Front suspension options..., looking for options/opinions Options

[914_1.8t]

I've lowered my front quite a bit to the point that I like it but it does not leave me with much/any supension travel (maybe 1/2").

What is the cause for this...is it the torsion bars or the bumpstops (i'm guessing bumpstops)?

Also I keep hearing that going too low will mess up the geometry. Why is that? Does it add positive camber when compressed further? Take a look at the pic below....wouldn't moving the shock top inwards (installing camber box/plates should take care of that).

[914_1.8t]

Also, i've thought of going the front coilover route (on the cheap of course)....removing the torsion bars and welding on a plate to hold the spring/coilover and reinforcing the top and adding camber plates/box. However, I currently have about a 1/2" between inside of my tire/wheel and the shock so this may not be an option unless I move the shock top towards the middle of the car enough to make room and still have proper camber...a pic of what i'm thinking:

[914_1.8t]

Thirdly, I am considering going all out and doing something like this: see pic below.

I'm looking for any pics of similar front setups on 914 to get some ideas from. But how are people integraging porsche hubs (and spindles) into these configurations? Do you end up with a different hub/bolt pattern (ie chevy or ford)?

Also, I'm aware of raised spindles that are being done also...but don't want to go that route..want to do something different.

[ArtechnikA]

QUOTE (914_1.8t @ Jul 25 2005, 04:27 PM)

But how are people integraging porsche hubs (and spindles) into these configurations?

if you have the resources to implement a double wishbone front suspension on a 914, hub BHC is the least of your worries. (in fact, if you can do that, just go to centerlocks and be done with it.)

[TimT]

On super low cars often you have to shorten the strut housing and shock insert

my car is superlow, I have about 3/4" ( not enough) compression travel. I occasionally bottom the car at Lime Rock (diving turn) and at the IMSA course at Pocono.. Its kinda wild when you spring rate goes to infinity

[brant]

what Tim said.
on my car we shortened the strut housing and bought custom length/valved carrera brand shocks to run inside of it.

1/2 inch of travel is not good.


brant

[914_1.8t]

QUOTE (brant @ Jul 25 2005, 12:56 PM)

what Tim said. on my car we shortened the strut housing and bought custom length/valved carrera brand shocks to run inside of it. 1/2 inch of travel is not good. brant

So are you runnig coils or torsion bars? And can you give me some more detail on the process?

[ottox914]

Talk to Jason at paragon-products about this. I'm running a koni 8610-1149 front insert, which is an oil dampened 911 fitment, but in the 914 it requires you to section 1 5/8" out of the strut housing, which means you can drop the car to a reasonable[B] level and still retain suspension travel.

[brant]

Torsion bars; as required by class.
I didn't actually do the strut housings myself.
I know the person that did do them claims there is a difference between the different brands (koni, bilstein, etc)

Its a modification he worked out himself and didn't share all the details with me.

I think he cuts around 2 inches out and then puts the housing back together. He is also a certified shock guy, so he then orders the correct length of shock in his preference of valving...... I think he also does his own revalving, but I imagine he orders what he wants to start with based upon our tracks here.

creates a body drop.
Since the body is going down, so are the mounts for the steering rack. We run the smart bump kit to compensate.

I've heard plenty of debate about the negatives of the smart bump kit, and even they claim in should only be used on modified spindle cars and not on stock street cars.

here is a pic of my strut. I think the seam is vissible a couple of inches from the top:

[Dave_Darling]

I have no idea what your drawing is showing, so I cannot comment on it. But lowering the front suspension will give you more negative camber, even if you don't touch anything else. In extreme cases, it will also affect the toe angle. I think you'll wind up with toe-out as the wheels move up and up and up.


If you really do have 1/2 inch of suspension travel, that is just plain wrong. (I assume the floor pan will scrape on any nickels lying in the street?)

When you get to the end of the suspension travel, you hit the bump-stops. If you don't hit those, then you have metal-on-metal contact somewhere which will beat the shit out of whatever parts are contacting each other. One good bottoming-out with no bump-stops will kill a Koni adjustable shock--it completely trashes the adjustment mechanism and I think messes up the internal valving too. Even if it doesn't destroy the shock, whatever metal is bashing into each other will not be happy.

