[willzilla]

Hello! I have the BMR adjustable front and rear sway bars as well as the BMR front and rear end links. Rear sway bar and end links are on the car, no problem, and I'm running the rear at the mid stiffness setting (155% increase over FE4) and planned to run the front at the stiffest setting (155% increase over FE4) which should keep the front/rear bias close to the stock OEM feel... I ran into a small snag with the front setup.

Instructions call for adjusting one of the BMR end links to match the length and dimensions of the OEM end link, to install it, and then match the size and dimensions of the second end link (but not to tighten the jam nuts) and to install it, adjust as needed to make it install smoothly for a neutral zero preload setup:



My issue is with the first end link is when I install the end link and lower down the front suspension the sway bar comes into contact with the control arm. This happens regardless of the position of the sway bar on the slotted sway bar mounts.



*** End link is unhooked for this but when connected the sway bar will make contact just like this when in the stiffest setting.

What is the solution to resolve this? Do I simply shorten the end links to shorter than OEM length? If this is the case.. I assume the adjustable sway bar is not compatible with the OEM end links in the stiffest position?

Also, in relation to this.. what settings would be considered a nice aggressive street performance twisty roads setup with a relatively neutral feel? Am I correct in thinking full stiff front middle stiff rear would be fairly neutral? Or would something like Mid front mid rear be better?

Thanks!

[willzilla]

BMR replied to an email I sent them with, "If you can adjust the endlink to clear that is fine. The zl1’s have some differences from a ss that cause that."

Makes sense and what I assumed, just wanted to get confirmation on that before I begin adjusting stuff and maybe throw off some of the overall dynamics

[cdb95z28]

A few things here. I've focused on what you have experienced on my current Gen6 SS 1LE and to a lesser extent my Gen5 SS 1LE. Anti roll bar preload has a few pluses and minus. It is not always a bad thing. Not sure why preload is such a dirty word. Bar preload is a tuning tool in the circle track world. Sure, it is possible to go to far, like anything else we do. I don't have any experience with the OE ZLE, base SS or LT1 model bars but I would not be surprised if they fall in line with the FE4 bars.

I'm currently at work and do not have my detailed notes in front of me on all my observations. But, here is a summary of my experience.

As installed, these car's OE bars DO NOT have zero preload. This is important to know. The OE setup should be a good baseline to go from. This conclusion comes from my own experience on the above cars and from the observations of others. I think we all understand that changing the bars can result in a much different balance or roll stiffness. Yes, there is a built in offset that shows up exactly like your picture. It may be due to a slight engineered in offset at the endlink mounting on the strut or the bar's arms being slightly offset. It seems that even when aftermarket bars like the BMR or Hotchkis are installed, this offset is still in play. I can tell you that it is not due to longer/shorter OE endlinks as both sides are the same part #. It could be debated whether GM intentionally provides this offset to create slight preload. Maybe they do to tweak the corner weights? Or maybe to add responsiveness to the chassis? I think it is more of the latter. When we add responsiveness we are reducing the time it takes the chassis responds to driver input. Adjusting bar preload does change corner weights but not to a significant amount (unless we go nuts). When one endlink is in the bar, the other is offset to the point where you have to pull or push the bar to get that other endlink into the desired hole. I found this on the Gen5 and Gen6 cars, front and rear bars. OE and aftermarket bars.

So that all being said, I would keep the endlinks the same length as a baseline. I have the SPL adjustable endlinks and I spent a fair amount of time adjusting for chassis response and corner weight fine tuning. The latter was more about a desire to see the how it changes. One important part of endlink length is when we change between different manufacturers (different lengths) is the relationship of the bar's lever arm to ground level. We want the arm to be parallel to level ground as a baseline. The ultimate goal is to have, at static ride height, the endlink and bar arm at a 90* angle. The provides the most efficient use of the forces acting thru the bar and endlinks. While some may question whether that level of detail really matters, I will say that these cars are so precisely built with tight chassis joints, on super responsive tires that even tiny changes can matter on the responsiveness and feel of the chassis. I've played with alignment and suspension tweaks enough to feel these small changes. These tires demand chassis perfection. To be fair, some people can feel the subtle changes where others cannot. But, I have felt the differences in this endlink/bar lever arm relationship. It was rather eye opening when I first played with this.

