chaoscreature

The racing GT2's I have seen all replace the rubber bushings with spherical bearings, effectively eliminating the "give" in the rubber bushings. This should eliminate the kinematic toe since that's all based on bushing deflection. Other than being able to get a "normal" alignment how would it affect the car if you ONLY replaced the kinematic bushings with monoballs leaving the rubber bushings in place everywhere else?

chaoscreature

I brought this up because I just installed some JIC's, had the car aligned but couldn't afford the corner balancing. IF I wanted to change the ride height or balance the car it will probably affect the alignment, which is a little over $300 around here. IF I didn't have the kinematic toe issue I don't see why any alignment tech couldn't do the same job for $40 if I hand them my specs. Of course once they see it's a Porsche they will probably charge double anyways...

race911

I'm having a hard time getting past the "couldn't afford corner balancing" on a $2K+ suspension install on a ~$30K car. And what alignment guy is going to string up a car, plus adjust, for $40?

In all seriousness, I can't believe one of us around here isn't similarly equipped as I am with scales, strings, gauges, you name it and would help you out if you're really pressed for cash. Just have to give a shout out.

trophy

Kinematic Toe can require checking (not necessarily adjustment) When you make any changes to the rear suspension that change the camber. If you lower or raise excessively it will change camber and will require the K-Toe to be checked. If there is no change in camber you are pretty safe that the K-Toe is fine (assuming it was ok in the first place).

I have aligned my own car at home many times adjusting both height and camber and there has been no change ti K-toe (i have a gauge). I am running stock rubber k-toe links.

You can adjust toe at any time as this has no effect on K-Toe.

chris walrod

However, adjusting the KT does have an effect on static toe.

trophy

True, I forgot to mention that one....

chaoscreature

Yeah, kinda silly but the suspension completely tapped me out. My mechanic told me that if I leveled the car well on a flat surface that the corner balancing should be okay.
I used to work as an alignment tech, we did alignments for BMW's and Audi's for $29 all day long... we never got a Porsche in but they don't seem like they would be any more difficult with a rack. German cars in general were usually the easier ones to align.

Trophy, that's good news that the KT doesn't need to be set EVERY time I do anything with the suspension.

Chris,
I put your bushings in. My 55mph shimmy is gone. Thank you for developing the control arm bushings, they are awesome!

I am still curious if the kinematic toe feature is considered a benefit or a hinderance for track driving though. Is that even part of the reason people switch over to monoballs?

race911

Let's put it this way, when I did the yellow car last year all I had to do was adjust the right front to get it right on 50/50 cross weights. (I made a thread and posted the photo--https://rennlist.com/forums/showthread.php?t=598118&referrerid=21505.) Where was it before? Almost 3% off, if I'm remembering right. And that was probably 1/4-3/8" movement.

Back to the question at hand. The yellow car has no rubber in the suspension. It really just drives like a really, really, really good version of any other 993 I've driven. So for my rudimentary level on the track, say 1 sec/min of lap time off a pro level pace, I'm not feeling it. On the street? No way you're ever at those limits consistently.

Viperbob1

First your premise is inaccurate. Yes GT2s have all monoballs as that is what you need for racing. No rubber deflection in the suspension. Next is Kinematic toe. It does NOT go away if you have monoballs.

The setting was Porsche's design to have the rear end automatically compensate toe wise for changes in vehicle dynamics in a turn. One of the contributing factors to Porsche swinging the rear end out was that in a turn the rear weighted section of the car is constantly moving up and down. This previously yielded wild instantaneous changes in toe as the body moved relative to the wheel causing instability. So now with the Kinematic Toe you have a more stable toe as you navigate a turn. This reduces this instability and leads to a safer more stable platform.

Bill Verburg

Bob, I'm not sure what happens when monoballs are used but according to Porsche KT depends on the elastic bushing at the inner end of arms #5

arm #4 is the Kinetic toe arm and is part of the pivot axis for any KT, if all the bushes are solid the axis is fixed, how can toe change

I agree it does need to be set, but don't see how it's kinetic or something that changes dynamically depending on what the car is doing

Viperbob1

Guess what... You are going to like this.... There is no monoball replacement for #5. You use as is. The Motorsports unit even came this way...

Bill Verburg

So when Smart Racing Specs 8 monoballs per 993 rear they are not replacing the bush on #5?

Bill Verburg

also 993.331.042.80>R< & 993.331.041.80>R< which are the race rear A arms only have 1 monoball?

the factory parts book also lists for the rear A-arms
x8 monoballs 999.593.067.00 >R<
x4 993.331.277.80>R< bush
x12 993.331.279.80 bush
x8 993.331.285.80>R< alu bush

this is confusing because there are 10 arms all together

race911

Hmm. Not something I've looked at either. So when I'm up at the track later today I'll have a look-see under mine and report back. (Unless Steve sees this first, and lets us know how he built the car.)

TheOtherEric

It looks to me like ERP does show a monoball for the radially soft bushing on link 5. What am I missing?

Chris Cervelli posted that he recommends replacing the link 5 soft bushing with these monoballs for a race car. Link.