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Advanced Suspension Geometry and Design

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Grantmac
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Re: Advanced Suspension Geometry and Design
February 04, 2014 09:13PM
Flip side of the pro/anti-dive geometry topic:
How does each effect the ability of the tire to find traction under acceleration?

In my foggy thought process I figure the pro-dive geometry will result in more body movement rearward under acceleration but greater weight actually being maintained on the tires.

-Grant
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Reamer
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Re: Advanced Suspension Geometry and Design
February 05, 2014 10:08AM
Quote
Grantmac
Flip side of the pro/anti-dive geometry topic:
How does each effect the ability of the tire to find traction under acceleration?

In my foggy thought process I figure the pro-dive geometry will result in more body movement rearward under acceleration but greater weight actually being maintained on the tires.

-Grant

Do you mean lesser weight actually being maintained on the rear tires? Or do mean more wieght staying on the front tires as the body rolls to the rear?



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Edited 1 time(s). Last edit at 02/05/2014 07:09PM by Reamer.
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Grantmac
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Re: Advanced Suspension Geometry and Design
February 05, 2014 07:24PM
Quote
Reamer

Do you mean lesser weight actually being maintained on the rear tires? Or do mean more wieght staying on the front tires as the body rolls to the rear?

If one were to somehow place a scale under each wheel under acceleration how would the weight shift with the different geometries?

I have to think of it in terms of corner weighting a car. If you want more weight on a given wheel you raise it's ride-height. If the geometry raises the nose under acceleration is it in fact actually increasing the downward force on the front wheels? Is it much like using anti-squat in the back of a RWD increases the load on the tires under acceleration.

I know everyone wants to talk about braking and whatnot but finding traction to accelerate earlier in the corner has always seemed like the tough part for FWD.

I've only played competitively with go-karts, autocross and dirtbikes, I dunno rally suspension from a tuna sandwich, so I might be right out in left field.

-Grant
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Reamer
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Re: Advanced Suspension Geometry and Design
February 06, 2014 11:33AM
This is hard also. I really only know from scaling my oval track cars. There are many ways to add wieght to a given tire. You can change load on any given tire and keep the same ride hieght.

Raising the front of the car doesnt add wieght to the front tires. On scales if you raise the RF ride hieght it will show more weight on that tire. Unfortunatly it took the weight off the LF tire putting you back to the same front wieght as you were. Only now the RF is holding more wieght then the LF making the car unbalanced. So you then raise the LF ride hieght to get the weight back on the LF. Now the front of the car is higher and yet the front weight on the tires is back to what it was before you raised the car. Now your just higher in the front.

What your asking is a good question and I think this is what Paul and all of us want to know more about.



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Pete
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Re: Advanced Suspension Geometry and Design
February 06, 2014 12:26PM
Quote
Grantmac
Flip side of the pro/anti-dive geometry topic:
How does each effect the ability of the tire to find traction under acceleration?

In my foggy thought process I figure the pro-dive geometry will result in more body movement rearward under acceleration but greater weight actually being maintained on the tires.

-Grant

That's what I'm thinking. When you stick anti-this and anti-that into your figurings, the dynamic loads on the tire don't have much bearing on where the chassis is on the suspension.

And the anti's don't anti if you don't have grip to begin with...

I think a lot of why antidive doesn't work in the front for braking is that to get it, unless you get wild with upper control arm/strut angle, you will end up with a suspension motion that moves the wheel forward under bump. That's not conducive to soaking up bumps no matter if you're braking or accelerating or what.

Maybe everyone should go to VW torsion beam front suspension smiling smiley (gack no!)



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Reamer
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Re: Advanced Suspension Geometry and Design
February 06, 2014 01:01PM
If I were to throw a test set up on a fwd car looking for more traction I would add tons of rebound in front struts soften front springs and stiffen rear springs.

My thinking would be get the wieght on the front tires under braking. Then hold it there with the front rebound. And have the rear stiffer to not let the weight get to the back of the car. This should make about as much bight as you could in a fwd car.

Now if this would be drivable in rough conditions I dont know?



