Fg Front Suspension Spring Rates For Circuit

[nelsonian101]

So here's what happened with my FGXR6T.....

I went from a custom Koni coilover with a 650lb spring (with revalved Koni reds) to a non coilover Revalved Bilstein with an 850lb King spring.

The car sat about 10mm lower at the front with the Koni's but then this may be a bad thing as there is not exacly 50/50 weight distribution with these Turbo Taxis.

My thoughts were that the higher spring rate in the second Bilstein set up would be stiffer and better for the track but seat of the pants feel at Wakefield yesterday were that of more front body roll. Laptimes were nearly 2 seconds down on average (but that could be down to inconsistent driving, traffic, conditions etc)

Both set ups used Michelin Slicks with 3.5deg of neg camber.

There is less travel with the coilover design due to the shorter spring (terrible for potholes etc) but would this be the reason for it feeling better at the track.

My only option is to try the 1100lb spring but then will the Bilsteins need to revalved again?

Thanks.

[Seaton]

I would speak to Heasman Steering.

They are the Bilstein experts for this sort of thing.

[senna_T]

Were the Bilsteins Dyno'd to confirm they have enough rebound rate to suit the 850lb springs?

The Longer coils will have more travel, however if the shock doesn't have enough rebound rate the car will suffer from the inside lifting in corners rather than the outside compressing.

[nelsonian101]

Yes, the bilsteins were revalved by Heasemans/Bilstein themselves for an 850lb shock.

Just seat of the pants feel yesterday at the circuit had the Koni Coilovers with a 650lb rating feeling a lot stiiffer.

(Koni Reds were actually revalved too)

If I went to the 1100lb linear King spring, would the Shock absorbers need to be revalved/dynoed once again?

[dustyae86]

I would personally try and play around with your front bar setting, if it's adjustable.

Either that or since you're feeling more body roll, maybe with the stiffer front the rear feels like it has more roll.

can you describe anymore characteristics that have changed? I.E oversteer and understeer?

\

[nelsonian101]

 

  On 13/03/2013 at 7:26 AM, dustyae86 said:

I would personally try and play around with your front bar setting, if it's adjustable.

Either that or since you're feeling more body roll, maybe with the stiffer front the rear feels like it has more roll.

can you describe anymore characteristics that have changed? I.E oversteer and understeer?

\

 

The front sway bar is non adjustable. It is a custom made solid version of the stock item. Biggest that fits. Have seen these both at Wholesale suspension and East Coast.

The rear bar is an adjustable whiteline.

This car has seen many circuit days over the years and has been developed over 4 years of testing. It is an aggressive set up getting closer to mid low 8's at Wakefield.

Car handles well and can be persuaded from slight understeer at the limit during turn in to slight oversteer mid corner to exit depending on throttle input.

Tyres are Michelin Porsche cup slicks. About 25cm wide run at 30psi hot.

I am thinking even though the spring rate is stiffer in the current conventional set up with 850lb (non coilover, non height adjustable), ramp up characteristics will be different with the original 650lb Koni Coilover with the shorter travel.

[senna_T]

Since the bilsteins are non adjustable I would say that the valving will need to be adjusted again.

One thing to ask Heasmans is whether they left the valving as digressive or if it is linear. Digressive valving will bleed off the strength of the shock the further it goes which is excellent for a street car and longevity of the shock however it may not be perfect for a track setup.

Are the Kings progressive/tapered wire design or linear?

[nelsonian101]

 

  On 13/03/2013 at 9:55 PM, senna_T said:

Since the bilsteins are non adjustable I would say that the valving will need to be adjusted again.

One thing to ask Heasmans is whether they left the valving as digressive or if it is linear. Digressive valving will bleed off the strength of the shock the further it goes which is excellent for a street car and longevity of the shock however it may not be perfect for a track setup.

Are the Kings progressive/tapered wire design or linear?

 

The King springs currently on there are an 850lb linear.

Even though they are 850lb, will they feel softer on the track than a 650lb (short spring/travel) coilover?

[dustyae86]

Just crazily thinking out loud now because it's clear you're not just a goober running a crap set up.

My thoughts after re reading it a few times is I think possibly that your new shocks (being a longer travel) aren't using all the stroke like the konis were, did you ever do the old cable tie on the shock trick to see how much stroke you are using?

I'm thinking that the konis were getting onto the bumpstops (koni bumpstops by chance?) and then in turn causing less roll.

Again I'm just thinking out loud here now, unfortunately can't really assess the situation easily on the net.

Good news is, you are getting your tyres at the perfect temp, that is what we would aim for in Carrera cup from memory, unfortunately I have lost all my data I had regarding tyre temps set ups etc for those cars (the joys of leaving a team, you have to hand all that info back)

[spinr33]

Could it be that the king springs your running are taper coil vs the coil over spring being progressive so your getting more body roll before it gets to its full spring rate ?