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HHP springs intall

5906 Views 61 Replies 8 Participants Last post by  HC5120
Installed the HHP springs today. I am not going tp list every step and the torque specs as those are easily found.
HHP said no realignment is necessary. I may do that in the future, but the difference in ride height is the difference of having 1, 2, 3 people in the car, or a full tank of gas versus almost empty, etc., so we'll wait and see. Car drives really good, though.

American Muscle has a good install video on it: video

And on the BMR site they have directions for installing their springs, but it's all the same. Go to this link and then click on "installation" down a little ways on the page. BMR installation instructions

There are a couple of ways to do the rear springs. In the AM video, they remove the inside A-Arm bolt and drop the A arm from there. If you do it this way, you have to drop the exhaust some to get one of the bolts out. That's pretty much how the BMR directions are, but they have you remove the caliper and also remove the bolt for the lower trailing arm.

In all it took about 3.5 hours with two of us (though my assistant helped about 70% of that time), and the total time just depends on how stubborn the suspension parts want to be coming apart and especially going back together. If doing it again, I am sure we could do the whole job in 2 hours if we were both completely focused on it, and after having done it once. Some of the rear suspension bolts were a bear to reinstall. That's typical with suspension stuff.

Here is the difference in ride height with the HHP springs for all four corners compared to the stock springs.

Front left: plus 13/16; Front right: 0
Rear left: minus 1/8; Rear right: minus 7/16

Here is a pic of the stock front springs compared with the HHP spring
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Installed:

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Rear springs side by side:
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Rear springs installed

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We used this Eastwood strut spring compressor. Worked awesome. I researched tool options quite a bit, and this seemed to be the best made. The directions say not to use an impact on it, but reading reviews online, etc., lots of people do. It worked flawlessly. Seemed very safe. $165.00 from Eastwood.
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All and all, it wasn't too bad of an install. The rear springs actually took longer because it was tough to get the bolts back in the arms and the lower shock.

The biggest worry with this install is probably compressing the springs for the front struts. I felt the Eastwood tool was very safe and solidly built and dependable.

The car drives good. I can't tell much of a difference, but I don't drive it that much just cruising around town. We will see what difference it makes at the track.

As I stated in the drag racing 101 thread I made, this isn't a necessity for 10 second cars or even high 9 second cars if they race on an excellent track with excellent prep. But it's one more thing to (hopefully) add consistency for bracket racing for me, and help me on my home track which is challenging (we'll see). I have run a 1.53 and 1.54, but my 1/8 mile 6.80 at 4400 DA in my sig was a 1.58. I think I can do quite a bit better, but we'll see in a couple of weeks. My goal is to hit high 6.60s in the fall when the good air comes back and I have fresh tires. That would be solid for a 2.85 pulley and 93 fuel at 4500 DA. I would like to go back to a 305-17 tire, too, so this might get me closer to being able to do that.

If I have something messed up that you see in the pics, thanks in advance for the heads up.
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Yeah but remember what goes up must come down. Goal is to put weight on the rear and keep it there. Bias ply is a totally different deal

Hellcat already comes pretty low in the back. If you want it to transfer weight at the track I would call Mercer motorsports and concentrate on the front (increase travel decrease rebound dampening) cha ching

The stance of the car at launch is important too. Car has most of its weight up front and drag radial requires dead hook. Lowering the back/raising the front will help at the hit. The first foot is so important with these tires
I know someone that swears a diff brace cost him 7 thou in the 60

Backs up what you are suggesting ^^^ sorta
Suspension setup is so particular to a given combo, and very complex, like you said above.

It's just such a crazy low first gear in these cars.
It could be worse…

@Unholy707

rofl 🤣🤣🤣
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Can you post before and after pics. I might go this route.
Can you post before and after pics. I might go this route.
Hey, the difference is hardly noticeable. And I can't tell a difference driving it on the street, but I take it pretty easy with the car unless I'm at the track.

The difference from stock in height for all 4 corners was the following:

Front left: plus 13/16"; Front right: 0
Rear left: minus 1/8"; Rear right: minus 7/16"

Here are the initial heights at all 4 corners with the street tires on with the before and then the after in parentheses:

FL-29 1/16 (29 7/8); FR-28 7/8 (28 7/8)
RL-30 1/16 (29 11/16); RR-29 7/8 (29 7/16)

I think I have pics of before and after with the stock wheels. I will also get pic of the car with the race wheel setup and post that as well.
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Here's my Hellcat after HHP springs going from Eibach pro-kit. Sitting on 335/30/20 front and 345/30/20 rear, 20x12 squared, for an idea of tire height. Here are the before with Eibachs:

Wheel Car Tire Vehicle Sky
Car Tire Wheel Land vehicle Vehicle


Not the best picture comparison as far as angles go but what I've got for now. The ride is MUCH better on the HHP springs, stance of course MUCH better on the eibachs. Haven't done a WOT pull yet to feel weight transfer difference with HHP's but I'm happy with the ride improvement and that the ride height didn't increase to an extreme extent with HHP. A little taller tire will likely fill in the fender gaps nicely.
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Hey, the difference is hardly noticeable. And I can't tell a difference driving it on the street, but I take it pretty easy with the car unless I'm at the track.