I adjusted both front endlinks the same amount to get to that 90* relationship, while maintaining the offset I had observed with the OE bar. As in your pic and what other's have seen, is about 1/4"-3/8" offset. I kept the offset for bar preload. This also adds chassis responsiveness. Bar preload also makes the bar act stiffer.

It is also worth noting that the OE bar mounts are quite different than the typical aftermarket poly mounts. The OE front bar bushing is rubber with a hard internal structure that is glued to the bar. The rear OE bar has a similar rubber bushing but does not use any glue. It physically squeezes the onto the bar when the metal mounting bracket is installed. The Gen5 SS 1LE/ZL1/Z/28 front and rear bar mounts are done this way also. Both methods create what some would call a bind, but I think GM does it this way to create some more (minor) bar rate and maybe for some other reason. This way is very different from the lubricated poly mounts from the aftermarket where the bar can freely rotate.


On the rear, the OE bar has a bunch of preload. EDIT:Both sides had built in preload, but my notes do not state by how much. But, the delta between the LR and RR was about 20mm worth.

All of the initial rear preload was in the form of resistance from the OE rubber mounting bushings at static ride height. When I disconnected both rear endlinks at the hubs at static ride height, both lever arms of the rear bar fell down. Meaning to reconnect the endlinks to the hub I had to push UP (against the rubber mount resistance) on the lever arms to get the endlink bolts to line up into the hub. The delta between the LR and RR was 20mm.

I recall that it is impossible to get the 90* endlink to bar relationship at the rear. So I shortened both rear SPL endlinks as much as I could.

Proving there is no free lunch on singular suspension mods, tweaking a bar effectiveness/responsiveness could also change the car's ultimate balance. While it might be a very minor change, it does play a part. All I have on my street/tracked SS 1LE A10, suspension wise that would matter, is Hotchkis/BMR bars with the SPL endlinks, ZLE cradle mounts,running 305/30-19 square. I even went back to the OE rear toe rods from the SPLs. With all of the fine tuning I am running full stiff up front, full soft out back. I found running my Hotchkis front bar at full stiff has resulted in less roll with no loss in front grip. This goes against the typical response of going full stiff up front (stiffer). Moving towards the front stiffer typically results in more understeer but sometimes better front platform control can create more front grip. As mentioned I run the rear BMR bar full soft. Part of this I believe was a result of my own rear bar mounts which provide about 50% more surface area vs the lousy BMR mounts. I am using Pedders Gen5 rear bar poly bushings along with the OE bar brackets which are very stiff. Less deflection of the mounts results in the bar becoming more effective (stiffer).

While I have the BMR rear bar, those shitty bar mounts on our cars are very poorly engineered. That creates some disdain for them. Not to mention their blind poly marketing usually results in a step down vs some of the excellent suspension mounts on these cars. I doubt their response comes from someone who has spent as much time as some of us on tuning these bars. If you go full stiff up front and track the car, expect the front mounts to fail. There is a thread here on the forums started by my buddy Jason (therealja105) who had BMR mount failures and he had an easy cheap fix. On the BMR rear mount integrity, there was someone here who had a failure, and I saw deformation in my mounts. The Hotchkis front bar mounts have been good, I have not had any issue.

khcoaching here on the forums did his own tuning of his Hotchkis bar with BMR endlinks and his observations fell in line with what I and others had seen.

Keep detailed notes and play around.

[cdb95z28]

https://www.camaro6.com/forums/showthread.php?t=576751

https://www.camaro6.com/forums/showt...php?p=11403849

[willzilla]

Originally Posted by cdb95z28

A few things here. I've focused on what you have experienced on my current Gen6 SS 1LE and to a lesser extent my Gen5 SS 1LE. Anti roll bar preload has a few pluses and minus. It is not always a bad thing. Not sure why preload is such a dirty word. Bar preload is a tuning tool in the circle track world. Sure, it is possible to go to far, like anything else we do. I don't have any experience with the OE ZLE, base SS or LT1 model bars but I would not be surprised if they fall in line with the FE4 bars.

