89 Iroc Z

Anyone know if this will work on a thirdgen? Is the upper panhard rod support interchanble between 3'rd and 4'th gens?

http://www.bmrfabrication.com/F-body...tm#panhardrods

vjo90RS8

iTrader: (1)

yeah, that will work on a thirdgen, looks like someone finally made a tubular panhard bar brace. I have a problem with my 3" exhaust rubing on my brace, but $200 is kinda alot, maybe ill get it in the summer.

Justins86bird

Fascinating.

Although it does seem pricey. May have to get one since that's the only part that I haven't replaced yet. But I think I'll wait for a sale and some reviews from the 4th gen guys.

vjo90RS8

iTrader: (1)

same here, that is the last suspension part i need other than a steering rebuild, so i think i might get mine this summer.

ebmiller88

iTrader: (7)

Me likey....and it's about time. IT is a bit pricey so I'll wait, but I'll get one eventually. And it'll work just fine. It's a dream for all you guys wanting to run true duals.


Ed

Dewey316

a few notes on that piece from BMR.

there has been alot of discusion about this peice on a F-Body raod racing message board i go to. it is no secret that lower in the roll height in the rear, via PHB relocation is a smart move. BUT when you do that the forces applied ot the brackets change significatly, UnbalancedEngineering makes a PHB relocation kit, BUT, it has weld in brackets, and extra support bracing. it also relocates the axle side mount. if you only lower the body side PHB mount, you through the geometry even more out of whack. then because of hte moment on the bracket you are suseptable to bending, or breaking at the mounting points.

i would like up the whole thread, but not sure how that would go over with the admins... here are a few quotes.

From Jason at UE

Justins86bird

Yep, thats true. Looks like the bracket could be welded on if the coating is ground off. From the pics it looks like the frame side is lower the the axle side. Hmmm

I just want a beefed up brace, not really a relocated one.

ebmiller88

iTrader: (7)

I really dont' think it's moved a lot. Judging from the pic on the BMR site, the only part that gets relocated is the passenger side mounting point of the panhard, as seen here. It still mounts in the stock location on the driver's side. The two bends in the tubing simply replace the straight angle run of the stock unit. This part, while very pricey right now, is great for the guys wanting to run true duals.


Ed

89 Iroc Z

Though it only lowers it about an inch that’s enough to throw the geometry off. If you have a lowered car the rear sits higher up into the body then stock so it just would make the panhard sit at an even greater angle instead of parallel to the ground. BMR needs to make a relocation bracket for the rear-end too to correct for this.

ebmiller88

iTrader: (7)

I agree...lowered cars will have a problem with the geometry.

Ed

drain89

iTrader: (10)

I agree, my ground control adjustable panhard rod come with a bracket that you weld on the bottom of the panhard rod mount on the rearend.

nolanr0413

id buy that if they did what you guys said to fix it. I want all the suspension stuff i can get .

JERRYWHO

All you have to do is this.

Jerry

JERRYWHO

One more picture.

vjo90RS8

iTrader: (1)

did you have that bracket made or did u buy it from somewhere

ME Leigh

Height

The height of the panhard bar helps to determine the height of the rear roll center. The roll center is an imaginary point around which the rear of the race car rolls. The height of the rear roll center (and the front also) is critical to handling. When you lower the panhard bar the rear roll center drops. A lowered rear roll center promotes side bite at the rear which tends to tighten corner handling. However, an extremely low roll center can generate excessive chassis roll which can cause suspension geometry problems. Also, excessive roll can delay corner exit acceleration. Raising the panhard bar raises the rear roll center. Generally, this adjustment causes corner entry handling to loosen and chassis roll to lessen. You can learn the "tuning range" for heights of your panhard bar by testing at the race track and taking good notes!

When adjusting for height, change both ends of the panhard bar. Otherwise you may introduce another handling effect by changing the angle of the panhard bar (more later). Also, if you adjust the height of the panhard bar just at the chassis, the rear roll center may move in the opposite direction(see illus. 1&2). Generally, a 1" change to the height of a panhard bar makes a noticeable change in handling on dirt race cars (asphalt cars = 1/2").

