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XR Falcon track car set up.

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Hi Guys

Im after some advice in regards to setting my XR falcon for track duties.

 

Currently the car has a 1" Shelby drop, Xf spindles, Clevo King springs in the front (think they are lows) GT leaf pack with a added rebound spring, konis all round and a 28mm sway bar up front.

 

I have entered it into a few hill climbs and have done fairly well, but I want to start doing some track days.

 

I was told buy another guy that races a XY (it is stupid quick) that I really need to lower my car, dial about 3' of neg camber and use 700 pound springs in the front.

 

I feel that my car is already fairly low but his is heaps lower but I don't understand stand how he gets his car to sit so low. Would need significant modifications I would think.

 

What do you think the optimal height would be for a dedicated track car?

 

Dose 700 pound springs sound about right and were would I go to get springs like that.

 

Sorry for all the newbie questions

 

Cheers,

Ryan00c84ceafc2890fa5fd541ea9f55c144.jpge8ddf6bb8a07a7023857b4a2b89d66b2.jpg

 

Sent from my SM-G973F using Tapatalk

 

 

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G'day mate, sweet machine you have there.

For starters, it looks like you've got bigger diameter wheels, so lower profile rubber will need less neg camber than the traditional wheel/tyre combo needs (less sidewall deflection).

So your mate's suggestion of 3 degrees might be good for his setup, but your low profile rubber plus the Shelby drop will actually increase neg camber as more compression comes on, so less static camber is needed. This is the whole point of the mod... So you don't need to dial in so much camber at static height to compensate for poor factory geometry.

Falcon/Mustang/Fairlane geometry is designed to provide a POSITIVE camber curve from factory, inducing "safe" understeer for your average mum and dad driver. The Shelby drop inverts this to a negative camber curve. Has your mate's car had the Shelby drop done?

The bigger wheel diameter will also make the car sit higher than your mate's. Going to a smaller rolling diameter will have it all sitting lower before you even touch the suspension.

I also did the Shelby drop, and it has transformed the car. Mine definitely isn't a track car though (XE wagon V8). A 1" drop is as far as you'd go on the street, but 1.5" or even 2" is not unheard of on race cars. This much of a drop requires wedged spacers under the ball joint mount face, to stop the joint from reaching its limits of articulation and binding/breaking off.

In the photo, despite his car being lower, it actually looks like he's got a similar amount of body roll to yours, despite stiffer springs. Maybe he runs less bar? 28mm on yours is pretty damn stiff. That's easily 4 times as stiff as a factory 6-cyl.

If you're running more swaybar than you have spring, it will turn in nice but will induce more understeer the more lock you wind on. It's really important to match rollbar stiffness with spring rate, and as a guide, you could start from factory settings and increase each as a percentage.

Just keep in mind, as you increase roll bar diameter, the stiffness increases to the power of 4 to that. I just found an online calculator and going from 22 to 28mm tripled the stiffness! Maybe you could go back to a stock one and see how it goes? You might be getting some mid-corner plough-steer with too much bar on there.

King lows aren't really that low. They're probably 1.5" lower than stock (dunno what the rates are). 1" Shelby drop gives 0.5" body drop, so altogether you have 2" based on my assumption about the King lows. If you have a bigger rolling diameter, then you've gone back up a bit from there.

Some guys on here have cut and shut their front bump stop plates to raise the bump stop mounting point, increasing the effective suspension travel. If you go lower, you might have to resort to this. There's one bloke on here who is doing this right now (search recent posts to see).

If it's a track car, you could try cutting a coil or two off to easily and cheaply lower it and increase the spring rate. The rate will increase by the amount, percentage-wise, of how much free length you end up chopping off.

The rear sounds pretty sorted, are you running a swaybar there too? That will make it more tailey especially when putting power on. Whether or not you have one depends on your driving style. I have one and would like to put it on mine.

Never underestimate a sorted leaf setup... They have the right kind of lateral deflection that provides a very controlled and predictable rear-steer effect, which can be very handy at getting the big girl through the tight turns. Just ask Dicky Johnson... He always talked of his XD as being a fabulously balanced racecar. Never go to a Watts link setup... It's a step backwards.

