Just curious what you drag racers know about this stuff. I have my opinions, so ill kick it off with a little bit of info on why honda unibody cars are going so fast and their suspensions are not breaking.

ever wonder why the upper balljoint is located above the tire? This steering knuckle's upper ball joint is placed ABOVE the tire to obtain near "0" scrub....not inside the wheel, which, restricts the location of the ball joint and the brake packaging.

Also, the "high knuckle design" allows you to reduce the input steering effort by decreasing the kinpin inclination angle, effectively lengthening the upper control arm. If you strain gage the knuckle, you will see that the UCA loading is roughly 1/3 to 1/4 the load on the lower arm, allowing the "thin contour" of the Honda knuckle to be durable.

anyone else care to discuss this?

 

I cant offer anything, but I'll certainly be willing to learn what I can from this discussion...

 

unfortunately, with big turbo cars running big/wide slicks, there isn't enough room for wheel backspacing. Scrub radius increases, and so does track width.

Anyone make a Honda replacement knuckle with more clearance for the wheel/tires?

I run a VW which came with a front strut setup. I've built custom strut housings that move the casing inboard (along with camber plates that move the upper mounting point farther inboard). The geometry looks a little bit like those running custom struts on the Hondas (JoJo, Gary, etc). We've had to make ajustments to the spring/shock rates since moving the strut inboard. This is definitely NOT the ideal setup for a road course car, but for drag racing, it's working.

I'd like to strain gauge the steering components to see what kind of stress and deflection/flex the cars are getting with the very wide track widths.

 

great info guys. but i was wondering about the strain thats caused in the hub where the shock meets on setups similar to garys, jojo', and kenny? thnx

stephs, lisa, chris seem to well without....

 

bump for this.....lets get a discusion goin...

 

We have a road race guy that dynos at our shop alot...He came one day when our race car was sitting in the shop and was staring at the front suspension. He talked about things we already knew and some that actually lost me. One thing I know about is the bump steer which is easily fixable. As far as the upper control arm...I know that with as low as our car sits , its not in a very good position. We need to actually cut the knuckle down to bring the upper control arm t down a little bit because right now there is way too much change in camber per inch of travel. Believe it or not the knuckle is forged steel which can be welded up very nicely w/o worrying about failure. I noticed that the Moroso car had something similiar done, also Larry Herrings lime green CRX has had the same thing done too. The one thing that my road race buddy said was something about the way steering axis is configured on these cars create more and less scrub and more control. This is the imagine line that goes through the upper and lower ball joint down to the contact suface. He said that the point that it touches the contact surface in relation to the tire makes a big difference in scrub and control. That point should be in the center of the contact patch of the tire...which on a stock Honda is perfect....but as soon as change the wheel backspacing and tire size you change this drastically. Kinda when you put a 17" low pro on a civic thats been lowered and it darts all over the place and you think its because you got these stiff wide tires causing it....

SAIA = steering axis inclination angle.....thats what its called....

Howard

 

One big question with the control arm length, angle, etc discussion is ...

How much suspension travel are we getting?
(of course I'm talking about fwd drag racing, particularly purpose built racecars with and w/o wheelie bars).

Our All-Motor Civic get ZERO compression travel in the rear. But we run it without wheelie bar (yet).
My car requires only 1/4" of compression before the wheelie bar is solidly on the ground.

So on an ideally flat/smooth track, how much travel will the front suspension have? Remember that alot of the front end "lift" that you might see at the launch could be tire growth.

I see more and more race cars with shock travel sensors. It would be fantastic if we could compare everyone's datalogs !!!
If we are seeing very little travel, that gives us a little more window in our suspension geometry tuning.

Anyone remember when people where using solid rods for front suspension!?!?!

One thing we also need is vehicle height sensors, to show much "lift" is simply tire growth.

One reason I dont' like to run severely low tire pressure is that cars seem to get a little unsettled after a shift. As the car unloads and "falls" back down, it might be 'bouncing' off the tire as it loads up again in the next gear. We use "flatshift" technique now, which gives very little time between shifts. So that 'bounce' is not noticable.

