Road Cycling - Top Tube Angle

Okay, I bet this is in here somewhere, but I did a search and didn't come up with anything that made sense to me. Right..so I'm at work trying to look busy by surfing. Looking at road bikes. I'm noticing that the 'front end' of some top tubes are lower than the rear. Or the opposite. Or they're completely horizontal. What's the purpose of that? I have an idea of how it would physically feel different, but I want to know which would be better for what size person, what kind of ride, etc. I don't know all the technical terms so please keep that in mind, and be very specific! I'm still learning! Thanks lots..
Nat

horizontal TT is the traditional way of doing it.Sloping TT,to the rear is commonly refered to as compact geometry.Compact often works for smeome with short legs and longer torso,looking for standover clearance,without a too short Toptube.Otherwise,Compact is more makerting and hype than anything.sloping toward the front is less common and probably only used on time trial bikes.

Nat,

wow, talk about a can of worms here. People get
very touchy about compact geometry vs traditional.
Here are some threads from here at BF.

Compact Geometry (http://www.bikeforums.net/showthread.php?s=&threadid=9099&highlight=compact+geometry)

Merlin Compact Frames (http://www.bikeforums.net/showthread.php?s=&threadid=8133&highlight=compact+geometry)

You can do a search for COMPACT FRAMES and get quite
a list. I too am at work, pretending to be busy!
Marty

With a horizontal TT, the height of the headtube is limited by the standover of the top tube.
There are good reasons for not wanting that.
Compact frames permit you to have a low standover clearance, but a higher head-tube, useful if you dont want your bars so low.
Also useful for a small frame with big wheels, so the headtube is not too short (the steering bearings of the headset are more effective with greater separation).

The forward sloping TT design is called Low Profile and permits a very short headtube for riders who like their bars very low. This is only used for specialist time trial and velodrome track bikes.

All compact frames do not give a higher headtube.Traditional frames are made, or can be made with HT extensions.

hahaaaaa so...really, I could just wear a skirt with the compact frame more easily than I could with traditional. Cuz I always ride in dresses...yeah.... Anyway, thanks guys. I wouldn't have ever found those other threads on my own; didn't even know to call it 'compact'. I suppose it doesn't matter too much for me which I get. I have long legs and arms. Not concerned about standover height. Won't have any idea what height of handlebars I want until I hop on a road bike and see! Which sounds like the one and only thing that matters, after reading all that! Thanks.
Nat

Hey check it out...senior member. And I don't know squat!