You need more suspension travel. Coil-over springs won't give that to you. (Hmm, actually, you could substitute a 3,000 lbs/in spring rate for the lack of suspension travel. That might work, and is something you could actually do with coil-overs. But I don't think that's a reasonable way to do it.)

Your choices are:
1- Raise the car back up until you have reasonable suspension travel. Even on a race car, I would think you'd want 2-3" at the very least.
2- Raise the spindle on the strut, then lower the strut back down until you have reasonable suspension travel.
3- Get shortened struts and shocks.
4- Completely redesign and refabricate the entire front suspension to drastically alter all of the geometry until you have reasonable suspension travel.

There are probably other alternatives I haven't thought of. The first one is the easiest, and the last is really immensely difficult to do a decent job of. You can probably combine the first three, in differing amounts, to get incrementally more and more travel... But at some point the tires are going to start hitting the tops of the fender wells!!

--DD

[Mueller]

if I was to go with a completely different front suspension,a 964 (1989 to 1994) or newer 911 and or Boxster front suspension would be my choice.....

tons of brake options (not too shabby as they come from the factory).......of course you are running that "goofy" bolt pattern (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif) ......so, maybe the front suspension from a modern VW/Audi would be better so no need for wheel adapters on the front..........

[neo914-6]

QUOTE (Dave_Darling @ Jul 25 2005, 01:29 PM)

Your choices are: 1- Raise the car back up until you have reasonable suspension travel. Even on a race car, I would think you'd want 2-3" at the very least. 2- Raise the spindle on the strut, then lower the strut back down until you have reasonable suspension travel. 3- Get shortened struts and shocks. 4- Completely redesign and refabricate the entire front suspension to drastically alter all of the geometry until you have reasonable suspension travel. --DD

Sonu,

I like option #2, Check this Raised spindles

BTW, can I get the "free" engine management for advertising? (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

[TimT]

Even raising the spindles doesnt really solve the problem, you still have the same length overall of strut housing, and shock insert.

I have RSR raised spindle struts in both of my cars.. To shorten the overall strut, you section the strut, and remove an appropriate amount of strut, and you cut off then rethread the insert, or in the case of the Bilstien RSR inserts, you cut the bottm rod which connects with a roll pin in the strut housing, and chuck it in a lathe, and turn a semicircle in the rod.



Truechoice can do these mods on Konis, Bilstien will do this, We did it in house for my friends car.

[914_1.8t]

QUOTE (Mueller @ Jul 25 2005, 01:43 PM)

if I was to go with a completely different front suspension,a 964 (1989 to 1994) or newer 911 and or Boxster front suspension would be my choice..... tons of brake options (not too shabby as they come from the factory).......of course you are running that "goofy" bolt pattern (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif) ......so, maybe the front suspension from a modern VW/Audi would be better so no need for wheel adapters on the front..........

Yeah...I've been looking at an Audi front suspension as well as some newer porsche ones...so far i'm thinking if i'm goint to make the effort to make those fit...might as well go to the one custom double wishbone suspensions. You can upper and lower arms for around $350..then figure out the spindle. I was looking at a 993 spindle and brakes.....might go for it if I can get it figured out how to work with the control arms. Can't find any pics of the back of a 993 spindles at the moment.

So far, the best solution seems to be the a shortened strut...maybe raised spindle.

[914_1.8t]

Pic...

[914_1.8t]

QUOTE (Neo914-6 @ Jul 25 2005, 01:48 PM)

QUOTE (Dave_Darling @ Jul 25 2005, 01:29 PM) Your choices are: 1- Raise the car back up until you have reasonable suspension travel.  Even on a race car, I would think you'd want 2-3" at the very least. 2- Raise the spindle on the strut, then lower the strut back down until you have reasonable suspension travel. 3- Get shortened struts and shocks. 4- Completely redesign and refabricate the entire front suspension to drastically alter all of the geometry until you have reasonable suspension travel. --DD Sonu, I like option #2, Check this Raised spindles BTW, can I get the "free" engine management for advertising? (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

Picked up the system but didn't get a chance to talk with him. I may be stopping by today to pick up some connectors and will talk with him.

