Those piezo disc and their coating are very fragile.  They can crack with just a bit of bending and the solder joints can easily off the conductive paint under mechanical stress.

If you want a bit better protection against rough road surface and small rocks, you might want to put that between the tire and the hub.  A stationary point e.g. the shock absorber mount would be a far better location as the power leads won't be spinning around at high speed.

You are absolutely right Lee , we know that fact. But just for a demo we are doing as it is. On further updates we will do it as you said, focusing more on safety against wear and tear. Thank you for your immense concern and tips, more are welcomed.