The difference from stock in height for all 4 corners was the following:

Front left: plus 13/16"; Front right: 0
Rear left: minus 1/8"; Rear right: minus 7/16"

Here are the initial heights at all 4 corners with the street tires on with the before and then the after in parentheses:

FL-29 1/16 (29 7/8); FR-28 7/8 (28 7/8)
RL-30 1/16 (29 11/16); RR-29 7/8 (29 7/16)

I think I have pics of before and after with the stock wheels. I will also get pic of the car with the race wheel setup and post that as well.
It looks good. I think I'm going to go with the HHP springs. I was just curious if there was somewhat of a drop. I originally wanted the eibach kit but don't want to worry about scraping.
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It looks good. I think I'm going to go with the HHP springs. I was just curious if there was somewhat of a drop. I originally wanted the eibach kit but don't want to worry about scraping.
Thanks, was just giving some feedback to the thread overall but I recommend the springs. I definitely feel like I was sitting higher on stock springs, the fender gaps were an eyesore. It's tolerable on the HHP's, but I'm a Charger widebody. Maybe the extra weight makes a difference in ride height over a narrow body Challenger.
Thanks, was just giving some feedback to the thread overall but I recommend the springs. I definitely feel like I was sitting higher on stock springs, the fender gaps were an eyesore. It's tolerable on the HHP's, but I'm a Charger widebody. Maybe the extra weight makes a difference in ride height over a narrow body Challenger.
It looks good. I think I'm going to go with the HHP springs. I was just curious if there was somewhat of a drop. I originally wanted the eibach kit but don't want to worry about scraping.
There wasnt any noticeable difference on my charger with ride height. I didnt measure anything though either.
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Both of these pics are with the HHP springs. Fronts tires are 28" and rear tires are 29.4", 315-50-17.


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Made a handful of runs with the new springs. Races and test and tune got cancelled on Saturday, so didn't have a lot of for testing and used bracket racing Sunday for that while still trying to be marginally competitive.

Prior to the HHP springs I had been running lower tire pressure because of struggling to be consistent off the line. I do have a diablosport suspension controller, too, which I also ran last year. I ran suspension on street for four runs, and made one run on track. Still need to experiment with that.

First run tires 16 psi cold (what I ran last year with stock springs), 1200 launch (just where drivetrain is loaded): the car almost bounced off the line, and then did that again on the 1-2 shift. 1.59 60'.

The next few runs I had 18-18.5 cold. 60' was bad. 1.65, 1.63, 1.62. I asked my buddy to video the run. The car was literally rolling off the line with launching at the rpm I was at. That is how dead hooking the tires were, lol. They were asking me, "Hey, maybe you should try launching the car?"

Last run, I was like, I'm gonna give it the beans and launch at 1800. Well, pushed through the lights; I think I was closer to 2,000. I need to see what the max rpm I can get out of the converter is.

No question the car plants far better, and I think I just need to add rpm for my launch and play with tire pressure.

Too bad I blew that last run. I'd run 104.65 mph the previous run (4200 DA), and if I could have gotten a good launch, I know I'd have gone 6.70s. Probably won't see that air again until September or October.

Like is always the case, whenever you change something, takes some work figuring things out. In two weeks when we race again, I will get a bunch of runs in because it will be three days, and include test and tune in the morning.

I do think the springs are going to work, it's just that the car is planting so hard that the lower rpm launch can't overcome that inertia. We'll see.
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Not ready to frame and tub it yet huh lol

Did you friend video it from the side?
Yes it was basically from the side. I was like, omg, it literally looked like I hardly even hit the throttle. I did mash it on the run where I rolled through after the other car took off, and it hooked pretty good, but I didn't get a time because I'd already pushed through the beams.

There's really nothing to see from the video, except that it's the laziest launch ever, lol. Pretty funny really once I saw the video. Kind of surprised it was still a 1.62. It's just completely different with these springs. I was running like 15 psi cold sometimes trying to get the car to hook. I wouldn't be surprised if I am able to run 20psi or more now.
Mine works better closer to 20 than it does to 15

How wide is the wheel?
Mine works better closer to 20 than it does to 15

How wide is the wheel?
You know, those skinny little 10" wide wheels. I'm still waiting for you to find me some 17x12 wheels that will fit on a 16 hellcat NB and are under a grand. Then I'd squeeze the 305R-17s on them.

I ended up at 15 psi cold because that's what it sometimes took to get the car reasonably consistent on my track. It's lower than pretty much everyone on this forum. I have usually run them at 16.5-17 cold, but sometimes needed to go lower. Will try 18-19 psi cold next time out and work up from there. Probably 1500 rpm launch and see what happens. The next race weekend we have I should get about 15 runs in, so I should be able to get things headed in the right direction.
Ha

My wheel is a lil wider than yers. If? our tires have the same width tread mine would have a lil more volume. Your car has almost 50% more torque than mine does tho, and we aren’t at the same track…Who knows

It’s only money frame it tub it. Good wheels are 5k ea these days. Crazy
It's a huge difference with these springs. Just need some rpm at the launch. I'll get there.
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