Why are people so hung up on steel frames? Oh, I like 'em too, 30 years ago. I just built a Colnago Master Light for my 15 year old out of my old parts bin so its period correct. You know how many times he has ridden that? Once. He has a brand new modern Trek full carbon with electronic 12 speed Ultegra (we built together) so when he can get up early enough on Sundays, that's the bike he wants to ride.
How tall are you and what size is that Cannondale? I raced on a CADD 3 Cannondale in the early -mid 90s. While it was a great bike for the typical US crits, it rattled my filling loose on the drawn out torture training rides. I didn't care then because I can take a lot of pain. Now, I rather not ride that for more then 50 miles. How much money do you want to spend? A typical modern bike with 10-11 speed mechanical will set you back 1500-2500 bucks?
https://www.ebay.com/itm/314455091460?hash=item4936fbe904:g:zQoAAOSwT6FkANi c&amdata=enc%3AAQAHAAAAwJi9GFhmIqDJxz%2FnBbiezBPW0S1 9btEQjtSvL7GHYSXVe0BatafSkyMYzXnVjzswlTfP2BF1DM1TS 3sKxIISiNh6UCAYvn1L2TH0paY6X3Vf8O5ss2lF8WP%2FKT9L6 cQwf69Fb7fcXmx%2FlrVM8u1gYdUB0p0rC%2BBp3I6dw6gbzjS R3U7kMtLDh0ccsG%2BbbzJOICYIvjmsFDDblXsaDnrKBor0yt3 ocOr%2Bo1pspt0RuY8D93ETPOjl85xzSJ%2Fi3HusfQ%3D%3D% 7Ctkp%3ABk9SR8iH8pTdYQ
This thing will run circles around an old steel bike.
I have been slaking off this year due to rain and my lazy ass. I am bearly able to hang on in our local training rides of about 50 miles. In exactly 5 weeks, we registered for the Levi ride up in Santa Rosa. I am doing the 80+ miles with, I think, 4000' of climbing. Tell you the truth I don't want to know how many feet of climbing because I just want to get through it and go and enjoy dinner with a few guys.
If you are disciplined, and know how to train, you have plenty of time to get up to those miles. If you rode 3-4 days a week with plenty of rest time in between the big heavy days, you should be able to do 50 miles within a month. I am 56. Went out to beat myself up last Sunday did 5o hard miles. Flat going out, hills coming back with a bit of wind. I found my power off the saddle lacking so I have to work extra hard to keep up with the fooking 30 year olds that are kicking my teeth in on the fast steep hills.
I am sure your sister will be able to give you training tips.
Please spin easy gears, about 85 and work up to 95 rpm for the first 3 weeks. The power will come without much effort after that.