"Traction Bar" and a FWD car

[Roy Dean]

First of all:

17.1.4.D.5.c.1 Any anti-roll bar(s), traction bar(s), panhard rod or watts linkage may be added or substituted, provided its/their installation serves no other purpose.

And:

GCR Glossary
Traction Bar - A link to an axle housing or hub carrier which resists torque reaction from the wheel by acting in compression or tension.


And now the question:

Can I replace my factory rear toe links (lateral links) with an aftermarket heim joint equipped "traction bar"? By the letter of the rules, the toe link could be described as a "traction bar" according to the GCR glossary. What do you think?

[Gary L]

I think you're stretching it here...

IMO, a traction bar cannot be a lateral location device, as it would therefore fail the very definition of something that "...resists torque reaction from the wheel by acting in compression or tension." That's not what toe links do for a living, is it?.

[lateapex911]

I'm having trouble picturing the set up, but, the resistance of tq at the wheels occurs on a forward/aft direction, on the longitudinal axis. But, the item you describe has the term "lateral links", which makes me think it's a no go.

But I might not be understanding the set up correcty. More details or pictures?

[PSherm]

I'm no expert, but aren't lateral links on a rear suspension of a FWD car in-effect "control arms"? And control arms are not to be modified from the OEM configuration?

[Roy Dean]

Ok, so so far everybody has responded with the traditional thinking, which is exactly what I thought until I examined the defination of "traction bar". Here it is again:

Traction Bar - A link to an axle housing or hub carrier which resists torque reaction from the wheel by acting in compression or tension.

Lets brake it down:

"A link to an axle housing or hub carrier" - The rear toe/lateral link is a link to the rear hub carrier.

"which resists torque reaction from the wheel" - Without the later link, the wheel will flop around due to torque reaction from the brakes. There is no disputing this, as the rear hub carrier is only free to move up and down (along the axis of the strut), and rotate along the axis stretching between the upper strut mount and the lower control arm bushing. The lateral link does not (and cannot) limit the travel along the strut housing, and thus ALL it can do is limit rotation of the hub carrier. And the only thing that can cause rotation at that joint are forces (which turn into torque's) transfered from the wheel.

"by acting in compression or tension" - it's a two force member with cylindrical bushings at either end, so it can ONLY act in tension or compression.

The only things I can possibly see in the definition of traction bar that may be the killer is that the wording is supposed to mean "a link to an axle housing/hub carrier" (ie, it's an axle housing or an axle hub carrier). Another wrench in the works could be that "reaction from the wheel" is meant to mean "reaction due to power transmission from the wheel.

However, the the lateral link still meets the definition of "traction bar" on all levels. Discuss.

I'm no expert, but aren't lateral links on a rear suspension of a FWD car in-effect "control arms"? [/b]

Not on my car. My Suzuki Swift has dedicated rear control arms (just like the front suspension), and the lateral links perform the same function as the steering links in the front (although, obviously, they don't steer).

[charrbq]

Cancel that, I was reading wrong. Must've had my eyes crossed.

[Conover]

Your missing the torque part, rear wheels on a FWD don't produce any torque.
Not anything like what a traction bar is for, traction. usually you find you've got too much traction in the rear.
I think the torque reaction the rule is describing is the torque from being driven.

[charrbq]

I'm having a hard time understanding why you would want to add ( I assume you're adding) a traction bar to a front wheel drive car. If there is no torque to the rear wheels, which is what it's supposed to limit, why would you think it was needed?

[Roy Dean]

Your missing the torque part, rear wheels on a FWD don't produce any torque.[/b]

Wrong. When I hit the brakes, they produce torque.

I think the torque reaction the rule is describing is the torque from being driven.[/b]

I think thats what was intended, too... but thats NOT what is written.

I'm having a hard time understanding why you would want to add ( I assume you're adding) a traction bar to a front wheel drive car. If there is no torque to the rear wheels, which is what it's supposed to limit, why would you think it was needed?
[/b]

I don't want to ADD one, I want to "substitute" one... the stock one is a piece of stamped steel with cheesy rubber bushings. Even if I could replace it with a new part (which I can't, as it's no longer produced), it's cheaper to replace it with a nice tubular or even solid link equipped with heim joints.

[charrbq]

I feel like many of us running older, out of production cars, you're screwed. Unless you can find a newer, stronger part from a wreck or such, replacing a stock part with a spiffy part such as you're describing is a no-no.

[Z3_GoCar]

I think you're stretching it here...