[Brett W]

Problems with lowerd cars, most have been covered, but here is one people don't often think about. When the car is lowered the roll centers go below the ground. The distance between the roll centers and the roll couple (mass centroid axis) will increase. This increase will affect leverage acting against the chassis in roll. Thus causing the car to roll more. You will have to upgrade the springs significantly to off set this. But when you do that the suspension will be almost solid, thus causing problems with traction in a mid corner bump.

Another problem is the lowered 914 has is roll center movement. When the car is lowered, the roll centers move way outside the wheel centerlines. This is bad. It can create an unsteady feel in the way the car feels in a turn. Makes it much harder to drive.

AS far as alternatives. This is kinda ugly, but very effective. Take a 911 or 914 strut housing. Cut the section above the the spindle off 7in from the top of the spindle. Then cut the bottom out all together. Weld in a piece of 1.75 .095 tubing to the bottom making it 6inches from the bottom of the spindle. Machine an insert that is the same as the inside diameter of the upper and lower tubes on the spindle. Drill a hole in the midde of these inserts and tap for a 3/4 bolt. Weld the inserts into the top and bottom of the "spindle". Now you have an upright with 10deg of KPI. Use a wheel with som positive offset to get the scrub radius down and you have the beginnings of a good dual a-arm setup.

The arms are a different situation. You can call AFCO and buy a setup for a stock car but you will still need to run the geometry numbers to find out all the important stuff like, Camber curves, instant centers, ackerman, swing arm length, roll center location, etc. This will take some time and experience to come up with good stuff.

[914_1.8t]

QUOTE (Brett W @ Jul 26 2005, 09:08 AM)

Problems with lowerd cars, most have been covered, but here is one people don't often think about. When the car is lowered the roll centers go below the ground. The distance between the roll centers and the roll couple (mass centroid axis) will increase. This increase will affect leverage acting against the chassis in roll. Thus causing the car to roll more. You will have to upgrade the springs significantly to off set this. But when you do that the suspension will be almost solid, thus causing problems with traction in a mid corner bump. Another problem is the lowered 914 has is roll center movement. When the car is lowered, the roll centers move way outside the wheel centerlines. This is bad. It can create an unsteady feel in the way the car feels in a turn. Makes it much harder to drive. AS far as alternatives. This is kinda ugly, but very effective. Take a 911 or 914 strut housing. Cut the section above the the spindle off 7in from the top of the spindle. Then cut the bottom out all together. Weld in a piece of 1.75 .095 tubing to the bottom making it 6inches from the bottom of the spindle. Machine an insert that is the same as the inside diameter of the upper and lower tubes on the spindle. Drill a hole in the midde of these inserts and tap for a 3/4 bolt. Weld the inserts into the top and bottom of the "spindle". Now you have an upright with 10deg of KPI. Use a wheel with som positive offset to get the scrub radius down and you have the beginnings of a good dual a-arm setup. The arms are a different situation. You can call AFCO and buy a setup for a stock car but you will still need to run the geometry numbers to find out all the important stuff like, Camber curves, instant centers, ackerman, swing arm length, roll center location, etc. This will take some time and experience to come up with good stuff.

Thanks for the info.

Where can I find formulas and such to calculate how to properly design the suspension if I go custom route? I wonder if there is any software that helps to calculate these things....any info appreciated.

[groot]

What are you doing with the car? Maybe I missed that part, but it's pretty important.

[ArtechnikA]

QUOTE (914_1.8t @ Jul 26 2005, 03:15 PM)

Where can I find formulas and such to calculate how to properly design the suspension if I go custom route?  I wonder if there is any software that helps to calculate these things....any info appreciated.

go to your local Barnes & Noble and buy a copy of "Race Car Engineering." in addition to really excellent information every month, you'll find ads for more books and design software packages than you can possibly afford... this month's suspension column is on steering geometry, as a matter of fact...

more information here: Race Car Engineering Web Site

Carroll Smith's books, especially "Engineer To Win" are pretty good in this area. Fred Puhn's "How to make your car Handle" is a standard reference. Paul Van Valkenburgh's "Race Car Engineering and Mechanics" presents most of the issues without glossing over too many nor getting overly mathematical.