JC in NY

Right guys! You don't need the expensive kinematic toe guages. An accurate digital protrator can be had for about $200 or less, and can read to .1 degrees. This is more than enough accuracy for the measurement. The problem is that the Porsche guage refers to "measurement units" or something like that. It's nothing more than a bubble level protrator. You just need to figure out how many degrees the "measurement unit" is. Then you make some measurements from horizontal and figure out the angles of the rear toe links. Really quite simple. Now the rough part is that there was a post that disected all of those angles on the "old" Rennlist 993 board and I copied the figures to a file but now the file is lost! I even forgot the guy who posted the info. All we need is to figure out how many degrees are factored into the "measurement units" listed in the shop manual and then you can check and adjust your own kinematic toe. I seem to remember 4.1 degrees or something like that. By the way you're not measuring the angle of the link itself but the difference angle between two links if memory serves me correctly.

Hank Cohn

JC:

I have the manual open in front of me now. You are absolutely right. The “measurement units” are actually called Scale Units (SKEs). The deviation between the toe adjusting arm and the non adjustable link where the second reading is taken for kinematic toe should not exceed 1.5 SKEs. It sounds like if you matched them perfectly, you wouldn’t need to convert SKEs into degrees. Each side is independent of the other, so as long as you have proper toe and camber on each rear wheel, kinematic toe should be rather simple to adjust. It does look as if adjusting kinematic toe would have an adverse effect on camber. I guess that makes the process somewhat iterative. I will continue to pursue the copy cat gauge in my quest for a proper home alignment system. Thanks for the input and insight!

Hank

addictionms

you should also check out the Smart Racing web page they have a table which converts toe in degrees to inches based on rim size, it is in their "Smart Strings" manual

<a href="http://www.smart-racing.com/" target="_blank">http://www.smart-racing.com/</a>

might make life easier


Jim

JC in NY

Hank,

When the kinematic toe is set properly the two links in question on one side will be at a specific angle relative to eachother within a tolerance of 1.5 SKE. That is not to say that the angle is zero. The angle may be 4.1 degrees for the sake of argument. 1.5 SKE is just the error allowed, let's say .5 degree. As far as I each side is done independently, so it is not enough to set the kinematic toe on one side equal to the other side - they will both be out of specification.

Perhaps I wasn't following you, but you still need to know the absolute angle required between the links to set it within spec. Do you think Porsche used vague "scale units" to purposely obscure this procedure?

johnsopa

JC, Hank,

I have been told two different things about how ride height/camber/toe changes impact kinematic toe. Here's what I've been told:

1. Changes in ride height is the only thing that changes kinematic toe. That is, once ride height is adjusted properly (and corner balanced, etc.), then adjust kinematic toe. Then, subsequent camber and toe changes will not affect kinematic toe.

2. All changes to suspension (ride height, camber, toe) change the kinematic toe.

Do you know which statement is correct? Looking at the suspension, I would tend to agree more with #1, in that toe would appear to have no impact on kinematic toe, and only severe camber changes would affect kinematic toe. But, heck, what do I know...

Thanks,

John

Hank Cohn

John:

The service manual is pretty specific. It says that “If only the toe-in has to be corrected (camber o.k.), the kinematic toe-in change dews not have to be checked.” If you change camber then you have to check the kinematic toe. If you change ride height, then toe and camber change and must be readjusted. To me, this means that a change in camber, which ride height affects necessitates at least a check of kinematic toe.

Hank

JC in NY

John,

If you look at what is actually measured when you check/adjust kinematic toe then it makes sense that ride height and camber are the two main things that would affect it. I would argue that toe has a very tiny effect on kinematic toe but as Hank points out Porsche considers the effect to be negligible.

Jim Sullivan

Hank.. this is about 3 years old, so it may be a dead trail, but below is a response to an inquiry about an aftermarket tool for measuring kinematic toe. The rap on the factory tool was that it didn't work so well on significantly lowered cars anyway.

