Softening the front suspension redux.

Time to get serious about the front beam in my little car. Floor pans are in, rear bearings and stubs re-installed, front end is next. The pan is originally from my '74 Ghia, ball joint front, double spring arm rear. Right now the rear has Bilstein (non-adjustable) Sport Shocks and a 3/4" sway-away sway bar installed, but that can go if it's too much for the light front end set-up.

The body shell weighs around 250 pounds. There's no additional weight up front other than a fiberglass valance, a Ghia gas tank, and a Holley blue pump and regulator. I'm running a set of shocks from a 60's Dodge Dart, other than that I need some serious help.

I would dearly like to know what everyone is running for a front beam set-up and the pros/cons that you each feel are applicable to your cars. The more info that you can share, the better off I'll be in rigging up my own beam for such a light weight car.

The end use will be mostly highway driving, I think that I have the front sway bar info in hand, but if there's something special about your ride that is particularly sweet, PLEASE include it here, would you?

I TOTALLY need a ton of help and info here ! ! !

Thanks,

TC

for me, the stock beam was too stiff, so i removed a few torsion bars (but kept the attachment points in the middle and ends). see my site for detailed pictures.

that plus oil filled air shocks. rides like a couch now when on air, but nice and firm (with a decent amount of travel) when air is out and it's back on the torsions.

TC.. I robbed a 78 malibu sway and rebent it for my D Its a 1 inch sway ,, BETTER... Don't forget a pair of wore out shocks in the front will be perfect for what your up to That gas Blistien on the rear is also perfect..

After you figue out exzactly how many springs to run. then make filler peaces 2 inches long to spot wield onto the ends of the springs to fill out for the ball arm notches..

The beam center part is tricky.. grind your fillers pointy so they go in easyer tape them on the springs with electial tape on the un pointed end I wish the aduster colars had be designe to be remoe able But they useally are not.. which is a pain.. BUT.

When you get that in .your home free.. Don't forget to grind them for the center stud point that will lock them in tightly.. in the collar of the center beam adjusters.

"so i removed a few torsion bars"

Oh no you don't ! ! ! How many, small or large, and from which tubes ? ! ? ! ? !

I SO sick of this fuckin' vague "And then I pulled a few bars and was done, and it rode like a Cadillac/go-cart/Porsche/million bucks!"

You did it, try to remember what you did and write it down for shit's sake . . .


And you too Barry . . .

"After you figure out exactly how many springs to run . . . "

No, NO ! ! ! You tell ME how many springs YOU ran ! I wanna build this thing ONCE, stick it in, and move onto all of the rest of the shit. I'm already married and HAVE a job, not looking to make a simple beam build and installation into my new career. Don't really want to HAVE to figure out exactly how many springs to run, I figure that with THIS many Speedsters on the site, you guys MUST have figured it out already.

Now lets have some numbers and facts ! ! !

Uhhh, you want fries with that, Mister?

are you serious?

i *was* trying to help - but now - figure it out on your own.

if looking at pictures is too complicated for you to understand, then maybe you should think twice about doing the work yourself.

you = dick

No onions on that order...(;-) Just give me a beer while I wait

dear team, get the book automotive math, or how to make your car handle. on the front end of race cars we always set them up to start by 1/3 spring rate for the total front end weight, so if the total front end weight 1500 lbs, you would start with a 500lbs spring, of course thats with a front eng car, but shoulndt make a diff, and in the rear it was 1/10 the weitht.if you go too soft under breaking it may nose dive badly. bill

Now that's neat info ! ! ! Do you know where I might find the spring rate on a stock torsion leaf bundle for the VW Beetle? I have access to a spring machine, but it's located in the shop and really only good for testing coils.

If nobody had any solid, serious info (other than a suggestion of looking at little pics on a web page) I kinda thought that re-enforced shock towers and adjustable coil overs might work with the usual through rods and such. I have some extra threaded sleeves and collars and a set of 350 pound (red) springs on the shelf.

