What are the advantages/disadvantages of rear coilovers? In and of themselves or compared to rear weight jacks?

I'm debating what I want to do for adjustable rear springs, and have noticed that there aren't really a lot of great answers for weight jacks (especially with a Moser rear). Of the top of my head it looks like weight jacks:

• more spring choices
• more shock choices
• larger more durable spring
• easier maintenance and parts swapping
• cheaper

where coilovers:

• Faster (I can just buy something, I don't know that I've seen a weight jack that I like that I can just buy)
• Lighter, potentially much lighter if you can cut off the spring cups on the axle (not an option, it's in the car, and the driver's side is part of the PHR adjustment point brace...)

I don't know which will potentially last longer or be easier to deal with on a daily basis. In this case, it's truly a multi-use car, I'll DD it when the weather is right, most of its track time will likely be dragstrip (possibly every weekend if I'm lucky), but it will spend most of its time set up more like an AutoX/Road Race car, and will likely see an AutoX a few times a year.

 

Problem with coilovers in our cars is, the upper shock mount is A JOKE.

If you can get a handle on that though, I can't see any reason that they wouldn't be satisfactory.

 

OK, but don't most (founders, UMI...) come with upper mounts that distribute the load across the original spring pocket?

 

They do; I just have trouble trusting that thin weenie area to perform that function, long-term. The whole entire area simply wasn't built to do that job. For a car that isn't used a whole lot, probably would be OK; but I would question how many hundred thousand miles it would make it.

If you're comfortable with it, like I said, I'd think they'd be a better option than weight jacks.

 

Are you trying to say the original spring pocket is not mean to handle the weight of the car, cause thats plain wrong.

I'll be installing the UMI kit as soon as it arrives, looks plenty strong to me.

 

The spring pocket is fine. It's the shock mount that's a problem.

 

OK, but the coilover kits that I mention come with brackets to transfer the load to the spring pocket.

 

It uses the Original Shock hole and an additional hole as well as a place that goes into the pocket.

https://www.umiperformance.com/home/...hocks-bolt-in/

Its like the 4th picture.

 

You know, I've never taken a hard look at that area/the way they're mounting.

1. I'm not sure that that ring in the spring pocket is adding anything significant unless you do something like weld it in, and even then I'm not sure how much it will do
2. it looks like the spring pocket and the shock mount use the same lower sheetmetal, the shock mount has multiple layers in it above it, where the spring pocket has those same layers separated. I wouldn't be surprised if the shock mount is actually stronger than the spring pocket.

 

As a few said above, Front coil-overs should be avoided in the front due to the way our uni-bodies are made. That and front coilovers make fitting wider tires more difficult. Fitting a 315 in front with coilovers means you have to use a STUPIDLY short spring.
Rear coilovers are VERY good and a HUGE improvement over weight jacks.
they are a HUGE weight loss, almost all unsprung weight.(20.6 lbs less in my case)
and have far better control on dampening forces. mostly due to a better shock design and solid rod ends for mounts.
I had nothing but issues with my UMI weight jacks.
they were noisy, and didn't sit well in the axle spring cups/pockets
the 5.0in spring always rubbing the sides of the UMI jack making that "spring" clung noise.
the thrust bearing started wobbling super bad within 6 months and there's no way to tighten them without a custom tool. a tool I didn't feel like making.
rear coilovers are simply better, but will cost more for a good set.
my coilovers had better handling, better launch grip, better ride quality, and better braking distances over UMI jacks+Koni yellows.

I have a good video installing a set of PENSKE 8300s rear coilovers on my car. They were valved by Jason at Unbalanced Engineering.
although they weren't plug and play, they went in without any huge issues.
I've run over 250 Autocross runs on mine and Zero things have bent or broken.
and I inspect my car VERY carefully every few events.(I inspect Aerospace parts so I got the eye for spotting issues)

 

I don't think that anyone mentioned that here. As far as I'm concerned front coilovers are a drag only mod for these cars, and only if you reenforce the strut towers.

huh, your weight jacks are one design I was debating on making something similar to, I guess that should be out. Honestly, I'm leaning coil overs- I don't like the cost and generally, I've been unhappy with $$$ solutions that look mostly bolt in, but I really need to get this thing back on the road and this seems one of the faster ways of dealing with it.

I'm curious:

• What spring rates are you running front and back and what suspension geometry changes do you have (primarily things that change IC which would change spring rates like lowering spindles/extended ball joints, PHR lowering bracket...
• What are you running for the front? I'm guessing some form of weight jack? Are you happy with it?
• What sway bars and endlinks are those?
• What is the car primarily tuned for (autox, street...) and are you happy with it?

​​​​​​​The video makes it almost look too easy.

 

--I run 1/2in extended ball-joints in the front, and have a lowered panhard bar in the rear.
so the springs I use for Autocross aren't even close to the average 3rd gen.
I've used a lot of springs so i can give you a recommendation based on your build and use case.
I still use UMI front jacks, after I re-welded them. i'm designing a billet set to replace them.(hopefully out of 6AL-4V titanium)
my 92 is 100% autocross and i love every second of it

as far as the end links, they are from Spoon, they are kinda heavy, but i haven't worn out a end link in 2-3 years since I've been using them

 

I will definitly take a recommendation but I'm curious what you're running (especially since I know your use and basic geomentry).

