05-02-2007, 08:02 AM
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 Quote:
Originally Posted by Grant
@Louis - I think the way a car will handle at the limit will be roughly the same whether you have cheap or expensive tires. I know steering response won't be as good with the cheapies, but I don't think and understeering car will turn into an oversteering car with a trip to the tire store. Eagle F1's are baller!
And, I think Louis' spring rates were too much for the dampers. Felt a bit underdamped from the short ride I got. Maybe with softer springs they'll be just right? What do you think Louis?
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The lightweight wheels rides better over fast up and down movements. You could use less damping and softer springs with light weight wheels. However, in terms of ride quality, the tire aspect ratio is going to form a spring and this is where we would perceive the car as being harsh.
So, in reality the suspension is a matched system consisting of the wheel, tires, shocks, springs, swaybars, alignment,etc... See why it's so damn hard to get it right!
I think what you perceive as damping is caused by the spindles. The extension in the front is too great with the spindles. The RS shocks are two inches shorter in travel than a stock shock and the springs aren't fully compressing. It's just my theory. I may buy a set of 100kg front and 50 kg rears to see if this might be a hot street setup. I still like how darty the car is with 125F and 80R.
My test track for suspension is a high speed connector ramp from 101 South onto 85 North. If the car doesn't feel stable at 100mph through here, than it's not on the money.
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Louis
1987 75 RS 24V
1987 Milano Verde ex RS Racing Special (1st RS kit in USA!!!)
2004 BMW M3
2002 Porsche Boxster
Last edited by Potenziato; 05-02-2007 at 08:10 AM.
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05-02-2007, 08:40 AM
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As long as you have a very unbalanced suspension setup front/rear (read: 116 car) you will totally change the setup when switching tires. High grip means more lateral load which generates more roll.
Apex hitter: suspension preload is a myth, or you are using straps or similar which gives zero rebound and that is really not intelligent.
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05-02-2007, 08:46 AM
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Quote:
Originally Posted by BigSwede
Apex hitter: suspension preload is a myth, or you are using straps or similar which gives zero rebound and that is really not intelligent.
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Preload on the shocks is not a myth! I have spent days testing at the race track where the only settings we change are ride-height, rake, and preload! It can make drastic changes.
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05-02-2007, 09:02 AM
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How do you define preload then? How can you load the suspension with more then the weight of the car?
Changing ride height and rake will naturally change the handling but how do you physically change preload?
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Mats Strandberg
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05-02-2007, 09:07 AM
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How do you adjust preload on a shock?
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05-02-2007, 09:08 AM
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Quote:
Originally Posted by BigSwede
How do you define preload then? How can you load the suspension with more then the weight of the car?
Changing ride height and rake will naturally change the handling but how do you physically change preload?
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Quote:
Pre-loading does not change roll resistant rates (rate from the springs and anti-roll bars). It changes the degree of jacking, and therefore the 'anti-roll' "stiffness" contribution of that effect.
For those who are unfamiliar with jacking effects, think of it as being the same thing as anti-dive, except lateral, not longitudinal - ie - a self-stiffening of the suspension in reaction to the lateral loads being fed thru the a-arms.
When finding that amount of preload that works for your car, you are actually looking for the amount of force left on the spring ( and weight left on the tire) for the particular lateral g level at which the push becomes noticable. It is at lateral loads above that level that you are changing the effect of jacking by actually reducing it a bit.
When the shock tops out, the ACTUAL roll center shifts to (nearly) the center of the inside tire contact patch - for any further roll, the car now pivots about that point. The only way it can pivot is to lower itself, and it is in that lowering that the jacking is reduced.
Roll rate from the springs and bar are not affected at all, as for every degree of roll, the distance traveled (for that remaining spring and bar link) is doubled, and the rate per degree stays the same.
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By "physically" change, do you mean how do I go about changing preload on a spring?
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05-02-2007, 09:14 AM
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Alright. To adjust the preload on the Dynamic Dampers we use (and just about all the other dampers out there)..
I turn the the circled part of the attached image either one clockwise or anticlockwise.
