BMX Frame Buying Guide

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12/29/2017 10:39 AM
Edited Date/Time: 12/30/2017 3:43 PM

Back to the Ultimate BMX Buyer's Guide

In this thread, we're going to go over all the different specifications & features of modern freestyle frames.
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These are all important specs to consider when purchasing a new BMX frame. The specs, or specifications, are the geometric measurements of the frame that give it it's own unique feel.

Top Tube (TT) Length
This is the first and most important spec to take in to consideration when it comes time to pick your new frame. It is the length between the frame's Seat Tube and its Head Tube, and it is used generally to describe the size of a frame. Most modern 20" frames come in actual sizes between 20.25" & 21.75". Typically you will choose a size based on your own height, but personal preference also comes into play. A slightly longer top tube will be more stable & comfortable, but harder to manipulate for some tricks. A slightly shorter top tube will be less roomy & stable, but can make a lot of tricks simpler. Here is a list of estimated frame sizes based off of height. Using the this plus the information above will help you decide on an appropriate frame size for yourself.
5'1" - 5'3" / 20.25"
5'4" - 5'6" / 20.5"
5'7" - 5'9" / 20.75"
5'10" - 6'0" / 21"
6'1"-6'3" / 21.25"
6'4" - 6'6" / 21.5
6'7"+ / 21.6 - 22"
Photo

Chainstay (CS) Length
This is the length between the Bottom Bracket and the frame's Drop Outs. They generally span from 12.7" to 14.5". This spec is solely based on personal preference.
The shorter the Chain Stays, the easier it is to manipulate the bike for tricks. They also make it easier to get up on the rear wheel for manuals and such, but at the same time makes it harder to "lock in" and balance it. Shorter chain stays also make for a twitchier bike.
The longer the chain stays, the harder it is to initiate manuals and rear wheel tricks, but the easier it is to lock in and balance them. Longer chainstays will make for a stable tail end of the bike. Photo

Head Tube Angle (HTA)
This is the angle of the Head Tube, which is relevant to steering, stability, and front wheel tricks. The Head Tube Angle will usually range from 74 degrees (mellow) to 76 degrees (steep.)
The steeper the head tube, the more responsive your steering will be, and the easier it will be to initiate front wheel tricks like nose manuals.
The mellower the head tube, the more stable your front end will be, aswell as it will be easier to lock in and balance front wheel tricks.

Bottom Bracket Height (BBH)
This is the height of the Bottom Bracket. It will usually range from 11.5" to 11.8".
Lower bottom brackets are renound for bringing a super stable feel to the bike, aswell as making it easier to balance manuals and other rear wheel tricks.
Higher bottom brackets make for a more "poppy" feel in the bike, especially when hopping and doing tricks. They make it easier to initiate rear end tricks, but harder to lock into them.
Also keep in mind that when you change your BBH, it changes the distance between your feet and your handlebars. Lowering your Bottom Bracket by .25" will make your bars feel .25" taller.

Stand Over Height (SOH)
This is the length of the Seat Tube. This will usually range anywhere from 7" to 10". The taller you go, the harder it becomes to do tricks such as can-cans or tailwhips, as the Top Tube is now that much higher and more in the way. Taller Stand Overs are also said to make for a stiffer, stronger frame. This spec is pretty dependant on personal preference and riding style.

Seat Tube Angle (STA)
This would be the angle of the Seat Tube. This alters the effective feel of the Top Tube, in correspondence to the Stand Over Height. The industry standard for STA's is 71-degrees, but can range from 69-degrees to 72-degrees.
Basically, when you change the STA, you have to add or remove some Top Tube material, without altering the position of the Bottom Bracket. And the taller the SOH, the larger the difference.
Example: A 21" TT frame with a 9" SOH and 71-degree STA will ride identical to a 21.3" TT frame with a 9" SOH and 69-degree STA (assuming all other specs are the same aswell.)
This is because the difference between the 71-deg and 69-deg on a 9" SOH is 0.31", meaning you have an extra .31" of top tube but your Bottom Bracket is still the same distance from the Head Tube. Photo
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Now that you've figured out what specs should suit your body and riding style, you are ready to choose a frame based off of its features. The features of the frame are the technical specifications that decide its structural integrity and its weight.

Heat Treatment
Most aftermarket frames are Heat Treated, which means the tubes have been heated and cooled in a way that strengthens them. There are two different ways a frame will be treated.
The first and cheaper method is to use heat treated tubes to build the frame. However, the heat of welding can alter the heat treated properties of the tube near the weld, which brings me to method #2.
Post-weld Heat Treatment is a process that consists of heat treating the entire frame post-production so that the properties of the metal are the same through out the weld. This is the most efficient way to strengthen both the tubes and the welds.

Investment Casting
Investment Casting in BMX is essentially a way to move a weld away from a joint for a stronger or larger connection. It is done by casting pieces of the frame, such as a Head Tube or Drop Outs, with segments of the corresponding tube built in to it. This usually, but not always, makes for a more durable section of the frame. Photo

Ovalized Tubing
Some frames will use Ovalized Tubing for the Down Tube and the Chain Stays. Due to the shape of the tube, they are much less likely to dent or bend on the bottom of the tube. This is preferable for riders who hit their their frame in those spots on grinds and such.