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Agreed, a well sorted leaf sprung rear end can be made to work extremely well. No tramp, no wheel spin, just squat and go. Having a look at the 2 pics, your buddys XY has the front tyre planted flat, and your XR looks like its starting to tuck under. Do you have a chassis shop/builder in your area.??

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You bring up a good point there Bear... I just realised that the inside wheel on the XY has gone negative, whereas the XR inside wheel is slightly positive, which is what happens with the Shelby drop. So that tells us that maybe the XY doesn't have that mod, and is relying purely on a severe camber setting.

I think the XY wheel looks flatter because of the aforementioned swaybar issue. I reckon that swaybar is softer than on the XR's. As a result, that wheel has gone so far into compression (starting from a very low ride height already) that the top arm is swinging inwards and tipping the wheel into neg camber, also starting from an extreme 3 degrees neg at static ride height would contribute. Same effect as the Shelby drop, just happening much later in the suspension travel.

I think OP could benefit from slightly lower ride height, stiffer springs, smaller diameter wheels/tyres and softer swaybar.

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G'day mate, sweet machine you have there.

For starters, it looks like you've got bigger diameter wheels, so lower profile rubber will need less neg camber than the traditional wheel/tyre combo needs (less sidewall deflection).

So your mate's suggestion of 3 degrees might be good for his setup, but your low profile rubber plus the Shelby drop will actually increase neg camber as more compression comes on, so less static camber is needed. This is the whole point of the mod... So you don't need to dial in so much camber at static height to compensate for poor factory geometry.

Falcon/Mustang/Fairlane geometry is designed to provide a POSITIVE camber curve from factory, inducing "safe" understeer for your average mum and dad driver. The Shelby drop inverts this to a negative camber curve. Has your mate's car had the Shelby drop done?

The bigger wheel diameter will also make the car sit higher than your mate's. Going to a smaller rolling diameter will have it all sitting lower before you even touch the suspension.

I also did the Shelby drop, and it has transformed the car. Mine definitely isn't a track car though (XE wagon V8). A 1" drop is as far as you'd go on the street, but 1.5" or even 2" is not unheard of on race cars. This much of a drop requires wedged spacers under the ball joint mount face, to stop the joint from reaching its limits of articulation and binding/breaking off.

In the photo, despite his car being lower, it actually looks like he's got a similar amount of body roll to yours, despite stiffer springs. Maybe he runs less bar? 28mm on yours is pretty damn stiff. That's easily 4 times as stiff as a factory 6-cyl.

If you're running more swaybar than you have spring, it will turn in nice but will induce more understeer the more lock you wind on. It's really important to match rollbar stiffness with spring rate, and as a guide, you could start from factory settings and increase each as a percentage.

Just keep in mind, as you increase roll bar diameter, the stiffness increases to the power of 4 to that. I just found an online calculator and going from 22 to 28mm tripled the stiffness! Maybe you could go back to a stock one and see how it goes? You might be getting some mid-corner plough-steer with too much bar on there.

King lows aren't really that low. They're probably 1.5" lower than stock (dunno what the rates are). 1" Shelby drop gives 0.5" body drop, so altogether you have 2" based on my assumption about the King lows. If you have a bigger rolling diameter, then you've gone back up a bit from there.

Some guys on here have cut and shut their front bump stop plates to raise the bump stop mounting point, increasing the effective suspension travel. If you go lower, you might have to resort to this. There's one bloke on here who is doing this right now (search recent posts to see).

If it's a track car, you could try cutting a coil or two off to easily and cheaply lower it and increase the spring rate. The rate will increase by the amount, percentage-wise, of how much free length you end up chopping off.

The rear sounds pretty sorted, are you running a swaybar there too? That will make it more tailey especially when putting power on. Whether or not you have one depends on your driving style. I have one and would like to put it on mine.

Never underestimate a sorted leaf setup... They have the right kind of lateral deflection that provides a very controlled and predictable rear-steer effect, which can be very handy at getting the big girl through the tight turns. Just ask Dicky Johnson... He always talked of his XD as being a fabulously balanced racecar. Never go to a Watts link setup... It's a step backwards.

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Hi Greg,
Cheers heaps for the advice.

