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Author: Subject: Sylva striker - Coil springs
sooty

posted on 22/4/17 at 07:35 PM Reply With Quote
Sylva striker - Coil springs

Want to uprate my front suspension by increasing the spring rate.

Problem, not a clue what the current ratings are.
The dampers are Spax coilovers with Red springs 60ID x 10mm thick coil x approx 250mm long.

Anyone got an original Sylva Striker with any clues who supplied the springs to Sylva or know what these ratings are.

Thanks





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Sam_68

posted on 22/4/17 at 07:54 PM Reply With Quote
You're not just uprating the front, I hope? You need to uprate the rear in proportion, otherwise it will screw up your handling balance.

Are there no markings on the springs themselves? Wire diameter doesn't help you much unless you also know the pitch.

If you know your corner weights, you can calculate the spring rate from the static deflection.

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sooty

posted on 22/4/17 at 09:02 PM Reply With Quote
Reason for doing fronts alone, is that under hard cornering the inner wheel lifts losing traction as its a live axle.

Watched a in-car video and its surprising how soft the fronts appear to be with the amount of deflection.

You refer to marking, what sort - figures ?

I do know the corner weights both unladen and with driver, this was adjusted balanced 2 years ago along with the castor and camber.

thanks





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Sam_68

posted on 22/4/17 at 09:38 PM Reply With Quote
quote:
Originally posted by sooty
You refer to marking, what sort - figures ?


Often either printed or painted onto the coil of the spring, or stamped onto the flat, exposed end of the spring when you take it off the damper.

But if you know the corner weights, then simply measure the static laden length of the spring and divide the corner weight by the compression from the spring's free length.

If my memory serves me correctly (someone else in the Sylva forum will be able to confirm, I'm sure), the 'normal' (factory) stock spring rates for Strikers were 180F/130R for road use and 230F/180R for track.

It's a good while since I ran a Striker, though, and my memory isn't what it was, so don't take my word for it.

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MadMaxx

posted on 23/4/17 at 02:49 PM Reply With Quote
quote:
Originally posted by Sam_68
quote:
Originally posted by sooty
You refer to marking, what sort - figures ?


Often either printed or painted onto the coil of the spring, or stamped onto the flat, exposed end of the spring when you take it off the damper.

But if you know the corner weights, then simply measure the static laden length of the spring and divide the corner weight by the compression from the spring's free length.

If my memory serves me correctly (someone else in the Sylva forum will be able to confirm, I'm sure), the 'normal' (factory) stock spring rates for Strikers were 180F/130R for road use and 230F/180R for track.

It's a good while since I ran a Striker, though, and my memory isn't what it was, so don't take my word for it.


Same rate than Fury.





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Camber Dave

posted on 24/4/17 at 07:08 AM Reply With Quote
From Sam
"You're not just uprating the front, I hope? You need to uprate the rear in proportion, otherwise it will screw up your handling balance. "

In Full agreement.
However from records I have found 3 rocker ratio's used on Furies, so the correct spring may not have been originally or subsequently fitted.

Answer to OP original question
From the Staniforth bible

Spring rate = G x d (to the 4th power) / 8n x D(cubed)

Where G = Modulus of the wire - Use 11,000,000 (works for Falkener and similar springs)
d = Dia of wire (ignore powder coating and measure to 2 decimal places!)
n = No of working coils ( ie count only the coils in the air and ignore the tapered bit in contact with the perches )
D = Mean diameter of the coil (ie disregard wire thickness)

Calculator or spreadsheet needed!

[Edited on 24/4/17 by Camber Dave]

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JimSpencer

posted on 24/4/17 at 07:45 AM Reply With Quote
Hi

Been down this route on a live axle striker.

Didn't bother with a calculator, just got a box full of springs and worked my way through the set up until we got a result that gave us a nice handling balance.

And this worked to a degree, (car was reasonably competitive in Hillclimbs and Sprints)
However it was bullet hard, useless on the road and simply didn't inspire confidence..

So went back to much softer springs (ended up at 250 / 150 IIRC) but with an adjustable Front Anti Roll bar (there's a couple available for the Mk2 Striker - same as the Fury)
And decent shocks - Protechs, valved for the weight of the car.

Car was totally transformed - still has some of the class records for road going kits in speed events, it's ridiculously quick on a track day, but if you raise the ride height (set at 40mm front for track work normally!) you can drive it down the road too.

Get an front ARB on it, make sure the shocks are half way decent and then look at the springs - would be my recommendation

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sooty

posted on 5/5/17 at 10:41 AM Reply With Quote
OK

Decided to look down the route of a ARB as I use this both for Road and Trackday, where the springs may suit one but not the other.

Looking to make my own, what grade of material (straight bar) would be best suited for the bar besides using seamless hydraulic tube.

Any suggestions

Thanks

[Edited on 5/5/17 by sooty]





Sylva Striker
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JimSpencer

posted on 7/5/17 at 08:52 AM Reply With Quote
hi

Sorry not got a clue on that one - had mine fabricated for me by Procomp in Birmingham.

There's a couple of ones available off the peg for a Mk2 though, but no idea of the material spec.

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sooty

posted on 11/5/17 at 08:18 PM Reply With Quote
OK,

Been trolling through Google and although for some cars an off the peg ARB assembly and for others this is not so.

Recently found from contact with a member who also has a Striker with a ARB fitted, but as we are using different engines and transmission, they are like chalk and cheese with the chassis for mounting an ARB.

Have found a Formula used for calculating a ARB and what arm lengths preventing the over twist of the bar.

All inputs are imperial not metric:-

D = OD
G = Shear Modulus (11,600,000si)
L = working length of roll bar
R = (radian) 0.0174533 x degrees
Tr = suspension travel

Max Shear Stress in the bar
Max Shear Stress (SS) = (D x R) x G / (2 x L)

Max allowable twist in the bar
Max angle of twist in radians (TW) = (SS x 2 x L) / (D x G )

Arm length needed to not over twist the bar
Arm length = (0.5 x Tr) / TAN (TW)

Any experts to say if this is close for help with the make up of a ARB





Sylva Striker
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bi22le

posted on 11/5/17 at 08:35 PM Reply With Quote
I have a striker and am planning on putting Caterham ARBs on.

They do them in 4 different thicknesses so you can just change them if required. I have everything here, I just need to get into the garage and do it!





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sooty

posted on 11/5/17 at 10:11 PM Reply With Quote
Yes they do supply and some others also supply this type.

But have been looking for a ARB within the confine of the bonnet and being adjustable.





Sylva Striker
2.0ltr Silvertop Zetec on 45 Webers with Megajolt V3

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