How to build a bike, unfinished.

---note--- unfinished! I'm still whipping up photos and more info. enjoy til then.



So you want to build a bike frame, eh?

Alright. Let's discuss.

It's not easy. It's expensive. It's time consuming. You may not get it right the first time. But it IS one of the most rewarding things you can do.
If you're thinking about building a frame because it'll cost less than buying a brand new high-end frame, you're wrong. it doesn't work that way.
This is going to be a long read- if you're really interested in building a frame, this will be worth your time.

That's about it for the disclaimer, so lets get started:

Step one- frame design

Frame design is what makes a bike unique. You can't quite just slap it together. The first aspect of the frame is its intended use.
Building a frame to do several things (street, freeride, cross-country) won't work. So you really need to decide what you want to do with it.
We're going to start with a dirt jumping style frame. You'll need to decide roughly what parts you want to run. The critical components include wheel size, tire size, fork and travel, and gearing.
In this case, for dirt jumping, we'll stick simple and clean. We're going to use 26" wheels, 2.3" tires, an 80mm fork, and one gear.
The easiest way to figure out geometry for your first frame is to base it off of existing frame geometry, like a bike you already have ridden and enjoyed.
Lets use a 2010 Specialized P.3 for the base.
Find your way to specialized.com and select your region, then bikes, then progressive HT, then P3. On the page, you'll be able to view the bikes geometry.
You'll find all of the measurements are in millimeters. This is common for most bicycle manufacturers, yet you'll often hear and see things referred to in inches.
Top tube, frame size, and chainstay length are the most common things translated to inches. I don't know why, but hey.
Frame size is an interesting and often misunderstood reference. I am 6'2", and your average shop employee would say I need a large or extra large frame.
In the case of dirt jumping and aggressive riding, its easier to use the top tube length to determine size. This is because the frame height should be low for stand over clearance and maneuverability.
A word on geometry: Geometry is the combination of angles and length of a frame. It is the defining factor of how the bike handles.
I highly recommend sticking to existing geometry when building your first frame. Drastic changes can have very negative handling effects.


Simplified definitions:

Head tube angle (HT)- this is the angle that the fork sits at uncompressed. Steeper angles (70*+) will offer nimble handling at slow speeds, and instability at high speeds. Slack angles (67* or less) will make bikes feel stable at speed, but feel 'floppy' at slow speeds.
Naturally, the angles in between are fairly ideal for what you're looking to do. This is measured in relation to the flat ground.

Seat tube angle (ST)- this, on a DJ bike, rarely matters, to be honest. Since the seat is often low and out of the way, its not exactly important. It is more a reference for the length of the bike. Some bikes will move the base of the ST forwards and then have the angle slack- this is often done to allow the rear wheel to move forwards, shortening the chainstays. This is also measured in relation to the ground.

Top Tube Length (TT)- This is effectively the size of the frame. Shorter top tubes are good for tight technical riding or shorter riders. Longer top tubes are great for taller riders, or when you desire stability and room to move. A lot of that is personal preference.
Personally I like a longer top tube- Like I said before, I'm tall, and like a bike that is stable in the air. I also find that longer top tubes offer more 'style' function when riding, because I have room to move around on the bike. The top top is mentioned in two ways, horizontal and actual. Actual references to the 'actual' length of the tube, from the center of the seat tube to the center of the head tube.
Horizontal refers to the 'effective' length of the top tube, from the top-center of the head tube to the theoretical intersection of the seat tube, in a line drawn parallel to the ground.
The horizontal/effective top tube is what to pay attention to in the design aspect.

Chainstay length (CS)- This is the distance from the bottom bracket to the rear axle. It is always measured from the center of the bottom bracket to the center of the rear wheel. On bikes with horizontal chainstays, the length is shown as a range. Short chainstays are nimble and quick feeling, letting the bike manual and jump easily. Long chainstays are stable, but make the front end harder to lift up. This, combined with top tube length, will have the greatest affect on handling. For example, a long top tube paired with a short chainstay will make a bike feel very stable in the air, and very quick at slow speeds. A long chainstay and a short top tube will not be any fun, however. If the chainstay is too short, the bike will feel unstable all the time. This is one of the many reasons to stick with existing geometry- trial and error is the method that most manufacturers use with professional riders in order to develop the perfect frame.

Bottom Bracket height (BB)- This is measured in two ways, like top tubes. One is called "bottom bracket drop/elevation", which is the distance below/above the rear axle. The other way is "height" which is in relation to the ground. The reason there are two ways, and sometimes both are listed, is because of tire/fork/wheel changes. Smaller tires will reduce the overall height of a bike. A longer travel fork will lift the front of the bike, and thus lift the BB too. We will use both terms throughout the discussion, but they will be indicated.
Handling changes from various BB heights typically include stability, and front end lift. Low bottom brackets tend to be stable- you're reducing your center of gravity. Higher BB's tend to be nimble and aggressive, but not stable when jumping. On a bike intended for woods use (DH bikes, etc), a lower BB is faster at speed, but harder to pedal because your feet are prone to rock contact!

