When I commuted a few years ago, I rode my MTB with 2.0 slicks and averaged around 17 MPH for 9 miles. The average speed on the same route on my Colnago with tubulars was close to 21 MPH. I don't think the weight difference(6lbs) was the contributing factor as much as the tires. I suspect the same is true with a folder. I recently picked up a Bike Friday NWT with 1.95 tires and expect it will perform about the same as my MTB. It as a Capreo 9spd configuraion with a 9 tooth to make up for the smaller wheels. I will likely add another chain ring or two to get a wider range.