[radz28]

09/11/2023 - UPDATE:

I'm probably the only dingus that this has mattered to, but I'll update anyways.

My OCD has been driving me crazy since starting this enterprise. Because of not doing research before my purchase, I did not understand that I'd be losing some measure of spring rate when moving to rod ends. I'm still not that positive on precisely how much spring rate I've lost, but, I did take a control arm, place it in a vice, and used a scale to see about how much pressure the rubber bushing applied at about 1-inch and about 4-inches of travel. The force I measured was about 7-lbs @ 1" and about 30-lbs @ 4". I was trying to get a spectrum from a little above ride height, to about full compression (I'll freely admit I hadn't tried to actually measure full compression, so I took a guess). I replaced 3-arms (per side), and each arm had a rubber bushing that was replaced by a rod end. So - even though I think I found a spring rate calculator for this, I didn't really take the time to calculate anything. BUT - I figured it couldn't be zero, so it was just driving me crazy.

In another moment of dingus, I thought if I slapped a bigger stab. bar on, it would make up for the difference, but that would only help in corners... Then - my OCD started going crazy because the front suspension balance might be off, so I, then, upgraded the front (aFe adjustables). I was still stuck with not compensating when going straight, and couldn't decide on risking more money and time on likely a fruitless effort, and, likely, possibly, losing some better weight transfer on the strip with softer spring rates in the rear (as a result of the rod ends). My OCD just couldn't accept throwing the OEM balance out of the window.

SO - I settled on a set of BMR springs, ONLY for the rear. The rate wasn't crazy-higher than OEM ZL1 coils, and even if it was, there were still 3-more rubber knuckle bushings I know I'll replace later, to compensate for (the lower control arm pivot looks like a spherical end), so I was future-proofing for my OCD. I was a little worried about ride height (as these are lowering springs), but more-so, losing ride quality. As it turns out, I am pleasantly surprised and happy with both. Before the coil install, my ride height was about 27.5-27.75", front and rear. It seems a little lower than stock from other information out there, but with the added weight of the 2650, and less spring rate from the rod-end-control-arms, it seemed logical. I've only put about 50-miles on the car, but it seems I haven't lost ANY height (it actually measures slightly higher than before). They might settle (or the rubber insulators) after a little more driving, but if I can keep it close to where it was, I'll be even more happy. The ride seems VERY comparable to OEM springs, too. It definitely wasn't too stiff at all. Driving over the same roads I have didn't yield much of any difference in ride quality and everything is about as good as I could have hoped for.

So - for anyone trying to make up for spring rate loss as a result of control arm rod-ends, these BMR (lowering) springs, with higher rates them OEM, seem to be okay. I recognize they may not be as optimal as YYZ and what not, but I didn't need and want a whole set, nor did I want to lower the car. So far - these seem to fit the bill great, and when I get around to replacing the last of the rubber bushings in the knuckles, I'll have some spring rate "in reserve". I wouldn't say I recommend this, but for my purposes: I am very happy and my OCD, for this aspect, is at rest.

09.02.2022 - UPDATE

Everything seems to continue to be as good as I have expected. This isn't a thorough review for strip/track experience, but it's probably about as far as possible for the street. I've put probably at least 500-miles on the arms now.

This will probably be a 1.5-part review, as I haven't put my Mickey's back on yet, but have about 200-street miles on the these parts. Chassis/tire-wise, my car's still stock. I have about 2400-miles on it, so it's still "new". I don't have specific plans for the car, though, I'll be hitting the strip by my house more than a course, even though I'd like to do that a bit. I didn't want to sacrifice much drivability or NVH though, which was almost tied for my biggest concern. My biggest being the rear sway on DRs, because the way the car moves around above 80-MPH was downright scary to me. THIS needed to be fixed. My .5-part of this review will be a small follow-up once I get the DRs back on a Hoon' a bit to see if anything's improved.

I purchased ZLE Cradle Bushings, and BMR Cradle Brace/Upper and Lower Trailing Arms/Upper Control Arm/Tie rods (all in rod ends). Unfortunately - I replaced everything at the same time, so I don't know how effective anything was on it's own. Everything else in the chassis is stock, and I had a wheel alignment performed right after the install.