Wheelbase (WB)- This is the distance between the wheel axles. It can vary all over, but later you will see how it is more of a 'result' of geometry, rather than an ingredient of design.

Seat tube length (ST)- This is length of the seat tube from the center of the bottom bracket to either the top of the seat tube, or the intersection of the top tube. I like to use the top of the seat tube personally, because it tells you the total frame height. This is also important if you use a brace from the top tube to the seat tube.

Standover- This is simple. It's the height of the top tube in the middle of the bike, in relation to the ground. Traditionally used on regular bikes for sizing purposes. It's a good number to know, but shouldn't be important for a street bike, assuming the frame will be low anyways.

Onwards with design

So having looked at the P3 geometry, and having read the definitions above, we can begin to derive a drawing. But wait! There's more. You're going to need to draw this beast. Whereas I HIGHLY recommend a drawing program like AutoCAD, its not the easiest to get or use. Student licences are the best legit way to get a copy of the software, and often include some instructions. They can run anywhere from $75-$300, so beware of that as your first possible cost. I have not used Google SketchUp, but I do believe it would work as well.
Believe it or not, paper and pencil do the trick too. Get some graph paper, a ruler, a protractor, and a pencil.

Start by writing out the intended use for the bike. Always helps. Write down the parts you'd like to use as well.

If you can, have each square of graph paper be equivalent to one inch. This is great for simple references and getting a good feel for the layout.
Lets start with wheelbase. The P3's is 1063mm. Thats 41.8", so lets draw a horizontal line 42" long (42 squares on the graph paper, 41.8" a drawing program). The start point on the left is the rear axle, and the front is on the right side. I don't know why, but I think almost ever manufacturer does this left-right layout. We're gonna stick with it.

Time to figure the wheels! This is more complicated than it seems it should be. 26" wheels are not 26" in diameter. The ultra-easy way to figure this is by measuring your current bikes wheel while its standing up straight. It will vary, but don't worry, because we can check and change it later. Lets use a radius of 13.5" right now.

Draw two vertical lines, upwards, from each end of the wheelbase line, 13.5" in length. These are now the centers of the wheels. Got that protractor? Using that as the center point, make a circle that touches back down to the wheel base line. Bam, two wheels.
Now, look at the chainstay length of the P3, which is 394mm, or 15.5". This is to the center of the slotted dropout. Don't draw a straight line! Draw a circle with a radius of 15.5". You should have (essentially) a larger circle than the wheel. Now look at BB height- its listed as 301mm, or 11.85". If you're using paper, we're going to say 12". Draw a line horizontal to the ground/parallel to your wheel base, at 12" up. Make sure it crosses the bigger circle you just drew. Where that line intersects with the 15.5" circle is now your bottom bracket!
Feel free to erase the lines not needed. This is where a computer makes life easy.

Welcome aboard dear readers, you're on your way to a detailed frame drawing. These steps will be repeated a bunch through out this guide, so if you're having troubles now, re-read it and try again.

It should look like this:
---insert photo---

Next up in the drawing process is the fork and head tube. This is challenging but straight forward. You'll need to find out the length of the fork- this is called the "axle to crown/A2C" length. It is the length of the fork, uncompressed, from the center of the axle straight up to the top of the fork crown. The first thing you will notice is that it is NOT a straight line between those points. There is fork offset, which is the distance between straight line of the steerer tube and the fork axle itself. Many manufacturers websites include this measurement in the technical specifications. Marzocchi is no exception, and informs you of both the offset and the length. How convenient! We see a length of 477.5mm/18.8" and and offset of 48mm/1.88" for the 100mm model DJ1. We of course are using an 80mm version, so we will need to reduce the length by 20mm, giving us a length of 457.5mm/18". Offset will remain the same.
Here is how we'll draw the fork: On a different piece of paper, use a scale of 1 square = 1/2" this time. This will be a drawing of the fork upright at 90*. Make a dot, thats the axle. Draw a line LEFT thats 3.5 squares long. Now draw a line from there straight up 36 squares tall. That is the offset and length. Now, at the top of the fork, there is a headset. It will affect head tube angle, so we need to draw that too. Specialized actually provides the information to figure this out- lets do the math:

