QA-1's on GT4

Discussion in '308/328' started by Hans, Mar 31, 2008.

  1. Hans

    Hans F1 Veteran

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    Jim: Take note!

    It's known that the rear shocks on the GT4 are somewhat longer than those on the GTB/GTS. As a result, I needed to adjust my QA-1's quite a way up in order to get a sufficient ride height. It works, but I ended up with a situation where the shocks would top out after I'd drive over certain humps in the road.

    While browsing the summit online catalogue, I cam across these:

    http://store.summitracing.com/partdetail.asp?autofilter=1&part=HAL%2D9029%2D164&N=700+400026+115&autoview=sku

    2" shock extensions

    Or the 1" variant:

    http://store.summitracing.com/partdetail.asp?autofilter=1&part=HAL%2D9029%2D163&N=700+400026+115&autoview=sku

    Anyone has experience with these? Sounds like just what the doctor ordered!

    Hans
     
  2. jimshadow

    jimshadow F1 Rookie
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    I"m taking note.....!

    I was planning on ordering the shocks today....I'll be watching this thread!

    JIM
     
  3. maurice70

    maurice70 F1 Rookie

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    I found that out the hard way alos when I ordered a pair of original Koni shocks for the rears and they were different length thatn the originals.I ended up sending them back and recoing my ones.The rears are NLA
     
  4. jimshadow

    jimshadow F1 Rookie
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    So will these help HANS' topping out problem in the rear?????

    1" or 2"

    An inquring mind wants to know....:) :) :) :)

    JIM
     
  5. Hans

    Hans F1 Veteran

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    Jim,

    When do you NEED to order the QA-1 parts?

    How about I order both the 1" and 2" lengtheners from Summit (they are only about $15 a piece) and try them, before you place your order? It's only about 45 minutes per side...

    My guess: both the 1" and 2" will work. I'll start with the 2" units. Let's just see what happens...

    Hans
     
  6. jimshadow

    jimshadow F1 Rookie
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    I have time....The place that I'm going to order from is only a couple hours away. I'll have the parts in 1 day by regular mail. :)

    Let me know what you figure out. MUCH appreciated.

    JIM
     
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  8. Verell

    Verell F1 Veteran
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    Those lengtheners are made for the QA1 racing series shocks, not the adjustable series.Don't plan on using the spring perch ridge on the lengthener's bottom as it's too way small for the adjustabls shock's perch. I researched these pretty thoroughly when we were doing the Birdman shock project.

    If you've already got the shocks, you might be able to use the extenders to just lengthen the rod with the std eye & perch on top. CAUTION: Make sure the threads are thoroughly clean & degreased, use red loctite threadlocker on the threads, & get them really tight.

    But if you don't already have the shocks, just get the next longer std shock & avoid having an extra mechanical joiner.
     
  9. jimshadow

    jimshadow F1 Rookie
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    Any idea off the top of your head which one that is????

    I'm going to order my front and rear shocks by the end of the week.....

    TIA,

    JIM
     
  10. Verell

    Verell F1 Veteran
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    OOPS, wrote up a reply & never posted it.

    You 'top out'when the shock's extended height is exceeded or you reach some other suspension limit, & 'bottom out' a shock when the compressed height is exceeded or you reach some other suspension limit.

    Most people have been getting:
    Front:
    HAL-DR4855P Compressed height: 10-1/8" Extended Height: 14"
    Rear:
    HAL-DR5855P Compressed height: 11-5/8" Extended Height: 17"

    The next sizes up are:
    HAL-DR7855P Compressed height: 12-1/2" Extended Height: 18-3/4"

    HAL-DR8855P Compressed height: 13" Extended Height: 19-1/2"

    HAL-DR9855P Compressed height: 15" Extended Height: 23-3/4"

    As you can see, the compressed heights go up in roughly 1" steps, but the extended heights go up in larger steps. You can find these specs, along with others such as recommended ride height for each shock in the QA1 catalog:

    http://www.carrerashocks.com/pdf_files/street_rods.pdf

    Their other catalogs for springs, etc., & the large complete catalog are located at:
    http://www.carrerashocks.com/motorsports.html

    Hans,
    Which shocks did you get for your GT4?
     
  11. jimshadow

    jimshadow F1 Rookie
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    I spoke to QA-1 today and the tech told me that the only real way to tell is to measure upper and lower shock mounting points with the car on the ground....

    JIM
     
  12. Hans

    Hans F1 Veteran

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    At the time, I didn't realise that the GT4 needs longer shocks than the GTB/GTS, and thus I got:
    Front:
    HAL-DR4855P Compressed height: 10-1/8" Extended Height: 14"
    Rear:
    HAL-DR5855P Compressed height: 11-5/8" Extended Height: 17"

    The extenders have been ordered. I'll keep your comments in mind, thanks!!!

    Hans
     
  13. Verell

    Verell F1 Veteran
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    Hans,
    I'm not totally convinced that the GT4 definitely needs longer shocks, altho I know you're convinced of that, & the following tends to support you:

    Actually,a better way is to use the suspension specs in the GT4 WSM so you aren't misslead by measuring with tired springs, etc.

    Front Suspension specs: See figure on page F6
    Rear Suspension specs: See figure on page G2

    F6 shows the at rest Koni eye center-eye center (C. STAT) spec as 338 mm/13.3".
    Looking at QA1's catalog, the closest shock for this length s/b the 5855. However, the table also lists the 5855 as being for a REAR application, so another call to QA1 tech support is in order to see what this means.

