Off-Set Upper A-Arms

[Blue Streak 21]

This weekend I changed out my upper A-arms from the equal length pieces to the off-set ones used by the pro series cars. The change out was very straight forward, with the excetion on the sway bar. I had run my set up with the sway bar on the soft setting. I had to disconnect each end of the bar during the reassembly. Once everything was reassembled, the end of the sway bar was sitting under the spindle. This occluded the hole for the soft setting. Since there are only two holes in the sway bar, I could only attach the linkage to the hole for the hard setting. I had to add a spacer to get the link to be more or less vertical when it's attached to the sway bar. The car is re-aligned and ready for it's next race.
Has anyone experienced this same problem? Any suggestions on potential fixes so I can get the sway bar back on the soft setting?
The reason for the question is that I liked the way the car handled on the soft setting, so I'd like to have the ability to get that adjustbility back. I guess I'll find out how it will handle on the stiffer setting. I expect that the difference will be small, but could take the car towards a push condition.

[AIMidwest27]

Originally Posted by Blue Streak 21

This weekend I changed out my upper A-arms from the equal length pieces to the off-set ones used by the pro series cars..

I don't have an answer to your question, but could you please post a part number and where you got the control arms. I need to make the same change.

Thanks in advance !

[Gatorac]

I installed the offset arms and did not encounter the problem you describe. The lower control arm should end up in just about the same position it was before and shouldn't effect the sway bar mounting at all. Could you post or send me a pic?

I'm sure you won't want the front bar on the firmer setting unless you have a rear bar installed.

There's a thread on her with part numbers and sources for the arms. I originally found some but when they arrive I found out they where made in China. Jim Mcgovern found some made in the USA and posted a link in that thread. "Search" and you shall find....

[AIMidwest27]

Originally Posted by Gatorac

There's a thread on her with part numbers and sources for the arms. I originally found some but when they arrive I found out they where made in China. Jim Mcgovern found some made in the USA and posted a link in that thread. "Search" and you shall find....

Yep, found the thread with the source, now if I can just get a part number that would be great. What about Panoz development for a source ?

Thanks in advance.

[Blue Streak 21]

Jim;
The car is in the trailer, so taking pics is difficult if not impossible until Friday. I'll take some pics and post them Friday evening. I agree with you that the lower A-arm should have stayed in approximately the same place. To get the caster to around 8 degrees, the brake strut rod had to be dialed all the way in (shortest possible length) on both sides. This moved the lower portion of the spindle rearward.
Another slight difference from the previous set up was that I had to move the upper A-arm further out in the slots where it is fastened to the frame. It's a full 1/2" further out in the slot than the previous placement with the equal length (non-offset) A-arm. I moved the A-arms position so that the there would be no interference with the spring. If I put the A-arm in the same position, the spring hit the forward tube of the A-arm. No go.
I've got about 1/2" clearance between the spring and the tube currently. I hope that is enough room so that I don't get interference during suspension travel.

[Gatorac]

Is the UCA mount parallel with the chassis? Mine is. It is close to the spring at full droop. Very close. Less then 1/2", but it does not hit. The LCA should be pretty close to perpendicular to the chassis. My brake strut rod is pretty close to the middle of it's range with 7* caster.

[Blue Streak 21]

Jim;
Thanks for working through the suspension set up with me.
I very carefully measured the placement of the UCA to make sure it was parallel with the chassis. I made each side identical in distance from the vertical frame member. I think the measurement was 1 7/8" between the center of each bolt head to the vertical frame member. This gave me the clearance between the spring and the forward tube of the UCA. So this sounds similar to your set up.
For the LCA, the rod is fairly perpendicular to the chassis. I say this because I have not measured the exact angle. I can't say it's perfectly square, but its close.
The off-set UCA has placed the wheel in the center of the wheel well. It looks much better than when I had the non-offset UCA in the set up. The non-offset UCA pushed the tire forward so that it nearly rubbed the fender lip while the car was static. In corners, I'm sure it rubbed a little bit (okay, it rubbed a lot). This was one of the prime reasons I wanted to change out the UCAs was to get ride of the rubbing.

