Peugeot 103 -- what is it?
 

Is Carbolite (or Peugeot's "Special Lightweight Tubing" for that matter) basically high tensile steel, or it is stronger, sort of like chromoly? I ask because I am looking at a few vintage peugeots and being a bit heavier than 150 lbs I need a frame that is strong -- I'd worry about stressing the forks on a high ten bike.

I weigh over 300, and I have no fear of stressing the forks on a high ten bike... what sort of riding do you do? ;)

It is my understanding that high ten frames are heavier, but generally are as strong as higher quality frames... the stronger steel alloys (chromoly and mangalloy etc) are usually exploited to make tubing that has thinner walls in order to make frames lighter, not necessarily stronger.

I am open to correction here, but I feel safer on high ten than on the high zoot chromoly frames when it comes to durability...

What is it? High carbon steel. Not bad, not good. Have no worries about riding on it.

I thought a Peugeot 103 was a small hatchback car from the 70's.

It was.....a moped.