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Discussion Starter #1
Just been looking at the new front suspension of the 2017 Ford GT where the chief Ford engineer says by having torsion bar (plus small spring in comfort mode) and a pushrod operated damper where it is in location (pushrods/rockers actually as there are "three" links to get to the electronic damper which is kind of an indirect and complicated route to the damper in my opinion) all the weight of the suspension is pushed towards the centre of the car...ie less unsprung mass.

So i guess Alfa Romeo had a good idea with the Alfetta front torsion bar suspension (projected pre 1970) as torsion bars are more tuneable than springs and provide less unsprung mass but in the case of the alfa the torsion bars attach directly to the lower wishbone, so low down also. No other car maker in recent times has used torsion bars I believe in front.
By having very light suspension and wheel hubs and wheels (in ali or titanium) unsprung mass can be reduced further. In any case I think Ford have a modern twist on a theme alfa romeo was occupied with, unsprung weight.... but pushing still further with the philosophy with a complicated pushrod/rocker linked electronic damper for further unsprung weight saving which is key to good setup.

The video of the 2017 Ford suspension as shown on youtube is below
 

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This is quite fascinating. I think the only other carmaker that sort of did the same thing was Chrysler, but on rather mediocre cars (e.g. Dodge Aspen). it didn't help their handling, though I think it's not the fault of torsion bars.
 

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Jaguar used torsion bars as far back as 1961 with the E-type, along with inboard rear brakes. Back in 61, few cars had disk brakes all around especially inboard.

The lack of rotors showing thru the rest wheels is what initially caught my interest with the GTV6 at an alfa shop where I had my Spider worked on. A week later we found one!

The GTV6 has half the cylinders of our e-type but being lighter it is just as much fun to drive !
 

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Ford did not even think of Alfa Romeo when designing their GT suspension ... every F1 car for the last 20+ years has had torsion bar suspension ...

Plus remember the 1934 Citroen Traction Avant had torsion bar suspension, + Tatra then VW, hardly a case of Alfa leading the way.
Pete
 

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Discussion Starter #7
Thanks all for the input guys and sure the cars mentioned had torsion bars but the coupes were not mainstream or recent and were not allied to a low unsprung weight dedion rear suspension, 50/50 weight distribution and unassisted superior rack and pinion steering. The point was unsprung weight and the ability to change ride height at the front easily.

The type 116 suspension design platform effectively lasted from 1972 to 1992 in Alfa Romeo sedans and coupes for a "sporting" application and it was as road and track noted the alfetta had kind of like a chassis that a fifties race car designer would have dreamed up for his street version. Again though the emphasis must be on unsprung weight and in period tests I noted said the steering the best of any post war alfa. Paul Frere (ex Ferrari lemans winner) also stated "there are very few cars that can give an enthusiast as much pleasure on give and take roads, away from heavy traffic. Those who revere the 2000 GTV will, of course query this. But good as the Bertone coupe is, the Alfetta coupe is in yet another class....rack and pinion steering lighter and more responsive than other alfas".

Pete, Ford has always respected Alfa Romeo and tried to buy it in 1986 before Fiat was allowed to. Maybe you are right that Ford did not look at Alfa Romeo but instead F1 but then why are'nt other brands using this setup (without front coil springs behind the front discs) for modern sports cars also since it saves on unsprung weight which has myriad benefits, "and" as Ford engineers said the gap (now unobstructed) made behind the front discs allow for positive aerodynamic air flow to be better chaneled and enhance handling further.
 

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Discussion Starter #8
... as a side note the ES 30 used coilovers instead of the front torsion bars and speaking with a very well known Alfa suspension guy it had, stock, major work needing doing to it for it to be able to perform at a track effectively since the coilovers were not designed to handle the load that the previous torsion bars had taken. The ES30 was designed and brought to market in a year so no wonder!
 

