pretty quick.

Good question- what I'm looking for setup what will let me brake into the corner and come on to the gas before the apex with a nice neutral slide at full throttle. Obviously dropping the rates in the front is a good start.

Based on this thread and a few others I searched I'm thinking of trying 19mm front T bars and 19mm ARB. Rear- leave the 150LBS/In springs and experiment with removing the rear bar. The car does hav a LSD.

After making these changes I'll measure tire temps and re-align. I want to get even temps on the twists without running too much camber to preserve tire life.- so that the balance I'm looking for.

I also have a set of gas burners with 185/70 XWX's if I want a more comfortable ride- and they are fun to drive as well. Another plus is that they bring the gearing up for a bit more of a cruise with the wife type of vibe.

In terms of torsion bars- any particular makers recommended or are they all decent?


Thanks again- great help here.

Peter

[Superhawk996]

The car does hav a LSD.

Which just drives in even more understeer than what you laid out initially.

[Superhawk996]

. . . with removing the rear bar.

Which will add more understeer.

[Superhawk996]

what I'm looking for setup what will let me brake into the corner and come on to the gas before the apex with a nice neutral slide at full throttle. Obviously dropping the rates in the front is a good start.

I’m not here to discourage you - vehicle can be set up to do what you but you’ve got some contradictory things in your wants.

When you want to go to the throttle hard before the apex you’re always going to fight the front end lifting, unweighting the front tires, and power on induced understeer.

You’re going to need to rethink the setup beyond what others are talking about here by radically softening the front and stiffening the rear.

[peteinjp]

what I'm looking for setup what will let me brake into the corner and come on to the gas before the apex with a nice neutral slide at full throttle. Obviously dropping the rates in the front is a good start.

I’m not here to discourage you - vehicle can be set up to do what you but you’ve got some contradictory things in your wants.

When you want to go to the throttle hard before the apex you’re always going to fight the front end lifting, unweighting the front tires, and power on induced understeer.

You’re going to need to rethink the setup beyond what others are talking about here by radically softening the front and stiffening the rear.

Not discouraging at all- appreciate the feedback. For me it's all about learning. I do tend to take baby steps but for the sake of conversation what would you try in this case if we go with a radical change? Perhaps I'm trying too hard to drive this car like I did my BMW 2002Tii.

[MartyYeoman]

19mm torsion bars, 19mm front sway bar, 140lb. rear springs, Bilstein shocks, Rebel Racing RSR bushings front and rear. Turbo tierods. No rear sway bar. Handles like a go kart!

Simple and effective. (IMG:style_emoticons/default/beerchug.gif)

(IMG:style_emoticons/default/agree.gif)