I'm currently at work and do not have my detailed notes in front of me on all my observations. But, here is a summary of my experience.

As installed, these car's OE bars DO NOT have zero preload. This is important to know. The OE setup should be a good baseline to go from. This conclusion comes from my own experience on the above cars and from the observations of others. I think we all understand that changing the bars can result in a much different balance or roll stiffness. Yes, there is a built in offset that shows up exactly like your picture. It may be due to a slight engineered in offset at the endlink mounting on the strut or the bar's arms being slightly offset. It seems that even when aftermarket bars like the BMR or Hotchkis are installed, this offset is still in play. I can tell you that it is not due to longer/shorter OE endlinks as both sides are the same part #. It could be debated whether GM intentionally provides this offset to create slight preload. Maybe they do to tweak the corner weights? Or maybe to add responsiveness to the chassis? I think it is more of the latter. When we add responsiveness we are reducing the time it takes the chassis responds to driver input. Adjusting bar preload does change corner weights but not to a significant amount (unless we go nuts). When one endlink is in the bar, the other is offset to the point where you have to pull or push the bar to get that other endlink into the desired hole. I found this on the Gen5 and Gen6 cars, front and rear bars. OE and aftermarket bars.

So that all being said, I would keep the endlinks the same length as a baseline. I have the SPL adjustable endlinks and I spent a fair amount of time adjusting for chassis response and corner weight fine tuning. The latter was more about a desire to see the how it changes. One important part of endlink length is when we change between different manufacturers (different lengths) is the relationship of the bar's lever arm to ground level. We want the arm to be parallel to level ground as a baseline. The ultimate goal is to have, at static ride height, the endlink and bar arm at a 90* angle. The provides the most efficient use of the forces acting thru the bar and endlinks. While some may question whether that level of detail really matters, I will say that these cars are so precisely built with tight chassis joints, on super responsive tires that even tiny changes can matter on the responsiveness and feel of the chassis. I've played with alignment and suspension tweaks enough to feel these small changes. These tires demand chassis perfection. To be fair, some people can feel the subtle changes where others cannot. But, I have felt the differences in this endlink/bar lever arm relationship. It was rather eye opening when I first played with this.

I adjusted both front endlinks the same amount to get to that 90* relationship, while maintaining the offset I had observed with the OE bar. As in your pic and what other's have seen, is about 1/4"-3/8" offset. I kept the offset for bar preload. This also adds chassis responsiveness. Bar preload also makes the bar act stiffer.

It is also worth noting that the OE bar mounts are quite different than the typical aftermarket poly mounts. The OE front bar bushing is rubber with a hard internal structure that is glued to the bar. The rear OE bar has a similar rubber bushing but does not use any glue. It physically squeezes the onto the bar when the metal mounting bracket is installed. The Gen5 SS 1LE/ZL1/Z/28 front and rear bar mounts are done this way also. Both methods create what some would call a bind, but I think GM does it this way to create some more (minor) bar rate and maybe for some other reason. This way is very different from the lubricated poly mounts from the aftermarket where the bar can freely rotate.


On the rear, the OE bar has a bunch of preload. Both sides have built in preload, IIRC about 20mm worth. But there is also an offset, one side has more preload than the other. I recall that it is impossible to get the 90* endlink to bar relationship at the rear. So all I did was maintain the offset.

Proving there is no free lunch on singular suspension mods, tweaking a bar effectiveness/responsiveness could also change the car's ultimate balance. While it might be a very minor change, it does play a part. All I have on my street/tracked SS 1LE A10, suspension wise, is Hotchkis/BMR bars with the SPL endilinks, ZLE cradle mounts,running 305/30-19 square. I even went back to the OE rear toe rods form the SPLs. With all of the fine tuning I am running full stiff up front, full soft out back. I found running my Hotchkis front bar at full stiff has resulted in less roll with no loss in front grip. This goes against the typical response of going full stiff up front (stiffer). Moving towards the front stiffer typically results in more understeer but sometimes better front platform control can create more front grip. As mentioned I run the rear BMR bar full soft. Part of this I believe was a result of my own rear bar mounts which provide about 50% more surface are vs the lousy BMR mounts along with the OE bar brackets which are very stiff. Less deflection of the mounts results in the bar becoming more effective (stiffer).