"993 alignment tool for adjusting and checking the kinematic toe. This tool &gt;replaces the original tool ( $ 2400) versus mine which is made to measure the &gt;angle of the spindle (caster). It is a lot easier to use than the original &gt;tool, compact, just as accurate and most important is that it works on &gt;factory ride height cars as well as lowered or race car height. The other &gt;benefit for the end user is the fact that you won't pay the dealer price. It &gt;sells for $ 400. There will be a flyer available within the next couple of &gt;weeks. Please call to order and for approximate time of delivery. &gt; &gt;Ivan 703-494-7606 after 6 PM"

E. J. - 993 Alumni

Gents, have to move this back to the top since the new Excellence propaganda magazine about boxsters arrived last night with a whole tech article about the 993 suspension. I think everyone already has it figured out, but here is a direct quote about what kinematic toe is:

[quote]It's the angle of the lower control arms, side-to-side. THe goal is to have the control arms level when the car is at rest, regardless of ride height. This ensures the suspension will deflect equally under load. If the difference from side to side is too much, the car will have a tendacy to steer under acceleration. In addition, it will increase tire wear and may cause cause premature ball joint failure due to excessive thrust loading. The kinematic toe adjustment is set using a pair of protractors (Porsche tools).<hr></blockquote>

Then in the spec chart it says:

[quote]Kinematic toe max difference between steering arm angle 2 and steering arm angle 5: 1.5 SKE for all cars.<hr></blockquote> Hank is right that SKE = scale units.

Here is a scanned photo of a drawing of the rear suspension from the article. I have a feeling the above quote refers the suspension arms as numbered in this drawing. This would mean that the kinematic toe is set measuring the difference of these two suspension arms relative to eachother, not each side of the car.




So my question from the first quote is is the side to side setting the individual control arms on each side relative to eachother like I try to explain above, or side to side from one side of the car to the other ?

You all are the experts on this, not me, so I leave it up to you. I will say that in the post above, Jim talks about Ivan having his own tool. Well John and I know Ivan and maybe a lunch visit is required to his shop, John?

E. J.

Tom Trew

You are right that what you are measuring is the relative angle of the two control arms, numbers 2 and 5 on the drawing, on the SAME side. You adjust those relative angles by turning the eccentric on a third arm, number 4. You do this adjustment on each side of the car. There is no measuring of angles between the two sides of the car.

As for the quote that the two arms should be "level", if they mean horizontal regardless of ride height, no way. If the car is lowered more than a half inch or so, those two arms will be sloped downward toward the center of the car. You can still get them to be at the same angle (or at least within 4 degrees on one another), but they will be far from horizontal.

E. J. - 993 Alumni

Okay, so knowing what we know, why couldnt you stick a digital protractor or level even on each of the arms and adjust until they read close to the same?

E. J.

Tom Trew

EJ - Indeed you can. I did just that when I installed my PSS9's earlier this year. I used the digital level that comes as part of the Smart Camber guage. There is a long enough flat on each of the suspension arms to place the level and measure the angle of inclination of each. You can then adjust the Kinematic toe eccentric to get the two within the specified 4 degrees. It is a bit of an iterative process; measure, adjust, measure again, but sure better than buying a set of guages from Porsche at over $2k. Once you have ride height set and corner balance done, it takes about 30 minutes to do the kinematic toe.

E. J. - 993 Alumni

Very Cool Tom, it took 26 posts but we finally got our answer.

Appreciate it.

E. J.

Hank Cohn

Tom, E.J., and others that helped:

After a couple of weeks of hunting around, I think I have amassed the necessary parts for a home alignment system. I bought a set of used Longacre scales. It is a very basic unit, but should serve my purposes. I also found a set of slide plates that need to be cleaned up a bit with a scotch bright pad or something similar. I bought the Smart Camber gauge and the Smart Strings new. I was lucky enough to find a brand new Longacre scale pad laser level at a very reasonable price. I also bought a new set of Longacre scale levelers. I found a kinematic toe gauge substitute that seems to work fine. I took it and my car to the dealership and matched it against the real gauges with consistent and repeatable results. Here is the price detail:

Scales $600
SmartCamber Gauge $236
SmartStrings $380
Scale Pad Levelers $270
Laser Leveler $250
Kinematic Gauge $450

Total $2186

I am going to set it up in my garage this weekend and see how difficult it is to use. I’ll post results after my setup and after taking it to the alignment shop for a check. Thanks to everyone who helped.

Hank

E. J. - 993 Alumni

Cool Hank, What'd you end up with for the kinematic toe? Also, don't forget to take some pics of your car on the set up...

E. J.