nowadays i go on-road.. can share some of my experience..
normally i go road cycling every friday or saturday night, ard
8pm i will meet my kakis then we go cycle abt 30km frm cck to lck
to jurong, back home via bukit batok road.. normally i keep my avg
ard 25km/h... lowest i went is 18km/h, which was when i was
climbing hills or anything... but for speed, i did cycle the whole
stretch of jurong - bb road - cck back home, i constant at
30-35km/h
you dont need a road-bike to go fast, just pedal faster and
choose a gear to make yourself comfortable.. my highest was a
brickland road, speed of 57.2km/h.. which was months ago...
Haha. My top speed is the same as yours, when i went down Mount
Faber. Mt Faber is pain in the ass to climb man. 
Anw, I sometimes do cycle every week. Each trip we maintain abt
30km/h over a distance of 25-30km. My longest trip was about a
100km in one day. My balls hurts the next day. 
Heres how i go :
From BP to ECP (Via Bukit Timah road, then Dunearn road, then
little india, turn elft at bugis junction, all the way straight
till Kallang then turn right to Old Airport road. Then i will head
to Tanjang Katong before arriving at Parkway Parade and
subsequently, ECP);
ECP to Changi Village & back.
Then head off to AMK Ave3 (going bike shop) via Eunos, Ubi,
Hougang Ave 2 and 3.
After AMK head back to BP via Machritchie Road(or Thomson road,
dun rly know), the Lornie road before arriving Bt Timah road (near
coronation plaza) again. All the way straight before arriving at
home.