    Hmm, If someone were to go & miss-apply ;) certain paperweights, they'd extend the 4855 just enough to match this spec!

    G6 shows the at rest Koni eye center-eye center (C. STAT) spec as 379 mm/14.92"
    Looking at QA1's catalog, this length is between the recommended lengths for the 5855 & 7855. But the 7855's lower spec is closer.

    I've always heard/assumed that the underlying chassis for the GT4 & 308 were identical, implying identical suspension specs. However, I'd like to know for shure what the 308/328 corresponding C.STAT specs are, but I don't have a 308 specific WSM that shows them.

    The WSM numbers are for nominal ride height of course.

    However, the WSM gives enough dimensions so that calculating the effects of changing the ride height on the shock's length just requires measuring the a-arm lengths and applying basic trignometry.

    My suspicion is that the 4855/5855 combination is about right if you want to optimize for about a 1" lower the ride height. Could that be the reason they were chosen back when?
     
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  15. jimshadow

    jimshadow F1 Rookie
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    From reading all the archived info, the 4855/5855 combo seems the way to go. It's HANS' topping out on the rears that started this thread. I'm watching it closely (AND have delayed ordering my QA-1's) to see what happens here. :) My guess is that the 7855 would work on the rear. You could always adjust to lower the ride height...(am I thinking correctly here?)

    JIM
     
  16. Hans

    Hans F1 Veteran

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    Verell,

    Mine is as low as it can get, and I can hardly put two fingers between wheel well and tire. And I needed to substantially jack up the spring on the QA-1 shock. The result is that in its initial position, the shock is almost extended all the way, resulting in a topping out during the rebound after a bump. Lenghtening the shocks (or picking slightly longer ones) will put the shock closer to a mid-way position to start with, eliminating the topping out.

    I remember having seen a table somewhere with the shock lengths of both the GT4 and the GTB/GTS, and they are definately different.

    The thought of using certain paperweights to lengthen the shocks has certainly crossed my mind (and in fact, I believe I mentioned that in my report here on the list when I had installed them). These would very likely work. However, the cost of these paperweights has held me back a bit. (Mind you, I fully understand why they cost as much as they do, and they are worth their weight in gold on the front end. It's just there might be a more affordable way to jack up the back than abusing a bunch of paperweights)

    Anyway, I think that by putting in the QA-1 extenders, and putting the springs at the original top position, I will achieve the goal of setting the shocks closer to halfway. And that at the total cost of $28.

    They are on order. Will report on the results once I get them in.

    Hans
     
  17. Verell

    Verell F1 Veteran
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    That should work, it's what I suggested earlier:

     
  18. jimshadow

    jimshadow F1 Rookie
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    I spoke to a QA1 tech today. Long story short, the DR4855/5855 combo is the way to go for the GT4. IF you have a 'topping out' issue like HANS, then a 1 or 2" extender is the recommended fix.

    FWIW, YMMV.....

    Jim
     
  19. Hans

    Hans F1 Veteran

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    :D

    Thanks Jim. Good to know that we are on the right track!

    I just got word from the company where I bought the extenters: He's expecting the parts by the end of this week, so I should have them here end of next week, I think.

    Hans
     
  20. Verell

    Verell F1 Veteran
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    Jim,
    What reason did the QA1 tech give for recommending the 5855 + extender over the 7855?
    Esp. since the 7855's specs are the closest match to the GT4 WSM specs.
     
  21. jimshadow

    jimshadow F1 Rookie
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    7855's come closer, however you need a longer spring for that shock (14" vs 12"). You would have to compress the spring quite a bit further to get the same ride height.

    JIM
     
  22. Verell

    Verell F1 Veteran
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    Hmm, remember that the extenders are moving the spring perches further apart by the extender's length. A 5855 with extenders will give you:

    Extended Height w/1" extender: 18"
    Just 3/4" lesss than the 7855's 18.75" extended height.
    Extended Height w/2" extender: 19|
    That's 1/4" more than the 7855! If a 14" spring is required for the 7855, why isn't required here?

    What am I missing?
     
  23. itraco

    itraco Rookie

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  24. jimshadow

    jimshadow F1 Rookie
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    I used the 1" extenders on the rear of my GT4. I could've gone either way, but with HANS' experience with the rears bottoming out over bumps, I decided to err on the side of caution and go with the 1" extension. It's works out fine and I have yet to bottom them out and I'm not shy about speed bumps. For the extra $ it was well worth it.

    JIM
     
  25. itraco

    itraco Rookie

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    Ok ,at what hight did you set year rear coils ?
    Looks like there more hight adjustment on the front then on the rear.

    Patrick
     
  26. jimshadow

    jimshadow F1 Rookie
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    I'll look this weekend when I have the wheels off, but I believe that I set it 11 full threads from the bottom....not sure what that is in inches or centimeters....

    JIM
     
  27. Hans

    Hans F1 Veteran

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    Whoa, this has been a long time ago.

    I ended up putting the 1" extenders in and never looked back. You need them on the GT4 (with the shocks that I used anyway), not in the GTB/GTS.

    The theory is pretty simple: After setting the springs at the correct height, the piston inside the shock would end up well above the halfway-point. So when the shock compressed, it would go down with no problem, but when the shock decompressed to slightly longer than when in rest (such as during the rebound after a bump), the piston would hit the top of the chamber with a nasty clunk. Putting a 1" extender between the eye of the shock and the rod that pushes down the piston, the spring (which sits right below the eye) is not affected, but the piston is simply pushed down by 1".

    Bottom line: it works :)
     

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