While I have the BMR rear bar, those shitty bar mounts on our cars are very poorly engineered. That creates some disdain for them. Not to mention their blind poly marketing usually results in a step down vs some of the excellent suspension mounts on these cars. I doubt their response comes from someone who has spent as much time as some of us on tuning these bars. If you go full stiff up front and track the car, expect the front mounts to fail. There is a thread here on the forums started by my buddy Jason (therealja105) who had BMR mount failures and he had an easy cheap fix. On the BMR rear mount integrity, there was someone here who had a failure, and I saw deformation in my mounts. The Hotchkis front bar mounts have been good, I have not had any issue.

khcoaching here on the forums did his own tuning of his Hotchkis bar with BMR endlinks and his observations fell in line with what I and others had seen.

Keep detailed notes and play around.

Thank you for the informative post!! I did note the preload in the OEM sway bar setup and only wanted to go neutral with the BMR setup as that was their recommended initial setup in the install docs. I had seen the issues regarding their poly bushings and fairly flimsy mount and have ordered the billet mount with Delrin bushings that I would think resolves any mount issues. They actually "should" arrive today and I will get them installed before I put the car back on the ground.

[VR Baron]

Originally Posted by willzilla

Thank you for the informative post!! I did note the preload in the OEM sway bar setup and only wanted to go neutral with the BMR setup as that was their recommended initial setup in the install docs. I had seen the issues regarding their poly bushings and fairly flimsy mount and have ordered the billet mount with Delrin bushings that I would think resolves any mount issues. They actually "should" arrive today and I will get them installed before I put the car back on the ground.

I have the hotchkiss front bar and the ends probably are different. But with the preload built into the bar I installed the bar with the car jacked up on one side, I then use a small jack under the lower arm bushing near the disc and raised or lowered the brake assembly till the endlink freely slides into the sway bar arm hole you want to use. Then do the other side. It’s the only way to get the link and bar hole to line up without the car sitting on ramps or lift with tires on and sitting at rest.All due to preload built into the sway bar.

A note on the stiffness ratings as you read them. And this is just ease for you to know which way to adjust. At least for me anyway. The front bar is 6%, 34% or 69% stiffer over the zl1 bars as to rate, rear is about 49,70 or 90% or there abouts. Those numbers differ from yours and are from a post from one member got from BMR . But the spreads are similar so doesn’t make a lot of difference. But the bars aren’t 155% stiffer for example.If you are running the stock staggered tires it’s hard to maintain the same balance with BMR bars. Closest is full stiff front and middle rear. You will have to play with it and get it best you can. To stiff on the street may lose grip, but only if you are going all out . Mid front is probably best on street and soft rear but you may get some oversteer.

[Msquared]

I would probably not retain preload intentionally unless I had access to wheel scales and could accurately corner-weigh the car. Then preload could be a tool to help zero out cross weight. Short of that, you're just taking wild guesses as to what it should be or if it should be there at all.

That said, if someone is determine to replicate preload but is also having a clearance issue on the full-stiff setting, then shortening both links the same amount should gain the required clearance while staying close to the original amount of preload.

[cdb95z28]

Previous post edited with more OE rear bar preload info in RED




Concerning corner weight change (with me in car) from individual endlink length change:

The change in (corner) weight movement due to a half turn of the SPL RR endlink was 4 lbs. The RR gained 4 lbs and the LR/RR delta went from 18lbs to 10lbs.

Even with the RR endlink disconnected, the preload difference was minor at 1lb change.

