dr bob

Correct on all counts.

"Modern" tires tend to like a little more negative camber than those available when the 928 suspension design was hatched. Especially for spirited driving, a little extra camber (~-1º total) will help avoid some of the outer-edge scrubbing particularly on the fronts. As you allude though, camber 'issues' need to be balanced with correct and even more precise toe control.

I suspect that 90+ percent of tire wear and alignment 'issues' are caused by worn/tired suspension and steering components. Adjustments can compensate for some wear, but ultimately no adjustment can correct for extra movement going down the road. We preach regularly that we don't want the front-end guys to raise the car and check for wear, but it's really a good idea to let a pro test for worn parts. Follow the guidance you receive and replace the worn parts. Then go drive the car to settle the suspension after the worn bits are replaced, and dial in the final adjustments on the settled car.

More than a few accounts of suspension restoration are here on RL, where the owner cites the fabulous improvement seen with upper control arm and ball joint replacement, tie rod and rack bushing replacement, and upper link replacement in the rear. If you car has passed 75-100k miles, these parts are due for replacement without question. Ditto tired springs and shocks at the same mileage.

eijun

It would be a good time for 928Int to sell those diy alignment tools so we can practice on our own cars after/during the session with the help of those who know how to do it.

Oh and nice meeting you Mark.

txhokie4life

Tom,

Who's the guy in Austin and what info do you pass along.

i've got a completely new set of upper/lower ball joints and all rubber.
Mine also has aftermarket shocks/struts -- so I'm not 100% what info you
have will work -- but at least they will be familiar.

I've got a small highway vibration I'd like to get checked out.

Would like to check/get alignment.

thx,

mike

dr bob

There are enough third-party tools and varying DIY techniques floating around in the market now that there's not much need for Mark to sell something more 928-centric.

There's still the minor challenge of finding a flat/level floor to demo on at 928 Int'l.

In the DIY alignment thread, I diagrammed the fixtures I use, made from locally-sourced aluminum stock. It's hacksaw and hand drill stuff for assembly. You'll want a couple laser levels, plus a standard 24" carpenter's bubble level for camber. Substitute at least one digital angle finder if you want to adjust caster, and it can do camber too. And a good tape measure and a 6" pocket machinist's scale/ruler. Masking tape and a pen too.

Earl Gilstrom shared a DIY alignment method using strings for the toe measurement. Mark K uses a stick against the tire. Both require very exact determination of measurement, since the differences between front and rear of a 16-18" rim for 15 minutes of toe angle is less than 1/16" total, smaller than I can reliably pick out with pen marks or string width. I'd be tempted to use coat-maker's heavy black thread for the string. Mark's stick-against-the-tire method adds the variable of sidewall flex to the toe difference measurements too. He has a way that works for Mark.

eijun

Some people want exactly that.
Tools just for the 928, kinda like the LiftBars, and other tools which makes our life easier to preform the task and/or easier to store.

I don't mean the measuring tool, I mean the tools to adjust/do the alignment (especially for those who just got 928 this year and have zero tools.... like me sadly)

flyrade

My son races his 911 RSR and it never touches a wheel alignment machine. The car is setup using a string box. You can google this technique to find more specifics.

dr bob

The tools needed are a 19mm socket on a 1/2"-drive torque wrench (to tighten the adjusting cams), 15mm and 22mm open end wrenches for the tie rods and locknuts, and the standard Allen key that fits the adjusting cams (8mm IIRC). Nothing special or fancy, stuff you can find at your local Sears, Harbor Freight, Northern Tools, Snap-On, whatever your toolbox likes to hold.

I made a couple metal fixtures that sit in the wheel lip/faces to hold laser levels. The fixtures support the lasers so they point exactly perpendicular to the wheel axis. Others have made similar fixtures out of wood with OK results. I recently added a couple digital angle gauges to the mix to make it possible to calculate caster angles, when used in conjunction with the lasers equipped with beam-splitters to measure steering angles. I bought the metal pieces at a local metal supply place (Industrial Metal Supply in Sunland). The laser levels and the angle gauges came from Harbor Freight. Total material investment is around $100, with an hour or two needed to assemble the pieces depending on your shop skills and hacksaw-rowing capability.

Others have made there own equipment, some more elegant, some a little more simple. Herman K in Texas has wheel mounts that attach a rotary laser to each wheel. Bill Ball has a three-legged frame to support the lasers, more easily adjustable for different wheel sizes (one screw) than mine which take three screws to change. The string/square method needs some supports for the strings to make sure they are parallel and close to the wheels, plus a tape measure and a small machinists scale/ruler to measure the distance from string to wheel lips. There are commercial DIY fixtures that span the spectrum of easy/expensive through complex to use/cheap to build. Look a SmartRacing Products for some pretty good DIY pieces if you don't want to make your own.



Keep in mind that I already knew well how to do alignments before I started looking at the 928 DIY option. My goal was and remains a simple system and method that doesn't require the user to remember multiple-keystroke trig calculations; measurements and calculations are all simple subtraction of tape-measure readings, or subtraction of angle readings from the little digital angle gauges. If you can subtract fractions read from a tape measure, that's all the high-level math you need to know.

Jim Devine

Fairly new at Harbor Freight is this thing- digital angle gauge-

http://www.harborfreight.com/digital...uge-95998.html

Also- instead of using string along side the car, try
using monofiliment fishing line. You can get some
lower test line that is very thin & won't cover up the
graduations on your ruler.

flyrade

"Carpenter Level" is a free iPhone app that seems to measure angles quite accurately.

dr bob

I have these and they do fine for this kind of work. A little patience for the settling time, good repeatability. Plus easily available and inexpensive.


I've tried several of these apps and they are OK, except that they are not necessarily reading square to the phone housing. Plus there's no way to clamp them to the fixture to get readings while you adjust.

The H-F angle gauge that Jim points to above has a magnetic base that makes fitup a breeze if you happen to have a steel fixture. Mine is made from extruded aluminum square stock, so I use a simple plastic spring clamp to hold the angle gauge to it. Simple-cheap-easy-effective for the duty.

Peter Bull

I made a "toe fork" out of a carbon fiber tube and some aluminum tube and flat bar. It works like a charm. Very rigid, very light and very little risk of denting the car. It can be used with a ruler as in the picture or a slide caliper for better precision. I've used it on my own cars, and it's been used quite a lot on race cars.



Toe angle is the difference in measured distance at front and rear of wheel.

/Peter