Suspension Control

[ddewhurst]

When an IT race car rear suspension/rear axle has 4 links for longitudinal location & traction control can these OEM links be replaced with non OEM links ?

ruel 17.1.4,D.5.c. & the GCR Glossary

Have Fun
David

[Greg Amy]

...and the make/model of this car is...?

[ddewhurst]

Greg, I was trying to make the question generic. But being that you asked, ZOOM ZOOM 1st gen.

Have Fun
David

[bill f]

Our understanding, dealing with a Mustang 4 link suspension, was that one could make ineffective the upper links working with the free bushing rule, and add a working repositioned upper traction bar under the rule governing traction control devices.

Many running this chassis attemped to do this. For some unknown reason, we had a virtually ideal bushing/ride height/spring package, and never needed to go this route. We had workable, acceptable handling without the vices that others attributed to this chassis.

Hope this helps.

Good racing.

Bill

[ddewhurst]

Bill, I race a 1st gen Mazda RX-7 in ITA/7 within the CenDiv mostly. The lower links are parallel with the chassis, but the upper links are not parallel with the chassis. The OEM bushings are rubber & with body roll the rubber bushings bind as compared to having Heim bearings. The reason I asked the original question is because a couple parts houses under the bushing rule charge approx $280.00 for the two OEM lower links with Heim bearings & spacers. By using tie rod sleeves with threaded rod ends I can do the same thing for less than $100.00. At this time I have the upper two links in place with air/foam bushings & use the Heim Tri-Link at the center of the car.

Have Fun
David

[Knestis]

Apropos of nothing, I think that the "air/foam" bushing is a really elegant solution that doesn't rise to the level of "tortured and strained."

K

[ddewhurst]

***The reason I asked the original question is because a couple parts houses under the bushing rule charge approx $280.00 for the two OEM lower links with Heim bearings & spacers. By using tie rod sleeves with threaded rod ends I can do the same thing for less than $100.00.***

Come on K, within rule 17.1.4,D.5.c. & the GCR Glossary can I use the tie rod sleeves & rod ends at $100.00 instead of the OEM links with Heim bearings & spacers at $280.00 ?

Have Fun
David

[dickita15]

david I feel your pain but I can see no way that you can replace the links with non stock ones, at least legally.

dick patullo
ita rx7

[This message has been edited by dickita15 (edited May 08, 2005).]

[Knestis]

I didn't get too technical because I'm sitting on a deck in Beaufort, NC, onstenibly traveling on business. The crab cakes and beer that I just enjoyed didn't seem SO businesslike but I don't have my GCR on this machine.

My intitial thought is that, while you can ADD suspension locating devices, there is probably no provision that allows you to remove the ones that came on the car in the first place.

K

[RSTPerformance]

Originally posted by Knestis:

My intitial thought is that, while you can ADD suspension locating devices,
K

Kirk,

Can you expand on this?? I am confused oabout what you are talking about and since I am redueing my suspension maybe I can take advantage of whatever you are talking about.

Thanks
Stephen

[Knestis]

Again, I don't have my rulebook but it's allowed to add Panhard rod and other axle location devices, to solid rear end cars.

K

[Bryan Watts]

Entire GCR or just the ITCS available for download here:
http://www.scca.org/Club/Index.asp?IdS=022...00&x=030|057&~=

[ddewhurst]

The rule 17.1.4,D.5.c. Suspension Control

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.

The 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.

Within a four link rear suspension if the links didn't resist a torque reaction the rear axle would not function. Second the word SUBTITUTED is used.

Come on K. & all other rules followers.
David

[Knestis]

You may well have a case there, Mr. D. I'd think that someone would have tested that one through the protest and appeal processes.

K

[SilverHorseRacing]

David,

If I remember correctly, that's basically the argument that made the Steeda 5-link allowed into A/S cars. Totally legal, and both upper factory arms are MIA.

