Analysis – Set up sheet explained

Kimi

Whenever an F1 car runs on track, the team will have planned what parts are fitted and the set up of every facet of the car. Now over a year and a half old and with an even older car, this set up sheet appeared on the Lotus Media site. It was from Kimi Raikkonen’s debut test at Jerez for the team in a R30 (from 2011). It shows some of the set up detail that the teams go into. This also gives us some insight into the spring\damper configuration modern F1 cars run.

Lotus_setUp

Vmax
Top speed, 317.51kph (197mph)

Aerobal Wt 225kph
This the balance of downforce front to rear, the car is running 40% front and 59% rear (the difference to 100% is probably a rounding error), which should nearly reflect the static weight distribution. It is set at a specific speed (225kph), as above this the diffuser starts to stall and alters the aero balance.

%FRS 100-200kph
Front Roll Stiffness, defines the forward roll couple percentage, basically the front-to-rear ratio of body roll. It’s speed dependent, in this case 100-200kph, due to the inertia of the sprung mass. From an established car, the number will give an engineer a quick reference to the front-to-rear relativity of anti-roll bar rates and set up.

Ride Height
This would be measured at the reference plane, the front height of 32 is typical, but the rear at just 60mm is low by modern raked F1 car standards. I’d predict Red Bull run a 100mm Rear Ride Height (RRH).

Outer Spring
OuterSprings
These are the torsions bars for each corner of the suspension, the specification would not normally give an indication of the springs stiffness to keep the actual figures secret. Torsions bars are fitted to all four corners of the car in this set up.

Antiroll Bar
ARB
Anti Roll Bars (ARBs) are an optional fitment and the torsion bars linking each of the suspension will alter in stiffness. Typically Front roll stiffness will be higher than at the rear and higher than front ride stiffness (outer springs). Again ARBs are fitted front and rear.

Centre Bump Stop
Centre_BumpStop
To manage suspension heave stiffness and travel at high speed, one of the set up option sis bump rubber on the heave (or third) element. None is fitted to the front, but the rear does have a bump rubber specified.

Centre Bump Stop Gap
This is the suspension travel before the bump rubber comes into play. With no front rubber fitted the full heave element travel of 100mm will be used before the element locks up. At the rear 30mm of travel is used before the bump rubber adds to the heave stiffness.

Centre Damper
CentreDamper
As well as springs or bump rubbers the heave movement of the suspension can be controlled by a damper. Although this specification is not always a damper per sé, but simply a un-damped telescopic strut to carry the spring and\or bump rubber.

Centre Spring
CentreSpring
This is the spring fitted to the centre damper. Just as with the bump rubber these control and limit the heave motion of the suspension. None are fitted for this test.

Centre Spring Gap
To maintain a low stiffness heave movement of the suspension at lower speeds, these centre springs do not engage until a certain amount of movement has occurred.

Outer Damper
OuterDampers
These are the four dampers fitted to control each individual wheel. It might come as a surprise to many, but no dampers are fitted in this case! The damping of the suspension movement comes from the centre damper and the roll damper. No further damping is necessary in this case. At other tracks teams will fit outer dampers and perhaps not centre\roll dampers.

Outer Bump Stop
Acting in the same role as the centre bump rubber, these control the last part of the suspension travel on each corner of the car. The same spec bump rubbers are to both front corners and the same spec to each rear corner.

Outer Bump Stop Gap
The free movement of the suspension until the bump rubbers are engaged, suggests just how little the inboard suspension moves. There’s just 17.9mm movement at the front and 28.4mm at the rear.

Roll Damper
RollDamper
As explained, a roll damper is fitted in this instance. This sits diagonally between the suspension rockers and is only moved in roll (i.e. not heave). In a normal racecar the roll movement is stiffened by the anti roll bar and damping by the outer dampers. Fitting a roll damper means roll damping can be decoupled front ride\heave damping. Running a roll damper is the reason Lotus have an asymmetric bump on the top of the monocoques. These are used to clear the right front roll damper mount.

Toe In
Known a tracking on road cars, this is the angle the wheels point in\out at. This set up features 1mm toe out at the front and 2mm in at the rear.
Rack Stops
These are sleeves that limit the steering lock that can applied at the steering rack. Limiting this movement prevents damage to the suspension and steering rack. Although none are specified in this set up

Castor
Castor is the angle between the top and lower upright ball joints.

Camber
This is the angle the wheel leans in at its top. Pirelli specify -3 degrees as a maximum for the front tyres, teams are known to run more camber angle. But -3.5 degrees is at the top of what teams tend to run. At the rear camber is traded for traction depending on the track layout. A value of between 0 and -1 degrees is normal.

Top Wishbone
The specification of top wishbone, different wishbones will be made to accommodate different set ups, such as anti dive\squat angles.

Lower Wishbone
The specification of bottom wishbone, at the rear this specification also includes the track rod to keep the rear wheel toe angle under control.

Rocker
Rockers
The bellcrank that takes the push\pullrod movement and translates it to the springs\dampers etc.

Anti Roll Bar Linkage
ARB
This is the specification of the links that connect the ARB to the rockers

PPS Actuator Area, Accumulator & Oil Offset

Initially I posted these as being part of the power steering system.  I’ve since confirmed that these are in fact the settings for the hydraulically interconnected suspension system.  So now we know that Lotus call their simpler version of FRIC,  PPS.  Perhaps PPS stands for ‘Pro Pitch System’?  I understand the Hydraulic unit is housed at the rear of the car around the gearbox,  it features a temperature and pressure sensors linked back into the cars telemetry system. 