"Stack" is listed in the geometry section as 574mm. In this case, they mean the total length of fork/headset/headtube up to the top of the heatube itself. So, we take the 574mm stack, subtract the now-known fork length of 457.5mm, and then subtract the also-listed headtube height of 108mm, leaving us with 8.5mm. Thats the height of the lower headset cup. Measure the headset you'll be using for extra accuracy if you'd like. Many manufacturers provide this as "cup height/stack" as well. Now go ahead and draw a line on top of your fork line of about 3/4 of a square. We now have the fork drawn. For the accurate types, who have been either doing it on the computer or measuring each bit out, measure the overall straight line that you've created. With that number in hand, head back to the frame drawing. It should roughly look like this:
---insert photo---

Ok. So for this situation, we have a fork/cup total length of 466mm/18.34" with a 48mm/1.88" offset. Go to the front axle, and draw a circle centered on it that is 1.88" in diameter. Now, with that protractor/angle finder, line it up at the head tube angle provided by Specialized, which is listed as 68.5*. Begin your fork line tangent to the smaller circle you just drew. Draw the line 18.34" long at 68.5*. You've now drawn the fork and headset! At the top of that line, you're ready to draw the head tube line. Specialized shows it as being 108mm tall. From the top of your fork line, in the same angle, draw that 108mm/4.25" line. At this point, you can erase the fork line if you wish.
---insert photo---

What you should be looking at is this:
---insert photo---

This is the full base for your frame design. Now the fun begins! At this stage, we've drawn the hard stuff, and from here it is mostly connect the dots. Lets go ahead and get started there.

First up, we need to draw the seat tube. Specialized shows both the effective and actual seat tube angles. Remember before how I said some companies are moving the seat tubes forwards to clear the back tire? This is why they show both. We are going to draw this without the bend, for simplicity. The effective seat tube angle is 72*, and is 370mm/14.5" center to top. Go ahead and draw a 14.5" line at 72* from the BB center. If you have not already, draw a line connecting the BB to the rear axle.

Now we get into specifics of materials and design and how it will affect the drawing. We're assuming here that you will be using steel as a frame material. It is an excellent choice for ride quality, strength, and manufacturing. 4130 is alloy of choice for most frame builders, as it is available in a plethora of sizes. Seat tubes are almost always best to be purchased versus being made- many places online offer them. I use True Temper Verus ST seat tubes. They are butted (meaning thicker at one end) and I typically use the 27.2mm seatpost sized tube. This tube is 1.125" in diameter, which is nice because you can easily source hole saws for mitering. So in your drawing, the seat tube line is your "center line", and by drawing a line 1.125" wide with the midpoint of the line at the end of your seat tube, you can easily sketch parallel lines down to the bottom bracket. Which leads us to the bottom bracket choices- This is a flexible option for most frames. Commonly used is the European bottom bracket- this is available from the same places that sell the seat tubes. They will be offered in 68mm and 73mm widths. I am traditional, and like to use 68mm shells with all hardtails. Commonly available and inexpensive. They will have an outside diameter of 1.5", again, easy for hole saw sourcing. Other options include the American BB, which was traditionally referred to as the "bmx bb". This is a 2.25" outside diameter shell for use with press in cups. Again, 68mm width and easy to source tooling for. There are several other options available including the Mid BB, most of which can be found online with specifications and sizes. In this case, we're going to use the Euro BB. So around your BB location, draw a circle 1.5" in diameter. If you would like, draw another circle inside of it that is 1.375" in diameter, this is just for looks.

With the seat tube and BB drawn, we can connect the rear axle. Since drop out design is personal choice, the following can vary, but here is a simple method: At the rear axle, draw a circle 1.5" in diameter. Chances are, when all else is done, you can find a dropout that will fit inside that range, or make your own, which I will help cover. But with that circle drawn, you can make chainstay lines! For the purpose of the drawing, we will keep it simple. Draw your connecting line, and then expand it, just like the seat tube, as a 1" wide line.
Chainstays will have to clear the tire, chainring, and crank. We will cover that later on. As of now, your drawing should look like this:
---insert photo---

Lets move on to the front end for now, leaving the seat stays alone.
For the downtube, there are several things to consider. The primary concern is fork crown clearance, when the fork turns. The easy way to figure this out is to measure the width of the fork crown at its widest point, and noting its distance from the top. Lets say the fork crown is 6.5" wide and 1" below the headset. Draw that as a single line in your drawing like so:
---insert photo---

