Materials to Maintain Your ZHP IIIII Hand Protection IIIII Tools to Maintain Your ZHP
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  1. #11
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    Derbo you gotta let me know how you like the 440/550 spring rates. I'm thinking of going higher, and Murph is talking about like 500/600 rates or more. But I assume he's talking Solo Nationals in Lincoln on AST double-adjustable dampers (wasn't he on AST 4200's?). And I need to do a few more AutoX and track days on my current 375/430 springs first.

  2. #12
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    I got a few different responses from GC. Jay@GC said that the struts can handle up to 800lb/in and at that point you should be on race dampers anyways.

    He suggested 550 be the absolute min for the rear for racing. I'm following the next step up at 440/550.


    Friend has a supplier than get me 6" or 7" swift springs. I'm torn from getting a 7" or 6" 10kg/mm for the rear. Otherwise, it would be with GC which is the cheapest option.

  3. #13
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    Did he say struts or shocks can handle 800 lb/in springs, or both? Because in the front the spring rate is pretty much what the strut sees, but in back the shock sees something like only 63% or 67% of the spring rate because of the lever action of the upper control arm. With 800 lb/in rear springs, the rear shock only sees about 536 lb/in. With 550 rear springs the rear shock would see around 368 lb/in. (This is me pretending to know something about BMW suspensions.)

  4. #14
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    Sorry I didnt clarify myself.

    1. What is the maximum spring rate allowed before the struts need to be
    revalved to handle the springs?


    The front, up into the 600-700s, the rear, up close to 800. After that, you should be in race dampers anyways. Ignore what people say about the damping, GC designed them.
    This is exact quote from him.

  5. #15
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    If they have similar valving, that makes total sense. Thanks for sharing. I did an AutoX yesterday and while the 375/440 rates felt good, there were a few tight turns where I felt like higher rates would help. At least a month before my next track day (Buttonwillow), so maybe I should do that before deciding on higher spring rate.

  6. #16
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    Derbo, I just ordered the 550 lb/in springs from Ground Control. Guess that means no M3 strut bar for me until at least next month!

  7. #17
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    so you are runnin 375/550?

  8. #18
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    I'm actually waiting on my buddy's friend for a quote from swift. I'm most likely going to order swift springs for my car.

  9. #19
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    Well that's the advantage of coilovers... as long the ID is the same and the length is right, you can use anybody's coilover springs.

    Still running 375/430. For the front I bought used 6" 440 lb/in springs from someone on m3forum.net, plan to use them with the new 6.5"/2.5"/550 springs from GC.

  10. #20
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    agreed! I'm excited for you. Hopefully you don't rub either . I'm most likely going with a 6" rear 10KG/mm spring. Someday we will see each other at a trackday and do shotgun rides to see the differences.

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