So the info we need is:
How much travel is the front seeing in 1st gear?
How much throughout the rest of the track?
How much tire growth are we getting?

Then we get into
What camber changes are we seeing in a run?
How much toe change is occuring? (from bump steer and component flex)

One thing I'd like to see (just for testing and comparison) is for cars to stage off the rear wheels. This would eliminate the huge variable of Rollout, and let us see what cars are really 60 footing well.


FFgoeff... which program are you using for suspension design (saw the screenshot in the other thread)

 

Nice to see a drag car with adequate brakes

 

i really dont know what im gonna do for front suspension on my crx, does anyone know what erick's racing did on his new crx? im gonna get some books tonight and start reading...


Modified by dmotoguy at 3:28 AM 10/22/2003

 

here is a shitty pic of my current suspension, it consists of stock torsion bars(22mm) and stock shocks. im trying to teach myself suspension design, but im not finding the best books/sites. im shooting for about 400hp at the crank, and dont know what im gonna need to handle it... traction bars seem like they would be needed, but im running into problems designing those too... anyone have any ideas on either what i should do or what i should read so i can get some designs done... if this is off the topic of the post i can delete it and post a new thread. thanks

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AR Fab &raquo;</TD></TR><TR><TD CLASS="quote">
SAIA = steering axis inclination angle.....thats what its called....

Howard</TD></TR></TABLE>

SAI (Steering Axis Inclination)
SAI is the angle between the centreline of the steering axis and the vertical line from the center contact area of the tyre (as viewed from the front of the car). SAI isn't adjustable, but provides (together with the caster) the steering with self centering and directional stability. With SAI you don't need a high positive caster and the drawbacks that gives. A variation or +/- 1° from the given value may indicate a problem with the steering / car damage. (eek!)

 

One problem I see with the factory Honda A-arms for drag racing is that you can not get enough caster. With the strut set-up like gary's you can get 8-10 degrees of caster which is ideal for drag racing.

 

Almost seems like a 9" solid axle up front is the way to go? No camber change!

 

hehe Only really quick gear changes in the solid axle.....Man I wish i hit the lottery.... me and Bob would get rich quick

 

the more caster you have the more of the car you have to pic up as you turn, the harder it is on the rack,caster help win you back up the car,i think on a fwd you can run less to help the driver

 

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chassis Guru &raquo;</TD></TR><TR><TD CLASS="quote">One problem I see with the factory Honda A-arms for drag racing is that you can not get enough caster. With the strut set-up like gary's you can get 8-10 degrees of caster which is ideal for drag racing.</TD></TR></TABLE>

I remember JUN's old HB drag car they chopped the upper ball joint off and welded it back on next to the stock location.

 

thay may have cut to make it shorter (spindles) so that they can fix the camber,becase of lowering the car

 

I could be adjusted when building controls arms though.....

Howard

 

a shorter spindle with the stock UCA mountin position would wreak havoc on a camber curve. The arms would not intersect at the intant center (there is none) and there would be chaos any time the upper arm is angled up and away from the lower.

anyone ever see where it mounted?

 

but the arm on top is so short that ther is to much -camber win the car is lowered

 

Camber would increase between shifts on this setup. Talk about a hell of a ride.

SO what about a dual pivoting upper control arm that lies inboard of the tire? It would put the actual pivot point near the center of the tire yet give you room. I think Audi A4s use it and 99-02 accord rear suspensions use it. Or am I smoking crack?

 

is there any possible way to make a fwd "plant" the tires??? without going to a 9 inch setup that tony speaks of???

is it possible to have a car that would get lift on the launch but still have the chassis and suspension work to push the front into the ground, thus giving the cars more traction?????? im not talking about wheelie bars here.

 

an idea were thinking of trying is, making the double a arm like most of the pro fwd cars run but mount the strut to the top a arm instead of the lower. since im not an engineer or chasis builder i figured id throw it out there and see what yall think.

 

Nate what is this "flatshift" you refer to.