Looking at the front coilover conversion kit for my 68 Barracuda. Any pros/cons going with either the 0-2in or 2-4in drop option? What is the difference between the single and double adjustment set up? Any significant modifying to make it work or is it a pretty straight forward bolt in system? Any rear suspension upgrades that would need to compliment the front? Also, any header fitment issues? I currently have Hedman tight tubes where the exhaust after the header flange slightly touches the tie rod ends.
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- Thread starter Mcfarlrm
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dano
Evil Handy Man
If you just want front coil over (i.e. no K member), Hemi Denny has a kit.
Appreciate the info. Looking for a full swap. Open to suggestions outside of QA1 as well.
@HemiDenny would probably be the best source of information on this. The various levels of drop will effect suspension geometry- bump steer, roll center, camber gain etc. With the torsion bar suspension a 2" drop spindle noticeably increases bump steer.
Suspension geometry aside though, the two major limitations on lowering the car are the header clearance to the ground and the tire clearance to the inner fender. I'm running modified torsion bar suspension in my Duster and am lowered about 2" from stock. At full suspension compression with 25.6" tall front tires, my tires just contact the top of the inner fender. So if I lowered the car further, I'd have to lose more suspension travel on compression. I also only have about 3.75" of clearance to the header flanges on my Doug's headers, which are one of the better ones for ground clearance. I probably lose ~2.5" of that under full suspension compression, so, that's not much ground clearance to account for an uneven road. My car is daily/frequently driven and a street car, it gets used on some pretty questionable roads, and I wouldn't go much lower than I have my car just because speed bumps and pot holes get to be too much of an issue. Show cars, race only and trailer queens could get away with being lower, but it wouldn't improve handling or driveability.
If you're talking about UCA's, single vs double adjustable means how you have to set the alignment. Single adjustable UCA's have to be removed from the mounts to adjust them. Double adjustable UCA's can be adjusted while still mounted to the frame, so it's significantly easier to set the car's alignment. If you're talking about coil overs, it double adjustable is adjustable on both compression and extension (rebound), single is typically only adjustable on extension. Obviously being double adjustable allows for more tuning of your ride quality. But even a good non-adjustable shock can produced a good ride quality if paired correctly with wheel rates, vehicle weight, etc.
For complete conversions I'd have to say the only two I'd look at are the HDK and the RMS. QA1 bought out Gerst, which was basically a knock off that had production issues. QA1 sorted the production issues and improved the design, but really I still think you'd be better off with the HDK. Both the RMS and HDK bolt in.
That said, ANY coil over conversion completely changes how the chassis is loaded by the suspension, and front chassis stiffness is already an issue on these cars even with the torsion bar suspension that carries all of the load in the crossmembers. So my opinion is that if you're installing a coil over conversion without stiffening the front chassis, especially between the frame rails and firewall, you're making a mistake.
And I'm sure everyone expects me to say this, but the only thing a coil over conversion adds that can't be done with the torsion bar suspension is the rack and pinion and some header clearance. From a handling perspective, anything you can do with a coil over conversion you can do with the torsion bars. There are pros and cons to both, and either system needs tuning and optimization. If you commit the time to tuning and optimization, either system will work just as well.
Suspension geometry aside though, the two major limitations on lowering the car are the header clearance to the ground and the tire clearance to the inner fender. I'm running modified torsion bar suspension in my Duster and am lowered about 2" from stock. At full suspension compression with 25.6" tall front tires, my tires just contact the top of the inner fender. So if I lowered the car further, I'd have to lose more suspension travel on compression. I also only have about 3.75" of clearance to the header flanges on my Doug's headers, which are one of the better ones for ground clearance. I probably lose ~2.5" of that under full suspension compression, so, that's not much ground clearance to account for an uneven road. My car is daily/frequently driven and a street car, it gets used on some pretty questionable roads, and I wouldn't go much lower than I have my car just because speed bumps and pot holes get to be too much of an issue. Show cars, race only and trailer queens could get away with being lower, but it wouldn't improve handling or driveability.
If you're talking about UCA's, single vs double adjustable means how you have to set the alignment. Single adjustable UCA's have to be removed from the mounts to adjust them. Double adjustable UCA's can be adjusted while still mounted to the frame, so it's significantly easier to set the car's alignment. If you're talking about coil overs, it double adjustable is adjustable on both compression and extension (rebound), single is typically only adjustable on extension. Obviously being double adjustable allows for more tuning of your ride quality. But even a good non-adjustable shock can produced a good ride quality if paired correctly with wheel rates, vehicle weight, etc.
For complete conversions I'd have to say the only two I'd look at are the HDK and the RMS. QA1 bought out Gerst, which was basically a knock off that had production issues. QA1 sorted the production issues and improved the design, but really I still think you'd be better off with the HDK. Both the RMS and HDK bolt in.
