Since I had an upper shock eye separate from a shock shaft during my last race: does anyone know why we don't use these:

https://www.pegasusautoracing.com/produ ... oduct=8004

It looks like the upper spring perch is designed to accommodate the jam nut, but I've been told that red Loctite on the shock eye is the preferred solution for an SRF.

Page 2 of this Penske manual seems to indicate that Penske recommends the jam nut (I don't know that our shocks are Penske 8100 series, but the diagram looks like our shocks):

http://www.penskeshocks.com/files/Adjustable_Manual.pdf

Sure looks like part #33 to me.
Are you sure there are enough threads for a jam nut to fit and still have access to the adjusting bolt in the window?

WhatsThatNoise wrote:Sure looks like part #33 to me.
Are you sure there are enough threads for a jam nut to fit and still have access to the adjusting bolt in the window?

Good point. I tested that today. No easy feat since a hardware store 5/8"-18 jam nut is twice as thick as it needs to be. I hack-sawed the nut to get it to the right thickness and gave it a try. As you suspected, with a jam nut you can't get to the adjusting screw holes when it's at full hard.

According to Mumm Bros..."After 18 flats softer than full stiff, nothing changes"....<snip>..."The adjustments are fairly liniar in their effect---except in the region near full sitff...where the first 3 flats have significant effect."

So I'm guessing that if you can get at least 18 flats with a jam nut...you are OK.

Maybe a really thin nut would work.

This needs to be addressed, one way or the other. Red locktite, jam nut, whatever.
I found my first "almost disconnected" one when we arrived at the Runoffs. I took it apart and screwed the top back on with red locktite. I asked around (including the Penske reps) and the general consensus was that the ~1/4" difference shouldn't affect my corner weights.
The Whites were nice enough to let me put the car on their scales and lo and behold - 40 lbs of cross weight.

Anyway, this seems to be a problem that is cropping up more and more. In the most mild case it apparently causes issues with corner weighting. At the extreme, the shock will come loose at speed and, well... ouch.

Denny

Thanks Denny.

I'd add a warning about what to look-out for. The obvious thing to look for is no shock strut threads at the base of the adjustment window. If all is well, there should be just a bit of the shock strut inside the window, maybe only 1/64" or so. Enough to catch the tip of whatever you're using to adjust your shocks. In my case, the warning was just the opposite. I had noticed during the past few races that so much of the shock strut was "in the window" that I could barely get to 14 sweeps from full hard before the the top of the adjusting screw hit the top of the adjusting window. That was also the case on Saturday morning of the MSRH race weekend. I didn't give it much thought, but in retrospect, it was trying to tell me that something was amiss.

I still don't understand the failure mode. If the shock strut had somehow screwed itself further into the upper eye, why would it then unscrew itself over the course of 60 minutes of on-track time? Regardless, it must have unscrewed because only the bottom few threads of the shock eye were damaged. The upper 3/4" (or so) of threads looked fine. Luckily there was nothing but grass in front of me. Two turns later, and the pit wall would have been there instead. That would have left a mark.