FabioSPRINT

Hi, I originally post this on the suspension section of the forum, but after that I was adviced to post here, so, here it is:

I'm starting a fwd project, and wanna build a full tubular chassis in the next month. One of the doubts I have is HOW a wheelie bar can improve the traction on a FWD?

I mean, it's being use for long time now and most people notice great gains using it, I know, but I want to understeand how it makes the car goes quicker.

Is it only by lenghten the car? It's by stiffing the rear end? Or the opposite, by making it softer until the wheelie reach the ground?

In that case, why the first wheelies touch the ground?

Also, if you built a suspension with a damper with 5in of journey in the rear...and after that a solid rear end...because when the wheels touch the ground is like a solid rear, don't?

If it was only to stop the rear end to go down when the car launch, why they are so long like these?



Well, anyone one who know, have data or understeand the fisics theory about, it's just doubts I have...

Thanks!

DaveF

think of it as using a short lever and a long lever, it is much easier to apply more pressure, using the long lever.

they are setup with low spring rates on the rear suspension, so the car will squat onto the bars, and sometimes ride them for a good portion of the track. on the top end, the front tires grow/expand... the bars help keep the front tires from "unloading"...

1992Si

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DaveF &raquo;</TD></TR><TR><TD CLASS="quote">

they are setup with low spring rates on the rear suspension, so the car will squat onto the bars, and sometimes ride them for a good portion of the track. on the top end, the front tires grow/expand... the bars help keep the front tires from "unloading"... </TD></TR></TABLE>

You don't need lots of rear suspension travel. Just enough for the rule box.

Like Dave said, As the slicks grow the bar forces the slicks back into the track. Think about when the slicks start to grow... that's when the wheelie bar starts to help.

FabioSPRINT

Oh, I see...like the lever analogy, it really is to prevent the rear squating, but pivoting in a point much further, forcing the front tyres more than they would if the car were pivoted by the rear tyres...

But, to understend more, the wheelie has no suspension on it, so, when the little wheels touch the ground, the car has no rear suspension work, is that it?


Modified by FabioSPRINT at 6:52 AM 12/11/2007

1992Si

Correct, basically. It just limits the squat. The shocks would still allow the tires to follow the small changes in the pavement. But that's really over thinking...

Here's a photo of rota92's car on the bar in 2nd gear. Look for the yellow hatch in the top left photo. That's the best I can do here at work.

http://www.thespeedlounge.com/...age=2




Modified by 1992Si at 12:02 PM 12/11/2007

jjspec

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rota92 &raquo;</TD></TR><TR><TD CLASS="quote">

The car still has rear suspension for weight transfer as you still want to have some when the car doesnt need the bar as much once everything is 'settled'

I'm sure someone else can explain the exact physics of what happens throughout the pass though</TD></TR></TABLE>
When a vehicle accerates weight is transfered to the back therefore unloading the front tires causing a loss of traction resulting in wheelspin. The wheelie bars help keep the weight transfer to a minimum by putting more weight on the front tires when they grow. You just don't want to preload them because when the fronts grow the rear tires could possibly be off the ground or close to it. Hope that helps.

word itz chris

This guy needs to learn how to spell.

But as its been said, as the slicks grow and the car starts to squat on the rear, the wheelie bars stop the car from going as far as it would, therefore giving you more traction.

T4 Neon

Another way to look at it, is they lengthen your wheelbase by 4+ feet when the weight transfer causes the wheelie-bar wheels to make contact with the track. This resists further weight transfer / unloading of the front wheels.

tony1

You guys are making it way more complicated than it is. It simply extends the effective wheel base making it harder for the front end to lift.

The amount of traction you have is directly proportional to the amount of weight on the front tire. If any weight transfers back, it comes off the front tire and you loose traction.

And they are on the ground from the starting line until you lift the throttle, they do not come up at half track if the car is even remotely fast and setup right.

wHOAlly

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 &raquo;</TD></TR><TR><TD CLASS="quote">You guys are making it way more complicated than it is. It simply extends the effective wheel base making it harder for the front end to lift. </TD></TR></TABLE>

heres a visualization.

do push ups the proper way, now do them on ur knees instead of ur feet.

Real_E-AT

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wHOAlly &raquo;</TD></TR><TR><TD CLASS="quote">

heres a visualization.

do push ups the proper way, now do them on ur knees instead of ur feet.</TD></TR></TABLE> My wife does them on her knees all the time.

tony1

I was trying to think of a good way to explain it, the push up deal is perfect.

wHOAlly

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ChopSuey &raquo;</TD></TR><TR><TD CLASS="quote"> My wife does them on her knees all the time. </TD></TR></TABLE>

that sounds SOOOO bad...lol

paulzy

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ChopSuey &raquo;</TD></TR><TR><TD CLASS="quote"> My wife does them on her knees all the time. </TD></TR></TABLE>

that's a self set up if you ask me

Fabman

haha

FabioSPRINT

Ok...the push up example is good.

Sorry about the spell, I'm not much good in english.

Rage Cayman

If you have to let the guys here explain wheelie bars effectiveness and traction issues, my suggestion would cancel that Pro FWD idea until you learn more..

adrenalinjunkie

Did you say you were going to build a full tubular chassis in the next month. Keep us updated with pics, thanks.

FabioSPRINT

Well... I'll will built it anyway.


And, sure, I'll keep it updated. I believe the best thing is create a thread for it.

Thanks!


Modified by FabioSPRINT at 11:34 AM 12/15/2007