Mountain bike question

Modern mountain bikes are totally different now in almost every way - frame design, wheel size, drivetrain, suspension, you name it…

I’m not a bike expert by any means, but I took an old 1996 Trek mountain bike and turned it into a 1x street cruiser, so I’ve got some experience with updating old bikes. If you’re looking to do serious mountainbiking, get a new modern one. If you’re looking to ride a couple times a month or less, probably fine just tuning up your old one.

Also, depending on the condition and model, your old Cannondale could probably get you 35% of the cost of a modern mid range mountain bike on the secondary market. What do you have?

If you give me a budget, I can suggest a few bikes in your price range. Also, what area are you in so I know the type of terrain. I'm assuming you are not doing big, long, technical descents? Mostly just mellow hills or flat dirt paths?

There are tons of different sub-category mountain bikes depending on your terrain and types of trails you plan to ride.

If you're actually going to be riding on trails, get a new bike. Bikes have evolved tremendously with even base model bikes (Sub 1k) being much, much better than older bikes.

29" wheels
Tubeless Tires
Modern geometry/kinematics
1X drivetrains
Hydraulic brakes
Dropper Posts

These are all pretty standard features on modern bikes that make the riding experience much more enjoyable. That being said, if you're just looking for a greenway cruiser, you can update your old bike.