1 inch of compression is about 12 turns, but that varies based on spring rates.
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05-02-2007, 09:17 AM
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Wow, that was a load of mumbo-jumbo... 
Why not just write droop-stops in plain language?
"When the shock tops out"? You mean to tell us that you ride on full rebound end of the shock? jeez, that must be a pretty perfect track without any change in radii in any of the three left handers. 
I see what you mean by "preload", but I have to say that in any form of racing that you actually "tune" to preload is just not Motorsport to me.
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Mats Strandberg
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05-02-2007, 09:22 AM
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Quote:
Originally Posted by BigSwede
Wow, that was a load of mumbo-jumbo...
Why not just write droop-stops in plain language?
"When the shock tops out"? You mean to tell us that you ride on full rebound end of the shock? jeez, that must be a pretty perfect track without any change in radii in any of the three left handers.
I see what you mean by "preload", but I have to say that in any form of racing that you actually "tune" to preload is just not Motorsport to me. |
Oh yeah, full rebound on those identical left handers.
edit: The series we are running in this year has a different tire brand and compound than last year. Our cars are the same, but our setups at the same tracks need to be drastically changed to compensate for the new rubber!
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05-02-2007, 09:27 AM
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Never ever mention F1 and Champ Car in the same sentence again because it's just wrong. There is NO team in F1 that runs their suspension to their end positions and expect the wheels to generate any side load, F1 cars sometimes do lift their inside front wheel but don't expect them to "tune" to a preload.
What series are you in btw?
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Mats Strandberg
GTV 2000 -77 [URL=http://www.alfapower.nu/gallery/gtv]Pics[/URL] <= These are picture links you know...
75 Turbo -87 *sold* [URL=http://www.alfapower.nu/gallery/75T-Modificata]Pics[/URL] <=
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05-02-2007, 09:34 AM
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Quote:
Originally Posted by BigSwede
Never ever mention F1 and Champ Car in the same sentence again because it's just wrong. There is NO team in F1 that runs their suspension to their end positions and expect the wheels to generate any side load, F1 cars sometimes do lift their inside front wheel but don't expect them to "tune" to a preload.
What series are you in btw?
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No one runs their suspensions to the end positions  (well actually, the backmarkers may) That was just some example post I quoted.
We are in the silly F2000 Championship Series http://www.f2000championshipseries.com/ with 8 cars.
Race #1 has some pretty good action, watch from minute 7 to 8:30 or so,
Race #2 videocast is bad because it was pouring rain, but still fun. We spun out in the lead on the last lap 
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05-02-2007, 09:45 AM
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Quote:
Originally Posted by Grant
Any idea what your alignment is like up front? I'm alwasy curious to see what RS guys are doing for negative camber up front.
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Medium: Toe in 4mm, Camber 2.5 degrees
Radical: Toe in 6mm, Camber 4 degrees
Castor: Governed by the space available in the A arm
Also, ride height as measured at the jack points is supposed to be always set at 1 cm higher than the front.
The ride height recommendation I have is 14.5cm front and 15.5 cm rear.
So when I dump the spindles, I should have 2.5 degrees of negative camber.
I thought according to my old info, 100kg front was recommended for four cylinders. I have a note for bad roads to use 115 kg fronts on a V6.
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Louis
1987 75 RS 24V
1987 Milano Verde ex RS Racing Special (1st RS kit in USA!!!)
2004 BMW M3
2002 Porsche Boxster
Last edited by Potenziato; 05-02-2007 at 09:57 AM.
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05-02-2007, 10:28 AM
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toe in 4 and 6 mm what is explanation of this setup  |
05-02-2007, 11:12 AM
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F2000? Looks like a local series? As I can actually see the pic you attached now I understand nothing. To me it looks like the only thing you would change by turning that "nut" is ride height. The only way to "adjust" preload withouth changing ride height would be to lenghten or shorten the stroke of the shock itself.
Potenziato: How old are those numbers? Are they from Ron himself? Looks like we will have something do discuss at the dinner table 1½ week from now because I totally agree with TS-turbo. | |