IMO, a traction bar cannot be a lateral location device, as it would therefore fail the very definition of something that "...resists torque reaction from the wheel by acting in compression or tension." That's not what toe links do for a living, is it?.
[/b]

Alright so remove the toe link and what happens is the wheel moves around, same as without a traction bar, so the bar definetly resists wheel torque. Secondly, any second year engineering student will tell you a link with a rotating connection (i.e. a heim joint) can only act in tension and compression. So by all acounts I think you could replace it same as a traction bar; however, the safe way to go would be to just replace the rubber elements with heim's in the stock stamped piece.

James

[lateapex911]

using the same logic, on a rear wheel drive car, the steering tie rod would then become free using this rules reading, ...right???

[GKR_17]

using the same logic, on a rear wheel drive car, the steering tie rod would then become free using this rules reading, ...right???
[/b]

True. That same logic had people calling coatings lubruicants (and therefore free) by torturing the glossary a few years ago.

[Roy Dean]

I feel like many of us running older, out of production cars, you're screwed. Unless you can find a newer, stronger part from a wreck or such, replacing a stock part with a spiffy part such as you're describing is a no-no.
[/b]

Right. Thats what I thought (and I was prepared to make bushings for the existing old links), until I read the rules to be certain that I could even do that (which, obviously, I can). However, after reading the rules, it looks very much to me that I can use the poor wording of the rule to my advantage.

[Knestis]

Wise man once say, "If rulebook say you can, you bloody well can."

Kirk (free of the bonds of Rules NERDism) :026:

[Andy Bettencourt]

Right. Thats what I thought (and I was prepared to make bushings for the existing old links), until I read the rules to be certain that I could even do that (which, obviously, I can). However, after reading the rules, it looks very much to me that I can use the poor wording of the rule to my advantage. [/b]

IMHO, this is a tortured interpretation. Traction bars are designed to work longitudinally, and see Jake's question on RWD cars (and tie-rods). Understand that once something like this comes up, be VERY prepared to have the rule clarified out-from-under you. Don't invest too much money in your solution because it will soon be illegal.

[Domino]

Wrong. When I hit the brakes, they produce torque.[/b]

Huh? Your interpretation conflicts with the definition of "Traction Bar" you posted. A traction bar resists the opposite reaction the wheel has when torque is APPLIED to the wheel. No torque is applied to the rear wheels in a FWD car.

[gprodracer]

Andy, Jake, et al,



Mark

[Roy Dean]

IMHO, this is a tortured interpretation. Traction bars are designed to work longitudinally, and see Jake's question on RWD cars (and tie-rods). Understand that once something like this comes up, be VERY prepared to have the rule clarified out-from-under you. Don't invest too much money in your solution because it will soon be illegal.
[/b]

I know exactly what traction bars are designed for, but the SCCA defines it as something much broader. As it stands, I can lose no more than $120 by putting in the aftermarket links (and thats if I buy them instead of build them)... so until it's officially illegal.... It'll be there.

Huh? Your interpretation conflicts with the definition of "Traction Bar" you posted. A traction bar resists the opposite reaction the wheel has when torque is APPLIED to the wheel. No torque is applied to the rear wheels in a FWD car.
[/b]

Every force has an equal and opposite reaction. The same is true for torques. So while you say no torque is "applied to the rear wheels in a FWD car", you are mistaken. The wheels, during braking, have TWO torques applied to them. One is the the force of the road on the tire times the outside radius of the tire, and the other is the force of the brakes times the effective radius of the [in my case] disc.

Additionally, torque is also applied to the wheel not only about the axis of the wheel rotation itself, but about the axis of the strut mount/control arm bushing... these torques being applied via normal racing accelerations (traditional acceleration, lateral, braking, etc.). Nowhere in the rules does it say that the torques in question must only be from axles....

I know what you are getting at, but the wording in the rules does not specifically state it that way.

Bottom line, if the rules are changed because of me..... I'm out $120, but I've got a neat bar story.

[charrbq]

WOW!!! That's a lot of stretch for a bar story. I can pretty well guarantee that before you get your stuff built, it will be made a no-no in Fastrack. You may only be out $120, but that's a large portion of the price of a tire, or brake pads, or an entry fee, or gas for the tow vehicle, or motel at the track, or any number of things which you need and can benefit from way more than a bar story. Bar stories are made for bench racing, not engineering marvels that you really aren't certain of yourself.

But...if that's the sort of thing that blows wind up your skirt...knock yourself out.