I hadn't heard of this Mk1 handling/adjustments?

Discussion in 'Track Prep & Tech' started by fthaimike, Sep 11, 2006.

  1. fthaimike Forum Addict

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    Hmmm springs seemed ok last time i used her but not sure what lbs they are?
    They were a lot stiffer than the Koni ones i had.

    Gary i had the rack mounts re-built but im hoping to get the plate mod done on the bulkhead & i can see other places that could be worked on also now the engine is out.

    Just checked & the steering rack is now 4 yrs old (wondered why it cleaned up so well when de-greasing the bay).
     
  2. paul_c Forum Member

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    Stock front hubs are riveted (in a fixed position) on the wishbone. By purchasing replacement hubs, they can be bolted onto the wishbone and this means that they can also be adjusted, to alter the castor.

    This is useful not so much from the ability to play around with castor, but that when you lower a Mk1 Golf, as you lower it castor decreases (and if you go too low, becomes negative, which makes the car unsafe). So you can 'wind back' to positive castor. Of course camber and toe in are adjusted in the usual way.

    Its impossible to give general guidelines for what is the best geometry to run, because its not related to straight line running, its to do with the amount of sideslip the tyre has once the car has started cornering and the suspension is 'loaded' with different forces from the centrifugal and other cornering forces. So its also optimised for a particular speed and road camber. Hence, racers have different geometry setups for different circuits.
     
  3. mr hillclimber Club GTI Supporter and Sponsor

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    Not the best pic, but this is my set-up, and oh yes... it does work ! Sorry bout the surface rust but the old boy does live outside !

    [​IMG]
     
    Last edited: Sep 13, 2006
  4. scottmk1 Forum Member

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    ooh thats looks fancy, is it home made or bought mr hillclimber?
     
  5. mr hillclimber Club GTI Supporter and Sponsor

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    Home made by a good friend of mine, though he does build rally cars for a livin :thumbup:
     
  6. fthaimike Forum Addict

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    cracking stuff there.
     
  7. I V - mk1 16v Forum Member

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    Hi mike,
    i'm running eccentric topmounts with some pretty stiff springs, so whilst they are pretty crashy on the road, they do give some adjustabilty, over castor, camber and scrub radius. The only drawback thou is that you cannot alter these independantly as rotating the top mount affects all 3 at the same time. Also you cannot in any position run the standard setting. Ideally i'd like to use the proper jobbies which are slotted, but they are a lot more money!

    i generally run mine with the centre of the mount at 2 oclock and 10 oclock, when viewed L to R from the front of the car. This is giving me increased castor, increased neg camber, (thou still fine tuned by the bolt on the strut) but also using standard et wheels this will increase my neg scrub radius angle.

    The castor increase gives more straight line stability, more self centring of the wheel (more feel), but increased steering weight. Castor as Chris said also gives more neg camber as steering lock is applyed. But too much castor will transmit more crashing thro the steering and make the steering very heavy.

    The increase neg camber is handy as you can only normally get about 2deg from the eccentric bolt on the strut alone with standard topmounts, so if you want more then you can get it.

    But if using standard ET wheels then when you move the strut top inwards you are affecting the scrub radius angle, making it more negative.

    Negative Scrub radius (usually on FWD) forces the wheel to toe in when in motion, this decreases torque steer (but also steering feel) and increases braking stablilty.

    Positive Scrub radius (usually on RWD) forces the wheels to toe out under motion, increases torque steer, (but also steering feel) and decreases braking stabilty.

    the greater the scrub radius (+ or -) the greater the steering effort and the more road shock. But if you have a no scrub radius ie a 0deg SRA, this means the pivot point of the wheel is exactly in the centre of the tyre and this will lead to a squirmy feeling especially under braking as scrubbing will occur in opposite directions when the wheel is turned.

    I was previosly using 15mm front spacers which not only increased the track but also partly counteracted the extra negative scrub radius i have put on. None of this is measured by the way, just done by trail and error and feel, but i have recently been reading up on it a bit to try and understand what i am actually doing.

    So all in all, eccentric topmounts are a good, relatively cheap way of having a lot more control over your aleignment but you are opeing a can of worms and you can only go back to standard by going back to concentric topmounts, either standard or uprated.

    There a good diagram on GVK's widetrack thread thats shows Scrub radius, and heres a couple of good links i found on google about alignment.

    http://www.ingallseng.com/terms.htm

    http://beluap.tripod.com/crash5.html
     
    Last edited: Sep 14, 2006
  8. A.N. Other Banned after significant club disruption Dec 5th 2

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    All good stuff [:D] Interesting thinking around the braking stability also.
     
  9. I V - mk1 16v Forum Member

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  10. I V - mk1 16v Forum Member

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    interesting snippets.

    "Like shopping cats caster, the distance between the Dave Point and the tire’s contact patch creates a torque reaction, which causes the steering to self-align. The driver perceives this reaction as greater stability and on-center steering feel. More positive caster means a bigger torque reaction as well as increased stability and feel.

    Unfortunately, this virtual lever arm also increases torque steer on front-wheel-drive and all-wheel-drive cars because the force is reversed when the wheel is driven. This is why most front- and all-wheel drive cars don’t have as much caster as rear wheel drive cars."

    "Here are some basics guidelines for adjusting caster:
    Positive Caster:
    Just Right:
    - Improves straight-line stability
    - Sharpens turn-in
    - Improves traction everywhere in the turn
    Too Much:
    - Very high steering effort
    - Provides sharp turn-in but increases understeer from midturn onward
    - Increases torque steer in front- and all-wheel drive cars.

    Caster Adjustment Guidelines:
    FWD/AWD - 3-4
    RWD - 4-10 "
     
  11. GVK

    GVK Paid Member Paid Member

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    Cracking stuff Finchy !
     
  12. vw_singh Events Team Paid Member

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    This is what I have been meaning to get for a while.

    [​IMG]

    I want to adjust the castor for reasons that Ian talked about but I want to change the scrub radius because of the silly low et wheels i like to use! May actually get some grip round corners! lol

    Gurds
     
  13. I V - mk1 16v Forum Member

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    Now they are proper!

    Quanta costa???
     
  14. mk1 driver Forum Junkie

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    Around 175 (+ shipping, + customs) at the current exchange rate (1 > $1.88) but we would need someone in the states to order them for us and send them across the pond, as Ground Control do not offer international shipping.

    I wouldn't mind a pair...
     
  15. I V - mk1 16v Forum Member

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    i'll be sticking to my eccentric's then.[:$]
     
  16. vw_singh Events Team Paid Member

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    Yea, 175 a set. Only fit coilovers too from what the guys at GC told me. Not that will cause any issues for the most of us anyway.
     
  17. fthaimike Forum Addict

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    I am loving this thread so far, so much info on here [:D] .

    Do you have any pics of your setups on the mk1's lads? & what work was involved.
     
  18. fthaimike Forum Addict

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    Are there any type that fit? (maybe after modification to tower) a set based around the vw non-coilover type.
     
  19. I V - mk1 16v Forum Member

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    i think my eccentrics would work with the non coilover type struts but you might need to get some little sleeves made up.
     
  20. fthaimike Forum Addict

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    Do you have to cut anything off the top of the struts? i was thinking that the last cupped bit in the middle had to be removed or is this what the sleeves would do?

    Thanks for the info.

    Mike
     

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