As expected - there's a little more noise from the rear. I don't feel like I'm getting drivetrain noise or whine or anything from the diff'. I can hear a little more rattling or chunking going over smaller cracks in the road, but nothing much from expansion joints or anything. I might get a small pop when the suspension flexes over going over speed bumps diagonally or when crossing gutters the same, but that's about it. I think I would say I can "feel" the rear more than hear it, if that makes any sense. The car seems to go straight as before (well - before swapping t the DRs), but I'll have to circle back to this assessment when they're back on. I think I'll be able to deal with the additional NVH though, if it doesn't get much more pronounced, and as long as it goes straight with the DRs.

It's my understanding that going to rod ends lower spring rate a little. I can't evaluate that, but it makes sense. I don't know that even if I were a driver good enough to notice, that I'd get the opportunity or even be serious enough to feel the difference, so I don't think that's a big deal. There are custom springs and such to make-up for that if the need arises anyways.
There might be comments about SPL-parts, but I didn't need to invest more than I did with these parts, and I've had good experience in the past with BMR stuff, as true as those comments might ring.

I'm pretty happy so far. I'll follow-up soon with DR impressions, so fingers crossed!

[Davescamaro]

I also got thr BMR front under cradle and rear, upper and lower trailing arms. All the youtube reviews say more NVH and sounds, but the drive is to rave about. I'm getting them installed next week and I'll update about a week later after break in and a few drag pulls.

[radz28]

Originally Posted by Davescamaro

I also got thr BMR front under cradle and rear, upper and lower trailing arms. All the youtube reviews say more NVH and sounds, but the drive is to rave about. I'm getting them installed next week and I'll update about a week later after break in and a few drag pulls.

Make sure to get replacement TTY bolts for everything that's getting replaced. I've had one back-out a little on me, but it warned me (by rattling) and I immediately addressed it. I have a complete set of new OEM bolts, but didn't want to risk stuff going out of alignment because I totally forgot about the TTY bolts when I did the arm(s) install.

Either replace the TTY bolts with OEMs, or get aftermarket equivalents

[Davescamaro]

Thanks in advance. I'll swing by my local chevy dealer and use my GM supplier discount.

[Davescamaro]

I ended up reusing the factory bolts and went by BMRs torque specs. I've not noticed any NVH so far and handling has improved alot. I would highly recommend.

[radz28]

Just recheck the bolts from time-to-time.

[Davescamaro]

Will do. I just ordered the lower trailing arms, upper control arms, and 3/16" tunnel brace.

[synolimit]

Why can’t you reuse bolts??

Also, why does everyone make aftermarket arms that are adjustable but the oem arms are not? From the looks of it, only the lower spring arm is adjustable and the rear toe arm from the essentric bolts. Why do I need an adjustable upper and traction arm? Last, if I got an adjustable upper arm I’d assume I could adjust camber but then that’d make the oem lower spring arm worthless right? Couldn’t I lock out the essentric bolt there?

[JSH]

Originally Posted by radz28

I purchased ZLE Cradle Bushings, and BMR Cradle Brace/Upper and Lower Trailing Arms/Upper Control Arm/Tie rods (all in rod ends). Unfortunately - I replaced everything at the same time, so I don't know how effective anything was on it's own.

I too am looking for suspension upgrades to help 60 ft. times. When I recently asked WeaponX, they only mentioned "BMR suspension arms."

[radz28]

Originally Posted by synolimit

Why can’t you reuse bolts??

Also, why does everyone make aftermarket arms that are adjustable but the oem arms are not? From the looks of it, only the lower spring arm is adjustable and the rear toe arm from the essentric bolts. Why do I need an adjustable upper and traction arm? Last, if I got an adjustable upper arm I’d assume I could adjust camber but then that’d make the oem lower spring arm worthless right? Couldn’t I lock out the essentric bolt there?

A lot of these bolts are TTY, so they're only good for a single use.

I'm not an engineer, so I won't purport that I know the reasons, but I'm sure it's a lot more expensive to make adjustable arms, not to mention they'd be a PITA to deal with at the factory. Keeping the adjusters, let alone the fasteners sometimes, can be a PITA if you don't torque them right, and even then, they can start backing out over time. I got these arms to eliminate deflection and try to keep the suspension from getting out of control under extreme acceleration events. I didn't say they're necessary, but I was trying to eliminate a problem I was having. These did not do that, per se, but I feel better having them.

They are noisier though, and for many, that could be an issue.

Originally Posted by JSH

I too am looking for suspension upgrades to help 60 ft. times. When I recently asked WeaponX, they only mentioned "BMR suspension arms."

