Front Suspension question.

Argeo · 03-14-2006, 10:37 AM

Really I just started with one question and it snowballed.

I am getting ready to change the front stabilizer bar bushings and replace my tie rods with turbo tie rods on my 77 911. After doing a bit of reading, a very little bit; I am thinking the tie rods control the toe in/toe out effect. Will I throw anything else off by replacing the tie rods, camber, caster?

Anyone want to take a shot at explaining camber and caster to me? I think camber is the angle of the tire to the road contact point but not sure. Caster, I just can’t seem to make sense of. Are these both controlled by moving the suspension strut top around? I was thinking about doing my own alignment and if this is true, I definitely will give it a try.

Any suggestions on removing the piece that existing tie rod connects to, that screws into steering gear? I will remove the stabilizer bar and the panel that protects I think the fuel pump.

Also, anyone have any suggestions as to why my front end would feel light and loose. My neighbor and I tried to examine the bushing on the wishbone which we thought looked ok. Actually he did, I haven’t a clue to what a bad one looks like. I also tried standing on the front bumper and jumping off to and it went right back to position without and bouncing up and down. I think that mean my struts are okay. Boge’s which I plan to replace soon with Bilsteins. Last, I was told if I had bad ball joints, I would feel a tapping on my gas/brake (forgot which one) which I have not encountered. .

What I do notice is that there is an occasional bang on the right front side when I hit a bump. Also, the stabilizer bar bushing that is visible with the tire off is split and needs replacing. Could it be steering related, maybe tires. Any guesses.

Thanks,

David

na2ub · 03-14-2006, 11:09 AM

Lots of questions ...

Here are a few answers...

Tie rods will only change the toe in / out. Measure accross the front and rear surfaces of the tire before removing, match the new rods to the old rods in length (by eyeball / measure) and install. Adjust to achieve your old tire measurement. Spec is slight toe-in. I adjusted mine to be 1/16" or so smaller measurement in the front of the tire vs. the rear, although you should probably get it aligned afterward by a profesionnal.

Camber is the degree your tires are tilted inward at the top. Negative camber means they are tilted in at the top, positive the opposite. Spec is about .5 degrees inward at the top (do a search).

Caster is the degree your tires are angled backward from the pivot point. Think of casters on the grocery shopping cart.

Both camber and caster are adjusted at the top of the strut.

Tie rods can be removed by detaching the end at the wheel (with a pickel fork or gear puller) and bending at the knuckle, using the tie rod itself as a lever to unscrew from the steering rack.

With torsion bars, the car will not "bounce" like a car with springs when jumping on the front to check the shocks. The shocks just get softer and softer and probably need replaced after 60-80K anyway.

As far as the bang on the right side, it's hard to say. I am sure someone else will chime in to fill out the gaps.

You can try an alignment yourself (do a search) but it is better left to the professionals, with proper equipment.

Doug

oldE · 03-14-2006, 11:18 AM

David,

Yes, your tie rod ends are vital in determining the relationship of your front wheels to the steering wheel and each other. Before you take one off, measure the number of threads visible on the end of the rack and try to get its replacement back to the same place. That should get your front wheels close enough to parallel (once you have repeated the procedure on the other side) to allow you to drive to an alignment shop.

Camber refers to the relationship of the wheels to a verticle line. Negative camber indicates the tops of the wheels are closer to each other than the bottoms. Positive camber means the opposite. Deviation from verticle can accellerate wear on one side of the tire or the other, but can help the tire perform better in hard cornering by cancelling the effects of body roll or sidewall flex. A bit of negative camber can help with a fender clearance issue, as well.

Caster is the term used to describe the relationship between the contact patch of the tire and the axis around which the steering pivots. We are all familiar with the steering of a bicycle. If you remove your hands from the handlebars, the moving bike continues to go straight. This is because drag on the contact patch (where the rubber meets the road) is behind a line extended through the steering head. A similar situation is engineered into our cars. A lot of caster gives a vehicle which will track straight and true, but doesn't like to corner much. A little bit of caster can (if taken to extremes) yield a car which is 'darty' and corners when you sneeze.

Very simplistic, but those are the basics.

Les

Dan in Pasadena · Dan in Pasadena's Garage

Simple way to remember these terms?
Toe in/toe out - think of the front of your tires that face forward as being your "toes". If they're pointing more toward each other that is a toe-in condition, if they are pointing more away from each other that is a toe-out condition.

This one is really stupid - Imagine a fisherman's casting motion to remember that the term "caster" is the angle of the contact patch of the tire more or less forward. On older American cars the kingpin (now there's an old fashioned term) was tilted more or less from vertical, like that fisherman's arm.

Camber? I don't know, I just remember that it is the tires leaning in or out away from the body.

Yes, I know these are stupid, juvenile ways to remember things...but what do you expect from a 51 year old who chooses to drive a 30 year old air cooled car? Stupid juvenile behavior - I'm guilty, sentence me to more of it

Argeo · 03-14-2006, 12:28 PM

Thanks everyone for the explanations. I like stuff as simple as possible so anything to help me remember is great. I am still a bit off on the caster. I am having a tough time visualizing what has been written. Not a problem, I can bother my neighbor.

Anyways, before I do my tie rods; what do you think about me using that tack and measurement tape trick where I can see where the toe in/toe out is already. I will first measure the existing tie rods and try to duplicate the size and then fine tune back to where they were using the tacks and measurement trick. I just need to see if my garage floor is level.

David