Building my own full suspension MTB: How to I select a frame?

Question

I've recently gotten back into mountain biking. I took my 5 year old Iron Horse full suspension out to the mountain with some friends that had recently purchased new bikes. I haven't ridden for a few years so i had to take my bike in for a major tune up before the trip. My bike was kind of a cheapo ($700) and really could just barely handle the terrain we were riding. I mean just barely.

We stopped at an enormous bike shop on the way back just for fun, and I was pretty envious of what I saw there. The technology has come pretty far in 5 years, and if you are willing to put $2000 to $3000 on a bike, you can get a serious machine. I'm tempted to simply purchase one of these premade bikes, but I hated how I always had to take my old bike in for tune ups because I didn't know how anything on it worked. This time I want to know the ins and outs of my bike so I can make all the repairs myself. I've already started a tool kit collection and recently got an awesome repair stand by ParkTool. I've turned my old MTB into a comfy commuter bike and have had some fun tuning it up myself. Now its time for my fun bike.

I know what I want is basically an all Mountain bike. Some thing I can tear down rough trails with, but still is useful enough for those long climbs to get to the top those trails. Here is what I want out of my new bike:

• Light: As light as I can go with a reasonable budget. I think carbon frames are most likely out. I'd like to spend less than $2500 for the whole bike.
• Durable: I'm a big guy. 220lbs when I'm fit, but 250lbs now. 5'10" tall. So sturdiness is a concern.
• Full Suspension: I just prefer the softer ride.

Everything is going to revolve around the frame. So I'm gonna start there. Here are some questions that have been piling up during my search for a frame.

1. Where is the best place to browse a good selection of frames? After some google searching, the only place that had a respectable selection to choose from was www.cambriabike.com. And my god they have a ton of frames, too many for me to figure out actually. There has to be other places though right? Most I saw had less than 20 frames, while cambriabike had about 1000. That doesn't make much sense.

2. What brands should I be looking for or avoiding? I'm not keen on many bike brands but I do know a few, Cannondale, Kona, Specialized, Iron Horse, Giant. But I see alot of brands on frames that I've never heard of. Should I stay away from unknown brands or are there some frame makers out there that are great who just haven't made a name for themselves in full bike assembly.

3. Get a frame with suspension shock already imbedded, or empty full suspension frame and install my own shock? I really would prefer to install my own shock so I can choose the exact one I want. I'd like to know a little bit about my shock and research it, plus I'd really like to find one that supports remote lockout. You see it on front forks, but not really on rear shocks. Anyways, I spoke with a guy at the bike shop and he said shocks had to be specially made for each frame. That eye-to-eye length had to match just right with compression ratios and yadda yadda yadda. I think he just wanted to scare me off so I'd buy one of the show room floor. After I get my frame, I should be able to take a look, and buy a freaking shock from Fox Racing or something that fits the bike right? Then I can make adjustments to its performance with it's built in features. Am I wrong here.... is it really so complicated that each shock has to be custom made for each frame?

4. How to tell the difference between a downhill frame and an all-terrain frame? I realize there are sectioned out on the cambriabike website, but dang, some of them look so similar. There are exotic looking down hill frames and exotic looking all-terrain frames. I wouldn't be surprised if some frames showed up under both categories. I haven't verified that, but I wouldn't be surprised. If you were to look at a stats sheet, how do you REALLY differentiate between a downhill frame and an all-terrain frame?

5. What is considered "light" for a frame? I guess you'd have to segregate carbon from aluminum frames, but what is actually "light". I'm looking at a frame here and it says 7lbs.... is that considered light versus the competition?

6. How do you pick a frame size? I see frames that say 18", 19", Large, Medium, what the heck is all this. What is 18" mean. 18 inches from what? And medium.... medium what?

