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914World.com _ 914World Garage _ How Low Can You Go?

Posted by: Joseph Mills Apr 8 2005, 05:55 PM

It never ends...

Corner balanced my car recently and acheived a "cross" reading of 50%.

However, instead of my front A-arms being level, they now angle downward towards the center of the car. I have read that you do not want to go beyond "level" to maintain correct steering geometry. How does this adversely affect geometry? For that matter, what is"correct steering geometry"?

Where do you check for levelness? The arms get thinner as they go out towards the wheel. Measuring under them with a level , I'm about a 1/4" too low. But measuring under the "seam" of the arm I'm level (By seam, I mean the flange on the side of the arms where the upper & lower halves of the arms are joined). Which does one go by?

My steering rods are also tilting down a bit going towards the center.

Here is the current ride height with Kumho V700s measured at the doughnuts:

LF 3 5/8" RF 3 6/8"

LR 4 2/8" RR 4 3/8"

Anyone else running this low to the ground? What are some of your measurements?

I'm sure I can achieve the same "cross" with the car slightly higher, although it will mean losing some of the current rake (not all).

Suggestions? Observations?

Have I just gone over the edge?

Posted by: Cloudbuster Apr 8 2005, 06:13 PM

Well, I was wrong on another thread, so I'll shoot for 0-for-2 today.

Bump steer is one aspect...

The ideal situation is to have the a-arm and the steering arm be the same length, that way their ends cover identical arcs through suspension travel. That usually doesn’t happen, and may not be desirable for other reasons (see Ackerman?)

So what happens is the a-arm and steering arm are different lengths, and their ends describe different arcs through their travel. The factory sets the car up so they swing through as complimentary arcs as possible in their normal operating range (green boxes).

If you lower the car too much the operating range changes (red boxes). When you hit a bump, the wheel goes up, the arc of the steering arm is radically different compared to the arc of the a-arm, causing the tire to turn inward or outward, depending on the differences of the arcs.

The usual way to address this is to add spacers under the steering rack (on 914s) so that the steering arms range moves back into the green boxes.

Attached image(s)

Posted by: ArtechnikA Apr 8 2005, 06:15 PM

QUOTE (joseph222 @ Apr 8 2005, 06:55 PM)
Where do you check for levelness?

My steering rods are also tilting down a bit going towards the center.

between the pivot axis of the A-arm and the center of the spindle...

you might want to consider raising the spindles a bit. just how much travel do you have down that low ?

the tie rods "should" be parallel with the A-Arm (for 'best' (i.e. - minimum - bump steer)

Posted by: Joseph Mills Apr 8 2005, 07:04 PM

Thanks for the diagram. That clears the picture up a bit.

The car does not exhibit noticeable bump steer even with a bit of toe-out that it has. The steering rack received a bump steer kit when it was initially lowered (about a 1/2" higher than it now sits).

Supposedly, with A-arms parallel to the ground, you have about 2 inches of travel. So I suspect I have about 1.5" left.

Raised spindles are not really an option.

The suspension setup is dedicated for AX.

Just seems dang low.

Posted by: Travis Neff Apr 8 2005, 08:54 PM

Damn that is low, my fronts are at 5 1/4 - but with 175x70's

My other car was set at 5.5 at the rear and 5 at the front.

Posted by: nebreitling Apr 8 2005, 10:54 PM

can you post some pics of the car's new stance?

Posted by: Aaron Cox Apr 8 2005, 11:48 PM

im 3.5" to the donuts in front

4 in the rear....

Posted by: jkeyzer Apr 9 2005, 12:11 AM

My car is 5.5" front and 5 7/8" rear and I think THAT is low! You guys are crazy!

Posted by: Aaron Cox Apr 9 2005, 12:23 AM

QUOTE (jkeyzer @ Apr 8 2005, 11:11 PM)
My car is 5.5" front and 5 7/8" rear and I think THAT is low! You guys are crazy!

im young.... dumb....and full of .....

my car is low, loud....and obnoxiously fun to drive.....

Posted by: J P Stein Apr 9 2005, 02:05 AM

With 22.5 inch dia tires, my front ride height is 4.75 inches to the doughnuts.
I use up all my strut compression (about 2 inches)....then I'm on the bump stops.....this is with 21mm T-bars.....I'm agin' it and have a set of raised spindle struts to get back another 3/4 in of travel. They aren't on the car yet....till I get the pitman arms bent to avoid bump steer.Curently at full suspension compression, my steering arms run pretty close to level.....with a bump steer kit under the rack.

Posted by: Brett W Apr 9 2005, 07:22 AM

Since a 914 uses a McPhearson strut in the front, there are several complications when radically lowering the car beyond what the factory design for a ride height. The factory designed the car to ride at a certiian ride height. The relationship between the roll centers, steering axis, ackerman, roll couple, and cg were all factored into the equation. When you lower a strut car you increase the distance between the roll centers and the CG. This creates more leaverage to induce body roll. When radically lowered, (I know looks cool as hell) you have to increase the roll stiffness significantly to keep the car from rolling beyond the acceptable range of roll center movement. Most 914 owners will not accept the penalty of the required increase in roll stiffness on ride quality.