Basically, your downtube needs to be clear of that. This will result in the downtube meeting to the headtube somewhere above its bottom edge. Lets draw the head tube to get an idea:
If you're running a traditional 1-1/8" headtube, this is simple. The inside diameter of that headtube, in order to have the cups press in, is 1.334". Conveniently, 4130 is offered in a size that works perfectly for that. Coincidence? Not sure, but I bet the tubing size has been around longer than the headset standard, so I believe the sizing was derived from the tubes! A tube 1.5" in diameter (same as the BB shell) with a .083" thick wall, will give you an inside diameter of 1.334", thus not requiring any machining for it to work. So go ahead and make that 108mm/4.25" long head tube line into a 1.5" wide tube. Feel free to draw the inside too. Now, using a ruler, line up one end at the center of the BB, and the other passing through the head tube. If you'd like to see how this is going to go, move the ruler until its tangent to the BB shell, and align the ruler to clear the fork crown. This is where your downtube has to meet the head tube. With that in mind, here is some info on downtubes: Diameter of the downtube will affect how the bike rides. Larger diameter tubes are stiffer, but traditionally heavier. However, there are multiple thicknesses available. Common 4130 thicknesses include .028", .035", .049", .065", and .083" walls. Common downtube diameters may include 1.25", 1.375", 1.5", and 1.625". In this case, I recommend running a 1.5" diameter tube for a great balance of stiffness and ease of building. If you are a lighter, graceful rider, running a .035" wall may be your choice. An .049" wall is a good general purpose thickness, and if you're a hack, better run .065". Right now, lets use .049" just in case. Using the 1.5" diameter downtube also makes headtube and BB miters quite simple. So go ahead and draw downtube lines like this: Tangent to the bottom side of the BB shell to the headtube, clearing the fork crown, and tangent to the TOP side of the BB shell, parallel to the line you just drew, up the head tube. It should look like this:
---insert photo---

If there is a bit of a gap between the bottom edge of the head tube and the downtube, you may need to consider a gusset. On my first freeride hardtail frames, we were able to drop the downtube to within about a quarter inch of the bottom of the head tube. Fork crowns used to be much narrower back then, so we did not need to use gussets. However, new forks get wider and wider each year, so a gusset may be needed. I'll cover that later.

Lets go ahead with the top tube now. Again, diameter and thickness play a big role here, but for the this exercise, we're going to use another 1.5" diameter tube. This time it will only be .035" thick. Traditionally the top tube can be smaller and thinner than the downtube, because it actually takes less force and impact. Now we get to decide the first "design" factor! If you like a traditional looking frame, the top tube will intersect with the seat tube close to the top. If you like the P3 style brace, you can drop the top tube down a bit. For now, we're going to go traditional. It will be easy to change later on if you wish. Now unlike the downtube, where we were constrained by the fork crown and the BB, we have room to play. For an easy reference point, start at the top of the seat tube, and make a mark that is 1.5" down. Now go up to the head tube. From the top of that, we're going to locate the top tube junction. If the tube is 1.5" in diameter, and we want say, 1/4" clearance from top of the head tube, then our mark should be down the headtube 1". We get that 1" measurement from adding half of the tube diameter to the gap desired. If you've drawn that mark, go ahead and connect the two dots you've drawn. Welcome to the top tube. Go ahead and offset that to make it 1.5" thick.
---insert photo---

You should be thinking that if the top tube is 1.5" in diameter... and the seat tube is only 1.125" in diameter.. how will they meet up? No? Didn't think of that? Ah yes, the first intricacy of frame design. Two options: One, draw the top tube extended past the seat tube, and plan on piercing the top tube for the seat tube to fit into. The other method, would be to squeeze the end of the top tube down until its only 1.125" wide, and then cut it to fit. This is definitely a "sleek" method, but takes some work. I like this method. If you're bored, go ahead and figure out how tall the tube would get for your drawing (its about 1.75" in reality). That would be called "flaring the top tube" to fit the seat tube. It will roughly look like this:
---insert photo---

Ok. We've got a front triangle drawn, and its starting to look like a bike now. This leaves the seat stays. Simply connect a line from the TT/ST intersection down to the dropout. Offset that line to create the tube you'd like. Seatstays affect the stiffness of the rear end, have to clear the tire, and are under a decent load. I like to use larger diameter seat stays with thinner walls, in order to keep the bike light. Most of the time I use a 1" diameter tube with an .028" wall. Another option is to use a 3/4" diameter tube with a .035" wall. Obviously the choice is up to you. If you get really into it, compare the weights for the same length of tube in the different sizes. This is one of the reasons I like the larger/thinner combo versus a smaller/thinner combo... The larger tube is lighter.
Right now, your drawing should look like this:
---insert photo---

And that, dear readers, is basically it for 2D frame design. Looks like a bike alright. Here is how to modify it when you are ready:

All tube diameters and thicknesses can change. Tube junctions can change. If you say, drop the top tube 3" at the seat tube, and bring the seat stays down too, then you could use a brace to support the seat tube, just like the P3. Most of the time you won't want the rear triangle to be too large or too small. Look at it for a little bit and you can see the range where it looks normal.