In my case 1" extended ball joints in the front (but currently disassembled and wondering if I should go 1/2" just to avoid some hassle, I don't believe the 1" will clear my 17x9" front wheels, I'm not sure about 1/2", thoughts? I haven't seen a good reason why a lot of people with well-sorted cars seem to run 1/2" over longer ones, but I'm wondering if it's just that the longer ones are harder to get and haven't existed as long) and have a lowered PHR.

Currently, I have all the parts for traditional weight jacks going through the front frame rails also have drilled 1/4" pilot holes guided with a 3d printed guide to see exactly where they'll line up so I can just stick the pilot of a hole saw in the 1/4" hole and drill. Prior to all this, the car sat like a 4x4, real, factory, non sagged stance, maybe a little worse when I pulled the AC, put in a lighter battery, aluminum heads...

Actual use- I've posted this before, it's complicated (yea, I sound like a chick): real world, it's >90% streetcar, but every f-body I've ever owned has been built somewhere between road race and autox and I've been happy with this. WRT to the rest of the time, most of it that will be competitive will be drag, though I will do an autox once in a while (back in the early 90's I was actually a competitive autocrosser and I will compromise street manners for a car that handles better, and honestly, I've never really had a problem with that suspension on the street. 100% of the time I run staggered tire sizes. My current "street" tires are Z06 F-17x9, 265/40-17 R-18x10.5, 305/35-18, my "I'm going dragracing" tires are either 165r15/26x11.5 slicks (and I have ended up street driving that combination for weeks at a time) or 215/65-15/275/60-15 drag radials. I'm not a big fan of low profile tires, and have had practically autox only builds that rode on 235/60-15 / 255/60-15 or 245/60-15 on all 4 Hoosier race slicks (again, I've ended up driving around like this for weeks). I would love to find something in old school sizes, something like a 265 or 275/50-15 front (I might need to go as narrow as 235/60 for it to clear the control arms) and a 295/50-15 or so rear (25 or more years ago you could get sizes like that in high-performance tires and competition tires, I've widened some factory firebird rims for something like that if I ever find it). Because of the tendency for bigger rear tires and everything being big and overbuilt in the rear (moser 9" with nodular case and 35 spline axles, detroit locker...) I tend to have to go slightly stiffer springs or sway bars in the rear than most like. I have most of the factory sway bar sizes but I'm probably going to run a factory 36mm hollow, maybe a 34 hollow on the front and I found one of the mythical 25mm solid bars for the rear (I have plenty of 19-24mm ones also).

My favorite setup so far was my '83 TA, lowered almost 3", 890# f and 200 (maybe 225) # rear, 235 and 255 60 15" tires (or 245 hoosiers), factory ball joint/PHR, F32mm solid bar, rear something smaller than 24mm, don't remember, but I ended up even putting rubber bushings on the rear sway bar with T-bird rear knoni yellows (they were pressurized differently than the f-body and valved softer so they worked better for autox, not as well for road racing).

I was curious, they look beefy and it seems like every time I look under any of my vehicles I've broken one. They also look like you can make them easily disconnectable (front for drag racing)

 

1in extended ballpoints would be my choice, but makes fitting wheels very hard. The outer tie rod is gonna be Super close to the wheel if not in the way.
my 18x11s fit under a bumpsteer kit, only because I used a low profile 180,000psi custom bolt.

As far as springs, this webpage has several Excel spreadsheets with suspension geometry goodness available. You can use it to get a good idea what springs to use. It even has a load transfer spreadsheet, pretty nifty as most of is can't do complex math like that alone.
​http://www.tracktuned.com/feed/2016/...ring-frequency

The #1 mistake I see people make for road race an AutoX cars is not using enough rear spring. Depending on if your panhard bar is relocated, it's usually north of 275+lbs even more of you get real serious.
Custom 316 stainless bump steer shim made by a buddy of mine.

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So do you think that I'd be better off getting 1/2" ones, or is it pretty much the same problem with all of them? Would it be as bad without the bump steer kit?

OK, but you offered to give suggestions for spring rate 😉

I've been doing this for a long time, and at one point measured out the suspension locations better than most, and I'm not sure that I could accurately enough fill out that spreadsheet to draw any real conclusions. Honestly, I was hoping to get a guess based on your experience and some clue how I intend to use the car. FWIW, the current plan is to tinker with the front weight jacks with either some cut stock springs or Eibachs, the cut stock springs lower the car about 3", eibachs lower the car about 2" (possibly half a coil cut getting it closer to 3) and the 1" ball joint should give me some room to play with weight jacks and end up with spring rates in the 8-900# range, which I consider a nice street performance range with a stockish suspension.

 

We've been running rear coilovers for about 5 years. The only real complaint I have is the packaging gets tight. You have the lower control arm, sway bar end, and the shock and spring looking for space in that area. It can get tight. We've got 400lb springs in the rear on the coilovers. The front weight jacks are running 1000lb springs. We log a bit more than 1000 track miles per year in the car with this setup. Plus a few thousand street miles.

 

400# springs? Is that a typo? What kind of car is it?

 

both of the thirdgens run 400 lb springs on the rear coilovers. Yes, it's a stiff ride. Yes, it sticks in the corners.

 

Agreed. For street I'd say 250+, but your definitely in the ballpark here.
The improved angle of the rear coil-over is a help, but probably minimal. With strong brackets, definitely an improvement. Don't think twice or over think it. Adapt to the new tech and take advantage of its adjustability! Just buy with knowledge of operating range.