The above corner weight checks were with the Hotchkis bar showing similar to the OE "twist" or lever arm offset at 1/4"-3/8". When the LF endlink was fastened to the middle hole of the bar, the RF endlink stud sat higher by about 1/4"-3/8" than the hole. I would have had to push up the bar to get the endlink into the hole.

When using the BMR rear bar set in the middle hole and poly mounts, some of the OE preload is eliminated but the bar lever arm offset was still there, albeit not the OE 20mm. It was about 5mm.

Lengthening the RR endlink resulted in weight being moved to the RR and LF, and this also lessened rear bar preload. The LR and RR weight delta tightened up.

From my notes, I had shortened BOTH front SPL endlinks from the OE length by 1.5 turns, about 4mm less. At the rear, I shortened both SPL endlinks as far as I could, approximately 13mm shorter than the OE endlinks. My notes stated the rear felt like it became less sharp.


Front weight delta was about 10lbs difference after my endlink changes. These cars are very well done on the corner weights. Beginning difference was 1lb. I basically tightened the rear delta at the expense of the front delta. Honing in on further tightening of the corner weights is doable with preloads but there may be a slight change in a bar effectiveness. This would be a very small change. As Matt mentioned, making changes without seeing how the weights are being distributed is a guess. You gotta know where you are starting from. But, in all honesty, I made my initial endlink adjustments blindly, without the aid of scales. I was more concerned with chassis response and a better feel. The car's response off center was lazy and I'm not afraid to play around. Soon after, I got the car on my roundy-round racer buddy's Longacre scales. And the weights were excellent.

[willzilla]

Originally Posted by cdb95z28

Previous post edited with more OE rear bar preload info in RED




Concerning corner weight change (with me in car) from individual endlink length change:

The change in (corner) weight movement due to a half turn of the SPL RR endlink was 4 lbs. The RR gained 4 lbs and the LR/RR delta went from 18lbs to 10lbs.

Even with the RR endlink disconnected, the preload difference was minor at 1lb change.

The above corner weight checks were with the Hotchkis bar showing similar to the OE "twist" or lever arm offset at 1/4"-3/8". When the LF endlink was fastened to the middle hole of the bar, the RF endlink stud sat higher by about 1/4"-3/8" than the hole. I would have had to push up the bar to get the endlink into the hole.

When using the BMR rear bar set in the middle hole and poly mounts, some of the OE preload is eliminated but the bar lever arm offset was still there, albeit not the OE 20mm. It was about 5mm.

Lengthening the RR endlink resulted in weight being moved to the RR and LF, and this also lessened rear bar preload. The LR and RR weight delta tightened up.

From my notes, I had shortened BOTH front SPL endlinks from the OE length by 1.5 turns, about 4mm less. At the rear, I shortened both SPL endlinks as far as I could, approximately 13mm shorter than the OE endlinks. My notes stated the rear felt like it became less sharp.


Front weight delta was about 10lbs difference after my endlink changes. These cars are very well done on the corner weights. Beginning difference was 1lb. I basically tightened the rear delta at the expense of the front delta. Honing in on further tightening of the corner weights is doable with preloads but there may be a slight change in a bar effectiveness. This would be a very small change. As Matt mentioned, making changes without seeing how the weights are being distributed is a guess. You gotta know where you are starting from. But, in all honesty, I made my initial endlink adjustments blindly, without the aid of scales. I was more concerned with chassis response and a better feel. The car's response off center was lazy and I'm not afraid to play around. Soon after, I got the car on my roundy-round racer buddy's Longacre scales. And the weights were excellent.

Great info, thank you! I'll see how it feels and go from there.. I don't have fancy corner scales and what not but I don't really track the car so being super precise not quite as important overall, for now

[willzilla]

Swapped the billet mounts and Delrin bushings into place:




Comparison:

[cdb95z28]

Originally Posted by willzilla

Swapped the billet mounts and Delrin bushings into place:




Comparison:

Very nice pieces there, a rarity from BMR.

I believe that those new mounts, being significantly more robust and having less deflection than the flimsy stamped steel mounts, would add to the effective total rate of the BMR bar. Not just from the better brackets but the Delrin is more stiff than the poly bushing.