Shock(ing?) experience

All things specracer!
User avatar
Needs a Life!!!
Needs a Life!!!
Posts: 766
Joined: Wed Nov 30, 2011 1:03 am

Chassis:
098
Facebook Page:
http://www.facebook.com/#!/denny.stripling
PostPosted: Thu Dec 29, 2011 5:54 pm
Hey all,
I figured I'd pass on a bit of experience that I've had with my Penskes over the past couple of years of owning them. Take it as one data point in what should be a much larger sampling size, but here it is.

After finally spending the coin to get a set in '08, I discovered last year that my RF was locking down to full stiff constantly. If I "popped" it up with quick velocity it would "break loose" and go back close to where I felt it should be, but I couldn't get it to match the LF. I don't have a shock dyno, so I did this with the not-incredibly-accurate but very-hard-on-the-back method of lifting a wheel and letting it fall (I knew that there was minimal to zero difference in the rocker movement, which would be the only large variable). I figured this was probably not a problem on the track as the hard rolling of the car should have "popped" the shock out of full stiff, but after that weekend I decided I might as well get them rebuilt.
So I took the shocks out, marked them with a permanent marker at each corner, and sent them off to be rebuilt late in the summer of '10.
When I got them back, the marks were gone so I had no idea which one came off of which corner. No biggie, though I wanted to monitor that problem child.

So I slapped them on the car and ran them all season in 2011. The car never felt exactly "right" but I couldn't put my finger on it. It wasn't terrible, but it just felt like it took a bit more work than I thought it should. This season I went with a widly different setup (like almost 3 degrees difference in caster, significant ride height changes, etc.) just for fun so I just always blamed it on the setup or me getting used to something new. Then at the Runoffs I really felt like something odd was going on (if you haven't seen the video, you can on youtube - search for phantom9192, my username).
At TWS in November the car still didn't feel right so I decided to check the shocks. Lo and behold, the RR shock was locked down at full (or at least VERY) stiff. It could not be adjusted. Full soft setting yielded an identical rebound rate (low velocity, which is all I could "test") to full hard, and that rate was very similar to full hard (or 1-2 flats off) on the LR shock. I have no idea if it's the same shock I had the "full hard" problem with before, but I figured it was definitely worth replacing, so I did. The car was much more predictable afterwards. A full stiff RR shock would certainly explain some of the handling issues I felt at the Runoffs, and since we found it the next time the car was on the track, I have to assume it was part of the problem.

Moral of the story is this: no matter how recently you've had your Penskes rebuilt, if the car feels "off" and you can't pin down what it is, check the shocks. The way I did it was to run the spring perches down as low as I felt was safe (keep count!), disconnect the sway bar, then with the car jacked up, just raise the wheel to full bump and let it fall. You should be able to see a difference in droop timing with just a couple of flats adjustment. You can really only compare side to side between fronts or rears, but that's enough IMO to catch anything egregious.

Hope this helps someone else down the road!
Oh and "Shock(ing?)" wasn't meant to imply anything negative here... it was just a silly play on words. :)
Denny
____________
Bay 12, please.

Needs a Life!!!
Needs a Life!!!
Posts: 211
Joined: Wed Dec 14, 2011 10:09 am
PostPosted: Fri Dec 30, 2011 9:22 am
Thanks for the info denny. I have a question for you and anyone who cares to express an opinion. I have konis and was considering upgrading to penskes. I am not very quick at the moment having just come back from a long layoff. The simple question is: Are the penskes worth the approx $2000 investment for someone who is still on a learning curve? Thanks to all for your input.
It's better to be last on the grid at a race track, than have pole position at the Funeral Home.
User avatar
Needs a Life!!!
Needs a Life!!!
Posts: 1200
Joined: Wed Nov 30, 2011 1:38 am
Location: Sunnyvale, CA
Chassis:
068 415
Facebook Page:
http://facebook.com/HSERacing
PostPosted: Fri Dec 30, 2011 11:44 am
I don't know how much faster tweaking shocks can make someone, but having them screwed up can sure make you go slower (or spin or wreck). We dyno ours on a fairly regular basis (like last week). My impression is there are a lot more factors (like gas pressure) that can affect the performance of Penskes, so you have to be a little more vigilant. Also more careful about bashing them they have more stuff to break.
If someone complains about unpredictable handling problems that don't make sense (and everything obvious is straight and tight), it's a good bet it is a shock.
There is also some "unfair advantage" stuff that I am not going to advertise to the whole world, but the basic deal is to make sure you are not shooting yourself in the foot with bad shocks...
@Lee, I have one car with Penskes and one with Konis. I have always gone faster in the one with Koni's, and most of the experienced drivers have preferred it.
Dave Harriman
"It looks crazy, I understand. But, we only live once and I am going to give it a good try." - Alex Zanardi
User avatar
Needs a Life!!!
Needs a Life!!!
Posts: 766
Joined: Wed Nov 30, 2011 1:03 am

