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Old 02-22-2003, 11:35 PM   #16
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kick up also effects the cars ability to handal bumps

if the track is smooth, less kick up is needed, less kick up makes the car more aggressive

if the track is bumpy more kick up is need

negative kick up reduces caster when suspension is compressed
"used on 12 scale at the worlds"

i recommened 0-1 kick up
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Old 02-23-2003, 07:29 AM   #17
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Negative kickup won't cause the caster to reduce noticeably under suspension compression (no more than the car's pitch under braking would affect it) - you're confusing it with reactive caster, where there is a difference between the angle of the upper and lower wishbones.

One thing I've been wondering though...

With the large kickups run on 2wd buggies (30degrees), are we encouraging more suspension compression under braking (slower weight transfer)? Or does the extreme angle mean that a large amount of the compressive forces are tranmitted through the hinge pins and mountings, negating the effect of the kickup?
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Old 02-23-2003, 08:56 AM   #18
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On a 2 wd buggy the front wheels are not braked so more suspension compression under braking is not a big factor. I think the main advantage here is the wheels go up and back when you hit a bump so the suspension is better able to absorb bumps. On four wheel drive buggies the front wheels are driven as well as braked so there is usually a lot less kickup.
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Old 02-23-2003, 04:49 PM   #19
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Fastburn: Martin Crisp's "Chassis Setup guide book" is my guide book.


Seaball and John S.
So from what you have explained to me, Kick-up and anti-squat, varies the rate or time frame for a weight to be transferred. Wow, Where did u guys get that info?
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Old 02-24-2003, 08:21 AM   #20
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Default antisquat

Here is a quote from Carrol Smith's "Tune To Win" p34 in the section on Andtidive and Antisquat suspension.

"Much nonsensense has been circulated about anti suspension. The most prevalent fallacy being that it reduces load transfer. It doesn't -- not to any appreciable extent."

end of quote.

Antisquat does speed the rate of weight transfer. For example, It will give an offroad 2WD buggy a little more rear traction on the ramp of a jump, when you give it lots of throttle to make the jump, by speeding the weight transfer to the back tires.

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Last edited by John Stranahan; 02-24-2003 at 08:35 AM.
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Old 02-24-2003, 05:53 PM   #21
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John,
While i reached the point when i was experimenting about kick-ups and ati-squat on my car for fine tuning, and reading about martin's book, This is the reason why i ask this question in this forum, Becoz, i was not getting any difference in results based on the book of Martin on kickups and anti-squat. So now I got it and would like to thank you for the info.

Do you also have a download version of your book? It faster and convenient. Here in the Philippines sometimes books ordered from the US will arrive for 2-3 months or will not reach u at all.Thanks
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Old 02-24-2003, 06:35 PM   #22
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'Wilfred-You are welcome for the info. I sent you an e-mail.
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Old 02-24-2003, 07:09 PM   #23
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I enjoyed reading all the informational content on this topic.

John,
If andisquat speeds up the weight transfer to the rear tires won't that cause the car to push more on power since weight unloaded form the front quicker?
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Old 02-24-2003, 08:17 PM   #24
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Mike-Unfortunately on our independent suspension 4wd cars, antisquat seems to make the rear end loose on power. I suspect that the faster weight transfer to the rear is overcome by the increased lateral weight transfer at the rear caused by the suspension acting stiffer on power. The increased lateral weight transfer reduces cornering power. You do get slightly more forward bite with antisquat on a two wheel drive car.

On a vintage live axle fullsize racecar, the antisquat could be used in sufficient quantity to actually cause the rear of the chassis and body to rise on power. This did load both sides of the rear axle and improve rear cornering traction. This is described in Herb Adams Book "Chassis Engineering". I note that current Transam race cars, which use a live axle, don't use much antisquat anymore.

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Old 02-24-2003, 08:44 PM   #25
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John, I agree with your points exept that you state stiffer springs dont reduce weight transfer.

a softly sprung car will dive off power and squat further on power than a stiffly sprung car, greater weight transfer.

It is evident when setting up your car that if the chassis is scraping on the track surface, one of the required steps to solve this is to increase the suspension stiffness, through changing springs, swaybars, mounting locations, or resisting the rolling forces through changing the vehicles roll centre, reducing its roll moment.

