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So I went to order a master cylinder bias spring from DRM today and saw these two brackets on their site. I'm not one to throw parts at a car for no reason, but since these aren't very expensive I was wondering. Would either of these help geometry for a lowered street car? I don't race (not legally anyway). But I am planning on a coil over conversion in the rear at some point, probably later this year. I already have the rear lowered about an inch with lowering bolts and the front with coil overs. I like that height and probably won't go any lower. Would either of these brackets be of any benefit to a guy like me? I also have the Van Steel rear toe rod kit. I didn't install this for a performance reason. My stock one was shot and I couldn't find a good used one. Not sure if that matters in this discussion but just putting that out there. Hoping @MatthewMiller sees this.
I'm gonna have to go through my slips. I have a set but don't remember which ones I have on my 89. I have no other suspension mods so I'll be looking forward to what others say.
The trailing arm brackets are completely wrong for drag racing. They spread apart the front pickup points which lengthens the Instant Center and lower the front of the lower arm... both of these things lower the Anti Squat... if you're ride height is lower than stock it makes thing even worse.
For drag racing you want the Anti Squat % to be higher and the Instant Center to be shorter.... Early 84-88 brackets have the highest factory A/S % and shortest IC.
The DRM camber brackets lower the inner pickup point and that will create less (or no)camber gain as the camber arm will be completely (or amlmost)parallel with the upper arm (Halfshaft in the C4). Good for drag racing if you have a bunch of rear compression/extension - but you don't want to have very much with the IRS... rear suspension movement on IRS at launch is always down in factory IRS (less than 100% A/S) and that suspension movement takes away from the suspensions ability to transfer force to the tire..... this is why you want the highest A/S and stiffest spring... anyway back to camber....
Now for turning corners low or no rear camber gain makes the car more stable after turn in but it slows how quickly the initially turns in... this is why the early cars have a really high inner pickup point on thelower camber arm... because the camber gain aids how quickly the cars turn... but it also makes them seem twitchy and loose (prone to oversteer at the limit) to non race car drivers.... GM learned #1 most C4 buyers werent race car drivers and #2 these people drove around on the street more than road courses.... After 88 they revised the rear pickup points and got less camber gain and less A/S% because it made the cars "duller" when thrown around occasionally by inexperienced drivers.
Will
The trailing arm brackets are completely wrong for drag racing. They spread apart the front pickup points which lengthens the Instant Center and lower the front of the lower arm... both of these things lower the Anti Squat... if you're ride height is lower than stock it makes thing even worse.
For drag racing you want the Anti Squat % to be higher and the Instant Center to be shorter.... Early 84-88 brackets have the highest factory A/S % and shortest IC.
The DRM camber brackets lower the inner pickup point and that will create less (or no)camber gain as the camber arm will be completely (or amlmost)parallel with the upper arm (Halfshaft in the C4). Good for drag racing if you have a bunch of rear compression/extension - but you don't want to have very much with the IRS... rear suspension movement on IRS at launch is always down in factory IRS (less than 100% A/S) and that suspension movement takes away from the suspensions ability to transfer force to the tire..... this is why you want the highest A/S and stiffest spring... anyway back to camber....
Now for turning corners low or no rear camber gain makes the car more stable after turn in but it slows how quickly the initially turns in... this is why the early cars have a really high inner pickup point on thelower camber arm... because the camber gain aids how quickly the cars turn... but it also makes them seem twitchy and loose (prone to oversteer at the limit) to non race car drivers.... GM learned #1 most C4 buyers werent race car drivers and #2 these people drove around on the street more than road courses.... After 88 they revised the rear pickup points and got less camber gain and less A/S% because it made the cars "duller" when thrown around occasionally by inexperienced drivers.
Will
i have had the DRM trailing arm brackets installed since 2011
i would have thought it is more desireable for drag racing to have less anti squat for purposes of bettering weight transfer to the rear (vs. the stock 1993 brackets)
-especially on non /prep surfaces like i see some drag race video talk about allowing more (faster rate?) extension up front to better weight tranfser to the rear
Last edited by dizwiz24; Jan 16, 2025 at 12:11 PM.
The trailing arm brackets are completely wrong for drag racing. They spread apart the front pickup points which lengthens the Instant Center and lower the front of the lower arm... both of these things lower the Anti Squat... if you're ride height is lower than stock it makes thing even worse.