In the Stumpjumper Anniverary book, one of the Specialized engineers is (roughly) quoted as saying, "If it looks right, it probably is". This is a profound statement to a designer- Often times, in simple designs, when something looks right, it is. Does the bike look goofy? Might ride that way. But since those are preferences, you have to be less opinionated about it. A bike that looks wildly different from any other (in the hardtail section at least) may not be the best option. There is a reason that successful products have similar designs- they've been tested and approved by other riders! This absolutely does NOT suggest that unique is bad- it means that if you draw a bike with 20" chainstays, it'll look funny. Coincidentally it will ride terribly. I suppose what I am suggesting, is, on your first frame, color within the lines. You'll be happier with a functional result than you will be with an 'idea' you had. My first frame was a combination of all the things I wanted in a bike. When I got it built, I hated it. It did nothing right at all. My next frame was based off of a 2001 Specialized P3, hence my use of the 2010 P3 as a reference. Lets call it a tribute. Building one frame can be a gamble. If you're like me, getting it 'wrong' was just not going to cut it, so I had to make another to get it right, and that refining process just keeps going.
The history of our first hardtail name, "V3", was in reference to it being the third version of the same frame. In my case, the third time was most definitely the charm.

The interesting backstory is important to remember at all times: that first frame, that did nothing right at all? It actually did a ton of stuff right, but I didn't realize it. It had an american bb, bmx dropouts and hub spacing, a rigid fork, v-brake mounts, low standover, was beefy, and really nimble. Since I was trying to design a freeride hardtail in 2001, it sucked. Ironically, a company called GeekHouse made a nearly identical frame about 4 years later, and was considered revolutionary. My first frame was like a caveman version of a street mountain bike. I just didn't know it. So was it really a failure? At the time, I thought so. But in retrospect, it reminds me that sometimes the thought process is more important than the final product. Call it a concept bike. The things I learned there heavily influenced our extremely popular and well loved Park Ave street frame.

Moral: You're probably going to do it wrong. Don't let that dissuade or discourage you. Learning from mistakes can quantify them. And yes I ran pegs on that old frame too. Haha.



Back to frame design: the hard parts

With our basic frame layout handled, its time to start considering the 3D aspects. We will cover things such as hub spacing, dropouts, crank clearance, foot clearance, and tire clearance.

Terms you'll need to know:

Hub Spacing: This is the width of the rear hub you'll be running. Mountain bike hubs are traditionally 135mm wide from clamping surface to clamping surface. It is the width between dropouts on a frame. Many suspension bikes use wider standards like 150mm. That is because they often use wider bottom bracket shells to help clear wider tires and suspension components. BMX frames use a 110mm rear spacing. In our case, we will stick with the 135mm standard.

IS51 Disc Mount: This is in reference to the dimensions used in disc brake mounts on frames. I will not be covering post mount version, because that is a serious pain for your your first frame. The "51" is the distance in millimeters between the disc mount holes.
There are other dimensions as well, and it will be covered.

Chainline: This is uh, the line of the chain. It goes from the chainring to the cog on the back. Shimano and SRAM provide specific numbers for geared bikes. In our situation with the single speed, it will be mainly be import to ensure that it is straight, and thats about it.
We will need to consider important things like where the crank arm sits, where the chainring sits, and where the cog on the rear hub sits. In order to simplify this, we'll try to keep things adjustable.

Rotor clearance: Consider this one to be like "Rotorline". Brake rotors sit 15mm inboard of the non-drive dropout. If you are running a big rotor, you may run into clearance issues with the chainstays, similar to the fork-crown-downtube clearances we talked about earlier.

Tire clearance: This is simple to understand, but often hard to create.

Chainring/tire gap: This is the very, very tight area that the chainstays have to pass through between the chainring and the tire. Chainring size and tire size will play big roles here.

Toe overlap: While you are standing on the pedals, measure how much you foot hangs over the front of the pedal. Now measure your crank arm length. Add the two together. Draw a circle with that radius from the BB. Does it overlap the drawing of the front wheel?
Move the wheel backwards 96mm.. Does it over lap now? What this checks is whether your toes will hit the tire while steering, and whether your toes will hit the tires when you barspin. Commonly overlooked, and directly proportionate to top tube length. Rocking a size 14 shoe? That 22" top tube bike ain't gonna be good for you. We'll show you how to deal with it.


