I know quarter elliptic rear suspensions have been discussed a lot here, and the consensus from those that have them seems to be that they ride well. My question that I haven't seen asked is whether they lean more or less in corners as compared to a transverse leaf? I know some people run stabilizer bars on the rear of their A's, is that less necessary with quarter elliptics? Just a thought exercise out of curiousity.
When I built my yellow highboy 32 roadster with quarter elliptic rear suspension in82-83 It's first real road trip was on interstate I76 west bound to Denver onto I70 and thru the mountains west of Denver. The car drove like a slot car thru the mountains then out into the wide open spaces west of Grand Junction into Utah & Nevada and California. Never got a ticket but got scolded by a highway patrol man for 90+. Coming home we went up the coast highway, stayed a week in Tahoe the another high speed trip home to NE on I 80. I never could understand how I was lucky to have hit the perfect suspension combination on the first try. Car is still going with the same suspension up in I think Oregon. Sometimes you get lucky?
I have quarters in my roadster and a panhard bar on both ends. The car corners at speed fine but a buddy driving out one night noticed the car likes to push out on the corners. I think that is the posi quick change. But there is no more leaving than any other car I own.
I had quarter elliptics on all four corners of my 27 T roadster in the late 90s. It had a full chassis width Panhard bar parallel with the ground. It handled very well in corners, mostly limited by the contact patch of the tires. I don’t think they would be my first choice for springs if I was building a road race car.
Quarterelliptic rear suspension, or front suspension for that matter, is not really any fundamentally different than a cross spring, AKA: a buggy spring. If you think about what a cross spring is, it's a single leaf spring assembly anchored in the middle. One side of that spring is attached to each side of the axle. Springs are just dumb pieces of metal. After the anchor point the spring has no idea that there's more spring on the other side. A quarter elliptic assembly is no different from that. It just doesn't have more spring on the other side of the anchor point, because there is no other side. Handling should not be any fundamentally different. That is largely dependent on all of the variables associated with chassis dynamics, as is the case with every other suspension system.
Thanks, good info as well. By push out do you mean oversteer or shift of the body compared to the rear end?
I would think he means it feels like it under steers. You normally fix that with a little more turn and a little more throttle in my experience. @BigJoeArt little bucket of purple handles like a slot car like everyone else has mentioned. Very flat and stable, and for a car damn near on the ground not harsh or stiff at all.
As already stated, the chassis tuning isn't any different than other spring configurations. The biggest variable that I have noticed in various build threads is the source of the springs used to convert to quarter elliptical. Everything from trailer, car, pickup truck springs have been used along with some purpose built springs from the major spring suppliers. The spring rate of the purpose built springs is probably much closer matched to the vehicle weight of the build than some random spring you cut up and maybe temoved a leaf ot two.
I disagree on this, my experience with buggy sprung cars is that they like to lean and have a lot of body roll with out a sway bar of some sort, or at least some stiff shocks. my T has quarter ellipticals and it doesn't have (or need) any sway bars, and handles very flat, because the place where the spring(s) mount to the chassis is wider on the quarter ellipticals. therfore it holds the car more steady in side to side roll, much like the difference from a ladder bar setup vs a wishbone. I did wind up putting a panhard bar on the rearend due to it not having enough control of horizontial movement, but the front hasn't posed an issue yet. I run a set of cheap speedway quarter ellipticals, and have put about 16,000 miles on them so far. I have gas shocks in the front, and oil shocks in the rear. It rides better than most buggy spring cars I've been in, and if i was inclined to put some wider tires on it, it would probably surprise people how well it handles. Even just the difference between the 135r15 front tires, to the 5.60-15 whitewalls I run, poses a noticeable difference diving into corners. I'm building two more cars with them, if that tells you anything. .
From a suspension perspective, sure, they're fundamentally the same because they're both springs. When the movement isn't strictly vertical, they're not the same. That's why I asked the question. As you said, the cross spring is anchored in the center, above the centre of the axle. Quarter elliptics are anchored in front of the axle, at two separate points. That should make the suspension resist movement more when the vehicle is trying to lean. In theory it's the difference between a teeter totter and a board supported at each end...
Krylon32 told me that the light duty ones are no good. Mine will be a full fendered roadster pickup. So far I have ladder bars and a panhard for the rear. For the front I have a buggy spring with a dropped axle and panhard bar as well (and hairpins). I think the quarter elliptics in the back will give me the ride height I'm looking for and a good ride and handling. I originally wanted the buggy spring look, but I think it's pointing more and more to the quarters for what I want, and I should have more space for exhaust that way too. I dig your T, the stance is awesome. I didn't know you were building two more cars with that setup, that's awesome. I appreciate all the info!
