Need help with Rockrider ST100

[Dennis Almeida]

This is my humble opinion: It would appear that your brake blocks are misaligned ... possibly due to the lock nuts being loose. Mudguards do rattle unless you have the better/more expensive types. The seatpost quick release on these models are the external cam types which do not generate enough clamping force, better to have an internal/Campagnolo type one or just use a suitable bolt and nut. MTB tyres are not impenetrable by sharp rocks unless you buy the Schwalbe Marathon plus tyres.
I have bought a couple of Rockriders when posted abroad. They are base model bicycles with cheap components but I was able to live their many deficiencies as I have sufficient knowledge and tools for bicycle mechanics. However if you are not confident about bicycle mechanics try to exchange the bike for something better.
On another point it would be good if there were a bicycle shop in Bangalore which offered an economic "build your own" service where the buyer can select the frame, components, etc and the shop builds the bicycle. This way the cyclist is not a prisoner to the whims of bicycle manufacturers.

[berkeleydb]

Get the bike checked/serviced by another mechanic. One good shop is RR Cycles, Madiwala.

I have used a bike with quick release clamp; had good experience. A different mechanic might tell you if something is mismatched.

Re: the puncture -- maybe it was just bad luck, but check the tyre pressure; lower pressure can increase the chances of a puncture.

-{db}.

[Jose Princely]

Thank you Dennis. Will try your suggestions. 

[Jose Princely]

Thank you berkeleydb. I am going to give a chance with the shop you have recommended for their opinion.

Meanwhile, I had three punctures on my front tyres yesterday. Luckily I was near to my home.