I also have a beem with a select-a-drop installed in the bottom tube. This would give me an option of releasing the tension on the lower leaf pack entirely and running just the uppers with or without the coil over option. If with the coil overs, I'd definitely need lower rated springs, possibly cut down rear motorcycle items.

I also thought that I could fabricate a small single coil over set-up between the lower leaf pack and an upper stable beam mounted bracket. Giving me a neat way of adjusting the lower torsion leaf pack with a spring mounted set-up but this would mean factoring in the spring rate of the different setting on the center mounted coil over as well as the compressed rate of the lower leaves as well.

Way, WAY beyond what's necessary or what the counter guy at the shop can handle.

Any more serious help, or silly insults, would be much appreciated. If anyone actually built their own car and is satisfied with the ride quality and can describe EXACTLY was done without the need for pictures or other visual aids, I'd STILL love to read what you have to say. Words and measurements, not pics.

Thanks !

TC

I've never seen any info on what the actual front spring rates are. I'd love someone to do some testing just to find out what the actual effects of removing leaves were on the spring rate.

Here's a way to test front wheel rate: put the rear torsion tube on jackstands so the rear wheels are just off the ground. Place a container directly centered over the front beam. Start filling the container with sand or something until the front end has dropped exactly 1 inch. Weigh the container. Wheel rate = container weight / 2.

If you want to measure each bar: pull a spindle off. Hang a container directly over the ball joint. Fill it until the arm deflects 1 inch. Weigh the container. The wheel rate for that bar is the same as the container weight. You'd have to do both bars on a side to find the actual wheel rate. But this method doesn't take into account the ability to preload one bar against the other which would affect the total wheel rate.

Now just multiply the motion ratio of the coilover mounting geometry by the wheel rate to find the needed coil-over spring rate. That would give you a stock ride.

If you want to try the center coil-over mount, remember that 1/Rn = 1/(Rt*(Lc/Lt)) + 1/Rc. Where Rn = new spring rate, Rc = coil spring rate, Rt = torsion spring rate from above, Lt = trailing arm length, Lc = length of lower coil-over mounting arm. This means the resulting lower bar spring rate will ALWAYS be less than the stock torsion bar rate. Removing leaves from the lower bar is a much simpler solution.

You can also use wheel frequency to determine needed coil-over spring rate. A calculator like this http://www.racingaspirations.com/?p=292 shows wheel rates in the range of 75-150 lbs/in should work well. The spring rates will depend on your motion ratio. Unsprung weight is 100% of wheel, tire, spindle, and brake plus 50% of control arms, tie rod, and shock. Those 350 lb/in springs would need at least a 1.7 motion ratio to get in a comfortable range.

Also, your rear wheel frequency needs to be about 20% higher than the front. E.g., 2 Hz front frequency and a 2.4 Hz in the rear. On a longer wheelbase car, values would be closer to 10%. The point of this is that when the car drives over a bump, you want the front and rear suspensions to reach max deflection at about the same time so the car doesn't pitch over the bumps. Since the rear tires hit the bump later, they need a higher natural frequency to make their peak deflection occur earlier and thus match the front's peak.

I'm not far enough along to give you actual numbers.

Superb information ! ! I'll have to do a rough figure the torsion leaf spring rate using your method, just so that I have it on hand. Just in case.

We do so many adjustable spring conversions on TR8s that I'm leaning towards that solution, just because I know the territory. I know that the shock towers will need reworking to support the car. I can get aluminum through rods threaded for the trailing arms and such, no problem. I might even use the 350 pound springs as a starting point. Looks like this is gonna end up being my new career after all.

Of course, I was hoping for the sweet and simple, "Just pull two small leaves from the top bundle and two from the lower one." but that ain't happening. I never thought of it, but it's probably because most folks buy their rides rather than build them, and even front beams are most likely picked up as "bolt-in" items. Makes sense. I wouldn't be into this if I didn't have to be.

I know what you're mentioning about the single centered adjustable spring set-up. Doing the math for the spring, and torsion bar, and built-in pre-load is sort of Formula I territory, and WAY over the rim for this silly street car based on an antique VW suspension. It just seemed like an elegant and interesting option.

