Went out riding today

Spin faster

 

First you put on road bike tires and added what looks like drop bars now you are worried about going over 20mph.....I'm thinking you should have bought a road bike...just saying....

 

20 mph is a pretty good pace, even for a road-bike on the flats. You have to remember, you do have a dual purpose bike that's going to sacrifice speed for functionality. Plus, not only is the frame stronger and heavier than a road bike, but you have all the necessities for your commute on there such as lights, lock, gps, etc. All this extra weight is working against you as you try for more speed.

Also, can and do you lock your front fork? Even a little bobbing when pedalling is going to rob you of precious energy if you goal is to go faster on smooth stuff where you don't really need that shock to be working anyway.

 

larger gear in the front and smaller in the rear is faster. i think your bike came with a 48,36,28 ring gear set up and a 11-32 9spd cassette
so- 48 ring in the front and 11 in the back and spin as fast as you can/ that is your top speed.
48-11 harder to pedal but fastest
28-32 easiest to pedal but low top speed
now when you are in the 36 ring you can actually find a gear that is repeated in the 48 and the 28
your gearing does have a top speed....
my road bike has 52 chain ring thus when i am in the 52-11 my bike can go faster than the 48-11 will allow you to.
ultimately this is not the biggest factor of speed however.
example: Mark Cavendish a pro rider who some would say is the top sprinter in the world rides a bike with a 53 tooth front ring... there are other riders who ride with a 54 but he still beats them. when he does it is because of riding ability team work and strength.
example 2: i can out sprint (go a faster speed) than my dad on my specialized that has a 48 tooth front ring when he is on his Pinarello with a 52... his bike is nicer, better geared and lighter(even in a larger frame size) but i ride more and have better endurance and can spin faster longer. thus, my bike goes faster....

all this being said, top speed does have to do with gearing and the rest of the bike set-up... i can hit and hold a higher speed on my Wilier road bike than on my Kona mountain bike. bigger ring is one of the reasons but not the only.

Would aerobars help? you asked...
of course with aerobars you can get in a more aerodynamic position, but they are honestly not made for sprinting and you stated you did not get a road bike because you wanted versatility. thus, don't get aerobars... i would not even put them on my road bike because they are very limited in design and purpose. you can not climb as well with them and you can not steer or handle the bike as well with them.

 

the post above(the one i wrote) is about speed... but i totally agree with rola!
get on the bike and spin.... put on enough miles to wear out your new rubber!

 

it is a little tricky because it has a mountain bike crank on it and it is hard to find anything larger than a 48 chain ring that will bolt to the crankset. most often road stuff is bigger than mtb stuff (chain ring size) because you generally don't go as fast off road. you have a 4 bolt 104mm bolt pattern outer ring... if you find anything that size(and the right speed) larger than a 48tooth it will bolt right on. then you just have to adjust the derailleur
to change to a road crankset you would have to change the rear cassette, chain, shifters and maybe the bottom bracket.. lots of bucks but worst of all you would be taking perfectly good parts off your bike.
honestly, it is hard to have a bike that does it all... fast, durable, off road, on road, commute and look good...
you have a nice bike! it will get faster as you get fitter(not saying you are not fit just the more you ride the fitter)... keep the versatility over gaining some top end speed.

most of us went through or go through a speed stage and then for most i have found it passes. but rarely do we not want to be able to go where we want to when we want to.

 

no, you would have to change out the front gears(chain rings)... but to do so i believe you would have to change out the crank arms that go from your bottom bracket to your pedals... thus, you may find a crankset that fits your bottom bracket but you may have to change it.
basically you need a front ring larger than a 48 tooth(i do not think anyone makes them in a 104mm 4bolt pattern, so you have to change your cranks)... to have a higher top end speed. they come all the way to 55 tooth. what will fit on your bike? i can't say. see if DirtyBobbysBikes, he is a member here, can help you with that. he is a bike repair/shop guy.

 

by the way, any speed over 35 mph on a flat road is going to be really hard to do on almost any bike! (road and track racing bikes excluded)

 

that is a 5 hole bolt pattern... for a road bike. i think your bike has a 4 hole pattern...
many road cranks hold the Chain ring on with 5 bolts while many mtb cranks use 4 bolts....