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i have an 911 with torsion bar fronts, they built a cazillion 911s with TBs till 88. the hot race version 935, 3.0 RSR replaces TB's with coils while the 934 and SCRS ran with coil helpers with TBs having to retain them for homologation reasons.

its ancient and was replace with a much better resolved suspension solution with coils in the 964 and updates on the geometry.

my old roomate was the design manager on the GT. torsions on the GT with push rods and rockers was primarily for packaging reasons for the aero tunnel.
 

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Discussion Starter #10
Davbert...thanks for the input and sure Porsche 911 also had them. However were you calling the early pre 88 911 front suspension ancient or the use of torsion bars? I would hesitate calling torsion bars ancient as they have notable benefits over coil springs...easy ride height adjustability and lower unsprung weight. Using torsion bards is just a different option and not necessarily the worst for that.
The use by alfa of a dedion rear axle with watts linkage in the type 116 sedan/coupe again has advantages over fully independent suspension like the BMW trailing arm setup like lower unsprung weight and excellent traction no matter the road camber. Again it is a different option to the norm and not necessarily worst.

Regarding the Ford GT sure as the video by the Ford engineer on aerodynamics shows (different one to the one I posted here) they sought to better control the airflow for superior downforce. OK so that was the principal reason for making that gap behind the front discs? I thought it was one of the reasons and not the principle reason and the Ford guy tried to talk up the benefits of moving a lot of mass towards to the centre of the chassis. Anyway it explains why the electronic damper is not connected directly but through pushrods and rockers, so as to move it to a certain place for airflow reasons.
 

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well yes an aircooled 911 is ancient since it came out in 63 and was intended to run on 4.5x15 wheels n 165mm bias tires. it had near zero camber gain and the torsion bars are more liable to bind due to the axial misalignment within their bushings.

torsion bars do have advantages primarily in packaging space over coils. it also has unsprung weight advantages but its not as large as one would think when u consider that you need to strengthen the suspension arm to take the transmitting loads of the TB. on a 911 you already have a reinforce turret mounting point for the dampers, why not use it for a coil over like they did racing cars ,later 964s or SZ :) ? it gives you much more flexibility in ride height, springs (rate, variable rate, compound, helper etc). TB's are limited to a fix rate and smaller window of poundage rate. your adjustments in height are are also limited before you have to re-index them.

adding push/pull rods for rockers or dampers add complexity and cost. not only the suspension parts but the mounting points on the chassis. im guessing the GT has and 10-12 extra rockers, rods, dampers, springs, pivots etc per axle. in addition to this, your chassis has to accommodate extra load bearing mounting points for dampers, extra coil spring module, pivoting bosses and TB fixtures. that is a lot to deal with hence the carbon LM like tub.

yes its all about areo. the intent was to win LM. the front is so effective that there are aero shutters to divert the airflow away from the tunnels unless the rear wing is deployed.
moving the components do have benefits outside for centralizing weight but not as much as a formula car since its a two seater. those long arms and the severe azimuth angle of the push rod gives it a falling rate geometry. the rocker arms help rectifies this to help with the damper resolution. so what happens when u have ample wheel travel and low damper resolution or travel? u have to buck up for formula type dampers with precision valving to do the same job for such short travel.

i think there is still a place for TBs, especially for packaging reasons. but like every on a vehicle its all about the compromise.

im a big fan of dedion for its lightness,simplicity but most importantly,its predictability. but its has limitations also which is packaging since its needs a central pivot and limits your anti squat geo. you also have to account for lateral link need to package being a panhard or watts etc. with the alfa, it lacks of camber adjustment which some of the racing GTV6 had retrofitted. even if you add camber u dont get camber gain through its travel. you are limited to brake disc size on inboard brakes, and because the are inboard contributes to lightness of the suspension. not all dedions have inboard brakes.

i wouldnt be so sure of its traction advantage over a Semi-TA since its an IRS and has advantages over bumpy surfaces. a dedion you cant dial positive camber like u can on a IRS on the inboard off loaded wheel. with the heavy lump in the rear a 911 on semi trailing has traction in spades. The biggest detriment for a semi-ta imo is the tow changes, which can make the rear end unpredictable. but then again in my experience, a E30 M3 , like the alfa is one of the most predictable cars to slide around in.

all the best!
 

