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Thread: Penski shock mounting

  1. #1
    Senior Member Roger Reid's Avatar
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    Penski shock mounting

    Here are some pics of the Penski's on the front of my build. I didn't want to hijack the chassis setup thread.

    Quote Originally Posted by The Stig View Post
    So far, I still have the yellow Koni's. But I am quietly looking at different coil-over options that will work with the RamLift Pro lift kit.
    Stig, I will share any of the shock info I have. The Ram Lift Pro is shown. Because I relocated the top UCA tabs 3/4" rearward I had to relocate the top shock mount to center the Ram Lift Pro so it didn't hit the center most tabs. I was able to modify and reweld the top mount with the aluminum panel in place.
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  2. #2
    Senior Member The Stig's Avatar
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    Hi Roger,

    If you moved your upper coltrol arms back 3/4", do you not need to move the lower arm mounts forward, to keep the tire/wheel centered in the wheel opening?

    I am interested in the Penske Shocks, but not sure of the availability and price. Looks like you have the new 40mm lifts... I've been waiting for a couple of months for mine.

    I'm glad to see that these are being shipped to others. Maybe I'll get mine soon.
    Last edited by The Stig; 05-24-2011 at 08:46 AM.
    The Stig

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    All I know is that I'm called "The Stig".
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  3. #3
    Senior Member Roger Reid's Avatar
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    Stig
    No one has to my knowledge cut and rewelded the lower front control arm mounts forward.

    I moved my upper mounting tabs 3/4". I read somewhere that the Gen II has the upper tabs moved back by 1". I hope that by using the alignment shims at the outer position on the lower rear mounts my wheel will be close to centered in the wheel well.

    There are some early threads on the other forum where when using the Corvette cam adjusters. The outside edge of the adjustor groove (the width of the diameter of the adjustor washer) that the washer with the offset hole sits into has been ground back allowing the entire bolt/washer to move outward. The outside of the oval bolt hole has been widened to the outside. Of course the inside of the adjustor groove has been welded and reground to make the adjustor groove back to the origional dimension. This is done only on the rear set of mounts. The front set of mounts doesn't need to be moved out.

    Crash has also made his alignment shims that better utilize the available oval bolt hole width.

    I imagine that you could use the combination of both techniques which would require some extra widening of the bolt hole width to the outside (on the rear set of mounts)
    Last edited by Roger Reid; 05-24-2011 at 10:02 AM. Reason: more exact language
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  4. #4
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    Roger, not to hijack your thread, but the axles are now sitting on my self, so once you verify length, I can ship them out same day.
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    Roger,,
    I'm definitely suffering from shock envy,,, looks like a trick setup. Can I ask about starting spring rates and if you have Dyno charts you might post? Also, are those spherical control arm bearings on the uppers A-arms? They certainly don’t look like mine. I know I asked about the sway bar mount before,, I’m still confused on that one. How does it pivot with that rod tied to the chassis? I’m clearly missing something on this one.

    Thanks!
    Fred

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    GTM #22 - Worlds slowest build

  6. #6
    LS MAN's Avatar
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    Really nice hardware you have there Roger, I too am interested with what rates you came up with. Can't wait to see this baby perform. Really nice build.
    It takes some effort to put sway bars on these cars doesn't it?
    Last edited by LS MAN; 05-24-2011 at 02:34 PM.

  7. #7
    Senior Member Roger Reid's Avatar
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    Fred
    The sway bar tube and arm pivot about the rod end bearings. I will try to make video and put it on newb tube.
    I am using (for now) the stock rate springs (450, 750) until I can drive it and sort it out.
    Those are Pfadt spherical bearings on the control arms. I will also post the dyno charts of the shocks.

    Crash, I'm working hard towards getting the engine and transaxle in. I'll let you know the length of the axles.
    Just an old man with a great hobby

  8. #8
    Member JCHRacer's Avatar
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    Quote Originally Posted by Roger Reid View Post
    Fred
    The sway bar tube and arm pivot about the rod end bearings. I will try to make video and put it on newb tube.
    I am using (for now) the stock rate springs (450, 750) until I can drive it and sort it out.
    Those are Pfadt spherical bearings on the control arms. I will also post the dyno charts of the shocks.