Ok I run quarter elliptic springs on the rear and ford style cross spring on the front. I have 46/47 ford shocks on the rear and early MG shocks on the front . As you can see I installed a panhard bar on the rear . The car weighs in at under 2000 lbs. It rides extremely well and corners like it’s on rails .
If spring rates and length are equal (which rarely is the case), the only restrictions to body roll in a QE setup that are not present in a cross spring are spring twist and spring deflection. Both can be mitigated by articulated shackles. The handling differences are more from construction/configuration variances rather than design function. The car that I built, shown above, has shackles with Currie Johnny joints on the shackles. The brackets on the axle mostly hide them. There is nonedible body roll, but it will seamlessly articulate over road irregularities. This car was finished out of my control, and had a tube axle and friction shocks. I could not drive it. The customer came back to me and I reworked the entire front end, including the steering, and added a beam axle, and tube shocks. Later, the rear got c-notches, tube shocks, and a dead perch. Now the chassis is done. The 4-71 will come when I get out of the wheelchair, and finish PT.
That's really cool, Gimpy. I would love to see more of the particulars of that suspension .Good luck on the recovery ..
I will be using a Model A stk front spring cut into two pcs for my speedster front suspension, and will do the same with the rear Model A spring for the rear. Will be interesting to see what happens.
I don't know why he would think these are "light duty" or that they wouldn't work for a fendered car. my T is (in my opinion) kinda heavy at 1900lbs, and it doesn't feel undersprung at all. Quarter eliptics make so much sense in the rear of a hot rod, they work great with hairpins on the back of my T, and are lining up well with a 4 bar setup in "the Wag Tag Special" it allows for way more room around the rearend, and if you think outside the box you can fit alot in a small space. let me know if you have any questions. .
But, is that because it also has wishbone radius arms mounted to the outside of the frame rails, which pretty much work like a sway bar? My 30 pickup also uses wishbone rear radius arms (in the front too), and it too corners extremely flat, no body roll at all. No buggy spring either, coil overs. But, I think the reason is due to the wishbones, not the springs.
Yeah, he said he learned that the light ones were too light in his experience. I think I'll have a conversation with Posies when I'm ready to buy to see what they recommend, since they have both a light and heavy option with some vague wording. I don't expect my RPU to be that heavy, but don't want it to be under-sprung either. I also don't want it to be unbearably stiff, and I'm not averse to running air shocks with a small compressor if I need to for a little extra support when I have things in the bed. I looked through a few of your build threads last night, you do really awesome work. I was hellbent on having a stock-style rear spring, the more I think about it the more I agree that the quarter elliptics make a lot of sense for packaging in the rear of a hot rod. There was a discussion about it on @Tim 's A build thread and it's been stuck in my head ever since.
If the wishbones work like a sway bar, wouldn't you and Joe be breaking heim joints, bolts, etc.? A surefire way to figure it out would be to unbolt your shocks and see how much it articulates. I'd bet it moves more than you expect.
You missed my point. your coilovers are working in the same way as my quarter elipticals. the mounting points on the frame are farther apart that the single center point mount of a buggy spring. since the frame side mounts are father apart that means the load will be spread across a wider area and should be less inclined to roll side to side. yes, the hairpins will allow less movement theoretically, but i've seen 3+ inches of travel in my T, and other than side loading clevis' on the rear (pre panhard bar) i've had no problems breaking stuff.
Actually, it's the axle itself that works like a sway bar. The hairpins force the axle to swing in an arc as it travels up and down. If both wheels move up/down together than all is well. If only one wheel moves, which in the case of body roll is essentially what is occurring, though it's the body moving not the wheel (actually it's more like one wheel moves up while the other side moves down), it forces the axle to twist, as the wheel moving has to travel in an arc, but the other side remains stationary; and round axles don't twist. So the axle resists the forces that work on the body to cause it to lean, just as a sway bar does. It works in practice because hairpins themselves flex and absorb the force. But yes, it does take a toll on heim joints and bolts, and welds, and frame rails, etc. And sometimes, or eventually, something breaks. Every metal part has a limit to the number of cycles it can take before fatigue derived failure occurs. It may work fine until that point, but once reached cracks happen. Sometimes they develop slowly, sometimes it happens fast.
I don't think I missed it, but I may be wrong. I just think the physics involved say the reason your T stays flat in a turn is more due to the reasons I outlined above, not due to the location of the springs. But, I may be wrong. Hey @gimpyshotrods what do you think?
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