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Discussion Starter #12
Davbert...thanks for the input again and those early porsche 911 has skinny 165 section tyres just like the alfas of that time. The 911 r of 67 was meant to be very well sorted however.

The Alfa SZ coilovers are not enough for the car to handle well. They are copied from the racing IMSA cars "but" without the racing cars myriad chassis strengthening tubing at the front not present on the road going 75/milano or the ES30 SZ. The coilovers were in a place not designed to take the weight of the cars even with welded supports and do not negate the role of the torsion bars as explained to me by a well known alfa suspension guy based at the nurnburgring.

Yikes that pushrod / rocker /dampers/ springs assembly for the Ford GT looks super complicated but the carbon fibre tub is a very rigid thing for mounting points of the dampers and more.

THe aero effect the Ford engineers have done is very clever and is a positive asset. However I ask myself why have a long arm and awkward angle push rod necessitating a race spec precision damper?! I mean race cars (and some road cars like the ferrari f50 with suspension and engine bolted to its carbon tub) have pushrod dampers "across" the car front and rear which would surely have been better? I am sure For would have thought of this but why did they not implement such a system? The race alfa 4c has front pushrods across the track of the car!

Regarding the Dedion I am also a fan but in the alfetta design the watts linkages can be bought ali and adjustable as used in the grp 2 alfettas in period. The racing dedions used in the imsa and alfettas were also trick and not like the production alfa transaxle cars.

Regarding traction the 2002 BMW had a lack of traction on roads with frequently changing cambers like mountain or country roads when really pushing fast compared to the alfetta. I would assume the same for the later 3 series that followed. The alfetta just puts power down more of the time. The dedion maintains the tyres at 90 degree angle to the tarmac. Of course the 911 is different with a whole engine hanging out back traction is not an issue but a strength...early 911s were tricky around bends.
 

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early pcar or alfa ran with 165 pizza cutter not modern 195-205-25 or some cases 245 radials trackcars no often run. i can assure most folks run neg camber today rather than zero camber or even the positive camber of the factory spec 105s. i cant say what a flyweight at 1700-1800 lbs 67 R is like which is a million dollars now but ive driven a half dozen long nose 911s... they cornered well for its day, have low grip or limits for its tiny tires and are tail happy widow makers if you lift. good experienced drivers use the wagging tail to trail brake into the corners to their advantage. i had a 930, its was a hopeless pig of a track car stock form. i now have a M491 widebody and removed about 400lbs to about 2600lbs but im not through yet.. its much more exciting than the 930.

I used to own a alfetta gtv but that was decades ago. im lucky enough to have driven a il monstro SZ but not in anger... so no comment on that. but is heavily based on a alfetta and like all amped up performance cars, they response to chassis reinforcements with increase grip and power. its no surprise the IMSA is reinforced since it has group 4 like racing rules liberty. group A and N cars are also reinforced. same as the 911 3.0RS with coils, if you dont reinforce the turret the pop off in the rear if driven spiritly.
here is an old link of the IMSA on how extreme the suspension mods were. apparently there was even a IRS dedion version and horse shoe upper link in front.
http://www.alfabb.com/bb/forums/milano-75-1985-1993/155906-alfa-75-imsa-tubolare-vs-alfa-gta-cup-***-3.html

street Ford GT complicated, race version simpler and does away with the 2nd damper/coil assembly i reckon. nearly all modern cars even to the mundane are strong chassis wise. this is primarily done for crash and safety reasons. the by product is stiff platform for good ride and handling.

its not how long the push rod is but the angle of the output direction in relation to the wheel travel. an attribute of the often bashed on McPherson strut is very good in this respect in where its close to 1:1 ratio. when your dampers are kicked over in a generous angle, as the wheel moves up there is less displacement of the damper or springs though out the travel mean its a falling rate suspension. typically more 45 degree is a no-no without some sort of variable springs, rockers or other means of amplification or change in vector. you will often see old formula cars at this 45 degree limit. still not ideal but there are many compromise with old racecars for low frontal area.

