Still trying to get a grasp on all the different "language" in the mtb world. Help out my ignorance. I understand the difference between full suspension, hardtail and rigid framed mtb's, etc. However, what I'm struggling with is the subtle differences between bikes listed for specific categories.

So, what are the differences in frames (geometry, specs, etc.), performance, weight, purpose - for bikes in the following categories:

1) All Mountain
2) XC
3) Trail
4) Downhill
5) Freeride

Goggle it....

My post count is low, but I'm no newbie so I'll help ya out a bit.

All Mountain entails all mountain trails. Lots of up and down steep hills. Very studly tires, don't want to slip on a root 95% of the way to the top. Usually middle-of-the-road for weight, can be FS or HT.

XC (cross-country) entails the same as above, but not on a mountain, and obstacles are probably not in the same tier of difficulty. Usually less-knobby tires, as the distances are longer and rolling resistance and weight becomes a larger factor. Freeride overlaps this largely, but generally shorter distances, more abusive trails (jumps to transitions, lots of splits between the "easy path" and "can I make it over that?"), and grippy tires.

DH bikes are the ones you take the lift to the top of the mountain with. Then pretend you forgot about the brakes and see how fast you can get down it. Weight is a non-issue as the true DH'ers pack on another 20lbs in armor, FS is mandatory to be considered DH, and there is usually a lot of travel in DH forks, the best of which are inverted for maximum travel (well over your standard ~80-120mm). These tires are huge (at least 2.4+), ideally tubeless with a low psi and some stans to fight off the pinch flats, since these guys literally roll over huge potholes at 30mph like it isn't even there going down the fireroads.

Geometry for every bike is different. You just need to feel what is right for you, and try to ride everything you can if you're considering a purchase. I mostly freeride, and I love my HT (especially for the climbs, it's a rocket uphill), but there are some downhills coming back to the trailhead that I wish I had a lower toptube on, as I would be quicker if I could get further over my back tire. A shorter stem (in the mail!) will alleviate some of this, for me. Specs and equipment is largely the same when it comes to the actual drivetrain across MTB's... the only real category with specific equipment is DH, which is always very heavy-duty stuff. Some DH'ers scrap quite a few gears as they aren't pushing themselves up anything and it's less stuff to break, which is an inevitability of DH'ing.

For my services I merely request your Teledyne. Please put some ultegras and pedals on, I'll look for it in the mail. Muahaha.

The Teledyne makes for a great conversation piece and is really light. I don't ride it because I'm afraid I'll break the frame.

Thanks for the info. That helps a lot. I pretty well understood the DH segment but was struggling with the differences in the bikes on the other three categories. With road bikes (especially vintage) there are a lot of variations in chain stay length (touring, etc), angles (agressive and relaxed), etc. I hadn't really figured out the key variations in frames on the mtb I don't get the opportunity to ride a lot of trails but when I do it's typically just a few rock gardens that I have to navigate.

My Klein is a taller frame and the top tube slopes slightly. It's much faster on the climbs and feels more planted on the downhill. The Scott is a smaller frame with a shorter reach to the bars so it handles a little better on the trails but doesn't feel nearly as stable on the downhills - in fact, it's downright twitchy and I often don't feel like I can get my weight back enough. Trying to get a feel for frame fit seems a little more involved than the vintage road bike scene - just a personal observation. No real clue if that's true or not.

Any time, mate.

Yeah, there is no way I could actually ride it, being 6'4" and ~220lbs. Still, I love vintage Ti frames.

My one and only is now an '01 Trek 8k 21.5" ... It sat around for a long time (about 5 months ago, got it ride-able again) and lots of stuff is getting replaced, slowly. If I could take my drivetrain and build a bomb shelter out of it, though, I would. Up next is new wheels and mounting a rear disc to match the front... will take a bit to save up that scratch, but it only complains a little bit when I slam it around currently. The Judy fork probably needs to be replaced pretty bad, too... I'll upload some pics when I get the hideous platform pedals off.

Yeah, trails? We've got trails here, all roots and rocks but no mountains. Hills we've got. Are "trail" bikes for tight gnarly, singletrack? Up and down foot high root balls and baby-head rock gardens? I am puzzled by that categorization. I ride a rigid late 90's Cannondale, usually three or four hour rides, short road rides to piece the dirt together, don't I love it!!!