Join Date: Jan 2013
Location: South West Pa
Bikes: 1995 Canondale 2.8 frame (R800) with a mix of same era Shimano and Campy parts
It looks like the diamondback sorrento comes in four sizes - 16" Small, 18" Medium, 20" Large, 22" Xlarge .... You could get away with riding a medium but a large or maybe an XL is really the size that you need in that bike. As has been already suggested, buy the road tires and put them on - the size is on the sidewall, probably 26"x1.95" or something like that... The 26" in the really important number as it's rim size. The second number 1.95" in the tire width. A smaller number = narrower width tire. Try to find the same size but realistically 26x1.75 to 26x2.125 or so will probably work just fine. Inflate them to the upper end of the mfg range and adjust for the ride that feel good. Raise the seat up - probably a bunchand maybe need a longer post ... road bike rule of thumb is about 120* angle behind knee (femur & tibia) but you will probably not get that high. Nor will you want to on this bike. You will feel more comfortable with a bit more knee bend when the foot is on the pedal and the pedal\crank arm is pointing directly to the ground (bottom dead center) - Too MUCH knee bend is really hard on the knees, and too STRAIGHT causes you to reach, rock on the saddle, and chafe or press and numb your genitals, and can make bike control more difficult when you are not used to it. Then the next concern is how far you are reaching to get to the bars and whether the seat is smashing, pressing, or rubbing your genital area (numb packages are not fun)....You might need to trade off parts - stem\bars to get a comfortable position, but I wouldn't go wild.... Realistically, you want to spread everything out so that you are balanced between the seat and bars, not "squatting" on the bike, or puffing a lot of weight on your hands...... In essence, you are changing the setup to something closer to a Hybrid style designed for more upright riding.
$300 is a very low budget, I would suggest that you put the minimum needed to make your current bike a bit more comfortable to ride . Put in some base miles on it while you save your beer money and search for your next bike. IWhen you are looking at road bikes, look for frames that are a not smaller than 26" (60-63cm) frame size - not wheel size - the frame size is measured along the seat tube from the center of the crank spindle to either the center line of the top tube or the top of the top tube. Referred as "Center to Center" or "Center to Top"... Different mfg will use one of these two and usually note how they measure..... if you got to look at a frame or bike and the owner has no clue on the size you can always stretch a tape measure from the BB to the top tube to check. Scan ebay, craigs list, (Do they have the classifieds here?) for possibilities then check back in here with the details and we'll advise you further....