That said, ANY coil over conversion completely changes how the chassis is loaded by the suspension, and front chassis stiffness is already an issue on these cars even with the torsion bar suspension that carries all of the load in the crossmembers. So my opinion is that if you're installing a coil over conversion without stiffening the front chassis, especially between the frame rails and firewall, you're making a mistake.
And I'm sure everyone expects me to say this, but the only thing a coil over conversion adds that can't be done with the torsion bar suspension is the rack and pinion and some header clearance. From a handling perspective, anything you can do with a coil over conversion you can do with the torsion bars. There are pros and cons to both, and either system needs tuning and optimization. If you commit the time to tuning and optimization, either system will work just as well.
a 2" drop (short answer) will allow you to lower your car 2" while keeping the same suspension geometry. HDK uses this to not only lower your car but to utilize a longer shock. Longer shock=longer spring= more travel (over all the other conversions available)= a nicer / less harsh ride.
modifications?....if you can drill a couple of holes, go to the advanced class, no welding, fully reversable.
rear is optional and IMHO the rear is about tire size and traction and would depend on your specific plan to use the car. I am a personal fan of rubber bushed leaf springs for a street car.
single adjustable gives control (stiffness) over both shock rebound and compression dampening with one knob, double allows you to control them separately. Popular in a drag racing application where you want the nose to rise easily (rebound) for weight transfer and you want the front to stay there (compression) to keep the car from porpoising / bouncing.
on header fitment.....imagine how easy it is to fit any header without the torsion bars, steering box, drag link, steering arm / idler to work around.
out of the box adjustability, drops appoximately 30 lbs ....manual steer vs OEM manual steer, way more on a power steering vs power rack and pinion comparison.
Sounds like a 2" drop option is the way to go here. This set up will be strictly for road use. No autocross/drag racing. Any suggestions on a power steering pump? What would be suggested to stiffen the front chassis?
additional stiffening for a street car?, nothing else is needed, just the HDK components. JMHO, unless your car is not a solid piece to begin with, the USCT stiffeners just add unnecessary weight.
an OEM (60's -70's) P/S pump works great. If you go aftermarket, buy one with the correct pressure (around 800psi), too much pressure will cause the seals in the rack to fail, not to mention a jerky / twitchy feel to your steering wheel. Holley makes some nice set-ups serpentine and V-belt depending on what engine you plan on running.
Using a 2" drop spindle changes the suspension geometry. No reason to misconstrue the facts in the name of brevity. If you compare the numbers between the stock spindle and a 2" drop spindle, they will be different. The "short answer" is it lowers the car 2" and don't worry about the rest, since most of your customers don't worry about suspension geometry anyway.
lol! The unibodies on these cars are about as stiff as a wet noodle. With a good modern radial and half decent suspension it’s readily apparent how flexible the chassis is, they were not designed to have the kind of traction that is available with a decent modern radial tire.
XV actually did a chassis deflection test back in the day and compared the stock chassis to one with their take on chassis stiffening. Their testing showed that the front of the chassis, from the firewall forward, was actually very flexible. Hence the need for some kind of inner fender brace/J-bar, lower radiator support, etc. And their testing showed that adding inner fender braces and forward chassis stiffening made a significant difference. Needless to say there are significant improvements to be made even just for a street car. Believe that article was published in the 12/2006 Mopar Action magazine.
I added subframe connectors, j-bars (triangulating the frame rails and firewall and supporting the shock tower), torque boxes and a lower radiator support brace to my lowly torsion bar equipped street going Duster, and the difference IS noticeable. If you take the suspension loads out of the crossmembers and put them entirely on the front frame rails using a coil over conversion without doing anything else and don't notice the difference you definitely didn't need to drop that kind of coin on suspension parts.
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I agree about @HemiDenny. He's a great guy and a member here. He's always participating in threads so it's not like he's gonna fall off the map if you run into an issue. Support mom and pop.
the 2" drop spindles are designed to do exactly that, a 2" drop on the nose, no idea why you feel the need to add the snarky remarks.
The drop spindles move the spindle pin up 2", thereby lowering the front 2". EVERYTHING else stays the same.
new year....same BS
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Zigtf216
Active Member
2” drop spindles change the center of gravity, and increases the front moment arm, unless you change the heights of the ball joints to make up for it. The increase of the arm causes more body roll, which most people increase spring rates to make up for. Or larger sway bars. (Same thing). Doing that decreases bite in the front. Once you start moving heights of suspension parts around you can chase that stuff all over the place. 72 blunblu is correct, there is another member here does autocross and road racing is very well versed on this,but I don’t recall his name.