Lets get started. With the front of the frame drawn, its time to think about things in 3D. We'll check over the front triangle: its fine. Not much to worry about there. From above, as long as the top tube, head tube, seat tube and down tube are all in the same line, everything is ok. The bottom bracket should be aligned in the middle as well. To draw the chainstay basis, you'll need a fresh piece of paper. Use the same scale as we used for the fork if you can. Start by drawing a box at the top of the page to represent the bottom bracket. This should be rectangle 68mm/2.6877" wide, 1.5" long. Draw an "x" through it corner to corner. Where those two lines intersect is the center of the BB. Draw a line from there downwards, the length of your chainstays. In this case it is 15.5". At the end of this line, is the rear hub. Centered on the chainstay length line, draw a line 135mm/5.314" wide. It should look like this now:
---insert photo---

In our front triangle drawing, we used a 1.5" diameter circle to represent the dropouts. For this drawing, centered on the ends of the rear hub line, draw two lines 1.5" long. Parallel to the left dropout line, but 15mm inboard and centered on the hub axle line, draw a line to represent your brake rotor. We'll be using a 6"/160mm rotor in this case. Your chainstays will have to clear this. To be on the safe side, draw the a similar line on the drive side, but put it 20mm inboard, and make it only 3" long. This will represent the rear cog.

From the center of the rear hub line, it's time to draw the rim and tire. Earlier, we drew the outside radius of the tire as 13.5". Draw this line towards the BB shell now. There should be 1.75" between the end of that line and the edge of the BB shell. Drawing the tire is really hard because it varies based on tires and rims. We'll play it easy here. It's not perfectly round. From the end of that line, go back towards the hub about 3/4" or so. Now make a line 2.3" wide centered on that mark. This is probably the widest point of the tire. Measure an existing tire if you'd like to get specific. Make an arc connecting the ends of the line to the tip of the tire line. This is roughly the profile of the tire while on the rim. It should look like this:
---insert photo---

Now its time to draw cranks. Again, wild variable because of all the different styles and brands. One point of advice is that Truvativ/SRAM offer many crank drawings in the tech section of their website. Find a pair or cranks and sketch away. They also have a couple chainring sizes shown there as well. You can relatively derive the diameter of a chainring by creating a ratio from two known sizes. Or, measure the one you'd like to use. Once that is drawn and added to your bottom bracket sketch, you'll begin to see the chainring/tire gap area. This is probably the hardest part of any frame to design. The first thing to do is lightly sketch a line connecting the chainring to the rear cog. This is that chainline we talked about. Is the line straight? You may have to adjust things to fit. Don't mess with the cranks unless the ring can be moved to the other side of the spider. If you plan on using bmx style cranks, this is easy because you can use spacers to move the arm. Make sure your drive side crank arm is back towards the rear hub.
---insert photo---

Back at the dropouts, offset each representing line about 1" outwards. Turn those into boxes so you can roughly have a target for your chainstays to hit. There are a lot of options for chainstay material. I like to use rectangular box sections because it is easy to cut and keep aligned, and by using the rectangle vertically, you can clear the rings and cranks easier. They also tend not to bend in a pedal grind-gone-bad situation. A common size there is 1" x 1/2" with a .049" thick wall. Realistically it will not be able to go all the way to the BB shell in a straight line. So, connect one edge to the dropout box, and get it as close as you can to being in the middle of the gap of the chainring and the tire. Do this on both sides. Does the disc side clear the brake rotor? I'll leave that one up to you to figure out.

So now the question is how to attach the chainstays to the BB shell. Its a tough one. When I faced this challenge, I came up with a simple and clever idea. I used a piece of thick, larger diameter tube, that I cut a gap in. The gap is wide enough to fit the tire through. I let the ends hang out enough so that the chainstays could mate to it from the dropouts. Then I connected the thicker tube to the BB shell with a large rectangular box section tube. I called this the "yoke", and have used it on all of my frames. I'm not going to claim it entirely on my own here, but I will say that I had not ever seen it done before. Backing up my statement, if you poke around on the internet you'll typically find that neither had anyone else. I used this in early 2002, and it wasn't until Union Street made a frame that I saw it anywhere else. So if ya use it, just mention it. Draco Yoke. Onwards with how it looks:
---insert photo---

You can change lots of dimensions about it to fit your scheme. On my DH bikes, I actually offset the box on the yoke in order to place pivots onto it. I like using simple geometric shapes!
This simple and elegant solution should basically solve your clearance issues.

Lets quickly review-
How close is the rear tire to the seat tube in your first drawing?
How close is the tire to the BB in the second drawing?

If its too close, you've just realized another challenge in frame design. Sometimes you can't have the shortest chainstays. If you need to, bump them out 1/2" or so. If you're adventurous feeling, perhaps you can slide the seat tube forwards, somewhat onto the downtube. This may make the bottom bracket less stiff.. it's a design compromise. Gotta think about these things 24/7. But hey, maybe consider this: if you're having issues with clearances, you may be able to offset certain pieces to help clear it. There's no simple answer here- its part of the challenge.