    Crash, I'm working hard towards getting the engine and transaxle in. I'll let you know the length of the axles.
    Very impressive work Roger!

    Are both rod-end balls bolted solid to the frame?

    I am setting mine up in a similar fasion and I am letting one of the rod ends on the bar float laterally in the frame mount. That way, the bar won't bind when twisted.
    Ciao,

    Joel

    Working ever so slowly on GTM #269, Twin Turbo SBC, Ricardo, Kit arrived April 5, 2009

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  9. #9
    Senior Member Roger Reid's Avatar
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    JCH, truth be known, I copied what you did after I saw your cad rendering.

    Both rod ends are bolted to the frame. I reinforced the area where the loads are. I wanted to minimize side load so I connected the load to the lower a arm vertically.

    The bar length is 31" so if one side moves back (front to rear), 1" at full stroke, the side load is .017" total. The rod end is welded to the sway bar arm. I don't think that will be a problem. What do you think?

    Roger
    Just an old man with a great hobby

  10. #10
    Member JCHRacer's Avatar
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    Quote Originally Posted by Roger Reid View Post
    JCH, truth be known, I copied what you did after I saw your cad rendering.

    Both rod ends are bolted to the frame. I reinforced the area where the loads are. I wanted to minimize side load so I connected the load to the lower a arm vertically.

    The bar length is 31" so if one side moves back (front to rear), 1" at full stroke, the side load is .017" total. The rod end is welded to the sway bar arm. I don't think that will be a problem. What do you think?

    Roger
    The springrate of the bar system should be low enough not to cause any significant problems. Should work fine as-is.

    I just like to eliminate as many variables as I can so allowing one end to float eliminates the twisting binding effects and also the potential to pre-load and bind the rod-ends upon assembly.....
    Ciao,

    Joel

    Working ever so slowly on GTM #269, Twin Turbo SBC, Ricardo, Kit arrived April 5, 2009

    http://photobucket.com/JCHRacer_GTM_Build

  11. #11
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    Quote Originally Posted by Roger Reid View Post
    Fred
    The sway bar tube and arm pivot about the rod end bearings.
    Now I see. I was thinking the tube was fixed as well. Thanks!!!
    Fred

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    GTM #22 - Worlds slowest build

  12. #12
    LS MAN's Avatar
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    Hey JCH, Roger - how did you calculate your the sway bar rate, as it looks like not only is the bar rotating torsionaly, but because the pivot point is not the center of the bar, it is in bending also?
    Last edited by LS MAN; 05-25-2011 at 11:36 AM.

  13. #13
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    Ted, I don't believe it is in bending any more than with a convential attachment. Maybe even a little less since the bar pivot point is out at the ends of the bar in this particular setup. We used this setup about 15 years ago on the TA car and I had some trouble wraping my arms around the theory then. We had the rod ends welded into the bar mid span on both ends, more in the areas of the conventional mounting locations, and the biggest thing I couldn't figure out was how having a rod welded THROUGH the sway bar affected the overall rate. Seems to me it had to, but to what extent, I still don't know. Think the easiest thing to do in both these designs is to test in actual use and see what you come up with. This can be difficult to do unless you have a way of attaching the car to the ground or scale itself.
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  14. #14
    Member JCHRacer's Avatar
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    Quote Originally Posted by LS MAN View Post
    Hey JCH, Roger - how did you calculate your the sway bar rate, as it looks like not only is the bar rotating torsionaly, but because the pivot point is not the center of the bar, it is in bending also?
    If the arms are strait and 90 degrees to the bar and the link arms are vertical, there is no bending in the bar, only pure torsion. You must account for the fact the the chassis reaction load is not centered on the bar and must be included in the stiffness calculation, but besides that it is the same as a conventional bar. When using conventional pillow blocks to mount the bar, you will always have both bending and torsion, that just one of the reasons I like to mount the bar this way.
    Ciao,

    Joel

    Working ever so slowly on GTM #269, Twin Turbo SBC, Ricardo, Kit arrived April 5, 2009

    http://photobucket.com/JCHRacer_GTM_Build

  15. #15
    LS MAN's Avatar
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    Understood, but as the system goes through its motion doesn't impart some kind of side load or bind at the chassis attachment points that may not be equal on a one wheel only bump.
    Last edited by LS MAN; 05-25-2011 at 12:32 PM.

