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Bob,

The "basic" pr

Bob,

The "basic" problems with the car are:
1)It feels unstable at speeds over 120kph.
2)It turns differently left and right. (Easier one way over another)
3)The most recent alignment specs indicate a 8 degree difference in SAI. Left side 21 degrees SAI, right side SAI 13 degrees. The WSM specifies an SAI of approximately 13 degrees.
4) The steering feels very numb and loose at speeds less than 100 kph.

So...even though I can achieve my desired toe, caster and camber...and toe offset, the chassis clearly is not "square". I suspect a bent spindle and/or control arms on the left front, but have little time to investigate this further. Visually all looks good...and tight.

What is a bit frustrating is that the car did not always handle this way...and I can't remember when the change occurred, as I drive the car so infrequently.

All...and I mean all of the suspension components are either new time-wise, or replaced in the last 10,000 kms, which translates to 22 years of ownership for me.

Thoughts?

Regards,
David

Wow, let me think about this f

Wow, let me think about this for a while. Agree that something is not correct in the left front and you may have bent parts as you suspect.The chassis not being square may be causing weird suspension movements, but usually you can adjust the suspension to within spec. Most if not all cars are not perfectly square, so if your car is not "waaay" out of square, I would look at the bent part theory first. It could cause you to not get the caster, toe, and camber numbers when turning thus the right/left difference feel.On oval track cars we use caster split,(different values left/ right) and the car will turn left all my itself. turning right, you can feel the front end lifting due to the caster.The feel is that the car falls over into a left turn.Do you feel anything like that?, I would do a "active aligement" and plot the camber and caster values every few degrees as you turn the wheel on the aligement table. Might show what is happening to the front end as it turns. Also, ride heights, seems to me we had a thread here about frozen or bent dampers. If you have not hit anything, bent parts may be due to cracking parts. might want to check carefully. Not sure if you have ball joints, but the tapered shank on a ball joint can bend and not show up until it it disassembled from the upright. Just my thoughts, would love to work on this one, keep us posted. Bob

1)It feels unstable at spe

1)It feels unstable at speeds over 120kph.

Alignment and/or ride height. {Assuming you have the tires set at appropriate pressures (within 0.2 PSI right/left}

2)It turns differently left and right. (Easier one way over another)

Caster, and/or corner weighting, but occasionally toe enters in here.

3)The most recent alignment specs indicate a 8 degree difference in SAI. Left side 21 degrees SAI, right side SAI 13 degrees. The WSM specifies an SAI of approximately 13 degrees.

Could also be that the 21 degree side was reassembled incorrectly. SAI is a major leading indicator as to what is wrong with this supsension system. Use it as an indicator of where to look. You may find the problem on this corner of the vehicle, or you may find the same side rear suspension is collapsed, or you may find the diagonally opposite rear suspension is frozen (too high).

4) The steering feels very numb and loose at speeds less than 100 kph.

Numb steering at speed is a Ferrari trademark, loose is not.

> So...even though I can achieve my desired toe, caster and camber...and toe offset, the chassis clearly is not "square". I suspect a bent spindle and/or control arms on the left front, but have little time to investigate this further.

A bent spindle would not cause improper SAI since this is measured at the hub. {I think this car uses hub-centered axle and not a spindle--but either way, SAI is a measure of the suspension to hub geometry} A bad wheel bearing could also play a part.

At this point I suspect that fixing the SAI so that it is correct will go a long way to putting this car right.

What I would do:

Take this car to a mechanic with a corner weighting setup and alignment jig. Have him check the ride heights first, then (if anywhere in the ball park) do a preliminary alignment (just get it close, but do fix the SAI). Then check the ride heights again, you could have a collapsing spring, a missing shim in the spring perch, a frozen shock, a mis-assembled shock tower,... Anyway, get the car to sit square on its suspension at the factory ride height. Otherwise, attempting to align the suspension is a waste of time. After getting the car to sit squarely on its suspension, we want the car to have (nearly) equal weights left/right at each axel, and have the diagoanls weighted equally.

Then set the car on the scales with 1/2 tank of gas, tires at 40 PSI (hot operating temps), and your driving weight in the drivers seat.

With the alignment "in the balpark", and the chassis at the correct ride height, then get the diagonal weights set to 50% each and manouver the side to sides as close as you can to 50% left, 50% right. But the diagonal at 50% is more important than the left/right at 50%.

After getting the car corner weighted, then put the suspension into final alignment. Finally, go back and verify that the corner weights are still correct.