Moving on to the seatstays- this is tough. Measure the line from the rear axle to the ST/TT junction. Now, just like the chainstays, draw it flat out. This time you don't have to worry about the chainring, but you do have to worry about the crank arms. Shouldn't be too difficult to clear those. Mating the seatstays to the front end is where lots of frame builders choose to bust out some style. On a custom XC frame I made for a friend, I got relatively artistic and it worked nicely:
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I don't recommend that style for a street bike, as your legs could be brushing over it. Our street bikes used a bent tube, which may be hard to make for your first frame. Our freeride bikes used a cut and welded angle in there. It does the job, and gives a muscular look to the frame. I recommend having the seatstays actually meet some of the top tube as well, for strength and added weld area:
--insert photo--

That pretty much covers the rear end tube design aspect.


Dropouts!

This section could be a mile long. Probably will be.
Dropouts can be purchased through the same places you found seat tubes and bottom bracket shells. A big shout out to Paragon Machine Works- the guy who runs it is awesome. I met him at interbike, and he is as much an artist as he is an engineer. They have many solutions for holding your wheels in place. That is definitely the easy route, with the hardest part being just cutting your chainstay and seatstay ends to fit their pieces.
But lets say you have access to a mill? Making some slotted dropouts isn't too hard.
First, figure out how to draw an IS51 disc dropout..
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boy that was easy. I will say that I found that info on Maguras website a long time ago, but I cannot find it any longer. Now, adding slots to this situation is tough, so think simple. If the axle is slotted 3/4" overall, then the disc tabs need to be slotted too. same amount. It can be a messy situation. It's often the case that you need to unbolt the caliper to remove the rear wheel. Its also a pain to set up! At this point, contemplate other solutions if you'd like. Creating your own adjustable vertical dropouts is fun, but a pain, and given that you can buy them from Paragon, I'd say just do that. The other option is an eccentric bottom bracket. It's much more svelte. You can use a modified bmx BB shell up front. Beware that it will possibly affect chainstay length and clearance! However, if you also consider that it offsets the shell front to back, I'm sure you can find a way to make it work. I mean, I won't do -all- the work for ya.. In regards to stereotypes of eccentric set ups: We have been running them on our personal street bikes for probably 5 years. Not a single broken one. Broken cranks arms and bottom bracket spindles, but not the eccentric itself. It doesn't loosen, and it doesn' creak. Bushnells makes one that is really light. Its a bit expensive, but since your dropout cost is gonna be next to nothing, it balances out. I really like the set up a lot. It also allows you to have two positions of the bottom bracket, high and low. Being able to change that is awesome on your first frame- it allows you to feel the differences on the same bike. Highly recommended. Assuming you do that, you only need vertical dropouts, which are really simple to make. Just add a fixed position IS51 mount and call it a day. The other HUGE perk of the eccentric is that you can run a quick-release hub on a single speed street bike without it ever moving. Also you can change a flt tire without needing chain tools or tensioners. See why I run it?

Time to check toe overlap. Go back to the first drawing, the 'side view' of the frame. Resketch the crankset and chainring. Also sketch the basic shape of a pedal. Easy enough to do as a rectangle at the end of the cranks. Now put your foot on the pedal and measure how far your shoe hangs over the edge. Add that to your pedal drawing. Does it overlap the front tire? Move the front tire rearwards about 96mm. This will simulate a barspin, with the front tire as far back as it will ever be. Does it overlap now? If it does, you're back into front end design. If it doesn't, you're set. Now for those that overlap- easiest way to deal with it is by moving the whole fork/wheel/headtube assembly forwards and stretching the top and down tube to fit. That will lengthen the top tube, so make sure to check and measure. You're on your own to solve this one- its mostly personal preference. This is also one of the reason that we copied a frame- its probably going to be fine.




So lets say you're reading this still (wow!) and are pretty set with the design. Nice. It's time to figure out how on earth you're actually going to make this thing. With that in mind, here are some thoughts on the big step:

How to actually build this thing:

First off, sometimes you can find someone with a jig and equipment already, who might be willing to fabricate it for a price. This is actually how I had our first couple frames made. Little did I know at the time, but the Service Manager at the bike shop I was working at (Craig Smith, now the Mendon Cyclesmith) had a jig, a welder, tube cutting stuff, and was nice enough to build my frame based off some parts I had made. Ask around and you may be surprised. When you do ask around, make sure you have these plans in hand. No one will really take you seriously unless you have some idea of what you want. Now lets say this ISN'T the case, but maybe you know a welder, have access to a shop, etc etc. Nice. Your biggest challenge will be jigging, which we will get to.
If you have none of these things, well, you're pretty much screwed. Unless of course, you have a bunch of space and cash. No matter what anyone claims, you're going to want your frame TIG welded. No exceptions. Yes I know race car roll cages are often mig welded. Listen- its not the same. A roll cage only has to work once. I think you'd like your bike to work every time you ride it. Trust me on this one. And yes, you're going to need a jig, because everything moves when you weld it, and I bet you'd like the frame to ride in a straight line.

