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.
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.
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.
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).
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.
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
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.
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 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.
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.
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.
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.
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 is the angle between the top and lower upright ball joints.
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.
The specification of top wishbone, different wishbones will be made to accommodate different set ups, such as anti dive\squat angles.
The specification of bottom wishbone, at the rear this specification also includes the track rod to keep the rear wheel toe angle under control.
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.
This is the spacer shim that fits into the pushrod to alter ride height.
Link Outer Spring Reaction
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