For drag racing you want the Anti Squat % to be higher and the Instant Center to be shorter.... Early 84-88 brackets have the highest factory A/S % and shortest IC.
The DRM camber brackets lower the inner pickup point and that will create less (or no)camber gain as the camber arm will be completely (or amlmost)parallel with the upper arm (Halfshaft in the C4). Good for drag racing if you have a bunch of rear compression/extension - but you don't want to have very much with the IRS... rear suspension movement on IRS at launch is always down in factory IRS (less than 100% A/S) and that suspension movement takes away from the suspensions ability to transfer force to the tire..... this is why you want the highest A/S and stiffest spring... anyway back to camber....
Now for turning corners low or no rear camber gain makes the car more stable after turn in but it slows how quickly the initially turns in... this is why the early cars have a really high inner pickup point on thelower camber arm... because the camber gain aids how quickly the cars turn... but it also makes them seem twitchy and loose (prone to oversteer at the limit) to non race car drivers.... GM learned #1 most C4 buyers werent race car drivers and #2 these people drove around on the street more than road courses.... After 88 they revised the rear pickup points and got less camber gain and less A/S% because it made the cars "duller" when thrown around occasionally by inexperienced drivers.
Will
I really appreciate your answer Will. I'll be honest I only understand half of it, but I appreciate it. I'm kinda thinking that since I really don't know what half of this means then I'll just stay away from these brackets.
i have had the DRM trailing arm brackets installed since 2011
i would have thought it is more desireable for drag racing to have less anti squat for purposes of bettering weight transfer to the rear (vs. the stock 1993 brackets)
-especially on non /prep surfaces like i see some drag race video talk about allowing more (faster rate?) extension up front to better weight tranfser to the rear
So on a non prepared surface you do typically run less A/S than on say like radial prepared surface..... however this is with regular straight rear axels that easily have suspension geometry over 100% A/S. We do this to take force off the tire (always bias tires in No Prep) and make the tire slip more forgiving because it's going to spin the tire... ALOT.... you don't want the suspension acting mechanically pushing the tire into the ground... that just wadds the tire up and causes it to run over itself and shake your teeth out. It's a way of managing a bad situation. FYI these cars still have more A/S than any factory IRS suspension....
With factory IRS you are so far under 100% A/S that the suspension cannot act mechanically on the tire to push it down... instead it naturally acts to allow the suspension to Squat. The only thing acting to apply force on the tire is the spring and shock compression damping. The higher A/S brackets in the C4 slow the rate the body can squat.... those brackets are likely why you're car hits the rear bump stops so violently and coupled with uncontrolled front extension causes the car to porpoise.
Again we are managing a bad situation just a different one by using the early suspension geometry and heavy spring/shock damping.
Will
If you install the DRM bracket, you will see a lot of big improvements due to much less camber gain. For the late model C4 you will likely see none... it's about the same as the late C4's. DRM brackets pictured upside down:
Not sure if the DRM comes with 10mm and 12mm versions, or just the 12mm.
The ADS bracket on the other hand, there are five positions. Top is about the same as the early C4... middle is the same as the late C4... and there are two more below that.
The bottom position keeps the tire fairly square to the chassis regardless of cornering or bumps or squat etc.
My personal favorite here is the one up from the bottom for autocross. There's at least one multi national champ running that bracket in the same position to confirm my recommendation.
For drag racing, if you bind up the rear you have instant tire load transfer, but if you want to soften that a little bit, you can let the suspension do a little work and run it in the bottom hole. Or if you want to drive the car on the street at all... you're sitting right on top of the rear tire so every bump is transferred to your spine.
The DRM bracket has the 12mm holes, so please don't run that with a sloppy bolt setup on early C4, make some small brass or steel bushings to press into the bracket holes, it's a thick beefy bracket... or do some welding... don't do what I tried which was to ream out the diff holes to 12mm, makes the boss too thin. Here's the After Dark Speed bracket with the five positions:
My 2 cents worth. For auto crossing or road racing you will benefit.
Look at their wins in Corvette Challenge series. They dedicated a lot of time on the track designing them.