Angle

During cornering the chassis exerts a side force on the rear axle and tires through the panhard bar. When the panhard bar is level, it transmits a wholly lateral force to the rear tires. However, when the panhard bar is angled downward to the right, it transmits a partially downward force to the rear tires and rear traction is enhanced. Conversely, when the panhard bar is angled upward to the right, it transmits a partially upward force to the rear tires and rear traction is lessened. The effect of an angled panhard bar on rear tire loadings is brief but very important handling. You can increase the panhard bar's effect on tire loadings by increasing the static upward or downward angle of the panhard bar. However, too much panhard bar angle can cause drastic changes in rear tire loadings during cornering and handling may become erratic as a result. Generally, a 1" change to the difference in mounting point heights of the panhard bar makes a noticeable handling change on dirt race cars (asphalt cars = 1/2"). A good rule of thumb is to keep the height difference of the panhard bar mounts to within 10% of the panhard bar's length (for example: 20" panhard bar = 2" maximum mounting height difference). When making changes to the angle of your panhard bar, be aware of any effects to the height of the rear roll center.

In order to determine the ultimate handling effects of the panhard bar's angle, one must consider where the panhard bar is attached to the rear axle--Read on!

Axle Mount Location

The forces transmitted through by the panhard bar are applied to the rear axle at the panhard's axle mount point. The lateral location of the mount on the axle determines how much each associated rear tire is loaded or unloaded by the panhard bar during cornering. If the panhard bar is attached to the rear axle near the center of the rear tire track*, the panhard bar will load or unload both rear tires by a similar amount during cornering. With this arrangement you can increase rear traction, hence tighten handling throughout the corner, by increasing the downward or decreasing the upward (to the right) angle of the panhard bar. You can loosen handling throughout the corner by making adjustments opposite to those listed above.

If the panhard bar is not attached to the rear axle near the center of the rear track, the panhard bar will load or unload the rear tires unevenly during cornering. The closer a tire is to the panhard bar's axle mount the greater the tire is affected by the angle of the panhard bar. Conversely, a distant tire is affected less by the angle of the panhard bar.

Generally, a 6" change in the lateral location of the panhard's axle mount point makes a noticeable handling change. You should keep the following in mind when adjusting the panhard's angle or its lateral location on the rear axle: *Any increase in the load of the RR tire and/or decrease in the load of the LR tire tends to tighten corner entry and loosen corner exit handling. *Any decrease in the load of the RR tire and/or increase in the load of the LR tire tends to loosen corner entry and tighten corner exit handling. *Increasing the load of the rear tires equally tends to tighten overall corner handling. *Decreasing the load of the rear tires equally tends to loosen overall corner handling. *Adjustments to the panhard bar primarily affect corner entry and mid-corner handling.

By now you should have a good understanding of how some of the design elements and tuning adjustments of a panhard bar have a collective effect on handling. If anything you have read is unclear, go back and reread the article before progressing.

Frame Mount Location

A panhard bar that is attached to the right side of the frame lowers during chassis roll. However, a panhard bar that is attached to the left side of the frame raises during chassis roll. However, the effects on handling of a right side versus a left side frame mounting are not always predictable. The location of the panhard's axle mount can counteract any predictable handling effects. The current tendency is to mount the panhard to the left side of the dirt car chassis and to the right side of asphalt chassis.

Length

During chassis roll a short panhard bar changes its angle, hence handling, more radically than a long panhard bar. Consequently, handling can become inconsistent if the panhard bar is too short (20" minimum length is recommended). Generally the length of the panhard bar is determined by the desired location of the panhard's axle mount.

Front/Rear Location

For clearance reasons, the panhard bar is generally mounted behind the rear axle whenever a long panhard bar is desired. Also, a rear mounting provides more potential mounting positions than a front mounting. Keep in mind that since the roll axis (an imaginary line connecting the front and rear roll centers) is usually inclined to the rear, a rear mounted panhard bar must be positioned higher than a front mounted panhard bar in order to maintain a given roll center height.

A front or rear location of the panhard bar makes little difference on cars equipped with solid rear suspension linkages. However, this is not the case for cars equipped with torque absorbing devices (5th coils, 6th coils, etc.) These devices allow the axle (pinion side) to wrap (rotate) downward during deceleration and upward during acceleration. During axle wrap, the height of the panhard's axle mount point changes. Consequently, both the angle and height of the panhard bar change during axle wrap and handling is affected.

