dirtydozen

Hey. I am quite passionate about the first decades of road cycling and I can find quite a lot of frames on the internet that are very old.

I am not very interested in riding them like people used to do at that time, I would like to have a compact with like 8 speeds maybe. I don't even know if that's possible.

My question is : with a very old (around 100 years old) bike, what components are close to impossible to upgrade/change, and what could be compatible with quite recent stuff ?

Maybe the BB makes impossible to change the rings, maybe there isn't even a bolt to put a sora rear derailleur, etc.. thanks

edit : i know quite a lot of stuff on recent bikes but i don't know anything about vintage bikes and specially those very very old bikes, so even if something is obvious i may not know it

Bandera

An astoundingly uninformed and hopeless aspiration.
As Sponge Bob Square Pants once said:

"Well, good luck with That!"

zukahn1 

For a bike that you can ride with 8 speeds you would need to go newer to bikes from the 40's or 50's. On 30's bikes your looking at 3 speed's for a rider you get older than that your pretty much into single speed and fixed gear flip flops for 1 or 2 speeds.

3alarmer 

Before their leap of faith at Kitty Hawk, Wilbur and Orville Wright made bicycles. More than a century later, their brand unveils two stunning commuter builds.

...and it comes with a Chris King headset.

Phil_gretz

So, please allow me to answer your question with a few questions of my own. Your answers will help to inform you about the practicality of this concept of "ancient frame modified with modern components".

Do you have any metal fabrication skills and access to tools for forming, welding, brazing, grinding and the like? Are you mechanically adept, and an above-average problem solver?

Have you set a conceptual budget for this build (i.e., what are you willing to spend)? Are all parts except the frame in hand now? Will you pay others to modify the frame and what do you expect the costs to be? What tools will you need to buy or rent to accomplish this? Are they factored into your budget?

Have you studied the design of, say, 1920s path racers to determine the sizes and types of all of the mechanical fittings, to include hub spacing, wheel diameters, have bottom bracket dimensions? All fittings. Written down.

Have you (alternatively) studied the design of 1920s path racers to determine which qualities (geometry, materials, finish) you would like in a modern frame made to be compatible with modern components? Would a custom frame fit within your budget?

In summary, what you are proposing will take an array of pretty specialized skills that you may or may not be able to acquire. The time and effort might be better spent looking for a more modern analogue of an older-style bike. Without a realistic look at the costs, you don't have a viable project.

ThermionicScott 

8 speed might be possible... if you're thinking a double crank with a 4-speed freewheel.

@Bandera's reply might sound a bit harsh, but I really don't see this project working out. Even if you managed to mount modern components on a 100-year old frame, you are likely to be disappointed by the vintage handling. I could well be wrong.