Answer 1

1. The internet. Bike magazines. Bike shops. Your friends.
2. Just as in any other industry there are good and bad brands. Good brands occasionally build awful bikes and vice versa. Read reviews, see the things in person, and test ride them.
3. It's very difficult to buy a frame without a shock. They don't have to be custom made as such, but rather custom tuned. Frame designers will usually work with the shock manufacturers to make their design work together with the shock. They come in all sorts of shapes and sizes, with a variety of tunes (high & low speed compression/rebound etc). Some shocks simply don't work well with certain suspension designs. Some won't fit due to piggyback reservoirs etc.
4. A downhill frame is designed to be thrown down mountains at ludicrous speed. Look for 180mm or more of suspension travel, a coil-sprung shock and very slack angles. Full-on cross-country bikes tend to be built for the exact opposite. Look for 100-120mm travel, air shocks steeper angles and ludicrously light weight. All-mountain bikes sit somewhere in between, with 130-160mm travel, air shocks, fairly slack angles and a reasonably light weight. There's hundreds of pigeon-holes though (Freeride, Slopestyle, Dirtjump, etc) so if you're not sure, google the thing and see what it's for!
5. ~7lbs including shock sounds about right for a longer travel (~150-160mm) aluminum all-mountain frame.
6. An 18" frame is usually 18" from the centre of the bottom bracket to the top of the seat tube. The best thing is to go to the bike shop, sit on a variety of bikes and sizes and see what fits you! Many manufacturers will also have a size guide on their website and/or in their literature.

In general, slacker head angles give more confidence when descending, as do lower bottom brackets, but both have their downsides when climbing (wandering front end, pedal strikes). Look our for ProPedal (on Fox shocks, similar tech on others), which gives you a partial lockout for use when riding on fire-roads and other less technical terrain.

Some other things that come to mind:

• Fit a super-short stem (50-60mm) and wide bars (710mm or wider). They'll feel weird for the first 20 seconds and then you'll never be able to go back. So much better!
• Drivetrain: Shimano and SRAM are the big players. My personal preference is for Shimano but they both make good stuff. Shimano SLX or SRAM X7 tend to provide the best "bang for buck", the XT and X9 being lighter and XTR and X0/XX providing serious bling. They aren't always compatible, so usually best to stick with one or the other.
• I run a 1x10 speed setup (1 front chainring, 32t, with an 11-36t cassette out back) with a chain device. Unless you live in some seriously steep hills/mountains or spend a lot of time on the road, I find it's a wide enough spread of gears for most things.
• There's a hell of a lot more to consider on top of that. Forks (how much travel? 15 or 20mm bolt-thru? Don't go for a plain old quick release!). Wheels (hubs, rims, tyres, go tubeless!). Brakes (Shimano SLX with 180F/160R rotors are really good). Grips (Get lock-ons!). Saddle. Seatpost (fixed or adjustable - check out the Rockshox reverb). Pedals (Flats or SPDs). Etc.

Answer 2

The biggest advantage of building your own bike is getting exactly what you want when you knew what you wanted from the git-go. Since you don't know what you want and admit to not really knowing what you're looking at, you're better off getting a built bike from a shop. Your first set of components are basically going to be an experiment. Those components will be cheaper on a stock bike and you'll be able to replace them with different/better parts as they wear out and you discover what you like. That said, I'll answer as many of your questions as I can...

1. There probably isn't a one best place to search for frames. Rather than looking for one place to shop, it'd be better for you to figure out what frame (or type of frame) you want and then shop around different places for that.

2. All of the brands that you mentioned are respectable. If you're not sure about a company's frames, just check around for reviews.

3. I actually prefer hard tails, so I don't have an answer on this one.

4. Downhill frames are generally beefier and allow more travel on the rear shock and the geometry will be optimized for a longer fork with more travel.

5. Again, since I mostly ride hard tails I'm not sure what a normal weight is for a soft tail.

6. The manufacturer's page for a given frame will usually list the geometry. Look for the "standover height." This is the quickest and easiest way to determine the fit of a bike, especially if your proportions are reasonably normal, i.e., you don't have monkey arms or super long legs. To measure your standover height, have someone hold one end of a tape measure on the ground between your feet and push the other end up as high into your crotch as you can. Uncomfortably high. Repeat a couple of times for accuracy. Buy a bike that has a couple inches less standover height than you do. You want a bit of clearance.