I have them on my 93. They are way above my driving skills, but with the DRM bias spring and the brackets, ZO7 springs and shocks, she handles real well.. When I auto crossed in BSP, I did fairly well, and my car was competitive. I let one real good driver of other newer Corvettes drive it and he loved it.
AZSP33D raises a good point. The Dana rear bolt holes in the housing are 1/2" but the bolts used are 12mm metric. There is actually a slight difference as you have a 12mm bolt in a 12.7mm hole.
I found this out the hard way, after using the DRM camber rods it cracked the bolt hole ears on my Dana 36. When I fitted the Dana 44 I checked it after the first Hillclimb event, and yes it had started cracking one of the ears. I pulled the diff out and had the crack welded, and when checking the setup found the .7mm difference in each of the 4 holes.
Had to do a bit of reaming and used this camber brace, and it's a real tight fit with 1/2" bolts. Then knock the bolts in with a soft hammer.
No more cracks.
I really like that big bracket... I was thinking about making my own camber brackets with a built in brace in a simiar same way... using slugs for adjustment rather than the concetric holes on the ADS... or the eccentric on the thinner DRM/OEM. I also like adding weight in this area, very low and close to the rear axle. Better placement than the lead weights I have now in the areas behind the seats, so a big thick steel one would work best for me.
Did DRM get notified about this? Just curious as they are a pretty on the ball outfit.
I don't bother with feedback to vendors anymore, it is rarely a positive experience. The last time I emailed Yella Terra because the installation instructions for LS7 rockers had the incorrect preload for that engine. Didn't even get a response. Usually most companies will never admit they have made a mistake.
My use is probably different to most being hillclimb. I use Nitto 01's at 100 treadwear and now Nankang AR1's at 80 treadwear in 315 size, with a 530 hp LS1. I am coming out of tight corners continuously at faster speeds than autocross would be. I imagine the stress levels would be high, especially taking into account the angle these brackets push the stress from each lateral arm. Putting 1/2" bolts in 1/2" holes fixed the problem.
I don't bother with feedback to vendors anymore, it is rarely a positive experience. The last time I emailed Yella Terra because the installation instructions for LS7 rockers had the incorrect preload for that engine. Didn't even get a response. Usually most companies will never admit they have made a mistake.
My use is probably different to most being hillclimb. I use Nitto 01's at 100 treadwear and now Nankang AR1's at 80 treadwear in 315 size, with a 530 hp LS1. I am coming out of tight corners continuously at faster speeds than autocross would be. I imagine the stress levels would be high, especially taking into account the angle these brackets push the stress from each lateral arm. Putting 1/2" bolts in 1/2" holes fixed the problem.
Understand. I dealt with Doug Rippie a few times. Always positive.
I will have to look at mine, a 93 model. I use their brackets and they have been in there for many years. I use Nitto NT 05's, not as sticky as 01s, but better than most..
I bought the Nittos about 2 years ago. Need to start wearing them out..
Nankang AR1. Need to check them out.
Don't forget there's a big difference in the size of the holes from early to late diff... so the early diff is a bigger issue with aftermarket or late style bracket, if you don't pay attention.
Don't forget there's a big difference in the size of the holes from early to late diff... so the early diff is a bigger issue with aftermarket or late style bracket, if you don't pay attention.
Cool. Good to know. Now to find out, when I get home, what diff was sold to me from Ikerds years ago
Those lower camber brackets are no longer made, if you order those now what you'll get is a set from VanSteel, which are not the same, and you can no longer adjust camber with the stock lower arms.
I really like that big bracket... I was thinking about making my own camber brackets with a built in brace in a simiar same way... using slugs for adjustment rather than the concetric holes on the ADS... or the eccentric on the thinner DRM/OEM. I also like adding weight in this area, very low and close to the rear axle. Better placement than the lead weights I have now in the areas behind the seats, so a big thick steel one would work best for me.
If you wanted to get real fancy, you could make one for the front of the diff housing and create a sandwich clamping effect !
Those lower camber brackets are no longer made, if you order those now what you'll get is a set from VanSteel, which are not the same, and you can no longer adjust camber with the stock lower arms.
i didnt even think about that.
so the DRM camber brackets (or whoever now makes them) eliminate the eccentric adjustment feature of the stock camber brackets
DRM Camber Rod and Trailing arm brackets