I wish that the select-a-drop was installed in the upper beam, I'd try running it without the connector rod, just letting the leaves rotate freely. Have the one leaf pack do the job of two would certainly soften the ride and might be perfect for SUCH a light car. However the problem with it being in the bottom tube is that it make me leery of have the entire sprung portion of the suspension essentially hanging un-supported from the upper ball joints, you know?

Anyway, thanks a TON for such great info, your idea for measuring torsion leaf rate is genius!

TC

TC:

Just did the beam on Bridget the Midget. For review, she's an MG TD on a full-length 69 Beetle pan, not too different from what you're doing in terms of weight and weight distribution. My guess--and don't you fuckin' insult me; it's a good guess--is I've got maybe 250-300 lbs over each front wheel.

That's about 200 pounds less than there would be over each front wheel if Bridget were still a Beetle.

I pulled all the small torsion leaves out of both the top and bottom tubes and reassembled with old oil-filled shocks. I set the adjusters at very near the top of their travel--maybe an eighth inch from max UP, meaning my ride height is just about an inch or an inch and a half lower than what "stock" would be.

Thing rides like buttah, especially compared to last year. Haven't pushed her hard yet into any corners but guessing (yes, guessing, for now) I'd be better off without the stock sway bar up front and adding one to the rear, as you have. That's 'cause I'm looking at something like a 35-65 weight distribution, front to back, and so she's likely to still want to understeer.

I's you I'd start where I finished. It's likely to be very workable with what you've built, and you can still play with ride height, sway bar and spring rates using the adjusters. I doubt you'll have to pull any "big" leaves out and make spacers and crap. And coil-overs would seem a needless complication in your app. No sense going there unless you find it's absolutely needed.

Beyond this advice it's all math to me.

". . . and don't you fuckin' insult me;"

I just sneezed coffee out of my nose, it burns like salt water at the beach, you know?

Thanks SO much for the sound and empirical knowledge ! ! ! A couple of days ago I sorted through all of the front suspension parts and pieces that I have, picked out three beams to experiment with, and I'll do as you say on the one in the best condition. Might still weld in some reinforcing "clam shells" on the shock towers, but otherwise as you say.

I'm honestly looking for your "like buttah" ride as well. One of my expectations is that, without some extra care to compensate for the lack of weight, the car will just bounce across the road surface and into the ditch in a hard corner on a less than perfect surface. And, being in Massachusetts . . . there aren't any of those. There's a relatively small frost heave on one of the Route 44 entrance ramps that pitches the Mustang about six inches to the left when I hit it at speed, even with the GT suspension package and new Pirellis. That same situation with the little Fiat, with a stiff suspension and tiny wheel height would put me into the rail or on my head I'm sure.

I've read the posts from some of the smart folk explaining the function of a front sway bar in an extremely light weight car and they recommend soft "springs" to make for a safe acceptable ride with a stiff bar that will slowly come into use as the road becomes more twisty and the driving more extreme. Once you're at speed and into it, you don't really notice that the ride has become stiffer but appreciate the stability offered by the bar. Around town, the sway bar doesn't come into play as much, but the softer springs are a pleasure. Sort of a perfect compromise from what I read.

With a short wheel base car, the rear sway bar is usually unnecessary I guess, since the rear follows the front quite easily and naturally, I've got a bigger rear bar installed because of my plans for the front I guess. Hoping that I can get things to come together in the end based on a bag full of opinions and a bit of someone doing it before me. Hoping, anyway.

I REALLY appreciate your hands on information, and especially hearing that you're pleased with the results ! !

Luck,

TC

Part of the issue with the Mustang is the panhard bar on the rear. Moves the axle side-to-side over bumps, but is especially noticeable in the corners.

On the soft spring/stiff sway: The sway bar effectively increases the spring rate on the outside tire and makes the car feel like it has stiffer springs than it actually has when it leans in a corner. However, the maximum effect (when sway bar is infinitely stiff) is to double the existing spring rate. Since the car is so light up front and the springs so soft anyway, you necessarily end up with a pretty stiff bar to get much change anyway. But a stiffer front sway bar increases understeer.