in the F50 case, (hey im lucky enough to drive one of these!) its not necessary imo from a pure geometry perspective since the push rod angle is no more than whats being used in most double A arm cars. but the shock/springs need to tie into a stout structure so sexy mounting member on the drivetrain under the unstressed bodywork will do. for a modern supercar this is expected whether need or not.

a dedion keeps its tires 90 to ground only in theory... why else would the autodelta go to extravagant lengths for modified a IRS or adjustable camber version? a dedion is just a solid axle without the pumpkin and drive. still it works well enough though.

i have driven a 2002tii but not tracked one so no comment since it was just a stock street car. the e30 m3 group A touring car absolutely decimated the 190-16 merc 5link and 75 milano dedion with a basic semi-trailing rear end which is probably one of my least favorite suspensions! all 3 cars have wonderful chassis even in street guise, but the 75 had the least traction, least grip and most torque in 3.0 liter form to steer with rear wheels over the pair of 16 valvers. im some cases make it more of a hoot to drive especially on the streets in my book.

thanks for the banter... cheers!
 

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Discussion Starter #14
my cap off to you Sir....clearly your understanding of handling dynamics is more in depth than mine!

Your experience of the driving characteristics of the 911 is very interesting. Vic Elford who raced the car in rally spec and won the targa florio and others said the 911R was very quick and he probably trail braked as you say into corners. Still using the car on mountain sections at full speed...brave!

THank you, yes the alfa and porsches respond well to chassis reinforcements; the link you provided did not work for me but i have seen the chassis reinforcements of the IMSA cars with the front bodywork taken away and major structural strenghening does not even begin to describe the modifications that were made.
I am setting up an alfetta for road rallies and am considering strengthening the suspension supports and the chassis stiffness but since the car is going to be still road legal without a roll cage i am not sure if i can.

I hope the Ford GT suspension and aero solutions find their way into lesser road Ford sports cars that are not already sold out!

I am very jealous you drive an F50 ...and sure it may not be necessary from a pure geometry perspective, but it saves a little unsprung weight and also has aero benefits as Ford has capitalised on right?

Having driven an alfetta 4 cylinder many times across Europe, for the limited 120hp and at modest speeds, not going flat out the dedion is superlative in my opinion. I drove a BMW 323i a little and for me, again at moderate speeds and stock it was not as adjustable or stable at the rear but just my opinion on the car i drove, maybe others are setup differently.

Regarding racing sure BMW would have, like Mercedes and Alfa Romeo made many more modifications over stock to handle the extra power and to race on circuits. However the Alfetta GTV6 won the European Touring Car championships four years in a row 1982-1985 against The BMW M3 won in 1987 and 1988 competing I suppose against the Alfa 75 turbos. Alfa Romeo would have stood a better chance with normally aspirated engines since the alfetta circuit cars from mid seventies until mid 80s were naturally aspirated and punched well above their weight. Anyhow a lot of the advantage was also the 50/50 weight slipt front to rear.
However not bad for a platform not substantially altered since the launch in 1972 (projected late 1960s) and one that went on until 1992 in production cars with the final alfa 75.
 

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I was having a little think about the whole 'pushrod suspension equals reduced unsprung mass' thing.
And it dawned on me that it wasn't the case. Well, the interpretation is incorrect.

It's basically the same as a pushrod engine. The camshaft lobe accelerates the lifter/cam follower, the pushrod, the rocker, the top valve spring retainer, the collets and about half of the valve spring. Each part has mass and inertia and that mass and momentum has to be retained against the cam lobe by the spring(s).

