Note: This is a physics mod that needs Kunos' original M3 E30 Group A model files, which are not included. Follow the installation instructions provided below. Additional "rally" pieces, such as the passenger seat and codriver, were supplied as CSP additions.






Features:
Front and rear suspension geometry created from scratch using picture analysis of previous Prodrive components.
Rear suspension geometry is intended to approximate genuine semi-trailing arm kinematics. Semi-trailing arm suspensions have nearly little anti-squat in reality; vanilla AC does not reflect this appropriately; cphys (CSP extended physics) corrects this.Front strut suspension geometry created from scratch using picture analysis of previous Prodrive components.Corrected tie rod position for about 25-30 degrees of wheel rotation.Historically correct spring rates, wheel travel, and damping rates.Note that certain precise figures for specific suspension data were unavailable, hence some estimates were used.For proper force feedback with this geo, ensure that the "MacPhearson struct FFB adjustment" option is enabled in CSP's FFB Tweaks.Historically correct engine performance based on the 1989 version (295 WHP)
Retuned torque curve using more recent dyno graph data; no historical prodrive dyno was discovered.Inertia values have been corrected to reflect the inertia of sprung weight.Six-speed gearbox ratios are faithful to the 1989 model.Differential lock is the same as the circuit variation, with 75% power and coast.
Differential preload was lower than the circuit variant, but I couldn't discover a precise figure. For the time being, the limit is set to 50 Nm.Steering ratio and wheel lock are identical to the 1989 variant: 14.4/1 and 720 degrees lock to lock.Brake bias is more evident in the rear than in the circuit vehicle - estimated at 63% due to a lack of specific data.Added a useable hydraulic love-handle;) S/M/H Tarmac tires adapted from Kunos touring car tyres from the 1980s and 1990s.
Accurate measurements with the center of gravity height adjusted appropriatelyLimited cphys tire integration, with new rolling resistance slip and lower values.Added a combined slip factor line to provide a more "squarish" traction circle.Rain tires and physics functioning (forced on, regardless of what you may have set on CM)Visual indicators include functional wipers, RainFX, and VAO.The front bumper carbon fiber aero (and its downforce qualities) were removed; they were not present on the rally vehicle.Removed the left fuel cap mesh, which was not present on the rally vehicle.Some rally elements have been added, such as a wind-animated roof antenna, tow hooks, and license plate extensions.Extensions include a passenger seat, codriver, and rally helmet for the driver.The animation for the exhaust pipe has been redone.The headlight refraction has been redone.



Installation
Requires Custom Shader's Patch - this car uses extended physics (cphys), so CSP is required - tested on version 1.79-p

Note: there's no need to activate extended physics on your content manager UI - the mod uses it automatically.​

• Extract the content folder to the assetto corsa main directory
• Copy these .kn5 model files from "content\cars\bmw_m3_e30_gra" to the new "soll_bmw_m3_e30_gra_rally" folder:
  • bmw_m3_e30_grA.kn5
  • bmw_m3_e30_grB.kn5
  • bmw_m3_e30_grC.kn5
  • bmw_m3_e30_grD.kn5
  • collider.kn5
• Go to Content Manager's "Content" tab, "Cars" and select the new BMW M3 E30 Gr. A Rally Spec
• Click on "Replace sound" and select the BMW M3 E30 Gr.A 92 (yes, the dtm version

Credits:
sollrakc