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Thread: Transformer arrives in Colchester

  1. #121
    Free user strat24v's Avatar
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    Re: Transformer arrives in Colchester

    Reading into that, track is wrong and a stronger arb is what's in order?

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    SEC Member Lancialulu's Avatar
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    Re: Transformer arrives in Colchester

    Quote Originally Posted by strat24v View Post
    Reading into that, track is wrong and a stronger arb is what's in order?
    John, not sure of point re ARB??? Please explain. Track was right when checked last week. I am sorting out this play identified at the MOT, It is minuscule hence no advisories. I have tracked down to a not tight outer wishbone bush and miniscule play on the inboard rose joint. All these have done less than 3000miles. I am getting a replacement high performance two part inner rose joint as we speak.

    Craig - unless I have got it wrong the Stratos tech data indicates a standard spring rating of 330lb/in (when converting from kg/mm). I seem to read in various parts of this forum 325 is a good standard for the Hawk but I understand for an Alfa V6 Hawk nowadays folk have gone up to 350. We shall see!?

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    SEC Member Strat Fan's Avatar
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    Re: Transformer arrives in Colchester

    Quote Originally Posted by Lancialulu View Post
    Craig - unless I have got it wrong the Stratos tech data indicates a standard spring rating of 330lb/in (when converting from kg/mm). I seem to read in various parts of this forum 325 is a good standard for the Hawk but I understand for an Alfa V6 Hawk nowadays folk have gone up to 350. We shall see!?
    There will be no real difference in the rear spring rates whatever the kit manufacturer provided the car is fitted with strut type rear suspension. The ratio of wheel movement to damper movement will always be all but 1:1 & a car with an Alfa V6 will always have roughly the same axle weights. The front end on the other hand varies considerably due to damper angle & mounting positions.
    I can obviously only speak from my personal experience and IMHO I find that 275lb is more than adequate for a the rear of a Stratos replica on the road, I have run the 325lb rate spring rate and it will work perfectly well but it is slightly stiffer than it needs to be for a road car but will offer a good compromise between a road car & a track day car.
    Last edited by Strat Fan; 15-12-2016 at 16:18.

  4. #124
    SEC Member Lancialulu's Avatar
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    Re: Transformer arrives in Colchester

    Thanks Craig. We will see. At the moment Shades had run 200lb in. so I will surely see some difference. I have some roads to exercise the suspension in a controlled way so am looking forward to getting back out.

  5. #125
    Free user Darkspeed's Avatar
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    Re: Transformer arrives in Colchester

    If I read it correctly the Stratos manual / tech data states that the stock spring compresses 142mm under a load of 300 - 330kg that's a spring rate of 22kg/cm or 120/130lb/in - which from my calculations is a compliant sports car ride stiffness on a strut. - so sounds about correct.

    325lb/in at near 3 times the standard stiffness seems a bit on the high side - For a 1000kg car with 40/60 distribution my calculator throws out 250-275 as being in the firm sporting area.

    350 lb will only have 1.75" of coil crush so if you have more than 2" of droop in roll or bounce the spring will be unrestrained. Stiff springs are all well and good but you also need to take into account the suspension travel you have on the strut and the bounce and droop you want to have. Having a wheel in roll unsupported and just bouncing against a loose spring is not good.

    I always want to have at least 3" of bounce and droop with the spring restrained in that movement - for 3" of coil crush - and no preload on the strut - assuming adjustable platform of course - you need a spring of 220lb/in range - the coil free length etc will depend on the open and closed lengths of the strut and position of the bump stop.

    Big subject
    Last edited by Darkspeed; 15-12-2016 at 19:45.

