Spring rates - Mk2 Race Series

Discussion in 'Track Prep & Tech' started by olly20vt, Sep 24, 2007.

  1. seanlazyass Forum Member

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    The calculations I did were purely to see if they were within the ball park of what people have been suggesting, not for myself, or atleast not for a while.

    And from my rough calcs and some assumptions it seems "theoretically" the spring stiffnesss are fairly accurate.

    They assumed modelling a vehicle as a whole and with a 50:50 weight distribution which the golf clearly doesn't have, so no I wouldn't put the same poundage springs on all four corners.

    If I had a day spare to accurately measure a mk2's chassis and do the calcs I could probably tell you "theoretically" the perfect spring rates for a desired application.

    Even then as Im sure you know "perfect" is never achieved without a whole lot of real life testing and will only apply to one particular circuit on one particular day.
     
  2. seanlazyass Forum Member

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    Do you like maths? [:D]
     
  3. seanlazyass Forum Member

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    If so I'll give you some equations.
     
  4. Rob Carvell New Member

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    We're talking about race car spring rates here aren't we?

    I don't know anyone who uses frequencies for race cars. Dominant factors for the race car are roll control (hence camber control), pitch stability, required handling balance and centre of gravity height.

    There is also a driver preference to worry about. Generally a stiffer spring rate requires more finesse to drive well, because mistakes have a much more unpleasant "snappy" result. Some drivers also need a bit of roll as another source of "feedback" on what the car is doing.

    Spring rate choice is usually an iterative process involving looking at tyre wear (temperature) patterns, and asessing the car's stability into, and through the corner. Photos are also a mega-valuable source of info!

    Regarding equations - no I don't like them (despite my first class honours engineering degree from Brunel) but it's always good to try and apply a bit of science to the black art now and again!
     
  5. sparrow Paid Member Paid Member

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    Yep! [:D]
     
  6. shockerboy Forum Member

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    There are actually unlimited amounts of spring set ups that work well, generally the front springs should be 2 ranges lower than the rear ie 120 n/mm rear 100 n/mm front we have found 120 front and 140 rear worked really well and this was with out serious A R B at the rear .A front A R B is a no no if you have no LSD fitted. If a serious rear A R B is fitted then the rear spring rates can be lowered . .A very stiff car IE well designed and efficient Roll cage can often be sprung a little softer too . a 50 / 50 weight distribution will be impossible with any sensible set up on front wheel drive VW but 60 / 40 works well . All this is assuming you have a race shock fitted and I thin k you said the Gaz shocks which are adjustable ?? these rates will work. Don't recommend helper springs in the front !! what camber and castor settings do you run on the front and camber toe on rear ?? assume the car runs approx. 950 kilos ??
     
  7. shockerboy Forum Member

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    Sorry forgot to ask how much droop you run at the back and is it limited with droop straps or the shock length
     
  8. Sirguydo

    Sirguydo Fastest milkman in the West Paid Member

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  9. 3hirty8ight Forum Member

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    zero droop.

    You want the weight transfering to the front wheels as fast as possible, for a long as possible. Especially if your not running an LSD.
     
  10. Alex12345 Forum Member

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    Not sure what kicked this thread off again but seen as it has ill ask. I'm going to race an 8v mk2 this year for the first time in production gti, I'm struggling to decide where to go regarding spring rates, as some will know the chassis is pretty std no big arbs or anything. The car currently has 400lbx8 front springs and 500lbx9 rears, there's so many different opinions on what to run that it becomes a minefield. Is there any racers on here that could offer a sensible opinion ? I understand that racing is racing and I'm not asking for all your secrets or a definitive answer to the black art, merely just a good starting point. I can't help but think mine feels a little soft on the front. All this said I'm no Senna
     
  11. shockerboy Forum Member

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    limiting droop at the rear allows the chassis to lift the inner wheel from the ground so that in a corner the toe out ( recommended for the rear ) doesn't cause understeer . if you limit it completely when the weight transfers to the front under breaking the droop limited rear axle will be lifted of the ground ( get light )
    . this will cause the rear tyres to lock up and cause the car to get very loose at the rear \( maybe spin ) it is difficult to find the sweet spot but we limit droop after 15 to 20 mm , we achieved this my making an adjustable shock mounting that we can move up or down to get the right position. A cheap way to do it is with droop straps ! Alex 12345 not sure what set up the car has (handling package) but the spring rates need to be higher and a bigger difference between front and rear ( always harder at rear of course )
     
  12. 3hirty8ight Forum Member

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    Are you a Motorsport engineering student by chance?
     
  13. Tim8v

    Tim8v Forum Member

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    Alex, if you want to PM me i can help, raced an 8v for 4 seasons. Would need to know what suspension you have and what has been done to it, on the face of it, your spring rates are too soft, but depends on how you drive and what you prefer.
     
  14. AjVR Forum Member

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    I ran for first time in PGTI last year and did 3 races ,had 12kg front and 10kg rear. I did this as I wanted something "easy" to drive. I found I was able to get a top 10 pace and car to me felt stable. Initially I felt like I had no lift off oversteer but by the 3rd race suddenly I had quite a bit. No setup changes at all I was just carrying a lot more speed as I got used to the car.

    Not sure where you are but 2 of us will be at brands for track day at end of February if you want to come say hi/passenger.
     
  15. shockerboy Forum Member

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    3thirty8ight , I am just wishing I was a student of any king ha ha , the reality is a 59 year old petrol head who raced VW products for 24 years in South Africa . I was instrumental in getting 2 VW based race formulas , both of which are 2 of the strongest race formula in SA off the ground . I had the privilege of representing KONI and H&R ( 2 of the best suspension products in the world ) over in SA which gave me access to technical people up to and including formula 1 expertise . GTI s in SA are driven by every second person and a small market like SA we were the third biggest consumer of GTI s in the world , VW is a very powerful brand there hence my interest in it . My Son and I have both won our national colours for motor racing over the past years and my son is the current Comsol VW Challenge ( www.vwchallenge.co.za ) overall champion and the first competitor in 20 years to win every single race overall in one complete season . So I guess what I am trying to say is we understand VW s and getting them to handle . I now life in U K and want to get involved with the local scene and help where I can . I would love to come to some track days and events and meet a few guys ,
     
  16. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    Hey shockerboy,

    In that case it would be great to have you at the Bedford Track day March 23rd.
    You will be able to meet some of us novices, enthusiasts, as well as some of the racers who are commenting in this thread ;)
     
  17. sparrow Paid Member Paid Member

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    Eddie, I think he's based in South Africa. Might be a bit of a drive...
     
  18. Sirguydo

    Sirguydo Fastest milkman in the West Paid Member

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    From South Africa but now in the Midlands :thumbup:
    He's closer than I am lol
     
  19. 3hirty8ight Forum Member

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    Thats quite a CV! - Reason I ask was your reference to lower front spring rates, or a large differece between front a rear spring rates. - There needs to be consideration for other mods whilst discussing spring rates.. Such as alteration to the front geometry and as mentioned LSD. And also Anti-roll bars

    The number 1 factor that has to be taken into acount with front wheel drive chassis handling is camber control. .

    The cars in question have VERY limited regulations with regards to the previous in the campionships in question.

    What sort of other modifications did the SA championship cars have?


    All interesting stuff! :-)
     
    Last edited: Jan 13, 2015
  20. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    That is what I read, hence I thought it would be a great idea to shamelessly plug our event lol
     

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