If you are building your own Speed Simulator and need to script the mechanics yourself, you can use legitimate methods in :
Using or distributing scripts that grant unfair advantages or manipulate mechanics violates Roblox’s Terms of Service and can result in permanent account bans or other penalties. Speed Simulator Script – Inf Speed | Inf Money
If you are playing , you can use active promotional codes to gain rewards like chows and skins without risking your account. 1billion: Redeems a unique "U chow". race to win: Redeems 100 race tickets. my Valentine's: Redeems the Valentine's Amy skin. If you are building your own Speed Simulator