On the rear, adding anti-roll increases oversteer. Depending on how the front reacts, no rear bar may be the way to go.

TC, also for review, I live just outside of Baltimore and once in a while (don't tell the insurance guys) cruise Bridget to work over Route 40. Going into the city this road is like something you might find in Afghanistan. My other car is a 2wd Nissan truck and that thing skitters on the ruts. Last year Bridget would hit that stuff at 30 mph and it was like driving a shopping cart on cobblestones.

Now, not so much. The suspension actually WORKs. It's bumpy, but mostly straight and true and not in any way like running naked through a hail storm.

Sorry about your coffee. I might (just might) run Bridget up your way this summer and, if so, I'll buy you one.

The front sway bar is a smidge over 3/4" diameter, I believe that I'll need it for what I have planned. With a bar that thick, I put the rear in place based on what others have "said." I rather of thought that with a 76" wheelbase it wasn't necessary, but I had it and . . . well . . . you know.

Thanks guys, I really think that I'm beginning to gain an understanding of this.

Kudos TC. Goading is a dirty job...

I practically BEGGED for the TB leaf info 5yr ago , coulda sworn there was a fatwa on it.

Dave,

How did you end up "solving" the problem? Was it right along the lines of what's being suggested? Love to know?

Thanks,

TC

sorry; gone a few d .
she's still stiff. Did nuthin . Drive it like a racer . It bounces , but a sway bar is out .

I pulled 5 narrow leafs from the top and bottom front beam. the leved it up with the advusters..

I have built several beams for dune buggies this way and with exellcent results bt thats a 6 and 6 standard spring tweek

For custom work .It's one of those things you ave to tinker with.

SORRY If i do another one anytime soon I'll doa photo shoot

but a differt weight car will have different needs . CUSTOM WORK

It's trial and error ,,I pulled my beam apart 6 times before I was happy with it's handling on the curves and smoothness of ride..

Get it road worthy then do the drive test. and give it what you want it to have.. Add or remove to your needs then adust the level ride height

I used Red 9's coil over set up and was really pleased with the results out of the box, springs were 11olb if I remember correctly. Still have yet to put on their A arm assembly that I got a few years back.

Thanks Barry!

Was that five small leaves top and five leaves bottom or five small leaves total?

Looks like one of the beams will be a simple leaf removal and adjusters, just want to be sure that I get the right leaves out of the right tube to have a sound starting point, you know?


Brian,

I like the rating of the red coils, they seem more manageable and easier to "get right" than the black coils. I got two pair a while ago when we were buying sets for the TR8s, one set is destined for the Mustang II set-up, that will eventually be for a 356 square tube frame. I'd like to use the other pair on a custom/altered VW beam that we've been poking at for the past two weeks. Nice to hear that you opted for red coils as well. I thought that mine were eight inch, but I'll throw a measure on them this weekend, I may have nines like you.

I know that you didn't mean to write that you had 11 pound compression weight springs, but I'd be interested in what rate you DID get.

Thanks !

TC

A bit of misunderstanding here TC...

I got a kit from Red 9 Design in the UK. The coil overs are actually yellow SPAX coil overs from the UK. SPAX told me that they specially build these coil overs for Red 9 however, a check on Ebay UK will result in a lot of SPAX coil overs for sale. Many have the bushings at both ends but I once saw a very simple adapter made that would adapt bushing shock ends to the bayonet kind like on a ball joint front end... a U bracket fitted and drilled for the shock bushing and then a threaded part of an onld shock welded to the top. There seems to be a lot more bushing shocks than bayonets on EBAY.

Opppsss . . . my mistake.

Forgot to answer your question...was 110 lb springs I think not 11. Simon at Red 9 suggested this spring rate as he had some experience with this kit on some Speedsters in the UK and this was what they settled on. My front end was tranformed with this kit. We have very shitty roads here and with the old KYB's on the car it was bone jarring. The Red 9 kit smoothed the ride out considerably.