  6. #126
    SEC Member Lancialulu's Avatar
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    Re: Transformer arrives in Colchester

    Hi Andrew. Yes I got the wrong page - how irritating is that! Calculated for front ARGHHHH. Having said that looking at the Stratos rear spec the spring is c12" whereas the LEDA strut takes a 9". The Factory spring is as you say c 125lb in....
    Strange thing is the LEDA guy thought the 325 spring was in the right area and said other Hawk users were going a little bit higher.
    I calculate I will get 2+inches of crush (625+kg rear axle when loaded) if I set the spring with zero preload. (Wonder what the ride height will go to...Need to aim for 175mm). The LEDA strut has 7 inches of travel. Looking at the Stratos tech book it seems the rear damper only has 5.75" travel. Not sure what to make of this other than wheels will dangle as early as my set up??? The setup I got for a Gp4 ashphalt Stratos works car (from Gianni Tonti) had a spec for "Molle" of 17 to 14 % for the rear and 40 to 35% for the front. Can anyone interpret this??
    I am aiming to set the car up as sporting rather than comfort (I have other Lancias that fit that GTouring bill!!!) We will see but if I have to go softer its not big deal. The debate goes on.
    Last edited by Lancialulu; 16-12-2016 at 09:39.

  7. #127
    SEC Member Strat Fan's Avatar
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    Re: Transformer arrives in Colchester

    Quote Originally Posted by Lancialulu View Post
    Strange thing is the LEDA guy thought the 325 spring was in the right area and said other Hawk users were going a little bit higher.
    The LEDA strut has 7 inches of travel. Looking at the Stratos tech book it seems the rear damper only has 5.75" travel. Not sure what to make of this other than wheels will dangle as early as my set up???
    Have you considered CV joint articulation with 7" of damper travel?
    The Stratos had a central differential so the drive shafts were much longer & consequently the angles the CV joints ran through were less. An Alfa V6 is quite wide across the drive flanges and therefore has much shorter shafts which leads to more extreme CV joint angles. If you have too much droop on the suspension then you will run out of motion on the CV at full droop or at the very least the CV boot could pull off of the cage. 5.75" of travel is more than adequate for a tarmac car even taking into account the bumpstop. Too much bump & you'll be rubbing the arches before you hit the bumpstops. 7" of travel will be fine for a full gravel spec car but I am struggling to see how you can use all that travel knowing the limits on the CV joints & wheel arches. You have got a smaller tyre than some which will certainly help with bump travel.
    175mm is quite high for the ride height but does help with the rear geometry & camber gain.
    Obviously its fine for Roger to give out advice on springs and travel but unless he's actually owned or driven a car then there is only so much theory & calculation you can apply. There is no substitute for bum in seat testing. 325lb or 350lb springs will yield quite a high spring frequency. A 325lb will be around 2.2Hz, a 350lb will be more like 2.3Hz.
    "You can lead a horse to water, but a pencil must be lead"
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  8. #128
    SEC Member Lancialulu's Avatar
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    Re: Transformer arrives in Colchester

    Quote Originally Posted by Strat Fan View Post
    Have you considered CV joint articulation with 7" of damper travel?
    The Stratos had a central differential so the drive shafts were much longer & consequently the angles the CV joints ran through were less. An Alfa V6 is quite wide across the drive flanges and therefore has much shorter shafts which leads to more extreme CV joint angles. If you have too much droop on the suspension then you will run out of motion on the CV at full droop or at the very least the CV boot could pull off of the cage. 5.75" of travel is more than adequate for a tarmac car even taking into account the bumpstop.
    I have this issue!!! At least one drive shaft has just pulled through the circlip retainer when I have "drooped" the suspension on a jack. Will have to think about this. What does a Hawk Gaz strut travel??

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    SEC Member Strat Fan's Avatar
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    Re: Transformer arrives in Colchester

    Quote Originally Posted by Lancialulu View Post
    I have this issue!!! At least one drive shaft has just pulled through the circlip retainer when I have "drooped" the suspension on a jack. Will have to think about this. What does a Hawk Gaz strut travel??
    That one I can't answer I'm afraid, you'll have to find a Hawk owner with current spec dampers to check for you.
    "You can lead a horse to water, but a pencil must be lead"
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    Re: Transformer arrives in Colchester

    Cheap solution is to fit some sort of limiting strap; a droop limiting cable from lower spring pan to chassis or (depending on spring length) tie wrap the springs to lower and upper pans.

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