How tricky is the rear wheel alignment?

[magaoidh]

Further to my topic re the "suspension on a 914 how good is it". The front susp. wheel alignment seems to be reasonably straight forward to align.
According to Haynes the rear suspension wheel alignment is done with bells and whistles!Does anyone know a practical method or can it only be done by a specialist shop?
Thanks Geoff

[Dave at Pelican Parts]

It doesn't take bells and whistles. It does take a good penetrating oil and the willingness to partly-disassemble the rear suspension.

There are three bolts that hold the outer end of the trailing arm pivot onto the chassis. You can loosen the bolts and slide the outer end fore and aft to set the toe, and you can remove the bolts and swap out shims between the mount and the chassis to change the camber.

The worst part is trying to convince those (often very rusty!) bolts to move. It is usually a good idea to remove the plastic caps from the top end of the through-hole and spray in there with penetrating oil, as well as spraying up from the bottom.

--DD

[Acox914]

dave summed it up. really nothing to add.

rear is just camber and toe.

[Scrappy]

Ya'll forgot to add "Bring your own shims" 'cause they ain't gonna have any.

[djpateman]

It is often much cheaper and easier to find a new car than to remove those six bolts and do a rear alignment.

[magaoidh]

Originally posted by djpateman
It is often much cheaper and easier to find a new car than to remove those six bolts and do a rear alignment.

Do you mean a new 914 or a new whatever???

[djpateman]

Well, I have my eye on a 914/6 GT at $100K and another at about $235K. They may be cheaper than those 6 bolts depending on how you value your sanity.

You may get lucky and not have any break. I was not so lucky, and that was 20 years ago.

[magaoidh]

Point taken!

[johnman001]

Well that is one opinion. I have only had a few of those bolts break off while doing alignments.

Two words PENETRATING OIL!!!!

The rear alignment isn't all that tricky, but it takes quite a bit of time to get it just right as when you tighten the bolts, it sometimes shifts unexpectedly.

I had a 4 wheel alignment done about 4 years ago. Well worth the effort. Just about doubled my cornering speed on Ortaga Hwy on street tires, my unofficial test track. Best to get the bolts loose before taking the car in, you really don't want to pay the labor if they do it.

Later, Don

[djpateman]

Okay, so I'm being a little facetious. The real problem is removing the broken bolts. You need a very good drill, at least a cobalt type. You have to drill straight and centered. Not easy upside down. And you have to drill undersize in order to not damage the threads. Best done by an experienced pro.

By all means, remove the top plugs and fill with penetrating oil a week or two in advance. Never forget to replace the plugs. I think an inpact tool is best. If the bolts are rusted, replace them, and take no chances. Mind the strength rating of the bolt. Make no mistake, these bolts are critical.

[magaoidh]

Wow,this is developing into a saga.OK,the bolts are loose, now do you set the toe in and camber as per the front wheels? Anyone!

Read the second posting on your thread, DD explained all of that, quite nicely too.

Don

[magaoidh]

OK,I need new glasses.

[djpateman]

You have guts, and you have good luck. I congratulate you on both points.

[porsche914ls6]

Here are the alignment specs I have my car set to. Randy Beck (owns a racecar fabrication shop in Rancho Cucamunga, CA) suggested these specs to me for a good STREET setting. I can say it works quite well indeed.

FRONT ALIGNMENT:

* -1/2 degree neg camber
* 6 degrees of caster (max adjustment aft)
* 0 degree toe or 1/16" out

REAR ALIGNMENT:

* -1 to -1 1/2 Neg camber
* 1/8" toe in

[Dave at Pelican Parts]

I would recommend against front toe-out for a street-only car. It tends to make the car "twitchy" on the road. A little toe-in at the front will make the car feel much more stable--and in fact, will make it track a straight path more easily.

I also usually recommend that the rear camber be about a half-degree more negative than the front--generally -0.5 front and -1.0 rear.

I have found those settings to work nicely on a street-driven 914, and to be OK but not great on a combo daily-driver/autoXer on street tires. More negative camber and front toe-out make for a better autoXer but a worse daily driver, IMHO.

--DD

[porsche914ls6]

Here are my exact settings:

FRONT:

full 6 degree caster. -1/2 camber, 0 toe

REAR: -1 camber. 1/8" toe in

My car feels very planted and no sign of twitchyness at very high speeds (over 150MPH). I went with the Beck stats knowing he has raced his 914/6 for many years and gained valuable data from Willow and other tracks. He also drives a 914/6 street only car...and uses the above street settings. I can attest they work very nicely on the street. I agree, I don't like the sound of front toe out...so I set mine at 0.

Bill

[magaoidh]

Thanks fellers,its falling into place. The only thing left is how to measure this data on the car.eg to measure toe in, do you check the distance between the opposite rims on the horizontal axis or on the wall of the tyres etc.How do you measure camber without specialist equipment.A true 90 degree square set on the floor against a tyre and measure the gap. Does Haynes enlighten?

[Dave at Pelican Parts]

Haynes does not. But you've got the general ideas on how to measure. I like the plumb-bob approach for camber--or you can use a carpenter's level, and measure the difference from straight up-and-down that way. Angle finders are neat but not very accurate, unless you go to the $$$ digital ones.

Toe can be measured at the tire or at the rim--just make sure you pick the same exact place but 180 degrees apart! A common practice is to find the centerline of the suspension pickup points on the car (easier said than done!) and set up strings on jack-stands an equal distance away from the center on each side of the car. (Say 6" or so from the bodywork.) Put the strings on the jack-stands up to the height of the center of the wheels. Then measure the distances from the edges of the rim to the strings. That will give you individual toe for each wheel.

If the front wheels are not quite straight, you can tweak the steering wheel to straighten them out or you can just add X amount to the one wheel and subtract that same amount from the other. (That isn't completely accurate but for steering angles near zero it's close enough.)

Take your time and you can get results that are more accurate than your local "high-tech" alignment shop!!

--DD