Still feeling ballsy? Buying a welder will set you back $5,000 equipped, tube cutting tooling (even the drill press/hole saw kit, saws) will set you back a grand easy, plus the jig materials (even in the most basic sense) can add another couple hundred dollars onto the total.
Remember in the beginning I said it wasn't the cheap way out? Right. Oh you're still going to need tools to make the jig like drill bits, mill bits, lions, tigers, bears, oh my!

Lets assume you have some access to some tooling. So it's time to get some materials Get at least two of everything you need, because you're going to screw something up unintentionally. Tubing can be found easily online, places like Wicks Aircraft Supply are good to start with. Look around and you'll be able to find it all.

Got questions on how to actually cut the tubes n stuff? Well, to be brutally honest, take a machining class. This stuff ain't the easiest, but its definitely not hard. All of the angle stuff you need to know has been created in your drawing. If you're not familiar with any of these tools needed to cut material, find someone who is. There is a little bit of a prerequisite for this part.

Jigging. Its tough. It's simple in concept- keep everything in line and symmetrical. A lot of people try to build jigs with straps on flat tables. You -could- go this route, but I'm gonna give you the real deal details.
If you build the frame standing up, you'll be able to weld it from both sides easily, which will help keep it straight.

You'll need a piece of something to use as a base. I have used Faztek extruded aluminum channel many times, and its great because of the inherent adjustability.
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This as a base, will allow you to make pieces to create upright supports that are also adjustable. Since the stuff is available in common sizes, its just a matter of building holders with spacers to keep it all aligned. Your critical points are the head tube, the seat tube, the bottom bracket, and the rear axle.

Start with the bottom bracket. A holder to get it locked in place is good. Easy numbers are important. For example, if you make a plate that bolts into the side of the channel, it can slide forwards and backwards. If the channel is 3" wide, then an insert for the BB shell with a .1561" spacer/shelf will keep the shell mounted in the center of the piece.

You're going to need a way to hold that head tube in place. I've done this by turning pieces on a lathe that slip into the head tube. A good fit will help prevent the tube from deforming when its welded. Two cups, one for the top and one for the bottom. Mounted via 90* aluminum angle, which is mounted to an angle-adjustable piece of Faztek vertically, allows you to adjust the height of the headtube as well as its angle. If your base if kept centered, then its aligned with the BB shell.

Make a 135mm spacer that fits into your dropouts. Find a way to mount the axle to a base plate that can slide. I would make a piece that bolts into the slots of the channel, and has two holes drilled in it to match two holes drilled through your axle support. This keeps the axle from twisting, and keeps it centered. Then, you can space either the plate or the axle itself up or down in order to be at the right height compared to the BB shell. Using your drawings, you can also measure the distance from the BB plane to the bottom of the head tube. This is the head tube height. Then you can set its angle, and slide the head tube base forwards or backwards for top tube length.

If you've cut your tubing properly, it will relatively self-jig. Keep the angles set tight and slide things around until they fit- you'll be able to see how well you made your cuts.

You'll need an adjustable arm and insert, like the head tube, for the seat tube. This spacing is a little harder- but not really. If you're using 3" channel, you need a piece turned down to 27.2mm to fit inside the seat tube. Beware!! You want it deep enough to pass through the top tube/seat stay junction to help with weld heat dissapation, but it may be VERY HARD to remove. I highly recommend using large hex stock, turned to fit inside the tube, but with probably 2" sticking out as hex. This allows you to put a wrench on it if it gets stuck.
And it will. You'll need to buy a reamer for cleaning it afterwards. Most shops have this tool, but will NOT want to use it to cut through weld, because it wrecks the tool.

As for holding tubes in place via their miters- I use zip ties run around the other tubes to act as little shelves to hold things in place, so you can tack weld it and then remove the ties.

If you manage to get this far, I'm going to assume you have an idea of what needs to happen. If not, you're already in over your head. With the info you have from here, you could probably find a mechanically minded person to help you set it up. The more accurate and adjustable the jig is, the better your frame will come out. Realistically, when it comes to building this stuff, you only need a helping hand to get started, and then you'll begin to figure it all out. Theoretically, if you've drawn the frame right, and made everything as accurate as possible, the rest of this will pretty much fall together.

That is pretty much it, believe it or not. There are a billion outside factors like tubing choice, how good of a welder your guy/girl is, your cut tolerances, so many others.. that can drastically affect a frame. But as this isn't so much a guide to manufacturing processes, moreso, how to come up with the plans, then you've got your bases covered.

I am happy to take questions and the likes- but make sure you read the whole thing first! I will be doing another guide on full suspension how-to also. If you have specific questions, I may start a thread with more detailed responses not covered here.

So- with that being said- good luck, and good night. Oh yeah, and welcome to the up-all-night-figuring-out-bike-frames club!