interested in a spring

 

second best mod I’ve done since purchasing 15 mos ago.

so much more natural.

 

I am trying to figure this out. In the purple circle there is a clip holding/positing, does that get remove?
where in this photo does the nail go?

 

can you refer to the picture above, where does this nail go ? ( i see the pin/clip on the top of the spring assembly), but where does this nail go?

 

The nail goes through the shaft to keep the spring compressed. There is a hole there.

 

In the teal? Where I drew the black line?

 

were you able to get it off? I am stuck on trying to figure out where this nail goes? they say in the shaft?
Thank you for posting this picture, this was the most helpful post yet, not sure why this is so car to figure out where the nail goes.

 

is this where the nail goes?
from the schematic, there is a clip pin already inserted.

 

im assuming this is where the nail goes? you tube for the win

 

Look in the circle at the other end of the assembly. You will see the point of a nail. The shaft has a hole in it. Depress the pedal, which compresses the spring, and drop a nail through the exposed hole.

A nice, strong nail...

 

nice video and explanation.

thank you.

 

THANK you. i get it now.

 

I fiddled around with this tonight. I did feel the bite point seemed “inconsistent” and I had a squeak, so the least I could do is pull it out, lube it, and see how it felt.

I learned a few things, stay with me.

With the spring removed, the first surprise was how high the bite point was. Much higher than I felt it was with the spring. Yes, I know these are unrelated physically, that’s more a reflection of the impact on feel. I could shift with the top 1/3 of the pedal action for sure… this car has grumpy synchros and the bushings are loose like a wizards sleeve so I’ve been diligently working the whole motion as it seemed to help, but with no spring there was much more clarity.

The real learning about this issue and the effect of the spring was in the removal. I used a drill bit to pin the spring as I had one on hand. As the pedal travels, the hole on the back gets more open (spring compresses) before the spring extends and the hole binds the spring. This was obvious with a drill bit as I had to move the pedal a little to get the bit in, then move the pedal more to where the bit was bound by the spring or else it would fall out.

What I am describing is the spring in an over center mechanism - where as the pedal travels the spring will get harder and then softer due to the relative motion of the pivot locations of the spring. The intent makes sense… a firm pedal at the top to get the clutch closed in a hurry, but a lightweight pedal at the bottom when sitting in traffic. The over center makes the stiffer part of the range longer too, but as you can feel, it’s not linear, getting stiffer then softer. This mechanism also reduces the load at the very top of the pedal for less clunk/standing force.

This issue with clutch feel and the overcenter are related effects. The high bite point on my clutch is almost right where that over center happens - so where I’m trying to modulate the clutch in a smooth/slick motion, the force required to do so is rapidly changing. I’ve had the car buck when taking off, because the spring is making the short section to the friction point increasing force, then the long section disengaging is reducing force - it’s an unstable system. No wonder some are frustrated by it! That’s probably why this mod is so polarizing. If your clutch is down in the unloading range it’s a smooth change in spring assist and a range that’s easy to modulate. Then this mod is just a heavy pedal. If your clutch is at the top and there is a lot of range behind it, then the spring assist is very non-linear at the friction point and it works against you.

For all the reasons in the thread (cruise control, pedal rattle), I don’t think no spring/return assist is a great plan, but the minimum viable assist is just whatever closes that cruise switch and holds the pedal upright. For less over center effect, a longer loaded spring length would make for a more linear spring rate over the travel as well. A different spring in the same pocket changes the proportional force at any part of the range, but isn’t the same as changing loaded length, which would affect the change in rate over the working length.

Interesting problem to be sure. I’ll probably start by finding a soft spring to fit the existing housing. If I were to guess, the squeak is the bushing on the side of the spring reservoir, and with some grease and less load, that should also be ameliorated.

Now a question: I read conflicting reports about whether a worn clutch is low or high in these cars. Some have said these are backwards to a typical clutch (would be dictated by pressure plate orientation). I haven’t had a chance to dig into it, and would appreciate some first hand experience. My car supposedly has a recent clutch (few 000 miles), and it is very high. As a YMMV based on anecdotes, I seem to see people often complain about a high clutch, replace it, find no difference, then do this mod and rave about it.

A second question would be in there is some adjustment for clutch friction point. Moving it further down the pedal travel out of the overcenter zone might make this mod useless, and is likely how Porsche intended this pedal to function.

As a final point, my car is a mid-99 C2 cable car. An early diagram in this thread shows the open ended spring reservoir, which I have. The replacement part has a closed end, and requires the replacement in tandem with an upgraded. “optimized pedal”. I would love to know what is different and optimized between the two.

 

Search "Porsche 996 Clutch pedal Spring" on eBay. It's Part # 996-423-081-19 M100
AFAIK, it's the same part across all 996/986 models