  16. #16
    Member JCHRacer's Avatar
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    Quote Originally Posted by LS MAN View Post
    Understood, but as the system goes through its motion doesn't impart some kind of side load or bind at the chassis attachment points that may not be equal on a one wheel only bump.
    Not really. The amount of lateral deflection is on the order of .010 inches with a one wheel bar end deflection of 1 inch. So if one rod end is allowed to float, there is zero bind.....no float......a small, small amount of bind.
    Ciao,

    Joel

    Working ever so slowly on GTM #269, Twin Turbo SBC, Ricardo, Kit arrived April 5, 2009

    http://photobucket.com/JCHRacer_GTM_Build

  17. #17
    LS MAN's Avatar
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    Good discussion guys, I too have seen that system on front engined sedans before, & Jim & I even talked about a similar design on the PDG GTM, but never got to it. Never worked through the details of the mechanics of it before. It does allow more options in packaging on some applications.

  18. #18
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    Wait till you guys see what I have planned for a sway bar setup on the GTM-R...

    I'll post a pic tomorrow.
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  19. #19
    Senior Member The Stig's Avatar
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    Quote Originally Posted by Roger Reid View Post
    Here are some pics of the Penski's on the front of my build. I didn't want to hijack the chassis setup thread.



    Stig, I will share any of the shock info I have. The Ram Lift Pro is shown. Because I relocated the top UCA tabs 3/4" rearward I had to relocate the top shock mount to center the Ram Lift Pro so it didn't hit the center most tabs. I was able to modify and reweld the top mount with the aluminum panel in place.
    Roger, I'm interested in the shock size that you're using. Is it 15 3/4 like the KONIs or did you go with different length. Also, with the RamLift, did you use shorter springs to account for the 2" height of the lift?
    The Stig

    Some say, that I only know two facts about ducks, (both being wrong); and that if I could be bothered, I could solve the "da Vinci Code" in 47 seconds...
    All I know is that I'm called "The Stig".
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  20. #20
    Senior Member Roger Reid's Avatar
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    Stig
    Here is all the data on the shocks.

    http://s376.photobucket.com/albums/o.../GTM%20shocks/

    Anyone who wants a set of these shocks is to use the Item Code on the invoice.

    I used the shorter 2" RamLift cylinders. I had to slightly modify the spring adjuster to let the RamLift fit over it (no big deal if you have access to a lathe). The stock 8" springs would not fit without pre compressing the springs so I bought a set of Eibach 7" springs through Summit (same 450 lb rate).

    I gave Naake all the info gained from everyone on this (the other) forum. We had long discussions about shock length and droop. I was assured this shock length was right for this application.
    Just an old man with a great hobby

  21. #21
    LS MAN's Avatar
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    Hey Roger, really good shock info. How far away are you from getting your car running? Noticed you went with 15" shock length, shorter than the Konis. We actually went with 16.5" on the PDG rear Biltseins, as we were concerned about topping out.
    Thanks for posting the complete info.

  22. #22
    Senior Member Roger Reid's Avatar
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    Ted
    I had several long conversations with the fellow from Naake specifically about my origional requested 16.5" length. He assured me that with these damping curves I would not bottom these shocks. He also insisted that the 15" length was the perfect shaft travel ratio of compression versus droop with the ride height I gave him. They are the experts so I went with it.

    I don't have the motor in yet so I'm a ways off. What was holding me back was the uncertanty of how I was going to fix the front end geometry. I was waiting for the aftermarket upper control arms that never made it to market. Now that I have my tabs moved back 3/4" I can use the Vette UCA's. Then proceed with the rest of the build.