A stiffly sprung car will transfer weight quicker, but it will transfer to a lesser extent, less dive and roll at full transfer.

I agree with all of you other points, just thought I'd put forward my opinion on this issue as I feel your point is incorrect.
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Old 02-24-2003, 09:17 PM   #26
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Quote:
Originally posted by King-G
John, I agree with your points exept that you state stiffer springs dont reduce weight transfer.

a softly sprung car will dive off power and squat further on power than a stiffly sprung car, greater weight transfer.

It is evident when setting up your car that if the chassis is scraping on the track surface, one of the required steps to solve this is to increase the suspension stiffness, through changing springs, swaybars, mounting locations, or resisting the rolling forces through changing the vehicles roll centre, reducing its roll moment.

A stiffly sprung car will transfer weight quicker, but it will transfer to a lesser extent, less dive and roll at full transfer.

I agree with all of you other points, just thought I'd put forward my opinion on this issue as I feel your point is incorrect.
I think it may just look that way. Its the same force but with less pitch. still the same porce is applied to the front or rear.

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Old 02-24-2003, 09:23 PM   #27
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King-g. I'll note that you also disagree with Carrol Smith, who is a fairly well respected authority on full size race cars.

Stiffer springs do not reduce weight transfer, they reduce roll and pitch. Weight transfer is speeded up. Stiffer springs are used on carpet race cars to quickly transfer weight to the outside wheels to reduce cornering traction. On low traction surfaces light springs can be used to delay weight transfer and improve cornering traction.

The ammount of roll does not affect lateral weight transfer in the same manner that the ammount of pitch does not affect fore and aft weight transfer to any great degree.

The physics of weight transfer is explained quite well in Carrol Smiths book "Tune to win" and in Herb Adams book "Chassis Engineering".

A stiffly sprung car has the advantage that it quickly takes a set in the corner and you can get on with the buisiness of driving the corner at the expense of some initial cornering traction.


Last edited by John Stranahan; 02-24-2003 at 09:48 PM.
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Old 02-24-2003, 10:57 PM   #28
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John, I hear your points, I have read Carrol smiths book along with many others on race car engineering.

I still feel overall that softer springs allow greater TOTAL transfer of weight, as the car is able to pitch deeper and squat to a higher extent exiting a corner. I do however agree that stiffer springs allow THEIR TOTAL transfer of weight to happen sooner, but this transfer is reduced by the weight of the spring resisting teh forces applied to them.

Springs are graded in Pound per square inch required to compress the spring, a stiffer spring therefore requires a greater force to acheive the same amount of compression. So a given force applied to a stiff spring will compress less than a softer spring, hence less weight is transferred, be it For /Aft or lateral

If a car had no springs, but was supported on solid blocks, there would be no or very little weight transfer. I feel that stiff springs Limit the maximum transfer of weight in the same way.


Just my point of view, and I am open to discuss it and hear others view on the topic, I am not saying i am right, but this is how I see it.

Last edited by King-G; 02-24-2003 at 11:03 PM.
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Old 02-25-2003, 12:15 AM   #29
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King G - no weight trasfer means that if the vehicle is accelerated in any direction, the weight supported by each tire would be constant. This is not possible. For example, If the car is acclerating forward, the front tire would be lighter than the rears because of "weight transfer". If turning left, the right tires would get heavier. There is always weight transfer regardless of spring rate.
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Old 02-25-2003, 07:48 AM   #30
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The position of the roll center is constantly changing as the suspension compresses AND rolls. A larger amount of chassis roll from softer springs will effect how much the position of the roll center changes. This can have a positive or negative effect on cornering stability.

Softer suspensions and increased chassis roll also effect the camber of the tires. The tire traction capabilities are greatly dependent on the relative tire angle to the road surface. Oversimplifing things, it all comes down to how the rubber hits the road.

Camber gain and roll center position are only two of many suspension characteristics effected by changing spring stiffness.

I'm not saying who's wrong or right because both of you are looking at the issue with different perspectives. Just dont forget that changing spring stiffness also changes a large number of other suspension characteristics that influence vehicle stability.
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