Hi all.

I am new in the mtb world, and I was wondering what factors determine if a frame is good?
the weight? the material? the geometry?
In other words, if I get a cheap frame that adjust perfect to my body, it will be as good as a expensive carbon frame?
assuming both frames has the same components.

Ah, the BikesDirect argument. Is a cheap frame with good components a good deal? While a cheap frame that fits you is better than an expensive frame that doesn't, when you're comparing a cheap frame and an expensive frame that both fit you, the expensive frame wins every time. In all likelihood, the expensive frame will be better made, lighter, less likely to fail, use proven geometry and technology, etc. Is this to say that a cheap frame is going to fail, or an expensive frame won't fail, or that every expensive frame is better than every cheap frame? No, of course not. But as a general rule, you get what you pay for.

Let's say, the main difference will be the quality of construction, and other add ons such warranty, support, etc?

I've been kind of wondering this as well. My example is a GT Karakoram that weighs a ton and handles like a super freighter. Should I get a better frame and swap everything over, or just live with it until I can afford a whole new bike.

There shouldn't be any issue with quality of construction now, frames have to pass EN standards (European standard, but most if not all bikes from CN/TW will conform) so they will all meet a basic standard of construction.

For warranty, this will vary between manufacture and type of bike, and has little relevance to the quality of the frame.

For support, that's not a manufactures job, but the point of sale, as in your LBS, how good will vary from shop to shop.

The MTB market is incredibly diverse which frames being available for lots of different riding types, the intended use will affect geometry, construction features & materials etc; you really need to narrow down what you are looking at to give a more detailed question to get a get a more specific answer.

A tale of two frames;

1: A Carrera Katalyst, about 1990 ish, strong, very heavy, - I think it was made from water pipe, slow - road based geometry; a function of its era.

2: A Giant Iguana' 1993, strong, light - high tensile chrome moly tubing, slow - road based geometry; a function of its era.

Both frames fulfilled their original purpose, both frames made/are making great commuter-tourers. I'll have the Giant frame every time because more design went into it's spec and manufacture, the other frame was not as well designed, where strength was an issue they just put in more metal, lots more metal. The result shows in the final products weight and finish, the Carrera frame weighed nearly twice what the Giant frame does and the weld finish was ordinary. As somebody on these forums said years ago "Strong, Light, Cheap, Choose two". So it is with frames, you will get what you pay for.

Schedule 80?

3lbs/ft, no less...

I wanted to get a specialized rockhopper. and I was wondering if as I progress, can I stick with the frame and only upgrade components or it will be better to get a better frame in the beggining ? in order to not purchase twice. I am mainly interested in XC, and I am not a pro Rider, but an enthusiast.