Actuator Area would be the piston surface area in each of the hydraulic heave elements. The front and rear elements are of different size, if they have a similar motion ratio it is possible the difference in size will allow the cars tail to squat at high speed due to aero load, this would reduce drag by flattening the car and wings at high speed.

Accumulator is the internal diameter and pressure of the accumulator.

Oil Offset is the total cylinder volume displaced by the heave element at full suspension travel.

Pushrod Lozenge

This is the spacer shim that fits into the pushrod to alter ride height.

Link Outer Spring Reaction
ReactionLink
Rather than the torsions bars (outer springs) being joined to the chassis, they can be allowed to rotate freely and a tie bar link the left and right torsion bars. This allows the torsions bars to stiffen the suspension in heave, but they simply rotate in roll. Thus the spring rate they add to the suspension can be decoupled from the ARB rate.

 

Many thanks to @BrianJee and the others who helped ‘off-the-record’ with this article

30 thoughts on “Analysis – Set up sheet explained

  1. Great stuff, makes it clear how much more refined the F1 suspensions are than the usual sports car set ups. But maybe the toe is described different from the set up sheet? Isn’t it 1mm out in the front and 2 mm in in the back, for crisp response to steering input (front) and enhanced stability (back). Thanks again.

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  3. Am I reading it wrong or are the rear springs one third as stiff as the fronts? Running a very stiff rear roll damper?

    • Spring stiffness itself does not tell the actual suspension stiffness. You need to take into account the wheel-to-spring motion ratio which we do not know. Motion ratio could be different front to rear.

  4. awesome post!
    the explanations along with your diagrams are extremely informative.
    as always, thanks for your work.

  5. Do teams typically run perfectly symmetrical setups? The cars are turning 360 degrees more in one direction than in the other, every lap.

  6. PPS is likely to refer to the hydraulic interconnected front / rear suspension system. It’s not conceivable that a modern F1 can run without heave support at each axle, and since the setup sheet says no heave springs are fitted, that heave support must come from somewhere else.

    A hydraulic system with pistons acting against accumulator pressure seems likely, and the 3 PPS entries could be interpreted to specify that kind of setup.

    Note also the bottom right of the sheet where there is a separate ‘Steering’ table which includes the words ‘Power’ and the acronym ‘PASR’ (Power Assisted Steering Rack), which suggests ‘PPS’ is chassis not steering related.

    Also, the Rear Ride Height looks to be 80mm to me, not 60mm (compare the font of the 6’s & 8’s below).

    Regards, Ian

    • Ian,

      very interesting…
      scarbs has a great following!
      perhaps Lin100Nmm20mm are:
      linear, 100N/mm, 20mm travel?

      • Agreed, that could be a rate and a travel specified.

        20mm at 100N/mm = 2000N = 200kg so unlikely to be enough to support all the downforce, though.

        • i was thinking that small figure was pointing to the spec of some kind of a shim stack within the accumulator.

          also, the rear motion ratio appears to be RR – rising rate, and since not indicated, perhaps a constant ratio at the front.

    • Interesting point,I was told that PPS was power steering related, but your theory makes sense. Also no inerter is specified, further suggesting that the interlinked system is installed as it acts as a fluid inerter too.

    • I suspect you are correct about this. The sheet indicates a rear actuator with area of 6.070 cm^2 which is inconsistent with steering.

    • You are right, PPS is in fact the hydraulic interconnected system, I have amended the text to reflect this…

      Thanks for all the help…

      Scarbs

  7. Toe measurements in mm is notated on the setup sheet.

    How is this measured is this the track rod length adjustment? or is this actually meant to be degrees? usually 1 degree toe out on the front and 2 degrees in the rear toe in. Would be a normal setup for a race car, I know the sheet says mm but it would make far more sense if it were actually degrees.

    • the toe is measured in mm as it is the difference between the track width of the very front of the tire and the very rear(or rim). If there is toe in, die distance between the front of the tires(rims) is narrower than at the rear of the tires, this is what the sheet says as 1mm toe in. with the radius/diameter of the tire(rim) its just arctan(toe in mm/2*tire radius) to get the toe as degree.

  8. Hi Scarbs,
    Great analysis as always! One very minor thing is that the AeroBal quoted is almost definitely 40.59% front (58.41% rear) , not 40%/59% with rounding error. Engineers only usually quote AB wrt the front

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  12. Hi, just wondering if this would be viewed as helpful to other teams in regards to how Lotus treats its rear tires?

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  14. Great article. The tie bar between the two main torsion bars blew me away, I’ve never seen that before. It looks like in your illustration that it has adjustable length. Is this how ride height is set with this configuration?

    • I don’t believe it is adjustable, besides ride height is adjusted at the pushrod with the lozenze\shim mentioned.

  15. Nice article Craig;

    The Front Center Bump Stop Gap is 1000 mm, not 100 mm. It might mean that there is no centre bump stop at all, as the travel is much lower than 1000 mm. It reinforce the PPS theory.

    Regarding to the 60 mm rear hide height , we should remember that the R30 F1 was a side blown diffuser car (not a rear one as all the other cars), which shows why Renault stepped down from this concept.

    At that time, the static weight distribution was about 46/54 front. The aerobalance limit is around 40% front, for not overloading the front tyres at high speed corners, and not spoiling braking stability.

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