Q. Dont you think Renault Triber a little under powered vehicle for 7 people?

First of all if you have 7 passengers you won't have any room for luggage. Regarding power, it depends on the road; if you have p0t holes on steep uphill road and have to stop and crawl, I wouldn't recommend that.I tried with 4 adults in such conditions but I had to turn off a/c quite often. It is extremely unrefined engine for this purpose. In my experience it is only good for highways. City mileage is in single digits!

For city rides, its perfectly fine and mileage is 11 kmpl, it can pull 7 people in hilly areas as well but sluggish not so aggressive like SUV. I think we need to change the tires with higher width.

Renault Triber is not a performance oriented car, it is a family car. Just look at it as a commuting vehicle but if you want to test its power or speed on highway then this is not the car to go for.