Generate every force that accelerates, turns or stops the car. The single most important component on the vehicle.
Hoosier R20 16x7.5-10. Tire behaviour sets the entire vehicle dynamics package: peak lateral force, cornering stiffness, load sensitivity, aligning moment and relaxation length all feed the kinematics and the lap simulation.
Selected by decision matrix with weighted criteria and stated justifications: cornering stiffness weighted 5 because the priority events are dominated by cornering and a stiffer car determines response; rotational inertia 4 because spin-up and deceleration response matters over a 22 lap endurance; load sensitivity 4 because consistency across load ranges is critical for driver confidence and predictability; maximum lateral and longitudinal 3.5 because peak grip matters but matters less than the linearity of force buildup; mass 3.5 and yaw moment of inertia 3.5.
CalSpan TTC tire data, processed with in-house MATLAB codes. Lateral force at 12 psi: 50 lbf FZ gives 131.82 lbf peak FY at 12.85 deg slip angle; 100 lbf gives 257.28 at 12.85 deg; 150 lbf gives 374.63 at 12.6 deg; 200 lbf gives 486.08 at 11.75 deg; 250 lbf gives 601.67 at 11.75 deg. Maximum peak lateral force across all tested tires was 631.98 lbf from the R20 18x6; the R20 16x7.5 is the only other tire within 5% of that. The R20 16x7.5 shows a gradual decline in friction coefficient as normal load increases, so it is more grip-efficient through changing normal load, and at peak normal loads its friction coefficient is larger. Aligning moment drops off gradually after peak, which allows predictability and stability, and it reaches peak aligning moment quicker than the 18x6 with a shorter relaxation length, making it more reactive in quick transitions. Longitudinal data for 16 in tires is approximated from 18 in data; approximating Pacejka coefficients with scaling factors and load cell validation are the identified routes to closing that gap.
Hoosier R20 compound. From the cost report drawings and CAD: From the cost report drawings: Carbon Fiber, 1 Ply (CR26E_SUS_R_TierodTube).
None recorded. This part has no entry in Knowledge_Transfer/Issue Logging/Fault Vault.xlsx, in either Issue Log.xlsx, in CR22/Issue Tracking/Shakedown 7-15-23.xlsx, or in any design review issue list found in CrimsonStorage or Box.
16 x 7.5 - 10. CR26I measured tire friction coefficients at 150 lbf FZ: lateral 1.16, longitudinal approximately 1.18, both adjusted by a factor of 0.448 to account for the testing surface. Static settings, Autocross: 0 deg camber and toe all round, 11 psi all round. Skidpad: 0 deg camber, 0 deg front toe, +2 deg rear toe, 9 psi front, 10 psi rear. From the cost report drawings and CAD: Measured mass, as built: CR25 32.0 g (0.071 lb) (weighed as: Tires). Dimensions called out on the cost report drawings. These are the figures printed on the drawing, not a labelled specification; open the drawing itself for what each one refers to. CR26E_SUS_R_TierodTube (mm): 279.6, 1.6, 11.1 Source: CR26e Weight Tracker.xlsx, Final IRL Weights (weighed, not CAD) | Cost report drawings: CR26i/Suspension/Competition/Cost Report Drawings/Suspension and Shocks/Rear Tie Rod Assembly/CR26E_SUS_R_TierodTube.pdf Quantity per car, as costed: 4
Nothing in CrimsonStorage covers these yet.