[Cobra4B]

What's the advantage to using the offset A-arm vs. the standard one? Yes you have to adjust the upper one at an angle the the chassis to achieve proper caster, but what's the big deal?

[Blue Streak 21]

Good question. Maybe one of the suspension guys on the forum can answer.
The main reason I did it was to get the wheel centered in the wheel well. My fronts were rubbing on the fender lip.
I ran the car this weekend and the handling is very consistent with the previous set up. No big changes. Best lap times were almost identical. I ran 1:31's with new Hoosier tires, where I had run that same time with sticky Kuhmos (V710's).

[PanozDuke]

Originally Posted by Cobra4B

What's the advantage to using the offset A-arm vs. the standard one? Yes you have to adjust the upper one at an angle the the chassis to achieve proper caster, but what's the big deal?

Is this another old tread that never got fully answered? Brian's question is important- Why did they switch to the offsets? What is the impact on alignment, if any?

Thanks,
Mike

[eric1h]

moving the top of the arm center backwards increases the negative caster, which in turns increases turn in response typically, but also allows for "dynamic" camber changes that help the cars traction in a turn.

The effect causes the outside wheel in a turn to gain negative camber, while the inside wheel gains positive camber.

[panozracing]

Originally Posted by eric1h

moving the top of the arm center backwards increases the negative caster, which in turns increases turn in response typically, but also allows for "dynamic" camber changes that help the cars traction in a turn.

The effect causes the outside wheel in a turn to gain negative camber, while the inside wheel gains positive camber.

the GTS comes without the offset. Which is better?

[PanozDuke]

Eric,
I think I finally understand the cornering effect of caster. Why not do more than 7 degrees? Are there adverse consequences of pushing it more? How do you know when it's right?
As I understand what Brian B. was getting at is that you can get the recommended caster with the non offset UCA by canting it toward the rear of the chassis which then has it bolted in the slots at an angle, closer to the frame in the rear than the front. He asked, what's wrong with getting the caster doing this rather than going to the offset UCA which can give you the desired camber bolted parellel to the frame (without pushing the lower arm adjustment forward to the point of the tire rubbing on the forward fender lip). Since you can get the commonly prescribed caster either way, the question boils down to why does it matter if the pivot axis of the UCA is parellel to the frame/ perpendicular to the axle axis? As I think about this, it seems to me that caster would change through suspension travel with a canted UCA. More on extension and less on compression. Don't know if that is good or bad or if other changes to toe or camber would be affected differently compared to the parellel UCA geometry. This is making my head hurt, but I need to know if the offset UCA and a parellel setting would be better or if it really doesn't matter. My thought was, if they did an upgrade, there must (should) have been a good reason. What do you think?

Brian (panozracing),
I thought the GTS does come with the offset UCA. Did I get this wrong? Where does the offset UCA get introduced into the GT series? Isn't PAD the source for them and don't they have a GTS part number? I think I need pain medicine.

Mike

[panozracing]

Originally Posted by PanozDuke

Brian (panozracing),
I thought the GTS does come with the offset UCA. Did I get this wrong? Where does the offset UCA get introduced into the GT series? Isn't PAD the source for them and don't they have a GTS part number? I think I need pain medicine.

Mike

I didnt even know panoz used an offset one. both cars came with straight non-offset UCA's. I have ordered the UCA alot (we replace them on a regular interval with all the spindles and hardware). I have NEVER been asked if I have the offset ones or not. So I was under the assumption that all GTS's have the non-offset UCA and only the GT (etc) had the offsets...... The GTS parts manual and users manual all show non-offset UCL....hmmmmm

[eric1h]

the reduced caster gives better straightline stability,but IMHO the offsets are better for a roadtrack course when turn in and handing are desired, not sure why they don't mention the offset when you order.... odd