    I already have your rear shock mount kit. If you had come out with your sway bar kit a little sooner I would have used your setup. As it was, my frame had been cut and welded when your kit was announced. Oh well.
    Just an old man with a great hobby

  23. #23
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  24. #24
    Member JCHRacer's Avatar
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    Quote Originally Posted by crash View Post
    Very trick. Love those things.....is this from an Indy car?

    Be careful, if designed for an lower mass/lower roll deflection vehicle it may not have enough strain energy capability to handle the larger GT requirements.
    Ciao,

    Joel

    Working ever so slowly on GTM #269, Twin Turbo SBC, Ricardo, Kit arrived April 5, 2009

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  25. #25
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    Yes it is from an Indy Car.

    It is probably timed out also, as the seller said he had no time data on it, so I must assume the worst. I won't use things like used uprights, A arms, etc since they my be timed out, but they are great for design and fitting functions. Figure this will be close because the GTM-R has much more travel, and therefore will need to move the bar a little more than the Indy Car, and also I will be using on a rocker style suspension, so I can rough adjust with different mounting points on the rockers. Combined with the added weight of the GTM-R as compared to the Indy Car, I'm thinking it may come out just about right. I've had experience with this style bar before, but not the blade adjustable style, so for $50, I thought it was worth it to at least hold it in my hand and be able to benchmark it.
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  26. #26
    LS MAN's Avatar
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    Hey Roger, I think you are right, with proper (stiffer) shock rates, you will probably see less wheel travel than with the standard Konis. That is why we tried the 350# on the front of Ron's car to improve the ride quality, & relied on the stiffer shocks / sway bar to make up the difference. I think we may have gone too far on shock length on the rear of the race car, & it has to be jacked up higher on pit stops, which costs time.
    Sorry it took so long to get the sway bar out, but wanted to make sure we got it right.
    Last edited by LS MAN; 05-26-2011 at 10:34 AM.

  27. #27
    Member jetsbaby's Avatar
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    Can't you adjust the compression level on the F5 Koni's for the GTM. I know you can for the Koni's supplied for the roadster..If you can I would suggest you put it on the stiffest setting...If I remember right there should be four compression settings on the shocks..They come set at the softest setting from the factory. At least you can do this for the roadster.

  28. #28
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    Quote Originally Posted by jetsbaby View Post
    Can't you adjust the compression level on the F5 Koni's for the GTM. I know you can for the Koni's supplied for the roadster..If you can I would suggest you put it on the stiffest setting...If I remember right there should be four compression settings on the shocks..They come set at the softest setting from the factory. At least you can do this for the roadster.
    IIRC, the early shocks supplied with GTM kits, the yellow shocks, were adjustable, but the later, black shocks, are supposedly "self adjusting". Whatever that means.

    Look, I think the "stock" shocks in the GTM kit will work for many builders, but, as with many other parts of the car, for those that are worried about getting ultimate performance out of their GTM there are better options than the "stock" pieces in some cases.

    Shocks is definitely one of those areas, and Ted is doing the leg work here to get us what we need to go faster more safely.

    Great work Ted.
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  29. #29
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    Quote Originally Posted by Roger Reid View Post
    Stig
    Here is all the data on the shocks.

    http://s376.photobucket.com/albums/o.../GTM%20shocks/

    Anyone who wants a set of these shocks is to use the Item Code on the invoice.

    I used the shorter 2" RamLift cylinders. I had to slightly modify the spring adjuster to let the RamLift fit over it (no big deal if you have access to a lathe). The stock 8" springs would not fit without pre compressing the springs so I bought a set of Eibach 7" springs through Summit (same 450 lb rate).

    I gave Naake all the info gained from everyone on this (the other) forum. We had long discussions about shock length and droop. I was assured this shock length was right for this application.

    Roger,,
    I somehow missed this before. Thanks for posting the charts on your shocks!
    Fred

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    GTM #22 - Worlds slowest build

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