And do not attempt to do this with old unevenly worn tires, you will just end up running around in circles. Finally, reset the tire pressures to standard cold pressures before hitting the road.

Here are some parts diagrams o

Here are some parts diagrams of the front suspension... Looking at the car today, the LF wheel is about 1/2" further back than the RF (in reference to the body opening). I'll have wheel base measurement later today. I agree with Mitch completely that the SAI problem is where to start...But, I'm not sure where to start, so to speak.

Thanks all,
David

Bob,

The caster measures po

Bob,

The caster measures positve...
Spec is 4.00-4.5 degrees. I can't get seem to get any more than 3.5 degrees.

As to cracked, twisted or bent...Are we talking about the car or the owner???

Time to take another close look at the LF...


Regards,
David

"Time to take another clos

"Time to take another close look at the LF... "

Remove the wheels and set the car back down gently on equi-height jack stands* under the ball joints. Bounce the car from the front nose to allow suspension to take a set. After careful visual inspection of both sides, and with the steering wheel dead straight, start measuring various geometry points on the LF and RF suspensions. I can see at least 25 mesurements that can be compared side to side for equality. Millimetre accuracy is important.

Start by measuring the SAI directly if you can. Proceede with lower ball joint to lower control arm pick up points (2), then upper ball joint to upper pick up points(2), ride heights at each geometry point, finally do all the diagonals. Do not forget compressed spring height. At this point you will have either found something in the LF suspension or not. If so, investigate further, if not start measuring the rest of the suspensions and chassis pick up points.

"Wheelbase measurements taken today are identical front to rear."

With the car sitting on jack stands* under the lower ball joints of each corner** without wheels, Take some diagonal measurements from the lower a-arm pick up points to the opposite corner of the car, and compare. You are going to need 1mm accuracy to diagnose anything here.

You might also measure the ride height along the frame rails on both sides--aim for better than 1mm accuracy.

[*] jack stands need to be the same heights to better than 1mm accuracy. Also the floor must be absolutely flat and level better than 1mm over the wheelbase and track of the car.
[**] so that the suspension is holding up the car and so that any chassis nonsquareness is unsupported and thereby visible.

"In a hard left hand turn, I swear I can feel the left front wheel lift... "

This points towards a frozen right rear shock or a collapsing left rear spring.

"As to cracked, twisted or bent...Are we talking about the car or the owner??? "

This is really two orthogonal questions!

But I am sure he is talking about the car and/or parts on the car.

Bob: the lifting force due to positive caster is accentuated by the width of the contact patch. However, as the width the the contact patch increases, the resultant force for recentering the steering is reduced. (E.g. wider tires are less self-stable.) Ref. Milliken and Milliken.

In addition, there is a small (0.5 degree) increase in the camber at full lock with 6 degrees of caster. The later is known as steering induced camber gain.

We call it caster induced camb

We call it caster induced camber gain. Definately talking about the car, not the owner on the twisted comment .
Mitch, you might be on to something with the right rear corner not holding its load or low roll control.
I think as Mitch said, get it on the surface plate and start from the beginning with ride heights, corner weights and continue. While you doing that, look at the chassis carefully for cracks or bends.

Suspension Follow-up:

The g

Suspension Follow-up:

The good news: The chassis is square on all measurements (side to side, front to back and diagonally). Ride heights equal in the front and back...

The bad news: The LF suspension hub sits 18mm further rearward than the RF. Evidently, we've got a few bent control arms and possibly pick-up points, as well.

The car now is back in my home shop for dissassembly and inspection...

How did this happen? I'm think that in the early years of ownership, this car spent a fair amount of time on a flatbed truck...and possibly she got tied down a bit to agressively??

Regards,
David

David, I bet you a beer a few

David, I bet you a beer a few posts back that something was bent or cracked.
Good to see you finally found the problem.

Nothing imported, Bud or Miller is OK

Mitch & Bob,

I hear you

Mitch & Bob,

I hear you...18mm difference is huge!

No wonder this car handles so odd...As nothing visually looks bent, other than clearly the LF wheel is further back in the wheel well versus the RF, I'm going to remove the "upright" first...and leave the control arms in place.

My feeling is that if they're bent/twisted, the travel of the control arms should bind thru their normal range of travel as likely they're no longer parallel to their respective pick-up points.

Then, with the upright on the bench, remove the ball joints and inspect them...as well as the upright.

With the right side being "in-specs", at least I have something to compare measurement to. You would think that with some much difference left to right, something would be so obviously bent to the naked eye...

I'll keep you all posted. Thanks!

Regards,
David