You've already started this, but I'd continue to find feedback from what others have posted. I can't see your signature, but thought you had a ZLE, so you're already good on cradle bushings. Depending on how serious about controlling the diff' you are, and what you're willing to tolerate with NVH, but you might look into diff' bushings.

I honestly don't see a lot of people posting about control arms for strip work. Maybe I've missed them. I don't know that I think they're necessary at my power level, and general purpose, but I think if you've got more than I, and if you're on sticky tires, whatever the activity, I tend to think replacement arms should be seriously considered. But - being the way I am, and because of the issue I was trying to eliminate, I'm happy with them. They didn't fix my issue because they weren't really related, but I know the suspension articulates better and is free'r of bind. I know the arms won't deflect as much, and know, from the past, that rear arms just help settle the rear a lot better. I replaced the rear lower arms on my 4th Gen with poly'arms, and it was night-and-day when getting into a sweeper with expansion joints. They car would skitter toward the outside with the stock arms (only 10K-miles on the odometer) and with the poly-bushed-arm, didn't get upset at the same sweeper in the least.

Your mileage will vary. I feel better knowing they're there. Each time I drive the car after the install, it feels more and more confident.

[Joshinator99]

Originally Posted by radz28

Your mileage will vary. I feel better knowing they're there. Each time I drive the car after the install, it feels more and more confident.

I feel the same way. My car seems to stay under control better, much more progressive when it does step out, and recovers better too. I haven’t seen any wheel hop anymore either, although the new alignment could have helped. I have zero regrets about doing this setup and would definitely recommend it to anyone shooting for big power.

[Davescamaro]

Originally Posted by synolimit

Why can’t you reuse bolts??

Also, why does everyone make aftermarket arms that are adjustable but the oem arms are not? From the looks of it, only the lower spring arm is adjustable and the rear toe arm from the essentric bolts. Why do I need an adjustable upper and traction arm? Last, if I got an adjustable upper arm I’d assume I could adjust camber but then that’d make the oem lower spring arm worthless right? Couldn’t I lock out the essentric bolt there?

I got the non adjustable ones, did not require alignment since it's an even swap out, but it wouldn't hurt. My cornering and launches have been rock solid difference. I know SPL makes stuff, but overpriced and BMR just seems like best bang for buck. Able to take turns alot more aggressive and no tire slip. I'm impressed so far.

[JSH]

I see that I needlessly started a new thread on suspension.

For improved 1LE 60 ft. times, BMR has made the following suggestions:

BK063 Bushing Kit, Rear Cradle, Lockout
BK060 Bushing Kit, Differential Lockout, Aluminum
UTCA063 Upper Control Arms, On-car Adjustable, Rod Ends
UTCA060 Upper Trailing Arm, On-car Adjustable, Rod Ends
TCA061 Lower Trailing Arms, On-car Adjustable, Rod Ends

BMR should know this topic well.

What do you think?

[radz28]

Originally Posted by JSH

I see that I needlessly started a new thread on suspension.

For improved 1LE 60 ft. times, BMR has made the following suggestions:

BK063 Bushing Kit, Rear Cradle, Lockout
BK060 Bushing Kit, Differential Lockout, Aluminum
UTCA063 Upper Control Arms, On-car Adjustable, Rod Ends
UTCA060 Upper Trailing Arm, On-car Adjustable, Rod Ends
TCA061 Lower Trailing Arms, On-car Adjustable, Rod Ends

BMR should know this topic well.

What do you think?

I haven't completely formulated a distilled opinion on a lot these mods' yet.

• I won't budge on the cradle bushings: frickin great, no regrets. I feel like anything you can do to add some stiffness is a good idea. If you're worried about NVH - choose wisely. I ran ZLE bushings at the same time I replaced all (available control/trailing arms with rod-ends, so I'm not sure how much NVH is due to the arms or the cradle bushings; obviously - the bushings transmit more NVH)
• Haven't done the diff'. I might look into a poly solution if there is one (I haven't yet looked that hard)
• UCAs: Maybe
• UTAs: Maybe
• LTAs: Maybe

I've got some more miles on these parts, and am pleased. I haven't gotten out to the track, still, but I can feel a lot more of the road out back now, and the noise isn't much. It's louder, but, for me, and what I like, it's fine.

It seems to me the more power you start making, it's probably a good idea to install these kinds of parts. Maybe the arms weren't twisting under stock power, but there's a good chance you guys letting all the smoke out will be putting the hurt on these arms.