finally i released my game 
,which i am working from 2.5 months,Thanks to Unity , it’s Community and guys who have asked same questions before me
screenshot
game is here http://www.kongregate.com/games/kiranmaya/x-racers
at present im willing to sell source
http://forum.unity3d.com/threads/78428-help-me-in-fixing-the-price-of-my-game-x-racers-source?p=502087#post502087
Wow man i really like that! perfect job!! Any chance on selling source code for timer and GUI?
timer? i still have to implement that,
between of all unity things,gui part is most easy thing .
which part of gui ,u want ?
that you, i sent you a PM!
The most popular questions on racing games seem to be about checkpoints, calculating position, and AI.
yeah, cause i suck at it…lol i get over excited when learning unity and drowed myself in code…seriously like every time i do a tutorial i just speed into it and miss vital points, or even a } cause im just excited… puppy dog syndrome?
new version is updated 
Nice work so far, here is my constructive criticism.
The road is completely flat… its a little dull.
Your car handling is not very good, it feels very unstable and oversteers allot, try reducing the maximum steering input the faster the car goes.
car steering is adjustable in options menu ,
when using nitrous i wrote something like this steer=steer-2;
maybe 2 is not enough
This will be available in my RapidUnity Vehicle Editor v2, I have it already working in a game I wrote, so I just need to make it usable with my product, and easy for others to use in their own projects.
I will be working on v2 over the next few weeks…