Another factory in lowering the car is where do the roll centers go when you travel through roll. The factory decided the suspension should operate within a certian set of parameters when you lower the car, by adjusting the suspension, you move the roll centers close to and even under the ground. Close to teh ground is OK but under the ground is bad. None of these is as bad as what happens in bump to the lateral location of the roll centers. It moves all over the world when you go droppin' your ride into the weeds. When the roll centers move this much you get weird handling and the car is much harder to drive.

Posted by: rhodyguy Apr 9 2005, 09:01 AM

right on. everything, including what you intend to use the car for needs to be factored in. too low without other compensation, and the ride and handling will suffer. see my alignment thread for the numbers i now have.

k

Posted by: Joseph Mills Apr 9 2005, 02:20 PM

QUOTE (rhodyguy @ Apr 9 2005, 09:01 AM)
right on. everything, including what you intend to use the car for needs to be factored in. too low without other compensation, and the ride and handling will suffer. see my alignment thread for the numbers i now have.

k

Couldn't locate your alignment thread.

All I'm looking for in the way of "numbers" is ride height (and tire diameter doesn't hurt), of other members cars set up for AX or track. I don't really need other specs.

However, if anyone has the full wheel travel specs, that would be very handy (so I can deduce how much travel I have at various ride height settings.

As always...thank ya kindly.

Posted by: J P Stein Apr 9 2005, 02:57 PM

Here's what I go thru to check this stuff.
The car is on blocks, relatively level. Remove the T-bar from it's seat (spline) at the front, disconnect the sway bar down link....this is on one side only.
Jack up the suspension at the A arm....tire on...till you get to your known ride height....with a hand level measure from the bottom of the tire to the doughnut.....write that number down . Jack up the suspension till the doughnut lifts off the block....at that point, you're on the bump stop. Repeat the tire/doughnut measurement....the difference is your travel.

I don't have dust covers on my struts so it's easy to see WTF is going on.

Here's a pic that shows a bit of this nonsence......suspension is on the stops. The idea here was to check tire clearances

Attached thumbnail(s)

Posted by: Joseph Mills Apr 9 2005, 03:35 PM

QUOTE (J P Stein @ Apr 9 2005, 02:57 PM)
The car is on blocks, relatively level. Remove the T-bar from it's seat (spline) at the front...

Another damn thing I've never done... might as well be on Voyager when I work on my car...

I'll look it up in my Haynes how to remove the torsion bar and save you for the more important head scratchin'stuff.

Your procedure makes sense - thanks for the JP BTDT tip.

Now just have to figure where that job goes on the list...

Posted by: J P Stein Apr 9 2005, 04:03 PM

QUOTE (joseph222 @ Apr 9 2005, 01:35 PM)

QUOTE (J P Stein @ Apr 9 2005, 02:57 PM)
The car is on blocks, relatively level. Remove the T-bar from it's seat (spline) at the front...

Another damn thing I've never done... might as well be on Voyager when I work on my car...

I'll look it up in my Haynes how to remove the torsion bar and save you for the more important head scratchin'stuff.

Your procedure makes sense - thanks for the JP BTDT tip.

Now just have to figure where that job goes on the list...

Just remove the T-bar adjustment bolt and pull the bar out.....with no load on the suspension, of course, but support the wheel tire.....try to pull the cap & bar out a couple inches as a unit and remember its attitude ..cause it's gud to put it back in the same spline
Thas what all the blocks & shittage in the pic are for.

Posted by: Brett W Apr 9 2005, 11:04 PM

JP
What kinda wheels are those? They look super light.

Posted by: J P Stein Apr 10 2005, 01:06 AM

They were made by a defunct outfit...Monocoque, IIRC.
They are light....11.5 lbs I'm told. The tire wheel combo weighs
33 lbs. NOT a street wheel. The seller tole where to get them repaired should anything happen to em'.

Got 2 good R35 slicks with the deal. 2 new schlicks are gonna cost me half of what I paid for these.

Posted by: chris914 Apr 25 2005, 01:38 AM

I have a question about the front height on my car. I took my car to a recommended alignment shop to have an alignment. I told them I was autocrossing the car and could they set it up to be more aggressive. They do work on sport cars and do work on 914's. The car steers much better straight but the height in the front is 5-7/8" and 5-1/2" in the back at the donuts.

1.) In the front there is 2" between the fender lip and the tire (50 series Kumo's). There are sport Bilsteins front and back and 140lb springs in the back. It doesn't even seem right even for a stock alignment.

2.) Even after reading all the posts, As it sits now there doesn't seem to much clearance between the control arms and the body. Are the control arms suppose to be level with the ground? If I lowered the car they would look like they would hit the body.