You are correct, the XY has 225/50/15's all round that have a side wall of 112mm (looked up a tyre size calculator) and I have 235 40 17's on the front with a side wall of 94mm.
But I still think I need abit more neg camber because you can see were the tyre was rolling over onto the triangle markers on the outer side wall, but on the inner edges I had about 4mm to the markers. There would of been close to 10mm difference from inside to outside.

Looking at the two different tyre sizes and my fronts would only account for 6.5mm of extra height. I would of thought it would of been more than that.
The rears would be 13.5mm higher (255/40/17)

I did the 1" shelby drop about 10 years ago so I don't remember it all but I do remember that I had to massage the towers to even achieve 1".
I had a balljoint wedges made up because the balljoints were binding before hitting the bump stop. I also modified the bump stop mountings in board slightly so the arm hit it the same spot because it was hitting on a edge.

Interesting what you are saying about the sway bar, I will definitely look into that and see what options I have. Might do a bit of experimenting.
Im not running a sway bar on the back at all.

I do feel the car handles well, it dose under steer a little mid corner if I really push it but it is very gradual and controlable.
I actually found running 2psi lower pressure in the front fixes this but my times are a little slower. But that could be inconsistency in my driving.

To start with I might try cutting the springs and see how that goes. (Have not done that since high school.) Then make sure I still have ample travel and nothing binds.

Thanks heaps
Ryan



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Agreed, a well sorted leaf sprung rear end can be made to work extremely well. No tramp, no wheel spin, just squat and go. Having a look at the 2 pics, your buddys XY has the front tyre planted flat, and your XR looks like its starting to tuck under. Do you have a chassis shop/builder in your area.??
Hi Bear,
At one stage I had crazy ideas about doing a 3 link rear, but I feel the set up I have works really well. The car makes some decent power and even when I used to have 225 street tyres it actually hooked up out of corners pretty well.
I very rarely have issues with axel hop and with the 255/40/17's if gets off the line real well.

I don't know of any chassis shops near by. Why is that?
Cheers for your help!

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You bring up a good point there Bear... I just realised that the inside wheel on the XY has gone negative, whereas the XR inside wheel is slightly positive, which is what happens with the Shelby drop. So that tells us that maybe the XY doesn't have that mod, and is relying purely on a severe camber setting.

I think the XY wheel looks flatter because of the aforementioned swaybar issue. I reckon that swaybar is softer than on the XR's. As a result, that wheel has gone so far into compression (starting from a very low ride height already) that the top arm is swinging inwards and tipping the wheel into neg camber, also starting from an extreme 3 degrees neg at static ride height would contribute. Same effect as the Shelby drop, just happening much later in the suspension travel.

I think OP could benefit from slightly lower ride height, stiffer springs, smaller diameter wheels/tyres and softer swaybar.

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Hi Greg,
Im fairly sure the XY has done the Shelby drop, I think he might of even gone 11/2" from memory of what he told me.
I have never heard of the aforementioned sway bar issue. I will have to do some googling / reading!

When you say I would benefit from smaller diameter wheels/tyres is that purely due to lower ride height or is there other benefit.
Cheers


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Hi Greg,
Im fairly sure the XY has done the Shelby drop, I think he might of even gone 11/2" from memory of what he told me.
I have never heard of the aforementioned sway bar issue. I will have to do some googling / reading!

When you say I would benefit from smaller diameter wheels/tyres is that purely due to lower ride height or is there other benefit.
Cheers


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Yeah mate, just the ride height in regards to the wheels. To exaggerate a little, it's a bit like the "elephant on roller-skates" effect. An inch overall diameter increase will raise the car by 0.5".

Just think of all those 4x4s out there with massive wheels, and the effect it has on ride height.

Tyres play a huge part too. Maybe you need a set of race tyres and wheels for it?

Swaybar tuning is a bit of a dark art, but 28mm I reckon is overkill on yours. A standard V8 one (I think they're 22mm) shouldn't be too hard to get, even second hand. It will increase body roll but don't be scared of that. Too stiff a sway bar will lift the inside wheel and overload the outside, bringing the limits of grip earlier.

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A lot of chassis shops build racecars, and they can set your car on a jig, measure it all up, suggest roll bar settings etc. Just thought they could offer some advice, like changing the diff U bolts to 9/16" for added strength, that sort of thing. 

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