Well the same is true of pushrod suspension design. When the wheel negotiates a bump, the suspension still has to accelerate the pushrod, the bellcrank, which ever side of the damper (surely the shaft and piston side of the damper is the lightest and would be the one used) and half of the spring and its seat.
All of the components, infact a pushrod suspension just like a pushrod engine has more moving components, need to be accelerated and decelerated as the wheel goes over a bump.
And all of those components have mass and inertia.
It is the mass of the moving suspension components that is the issue, not simply the fact that they are going up and down with the wheel itself.
A simple way to prove the point, and obviously there aren't too many pushrod suspension cars around to actually try this on, but I'm sure that most people would be able to understand it inside their own noodle.
But imagine replacing the bellcrank with 1 that had a long arm on it (say 300mm/12"), with a significant mass on the end of the arm (say 2kg/4.4lb). Now the bellcrank has a vastly different pollar moment of inertia and just like a large diameter flywheel (or a standard TA Alfa engine flywheel :001_tt2:) has much more inertia. So it is harder to accelerate and once it has its momentum up and running, harder to decelerate.
I'm sure that everyone could understand how that sort of thing would effect the ride and handling of the car even tho the mass isn't directly attached to the part of the suspension that is going up and down with the wheel itself.

It looks like the real advantages of pusrod suspension is that motion ratios can be increased so that there is more displacement of the damper for a given amount of wheel movement.
The loads can be directed into the chassis in a different way to take advantage of sections of the chassis being in tension rather than trying to rely soley on the beam strength (bending) of the area.
It places the havier spring/damper package more central in the car and that should allow a improved yaw rate.
The spring/damper package can also be mounted lower, helping to lower the centre of gravity.
And the profile of the chassis and body can be made lower while keeping the motion ratio of the damper high.
 

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Pushrod suspension is not about unsprung weight as you say but aero and rising rate.

Thanks to angles of operation you can effectively create a suspension system that becomes stiffer the more it is compressed, which is ideal as you want to keep off the bump stop.
Pete
 

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Discussion Starter #17
The pushrod suspension on the Ford Gt as pointed out by Davbert whose friend was one of the engineers involved was used and placed where it was principally for the aero purposes as he mentioned.

However as a whole pushing the whole body of components nearer the centre of the car does positively affect unsprung weight as shown on the video. However this was a pushrod system taking second place to the aero effects wanted by the engineers.

The more common pushrod suspension that I have seen, example f50 and 4c racer, the pushrods are "across" the chassis at front and rear and this has significant improvement on unsprung weight.
 

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I called a buddy of mine who is an engineer at Haas, and he said the main advantages of a torsion bar, at least in terms of Formula1 use, are a combination of packaging and a torsion bar's lack of "hysteresis." (My first exposure to the word - apparently the state of a system's dependence on its history.) He said a coil spring, which always suffers at some level from hysteresis, "is far more difficult to model in dynamic conditions."
 

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I called a buddy of mine who is an engineer at Haas, and he said the main advantages of a torsion bar, at least in terms of Formula1 use, are a combination of packaging and a torsion bar's lack of "hysteresis." (My first exposure to the word - apparently the state of a system's dependence on its history.) He said a coil spring, which always suffers at some level from hysteresis, "is far more difficult to model in dynamic conditions."
And that is why valve spring in Formula 1 engines for the last 20+ years have been pneumatic.
 

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And that is why valve spring in Formula 1 engines for the last 20+ years have been pneumatic.
Does hysteresis cause valve "float?" I remember when pneumatic valve actuation appeared in Formula1 (back in the 19,000RPM days) and the reason given at the time was that a traditional valve spring simply couldn't be manufactured that would close a valve quickly enough at such elevated engine speeds, which was resulting in valve float at very high rev ranges.

I am not an engineer, but other than pneumatic tires, traditional valve springs seem to me to be the automotive technology that has somehow held on long past the point at which I would have thought it would have been replaced by something better. Valve springs, even when I was a kid in the 1980's, seemed like a bad way to do that job and the only apparent alternative at the time - Desmodromic actuation - always produced less rev-happy engines than their traditional counterparts. (Not enough evidence to stop me from buying a string of Ducatis throughout my life, however.)

But man, don't get me started on pneumatic tires. There absolutely MUST be a better way of doing THAT job.
 
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