Chassis:
098
Facebook Page:
http://www.facebook.com/#!/denny.stripling
PostPosted: Fri Dec 30, 2011 1:55 pm
Lee,
I would stay on the Koni's. I ran them successfully all the way up to 2008, and that was in very solid fields much of the time. They are, quite simply, "softer" than the Penskes in pretty much every way. I think there is a school of thought out there that believes that softer might be better overall with the Goodyears (stiffer sidewall than the radials?). The reason I finally bought the Penskes was that I wanted to continue to be very competitive. To do so, you need your shocks in good working condition, which means occasional rebuilds. The Koni rebuild expense became quite significant, as I recall. So much so that a rebuild of them was a reasonable percentage of buying a set of Penskes, so that's how I made my decision.

Dave, good info, and I have always loved the soft feel of the Konis. I do evnjoy the externally adjustable nature of the Penskes, but I believe that is where I am the weakest from a knowledge perspective. I usually shoot for a "middle of the ground" setting and just leave it, as I never get the chance to just go out and test shock settings. One night, after you've had too much wine, just toss me an email with some of those secrets if you don't mind. 8-)
____________
Bay 12, please.

Needs a Life!!!
Needs a Life!!!
Posts: 211
Joined: Wed Dec 14, 2011 10:09 am
PostPosted: Fri Dec 30, 2011 2:23 pm
Thanks Guys Seems like you just saved me 2K I can spend foolishly some other way!
It's better to be last on the grid at a race track, than have pole position at the Funeral Home.
User avatar
Needs a Life!!!
Needs a Life!!!
Posts: 767
Joined: Wed Nov 30, 2011 12:21 am

Chassis:
595
PostPosted: Sun Jan 01, 2012 12:45 am
Lee, I would agree that staying with what you have makes sense until it really will make a difference. That said, make sure they're in decent condition; worth a small investment in running them on a shock dyno to make sure one isn't "dead". At the least, you may find the information useful for tuning the turns to get then more balanced.
Bob Breton - SRF 51 - San Francisco Region
User avatar
Needs a Life!!!
Needs a Life!!!
Posts: 1200
Joined: Wed Nov 30, 2011 1:38 am
Location: Sunnyvale, CA
Chassis:
068 415
Facebook Page:
http://facebook.com/HSERacing
PostPosted: Sun Jan 01, 2012 9:56 am
breton wrote:Lee, I would agree that staying with what you have makes sense until it really will make a difference. That said, make sure they're in decent condition; worth a small investment in running them on a shock dyno to make sure one isn't "dead". At the least, you may find the information useful for tuning the turns to get then more balanced.

Bob, I forgot to talk to you about this at the track yesterday. I used your bowling ball method to catch my first bad Koni (hang a weight from the shock and see how long it takes to extend).

Denny, I don't think I said "secret", nothing you can't find in a Carroll Smith book. With our stream-of-consciousness conversations, some things are more applicable than others. Next time we get together we'd better have an agenda laid out. Last time you were here, I think I remember talking out in the street at 2am?

Dave
Dave Harriman
"It looks crazy, I understand. But, we only live once and I am going to give it a good try." - Alex Zanardi

Return to General Discussions

Who is online

Users browsing this forum: Majestic-12 [Bot] and 15 guests


cron