Bent Strut/Broken Sprindle or....?

KSUGreggy · 03-15-2010, 05:20 AM

I took the car in this weekend to get an alignment done after doing some suspension work including new camber plates, bump steer kit, and 400# springs on the front of my coilover-sprung 84' 911 M491. We ran into some issues on the alignment that I did not have last year.

The most camber we could get was around -1.0 on the driver's side. We were able to get -2.3 on the passenger side though, which was about what I expected for camber after the modifications. The caster was equal at around 5.9 When the car was aligned last summer I was around -1.4 camber on both sides.

From what I've found on the forums when someone has a broken spindle it usually causes negative camber. I don't think that is my issue since I got what is expected on the right and suspect something is up on the drivers side. I verfied the plates were installed the same on both sides. From the top they both look equal.

The car is only tracked/autox with occasional street drive. I never had any funny tire wear to indicate something happened either. Car was never wrecked, shows zero signs of being repaired anywhere on the car and never exhibited this issue before from what I can tell (it's been a family car for almost 10 years now).

Any thoughts as to the issue? My gut says broken spindle/knuckle unless the chassis somehow tweaked itself. I don't see anything that looks different between the arms. How can one check for a broken spindle? They both look identical from what I can tell. I'll try to post pictures later though. I could always set the camber to -1 on both sides, but that kind of defeats the purpose of all the work I did.

Another thought was MAYBE the corner balance got screwed up big time since I switched the springs in the car. But could that really cause that big a discrepincy between the front cambers? The rear is basically identical.

I had a full weekend for autox this weekend, looks like that might not happen.

KSUGreggy · 03-16-2010, 09:57 AM

No one?

Here are some spindle photos (well the best you can get with the brakes still on) from last night as well. I didn't see any fresh paint on the passenger die that would indicate the spindle broke off from the welds or shifted. The pics aren't great but its better than nothing.

Drivers side from the top looking down:

Drivers side from the bottom looking up:

Passenger side from the top looking down:

Passenger side from the bottom looking up:

Steve@Rennsport · 03-16-2010, 10:46 AM

Hi,

Without magnaflux inspection, you cannot tell if anything is really cracked but offhand, it appears that the strut tube has moved inside the spindle forging.

I would remove the strut, clean it up very throughly, magnaflux the spindle and tube in that area, and if it passes the crack tests, TIG weld the circumference of the spindle.

KSUGreggy · 03-16-2010, 10:51 AM

Steve, thanks for offering your thoughts. What is the clue that something has happened? I don't see any visible difference between either side, then again I don't have a trained eye for this sort of thing either. The rosette welds you can see in the photo appear to be ok to my untrained eye. Would this cause a positive camber issue? The car drives fine other than a pull resulting from that increased right side camber.

rusnak · 03-16-2010, 10:56 AM

Interesting but I agree, you can't tell unless you have a jig. I have a pair of RSR struts that do not allow for a lot more than 1.0 negative but they have triangulated braces welded between the spindle forging and strut lower body for extra strength. If yours do not have this extra bracing, then I would suspect the strut broke, not the chassis.

KSUGreggy · 03-16-2010, 11:05 AM

Quote:

Originally Posted by rusnak

Interesting but I agree, you can't tell unless you have a jig. I have a pair of RSR struts that do not allow for a lot more than 1.0 negative but they have triangulated braces welded between the spindle forging and strut lower body for extra strength. If yours do not have this extra bracing, then I would suspect the strut broke, not the chassis.

Just to be sure we are thinking the same thing. The passenger side that is around -2.3 is what I expected to get after adding camber plates. The driver's side is around -1.0. Previously I was getting -1.5 on both sides with the stock camber plates. All the broken spindles I have seen seem to be hte opposite, that you GAIN negative camber. Somehow I've lost negative...one side is what i expected, the other not so much. Clear as mud right?

Steve@Rennsport · 03-16-2010, 11:41 AM

Quote:

Originally Posted by KSUGreggy

Steve, thanks for offering your thoughts. What is the clue that something has happened? I don't see any visible difference between either side, then again I don't have a trained eye for this sort of thing either. The rosette welds you can see in the photo appear to be ok to my untrained eye. Would this cause a positive camber issue? The car drives fine other than a pull resulting from that increased right side camber.

Honestly, I cannot tell you anything conclusive based on your pics but does appear to have an excess gap between the strut tube & spindle. If the tube is moving inside the spindle, you will get "variable" camber.

Bilstein doesn't weld the spindle forging all the way around the tube,..they are simply spot welded and the braces welded in place (which I can see).

I would really need to see them for myself to offer anything accurate and constructive.

rusnak · 03-16-2010, 04:54 PM

You would think that if a weld was failing, and the spindle forging were coming lose, most of the tendency would be toward positive camber due to cornering force. If the car were to take a hit on one of it's wheels, wouldn't that also result in postive camber?

Chuck Moreland · 03-16-2010, 06:32 PM

Quote:

Originally Posted by KSUGreggy

The most camber we could get was around -1.0 on the driver's side. We were able to get -2.3 on the passenger side though, which was about what I expected for camber after the modifications. The caster was equal at around 5.9 When the car was aligned last summer I was around -1.4 camber on both sides.

How was camber measured?

What are the modifications performed?

KSUGreggy · 03-18-2010, 09:50 AM

Alignment was checked on a hunter machine. I verified their findings with a home depot special camber gauge.

A local p-car shop recommended measuring the strut towers to see if they have spread somehow since last year. The car was running a strut brace the last several years. Does anyone have a diagram of where to measure? And what those numbers should be optimally? Obviously I'm trying to triangulate so top of one tower to the bottom of the other and vice versa to get an idea of what's up.

CMXI · 05-26-2010, 03:48 AM

In the same situation. Did you solve the problem?

KSUGreggy · 05-26-2010, 05:11 AM

The issue ended up being a corner-balance related problem. The front left was VERY light and the passenger rear very heavy.

CMXI · 05-26-2010, 10:59 AM

OK.. thanks