First rally 2013
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Total rallies as driver 6
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john vanlandingham
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Re: Advanced Suspension Geometry and Design
February 06, 2014 03:16PM
Quote
Reamer
If I were to throw a test set up on a fwd car looking for more traction I would add tons of rebound in front struts soften front springs and stiffen rear springs.

My thinking would be get the wieght on the front tires under braking. Then hold it there with the front rebound. And have the rear stiffer to not let the weight get to the back of the car. This should make about as much bight as you could in a fwd car.

Now if this would be drivable in rough conditions I dont know?

ACK! I maybe should phrase it clearer...OK then ACK!!!!

Uhm er, we have BUMPs here and there. And when we brake---those that bother too anyway, we hit a bump, suspension moved in, the another, it moveds in more and add braking and a bump it moves in MORE---no in left.
Then we hit another bump..while on the bump stops...

¿ǝnןɔ ɐ ɐʎ ǝʌıƃ sıɥʇ sǝop ¿uǝɥʇ suǝddɐɥ ʇɐɥʍ ʍouʞ noʎ


˙ɟooɹ ǝɥʇ uo uıɐd ǝɥʇ sǝɥɔʇɐɹɔs uǝʇɟo ʇı 'ɹǝʍoןs ʇsnɾ ʇou sı sıɥʇ ǝʞıן punoɹɐ ƃuıʌıɹp ǝsnɐɔǝq ˙uo sǝʞɐɹq ǝɥʇ dǝǝʞ ¿ǝɹǝɥʇ ʇı dǝǝʞ oʇ ʇuɐʍ puɐ pɹɐʍɹoɟ ʇɥƃıǝʍ ʇuɐʍ
˙˙sʎɐʍǝpıs ƃuıoƃ ʎq ɹo ƃuıɹǝǝʇs puɐ sǝʞɐɹq ɥʇıʍ ʎןןɐuoısɐɔɔo puɐ ʎןuıɐɯ sǝʞɐɹq ɥʇıʍ ʇɥƃıǝʍ ǝɥʇ ǝʌoɯ ǝʍ puɐ 'sʎɐʍ ɥʇoq ƃuıɹds ǝɥʇ ƃuıןןoɹʇuoɔ ɹoɟ ƃuıdɯɐp ɥƃnouǝ ʇsnɾ ɥʇıʍ dn uoısuǝdsns ǝɥʇ ʇǝs ǝʍ ʎɐs ı os ˙ɹǝʇsɐɯ oʇ ɯǝʇsʎs ןɐɔıʇıɹɔ puɐ ןɐɹʇuǝɔ ǝɥʇ ǝɹɐ sǝʞɐɹq ǝɥʇ ʇǝɥʇ ʎןǝʇǝɹɐdǝs puɐ 'ǝʌoɯ oʇ spǝǝu uoısuǝdsns ʇɐɥʇ uoısuǝɥǝɹdɐsıɯ ǝɥʇ ɹǝpun ɹoqɐן ı



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Grantmac
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Re: Advanced Suspension Geometry and Design
February 06, 2014 03:28PM
Wouldn't running a bunch of rebound also result in less traction because the wheels wouldn't be able to respond fast enough to chances in surface?
I understand jacking-down from autocross and motorcycle racing, very comfortable feeling on a rough surface.

However the idea of running stiffer rear springs vs. lighter springs and a heavier sway-bar definitely makes sense to me.

-Grant
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buerckner
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Re: Advanced Suspension Geometry and Design
February 06, 2014 03:51PM
Quote
Grantmac
....
I know everyone wants to talk about braking and whatnot but finding traction to accelerate earlier in the corner has always seemed like the tough part for FWD.
......
-

When properly powered it is, when (as normal) underpowered is not so much of an issue. Better to slow as little as possible and maintain your speed through the twisties as it takes FOOOOORRRRREEEVVVVVEERRR to regain that lost speed.


