Geo Setups
Geo Settings
| Geometry | Ride Height Front/Rear |
Front | Rear | |||||
| Castor | Camber | Toe | Camber | Toe | Bump Steer | |||
| Standard S1 & S2 | 130/130mm | +3.8° | -0.1° | 0.2mm OUT Overall | -1.8° | 1.2mm IN each side | ||
| S2 135R | 120/120mm | +3.7° | 0° | 0mm | -1.8° | 1.2mm IN each side | ||
| 340R Road | 100/110mm | +3.8° | -0.5° | 0.2mm OUT Overall | -2.0° | 1.5mm IN each side | 2.0° to 2.5° toe in | |
| 340R Track | 100/110mm | +3.8° | -1.8° | 0.5mm OUT Overall | -2.7° | 2.5mm IN each side | ||
| Exige S1 | 112/122mm | +3.8° | -0.5° | 0.1mm OUT Overall | -2.4° | 1.2mm IN each side | ||
| Msport | 100/110mm | +3.8° | -0.3° | 0.2mm OUT Overall | -2.0° | 1.2mm IN each side | ||
| Non-Standard Geo Settings | ||||||||
| hbaumhardt S2 race | 104/114mm | +3.6° | -1.4° | 1 mm OUT overall | -2.6° | 2mm IN each side | ||
These settings are used when car is loaded with 2x75kg passengers and half tank of fuel.
Converting from mm to degrees:
- Multiply rim diameter in inches by 25.4 to get rim diameter in mm.
- Multiply the result by PI to get the circumference.
- Divide the result by 360 to get mm per degree.
- Divide the toe mm by the mm/degree result to get toe in decimal degrees
Geo setting X does Y
Some starter guidelines although its really really complex stuff and dependent on many other factors;
Increasing front camber from the default -0.1° to -0.5° each side will dramatically improve the understeer, although the inside edges of the tyres will wear slightly faster. Increasing past -1.0° is great for high speed corners but will compromise low speed cornering, will reduce breaking effectiveness and it will tramline on the road.
Increasing rear camber from the default -1.8° to -2.0° (or higher) makes the car more neutral after you've removed the under steer.
Front toe affects stability or responsiveness of turn in. Front Toe out (standard) makes the car more responsive turn in but causes additional drag in straights. Front toe in is more stable in straight line.
Rear Toe controls the stability of the rear through the corner. Rear toe in (standard) makes the car more stable and apparently the elise toes in more at the rear as the suspension compresses. Rear toe out causes the rear to steer out from the corner, reducing stability.
Setting your own geo
Whilst a race prep specialist can charge £200 for a Geo you can DIY castor, camber and toe settings. With a lot of variability in quality at alignment centres (and Lotus dealers !) for the best results put the effort in yourself and build a string based alignmnet rig which can be more accurate than a computerised lazer system. To make a DIY geo/alignmnet rig see:Geo Alignment Rig (Home Made)
1. The Hunter computerised lazer alignment system is one of the best (the variabiltiy is quality of the operator) http://www.alignmycar.co.uk will find a local place with a Hunter alignment system who will provide a setup sheet showing castor, camber and toe (probably in dd:mm:ss rather than decimal degrees) for £15 and can set the frotn and rear toe for another £30.
2. If you are going to DIY you must have the relevant S1 or S2 service manual suspension sections. Setting castor and camber is straightforward as a caster washer and camber shim have fixed values, whereas toe is delicate - which way do you wind the flats and a quarter turn of the track rod can alter the toe by 2mm (e.g. just tightening the locknuts).
Absolutley critical to getting a good geo is having the right ballaat in the seats e.g. for a 780Kg race Elise the difference between empty and an 85Kg driver is 5mm ride height, 0.2° camber and 1mm toe. Don't let your alignment place guess the ballast
See Also
- http://forums.seloc.org/viewthread.php?tid=52913 - The pole & string thread by Randy
- http://forums.seloc.org/viewthread.php?tid=49382
- http://forums.seloc.org/viewthread.php?tid=106461