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PostPosted: April 1, 2016, 11:06 pm 
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Joined: February 18, 2011, 3:02 am
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If you were to build your car's suspension from scratch, specifically to use the car in autocross, what design attributes would you be looking for?


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PostPosted: April 2, 2016, 12:01 am 
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Location: SW Missouri
I have only just begun my build, ease of adjustment seems to be high on my list.


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PostPosted: April 2, 2016, 9:04 am 
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autoxinvr6 wrote:
If you were to build your car's suspension from scratch, specifically to use the car in autocross, what design attributes would you be looking for?
Autocross is a bit like juggling chainsaws - running chainsaws - the car is always in a transition, always doing something to "upset" the balance of the suspension. There almost never a "steady state" like a long straight or a sweeping, banked curve.

I think that's why autocrossers pay so much attention to shocks and swaybars. Good shocks control the rate of suspension movement, especially the slowing down of "cyclic" movement of the suspension. Swaybars limit body roll and keep the car more level. Guess they limit weight transfer too. Between those two items, that seems to be the focus of autocross suspension design. (I think...)

So, really, I'm giving you a non-answer as far as "design attributes" go but I would recommend you consider the shocks other folks in your class are using, what kind of spring rates and swaybars they have, etc. That should get you close to a good setup. You'll probably need to experiment, try some different bars, shock settings and/or shocks to find the combo that works for you. Depending on your car, your driving style, and where you tend to run, the demands on a particular suspension could be different.

And, like the man said, adjustability is a very good thing!

All of this in IMHO, my .02, YMMV, etc, etc.
Good luck!
:cheers:

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PostPosted: April 2, 2016, 9:06 pm 
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Joined: February 18, 2011, 3:02 am
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GonzoRacer wrote:
So, really, I'm giving you a non-answer as far as "design attributes" go but I would recommend you consider the shocks other folks in your class are using, what kind of spring rates and swaybars they have, etc. That should get you close to a good setup. You'll probably need to experiment, try some different bars, shock settings and/or shocks to find the combo that works for you. Depending on your car, your driving style, and where you tend to run, the demands on a particular suspension could be different.



That's kind of why I ask. There's a lot out there about making specific cars handle well but, not much on a suspension specifically for autocross from scratch on a car from scratch.


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PostPosted: April 2, 2016, 9:34 pm 
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Joined: June 8, 2010, 8:02 pm
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Location: White Rock, BC, Canada
I'd suggest that there are two main types of autoX cars:
-point and shoot cars where it's more about getting on the gas in the "straights"
-momentum cars where it's more about not losing speed in the turns

Locosts can be either. If the former, leaning towards acceleration traction, torque, and stability on braking make sense. If the latter, as mentioned, it's probably going to come down to shocks/bars and having lots of rubber. Things that keep you smooth, stable and planted are key. With momentum cars, your most boring run will usually be your fastest.

Most of my seat time is in a Stock Yaris which is the epitome of "momentum car". I'll be running the Locost this summer, which is definitely a "point and shoot" sort of car. Should be..... interesting :mrgreen:

Cheers.
Cory

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PostPosted: April 3, 2016, 5:54 am 
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Location: Sarasota
I found that you are mostly on your own with suspension design for our cars. No one has the same setup as you, as an example small changes in control arm angles make large changes in spring rate requirements.
You should learn to calculate wheel rates (effective spring rate on the wheels). Then build the suspension to the desired wheel rates.

The more adjustments and adjustment range the better. I originally lost about a 3rd of my adjustment range just getting both sides the same. Then if you change the ride height you need a different range again.

I'm currently on the 3rd major changes too the rear suspension and 2nd on the front. But have a small change planned for the rear and an overhaul for the front.

I'm happy to help with more specific questions along the way though.

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Last edited by wrightcomputing on May 1, 2016, 12:54 pm, edited 1 time in total.

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PostPosted: April 3, 2016, 7:56 am 
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I found that you are mostly on your own with suspension design for our cars.
And the congregation shouted "AAA-MEN, BROTHER PAUL!"

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"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom


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PostPosted: April 4, 2016, 11:54 pm 
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I agree with JD that it's all (mostly) about the shocks. That and keeping as much weight as possible on the inside rear tire. I've seen that done in some odd and creative ways.

Shocks are important for the reasons JD gave--in an autocross you're almost always in transition, and that's when shocks are doing their job. You're almost cornering more on the shocks than the springs.

Since you're always (mostly) in transition, you have to figure out ways to get the power down when the car is unbalanced. In a RWD car you try to have equal weight on both rear tires. This usually means a giant front sway bar and/or a really stiff front end/or really stiff front shocks, as much as you can get away with and still make the car turn.

As everyone says, you have to be able to make adjustments, especially to shocks and sway bars. You can't calculate it all in advance, because some adjustments work against other adjustments, and you have to be able to find that spot in the middle that produces the best lap times.


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