Jotjepoes said:I'm not sure about the custom route, seems a bit scary for me. I once got a suit tailored in Hong Kong to fit but it didn't quite turn out right, so I kinda like the idea of trying out before paying.
Yes your spot on with this observation. If you went straight to a custom builder and asked for a custom frame they would start by selecting a crank length of 165 mm and build around that making exactly the same mistakes that the mass producers make so there is no benefit there for you.
They need to build a bike for you around significantly shorter cranks and you will basicaly be a difficult customer for them but its a learning experience for all.
Now let me go back a step. Its your money so buy what YOU want. I'm just trying to give you good, independant and unique advise based on my own experience of finaly getting a good fit on a bicycle at 5' 1" after MANY years of riding poorly fitting bicycles.
Now I agree that starting straight off with an expensive custom bike isn't the best way to go and I was riding around on a cheap "test mule" for a while before committing to an expensive frame. Now my "test mule" was a cheap 24" wheel bike and I am reccomending that as far as off the shelf bikes go a juvenile 24" wheel racer is probably the best place for you to start as well.
So you feel OK on your current bike so why would you wan't to follow my advice anyway?
The issue is that your current bike is OK as long as you have an upright riding position. As soon as you try to get into a more aerodynamic position it all falls apart and you have stated that you wan't to go to a drop bar road bike to get more aerodynamic, hence my advice to you thus far.
i'm going to post part 1 now and edit.
Part 2,
Compared to taller riders short riders using the same crank length have cranks that are a greater percentage of their leg length. This means that the hips and knees are going through a significantly larger range of movement and quite importantly our knees are lifting up significantly higher. Now what bike makers do is move the small rider further forward putting them further on top of the cranks which opens up the leg angles making it easier to handle. The consequence of this is that it places more weight on the hands/shoulders of small riders making it far more difficult and uncomfortable to remain in a aerodynamic position and you may notice that small riders spend far more time on the "hoods" rather than in the "drops" compared to larger riders or as in your case with the flatbar bike you have a more upright position anyway which moves your centre of gravity rearward so the balance isn't too bad. So as you say your current bike is OK but you wan't better.
So you lean forward on your currently sized bike and your knees rise into your chest and you have way too much weight on your hands/shoulders so you can't stay aero for long, its rather uncomfortable and your not going any faster than you can on your current bike.
But you wan't it better for long rides.
What you need is a bike that has your legs going through the same range of motion/angles as that of a large, long legged rider with the same sort of weight distribution as a larger rider and how you do that is start with significantly shorter cranks (see http://www.cranklength.info ). You also want to have a frame with a normal or relaxed seat tube angle of 72-73º which takes the weight off your hands/shoulders to the point that even I who is a serious weakling in the arm/shoulder department can ride in the drops with no weight on my hands. This just can not be acheived with a standard 700c wheel bike for small riders and their 75-76º seat tube angles.
The other big problem with larger wheels is that it limits how short the top tube can be because when you push the seatpost back in relation to the Bottom Bracket then next thing you need to do is pull the head tube back towards the Bottom bracket and this can't be done with larger wheels.
OK I'm ranting again.
My advice is that if you wan't to acheive your stated goals of being able to ride comfortably in a more aerodynamic position then you realy should start with a 24" wheel juvenile road bike with cranks no longer than 150 mm and possible fit shorter cranks anyway. Use it as a test rig and you will probably want to buy a rear set seatpost to move the saddle further back. When your happy with that you can go to a custom builder and get a 650c wheel bike built to your specs that you are happy with based on your experiences with the test bike.
Regards, Anthony