------------------
-Marcello Canitano
www.SilverHorseRacing.com

[lateapex911]

This is/was posted under Rules with so so responses. I have a 1st gen RX-7 ITA/7 car. The car has a Heim joint 3rd link with the air/foam bushings in the OEM upper links. I would like to have lower links with Heim bearings. Eliminate the bind within the rubber bushings during body roll. I am not crazy about paying a parts house $280.00 for two reworked Heim bearing OEM lower links when I can do the same thing with tube sleeves & rod ends for under $100.00. Therefor please read the rule & glossary & tell me if I would be legal with the tube sleeves & rod ends.
The rule 17.1.4,D.5.c. Suspension Control
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.

The 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.

Within a four link rear suspension if the links didn't resist a torque reaction the rear axle would not function. Second the word SUBTITUTED is used.

Thank You
David

I took the liberty of copying your post in the Mazda section here, as I felt it was clearly written.

Your thought, if I understand you correctly, is that the GCR says you may substitute traction control devices freely if the car was so equipped, and that the GCR definition of a traction control device is: a link that resists axle torque in either compression or tension, and as the lower link on the car resists axle torque (and therefor rotation) in compression, it must be considered a traction control link.

Therefore, you are saying that it is free, and you can just fab up some links and rod ends... and be perfectly legal

And it is interesting and open minded thinking. I think you might just have something there...

------------------
Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

[This message has been edited by lateapex911 (edited May 07, 2005).]

[bill f]

Ya know, I'm now re-reading this for the first time (with some accuracy)...The mention of "...serves no other purpose." leads into an interesting area. Specifically:

When ever one adds a device like a traction bar (one that come to mind is the dual devices used on '70's solid axel cars), but it can be extended to the single torque reaction bar of the Camaro, you WILL have positive alteration of the geometry which depends on the effective length of the device(s).

Also the case with the Panhard rod...suspension now follows the geometry of the device (axle follows the arc of the bar transversly, and has a new roll center created by its position) which is/are different than that of the original factory geometry.

Seems to me the "...no other purpose." has been violated.

Thoughts?

Given the above thoughts: what is actually said, much less intended by the written rule?

Kirk, and Darin...have any thoughts on this?

Good racing.

Bill

[This message has been edited by bill f (edited May 07, 2005).]

[eh_tony!!!]

We've discussed this before, I think.. back maybe as long as a few years ago.

My interpretation is/was that the locating links act against axle torque so it can indeed be considered a traction bar.

I have an email somewhere because I wrote the CompBoard for a clarification. the matter was not put before the board, but whoever replied disagreed with my viewpoint. The issue accroding to him was the 'serves no other purpose'.

IMHO However now, that brings us to redefining 'traction bar'. In reality, the only way a traction bar cannot serve another purpose is for it to be disconnected when there is no axle torque. (like an old ladder bar). Even then, I'll be damn sure that I can make an argument that even that serves as 'ballast' as well.

So, my opinion is that still lies in the defensible gray area.

[ddewhurst]

Come on guys keep the thoughts flowing.

I would like to add another point with respect to the function of the upper two links at the rear of the 1st gen RX-7. But first I'll ask a question. What are the two upper links called & what is their function. We know it's legal to add a center link while leaving the two OEM links in place with air/foam bearings. The upper links are called link traction bars otherwise the center link could not be installed. If one looks at the named devices within the rule the third link is not a anti-roll bar, it ain't a panhard bar & it ain't a watts link. That only leaves one identification within the rule names & that is traction bar. Again the two upper links & the two lower links in a four bar system are dual purpose links. The locate the rearend length wise & radially & they all are link location traction bars.

I'll make them the same length as the OEM links.
David

[lateapex911]

Originally posted by ddewhurst:
Come on guys keep the thoughts flowing.

I'll make them the same length as the OEM links.
David

Well, take it a step further.

IF you are free to take the link bar, and gut the rubber bushing and replace it with one of your own under the free bushing rule, then you are free to use offset bushings, correct? Of course.

So I would think that there would be an allowable range that should meet the criteria. As the openings in the stock peice are about an inch and a half, there is probably a range of at least that available.


------------------
Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]