The location of the panhard's axle mount (ahead of or behind the axle), determines whether the mount will move up or down during deceleration or acceleration. During deceleration, the panhard's axle mount point drops if the mount is ahead of the axle but raises if the mount is behind the axle. During acceleration the height of the panhard's axle mount point changes opposite to those listed above.

For tight corner entry handling, the panhard bar should be mounted to the front of the axle. This arrangement causes the panhard's axle mount point to drop during deceleration. Consequently, the height of the rear roll center drops & rear side bite is enhanced. Also, if the panhard is attached to the left side of the chassis the angle of the panhard bar changes during chassis roll so to increase rear traction and further tighten handling during deceleration.

However, if the panhard bar is attached to the rear of the axle the panhard's axle mount point raises during deceleration. Consequently, the rear roll center raises and corner entry handling tends to loosen as a result. Also, if the panhard is attached to the rear of the axle and the left side of the frame, the angle of the panhard bar changes during chassis roll so to reduce rear tire loadings and further loosen handling during deceleration.

The effects of axle wrap on the panhard bar appear to influence corner exit handling to a lesser degree than corner entry handling. At this point, you should be able to analyze any effects the panhard bar may have on corner exit handling.

It should be mentioned that during cornering, a front mounted panhard bar resists axle wrap-up (acceleration) and enhances axle wrap-down (deceleration) whenever the panhard bar is angled downward to the right. A rear mounted panhard bar gives opposite effects. However, the effects to handling appear to be minimal.

vsixtoy

Good article, just want to note for any reading it that the above examples of lateral axle mounting and results pertain to a lefthander only roundy round car.

Dewey316

Yes, but changing roll heights can have a nice effect on the cars atributes during transisitions. what you really get from panhard relocation, is a car that is more stable when changing direction. and when you adjust the springs/shocks to match, it will retain its handling in a long sweeping corner.

ME Leigh

Yes so what would be a good height to lower both mounts? I'd like to get the rear roll center as low as possible without unsettling the chassis or body. I was thinking of building and reinforcing some mounts to lower it 2".

Dewey316

you should try to match the rear roll height, with the front roll height.

the front roll height changes very easily, things like camber, and the angle fo the a-arm, and track width, all come into play. it is very hard to figure. the more you car is lowered, the lower the front roll height gets (it changes much faster than the rear), the the more the rear would need to be lowered.

92 zzz28

I recently installed one of those relocation bars mainly because I am going to be installing a true dual. Just figured it would yield more clearance.

THe only thing I encountered with the bar was the brackets supplied had to be either ground down some or the body had to be modified slightly. According to BMR, they say that since the 3rd gens were changed during their production, they never "designed" the bar for our cars, per se. It will fit, and work fine, they just set everything up for a 4th gen. When I put mine it, instead of grinding or beating on anything, I just did as the tech guy at BMR suggested and installed the brackets differently than they had intended. He said it wouldn't hurt anything, I don't see how it could. I am also using a Spohn double rod end panhard bar. Also the bolts supplied didn't fit!! So I went to my local hardware store and bought a few 10.9 metric bolts.

If anyone wants to see some pics of it, let me know and I will get some...

91banditt2

iTrader: (1)

i would like to see some pix

ebmiller88

iTrader: (7)

Pics pls....

Ed

Mkos1980

iTrader: (8)

BTT from the past. I'd also like some pics if your still on here.

92 zzz28

yeah, I'm still here but no pics, car is at home and I am in N. Carolina...

drain89

iTrader: (10)

Great thread!

Kennerz

Very technically sound replies, thank you for the education.

Someone already mentioned this, but I thought they (BMR)only made this piece for the purpose of clearance when running true dual exhuast, I didn't know there are handling claims tied to this as well. On the ls1 technical site this was implied as the sole purpose (Dual ex.) - it just happens to be alot beefier than stock

Bradlyj8Z28

iTrader: (2)

and the pics never came...

tvfunhouse

I know this post is like 8 years old, but do you recall what the BMR tech told you to do for mounting the backside bracket? I don't want to beat in or grind on the body mount if I can avoid it, but I also don't really want to cut this bracket so close to the bolt hole at the top to clear the bulge.