Exactly. Moving the spindle on the knuckle by 2" by itself changes the geometry of the suspension. And while lowering the COG is usually a good thing for handling, it's not without its additional consequences that have to be dealt with.
The control arm angles don't change (maybe), but that doesn't mean everything stays the same.
And even the control arm angles staying the same depends on whether or not you actually lower the car the full 2" built into the spindle. Because if you don't, well, now the control arm angles change and EVERYTHING changes. I get that with the coil-over suspension its not as easy to change the ride height without the use of a drop spindle so it's not exactly apples to apples comparing it to a torsion bar suspension lowered with the adjusters vs a drop spindle. But I would still bet that not everyone that runs a 2" drop spindle with a coil over suspension lowers the car exactly 2" compared to a standard spindle.
I ran 2" drop spindles on my Challenger for awhile if you remember, and had the numbers run between the car lowered 2" with the drop spindles and the car lowered 2" with the torsion bar adjusters. The roll center and bump steer were substantially different between the two. Peter Bergman also ran drop spindles on his Dart for awhile before he also abandoned them and went back to standard spindles.
And again, I get you can't just easily lower the coil over suspension 2" with the standard spindles. But saying that drop spindles don't change the geometry is just not accurate.
No ****, if you install 2" drop spindles in a car designed for a standard height spindle and do not drop the car 2", then yes the geometry changes. Just like if you drop the car 2" with non drop spindles, the geometry changes.
To be clear......front end geometry revolves around and is calculated (and adjusted) by the angles of the control arms and steering tie rods. Control arm geometry and center of gravity are two separate variables. Changing the center of gravity does not change the angle of the control arms.
answering the OP question ............Any pros/cons going with either the 0-2in or 2-4in drop option?
here is a tip......95% of the front ends HDK sells utilize a 2" drop spindle but the noses are not dropped 2".....HDK front end geometry is built around the pin placement. Seems to works great, I guess you could ask Racer Joe.
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mopowers
Well-Known Member
That silver car is badass.
Question - if a car with a 2" drop spindle ends up at the same ride height, what's the advantage of having the 2" drop? Does that mean for a drag-oriented application, the car would have additional extension travel than with a stock height spindle?
The silver Duster was built almost 20 years ago and while a power rack was added only a few years ago, the Duster has always had 5.5" of travel, a smooth, non-harsh street ride utilizing unmodified 2" drop spindles and tie rod ends (vs heims).
I guess you might say I figured a 2" drop spindle can be used for more than dropping the nose 2".
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mopowers
Well-Known Member
Thank you. What are the other benefits? Are you saying the drop spindle provides a smoother ride than a stock spindle? If so, how?
No, a shock with greater travel utilizing a longer spring IMO, affords a smoother ride. Don't believe me?......check with an off-roader
The specific HDK design is what allows the other (proprietary) benefits.
mopowers
Well-Known Member
I asked what the advantage of the drop spindle provides. Since it can provide more extension at a given ride height (as compared to a stock height spindle), a longer coilover shock (and spring) can be used? So that's what provides the smoother ride? So it's not just a benefit for a drag-oriented car?
I'm just trying to understand what benefit a 2" drop spindle provides if the car is ultimately setup at stock (or close to stock) ride height.
I understand your question, but I don't necessarily agree with your conclusion.
Using a 2" drop on an OEM suspension, the only advantage I see is what they are intended for, to lower the nose 2" while keeping the control arm and tie rod angles the same.
On an HDK, the 2" drop was incorporated into the original design of the K to remedy several issues. To be clear, you cannot simply add a 2" drop spindle and a longer shock package to your AlterK (or any other aftermarket rack and coil over conversion) and get the same result.
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mopowers
Well-Known Member
I haven't made any conclusions. I'm just a bonehead trying to understand why anyone would install 2" drop spindles if the car ultimately ended up at stock ride height anyway. What would be the point?
Here was my original question:
"Question - if a car with a 2" drop spindle ends up at the same ride height, what's the advantage of having the 2" drop?
Maybe that's where the confusion lies. I wasn't referring to any particular suspension type. I think I finally understand the answer though. There is no benefit to running a front end with drop spindles at stock ride height unless it's with a HDK specifically. Then the drop spindle provides additional benefits associated with a longer shock/spring package while maintaining the stock ride height. Is that correct?
There is no benefit I see to running a front end with drop spindles at stock ride height unless the suspension is designed for it. With 2" drop or standard height spindles, HDK could not run the longer shock without the HDK (exclusive) upper shock mount / support hoops. It is a combination of components that work together that allow various ride heights utilizing the longer travel shocks.
HDK has never been a fan of "one size fits all" . Different rims / different offsets, tall and short tires combined with customer individual ride height preferences means you better have the ability to adjust and accommodate.
HemiMarks 68 Dart sports standard height spindles and the longer shocks.
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