Quote
Grantmac
However the idea of running stiffer rear springs vs. lighter springs ......
-

Too heavy in the rear and they get very skatey at speed. But considering the weight different front to rear we were running stiffer rear springs than front. IIRC we ended up with 180lb/in front and some progressive springs that were around 160 at ride height.
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john vanlandingham
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Re: Advanced Suspension Geometry and Design
February 06, 2014 04:06PM
Quote
Grantmac
Wouldn't running a bunch of rebound also result in less traction because the wheels wouldn't be able to respond fast enough to chances in surface?
I understand jacking-down from autocross and motorcycle racing, very comfortable feeling on a rough surface.

However the idea of running stiffer rear springs vs. lighter springs and a heavier sway-bar definitely makes sense to me.

-Grant

Too bad its backwards



John Vanlandingham
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john vanlandingham
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Re: Advanced Suspension Geometry and Design
February 06, 2014 04:18PM
Quote
buerckner
Quote
Grantmac
....
I know everyone wants to talk about braking and whatnot but finding traction to accelerate earlier in the corner has always seemed like the tough part for FWD.
......
-

When properly powered it is, when (as normal) underpowered is not so much of an issue. Better to slow as little as possible and maintain your speed through the twisties as it takes FOOOOORRRRREEEVVVVVEERRR to regain that lost speed.


Quote
Grantmac
However the idea of running stiffer rear springs vs. lighter springs ......
-

Too heavy in the rear and they get very skatey at speed. But considering the weight different front to rear we were running stiffer rear springs than front. IIRC we ended up with 180lb/in front and some progressive springs that were around 160 at ride height.

For those numbers to mean hannything we need to know vehicle weight, and travel.



John Vanlandingham
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Mad Matt F
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Re: Advanced Suspension Geometry and Design
February 06, 2014 04:48PM
John,

Didn't you do some offset stuff for Volvo's to use ears instead of plug-in's...

Couldn't you go one step further?

So with the rear steer upright (like the justy, wink, wink) you could move the strut forward as seen in my CAD drawing below. Now you have 2013 WRC travel for the cost of a RWD front strut cartridge leaned back a bit...

Sure it doesn't follow the true arc, but it didn't in the first place, maybe just changing the plane it travels on a bit.

Oh yeah, copywrite matt follett, patent pending, this is the next "gonna save rally, make a million" idea
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fliz
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Re: Advanced Suspension Geometry and Design
February 06, 2014 05:09PM
Is it bad when I looked at the picture the first thing I saw was some weird torture device that attaches to your skull?
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john vanlandingham
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Re: Advanced Suspension Geometry and Design
February 06, 2014 05:33PM
Quote
fliz
Is it bad when I looked at the picture the first thing I saw was some weird torture device that attaches to your skull?

No you're probably thinking "What could be a a relief from reading 50-60 of the posts in this thread?" And something that crushes your skull from the outside would be a relief compared to reading utter wankity wank shit that makes you head want to explode from its inanity and pointlessness.



John Vanlandingham
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john vanlandingham
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Re: Advanced Suspension Geometry and Design
February 06, 2014 05:37PM
Quote
Mad Matt F
John,

Didn't you do some offset stuff for Volvo's to use ears instead of plug-in's...

Couldn't you go one step further?

So with the rear steer upright (like the justy, wink, wink) you could move the strut forward as seen in my CAD drawing below. Now you have 2013 WRC travel for the cost of a RWD front strut cartridge leaned back a bit...

Sure it doesn't follow the true arc, but it didn't in the first place, maybe just changing the plane it travels on a bit.

Oh yeah, copywrite matt follett, patent pending, this is the next "gonna save rally, make a million" idea

Your a genius..2 things to do: 1 you have some photo you sent me of the knuckles. Post that.. second do me a big favor and measure and make a drawing of that 240 so called "Haitch Dee"...I have saved somewhere the valviing for those and its simple limp---for a 2900lb street car, but for a svelt little thang like the Mighty Justy it might be just about right.. so LOA and how much of the 40mm body from the yellow case to the obvious end of travel (I think there is a band of unchromed tube at the top..measure to there) I have a bad feeling the travel is kinda short.



John Vanlandingham
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www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
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