Difference between revisions of "Geo Setups"

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== Setting your own geo ==
 
== Setting your own geo ==
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Whilst a race prep specialist can charge £200 for a Geo you can DIY castor, camber and toe settings.
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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)]]
  
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1. To baseline your current setup 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
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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.
  
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2. If you don't have the S1 or S2 service manual suspension sections you really should get them as this is only a small part.
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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).
  
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3. Set the front castor by "shuffling washers" on the top wishbone pivots (caster is not actually that important).
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Absolutley critical to getting a good geo is having the right ballsat 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.
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4. Set the front and rear camber by adding & removing shims; removing a 1mm shim plate will alter camber by approximately -0.25° at the front and -0.30° at the rear (see above for camber effects).
 
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5. You could set the toe yourself, but since a quarter turn of the track rod can alter the toe by 2mm its a damned delicate affair without a real time readout (toe settings are critical for handling).
 
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6. Back to the alignment centre to check your config for another £15 and set your front and rear toe for another £30. You can now alter the camber without materially affecting toe.
 
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MEMO: Someone else can explain how to create a DIY geo rig and set bump steer !
 
  
 
==See Also==
 
==See Also==

Revision as of 09:01, 8 July 2007

Some standard Geo settings

Geometry Standard S1 & S2 S2 135R 340R Road 340R Track Exige S1 Msport
Ride Height F/R 130/130mm 120/120mm 100/110mm 100/110mm 112/122mm 100/110mm
Steering axis inclination 12° 12° 12° 12° 12° 12°
Front Castor +3.8° +3.7° +3.8° +3.8° +3.8° +3.8°
Front Camber -0.1° 0° -0.5° -1.8° -0.5° -0.3°
Front alignment/toe 0.2mm OUT Overall 0 mm 0.2mm OUT overall 0.5mm OUT overall 0.1mm OUT overall 0.2mm OUT overall
Rear Camber -1.8° -1.8° -2.0° -2.7° -2.4° -2.0°
Rear alignment/toe 1.2mm IN each side 1.2mm IN each side 1.5mm IN each side 2.5mm IN each side 1.2mm IN each side 1.2mm IN each side
Bump Steer 2.0° to 2.5° toe in

These settings is to be used when car is loaded with 2x 75kg passengers and half tank of fuel.Converting from mm to degrees: 1. Multiply rim diameter in inches by 25.4 to get rim diameter in mm. 2. Multiply the result by PI to get the circumference. 3. Divide the result by 360 to get mm per degree. 4. Divide the toe mm by the mm/degree result to get toe in decimal degrees


Some Non standard Geo settings

Geometry hbaumhardt S2 race
Ride Height F/R 105/110mm
Front Castor +3.6°
Front Camber -1.5°
Front alignment/toe 1 mm OUT overall
Rear Camber -2.6°
Rear alignment/toe 2mm IN each side
Bump Steer

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 ballsat 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.

See Also

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