Wave Tubing
This option is only available from Sunday Bikes. Similar to Ovalized Tubing, they make the tube dent proof by adding "waves" to the bottom of the tube. This feature is limited to a few of their frames. Photo

Tapered Tubing
Some companies will use Tapered Tubing to save weight without a significant difference in strength. A tapered tube is one that is slightly narrower in diameter on one end than it is on the other.Photo
Butted Tubing
Butted Tubes are tubes that are thicker on the ends than in the center. This can be done for two very different reasons.
The first being that you can essentially beef up the end of the tube for a stronger weld with very little difference in weight compared to a straight gauge tube.
The second method is to remove material from the center of ideally a straight gauge tube, making a lighter tube without sacrificing strength from the weld.Photo
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Questions?

If you have any questions or suggestions for this post, leave them in the comments below and I will address them & add them to the OP.
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Back to the Ultimate BMX Buyer's Guide
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12/29/2017 7:06 PM
Edited Date/Time: 12/29/2017 7:15 PM

I see it is presented as center to center in the illustrations you have provided but I think it would be worth adding the phrase "center to center" in regards to describing top tube length and such. I have seen people measure from the inside of the headtube to the inside of the seat tube and outside to outside even.

Another good post! Helpful to many!

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12/29/2017 7:33 PM

Thank fuck . Now if you can help people decide what they want , that’d be great . Can’t count how many frames I change my mind about , before sporadically buying a completely different one .

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Instagram : braydenbuckingham
My Cult 2 Short

12/29/2017 7:42 PM

Agreed... Great post(s)! Can't believe this hasn't been done before at this level. Hopefully, it can get stickied as it's own thread permanently listed at the top of the forum.

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12/29/2017 10:45 PM

This is perfect. But where was this thread months ago when I got back into BMX? Lol

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12/30/2017 8:00 AM

Thanks guys! I plan to finish up this thread in a bit, then I can focus on pumping out the shorter threads such as Forks and Bars and what not..

I appreciate the input and kind words, fellas.

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Refs : SnM An1mal, GThompson121, Chuck8273, blizzbikes, bmxsteve99, kevin.brock.338, zinum, Brian_Griffin, billyhandyjunior, riverM, tomdon
Instagram : @timhankinsbmx


12/30/2017 9:58 AM

Bulletpup wrote:

I see it is presented as center to center in the illustrations you have provided but I think it would be worth adding the ...more

Maybe someone selling a bike on eBay, but manufacturers will all measure from center to center for the top tube. That's pretty standard.

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12/30/2017 10:00 AM
Edited Date/Time: 12/30/2017 10:04 AM

I want to add that most aftermarket frames are NOT heat treated. Actually only one company that I know of, and that's Sunday. There might be one or 2 other small companies doing it, but not any of the mainstream popular companies.
This is great though, now hopefully kids will actually read it. Thanks man.

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12/30/2017 10:16 AM

ggallin422 wrote:

I want to add that most aftermarket frames are NOT heat treated. Actually only one company that I know of, and that's Sunday. ...more

If you are referring to PWHT then you're close.. WTP post-weld treats their frames aswell & I know I've heard of a few other frames here and there from companies being PWHT.

But most aftermarket frames that arent PWHT are built with heat treated tubing, and the ones that aren't are usually significantly cheaper or are claimed to be "built to keep costs low." The company likely doesn't treat the tubes themselves, they buy them pre-treated.

I also know there is many different ways to treat a tube with different results and costs.. But I haven't seen any companies speak out in detail about how their tubing is treated, so I'm assuming there is an industry standard for it and they likely all use the same stuff. I would think. Guess we'll never know for sure.

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Refs : SnM An1mal, GThompson121, Chuck8273, blizzbikes, bmxsteve99, kevin.brock.338, zinum, Brian_Griffin, billyhandyjunior, riverM, tomdon
Instagram : @timhankinsbmx


12/30/2017 10:30 AM

ggallin422 wrote:

I want to add that most aftermarket frames are NOT heat treated. Actually only one company that I know of, and that's Sunday. ...more

HardBMX_Tim wrote:

If you are referring to PWHT then you're close.. WTP post-weld treats their frames aswell & I know I've heard of a few ...more

Frames would be heat-treated in the factory. There's no such thing as pre-heat-treated tubing, the welding would destroy any properties attained by such prep work. The frame as a whole would be heat-treated to achieve a similar strength throughout in order to avoid there being a strength difference between different parts of the frame. Most heat treatment, at least in BMX, is literally just sticking the frame(s) in an oven at a given temperature for a certain length of time. That leaves the entire frame as close to uniform in strength and other properties as possible(there'll always be more strength around the welds).

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My Sunday Soundwave V3 Build
Insta: @p.gibbons

"You can't educate pork"
- grumpySteve

"Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming "Wow! What a Ride!""
- Hunter S. Thompson

12/30/2017 10:51 AM
Edited Date/Time: 12/30/2017 10:53 AM

ggallin422 wrote:

I want to add that most aftermarket frames are NOT heat treated. Actually only one company that I know of, and that's Sunday. ...more

HardBMX_Tim wrote:

If you are referring to PWHT then you're close.. WTP post-weld treats their frames aswell & I know I've heard of a few ...more

p1p1092 wrote:

Frames would be heat-treated in the factory. There's no such thing as pre-heat-treated tubing, the welding would destroy any ...more

Here is one example.. from Mike Laird himself, "The material I use to build my chromoly frames with is Vari-Wall's BMX specific Thermlx double-butted or straight gauge tubing. The tubing has been heat-treated (air hardened). Giving it a very high strength to weight ratio over traditional chromoly found in other frames."

Also, I recall Standard or S&M claiming their tubing to make for a stronger weld due to its properties and heat treatment.

You are right though, upon further review it seems a lot of frames only offer heat treated head tubes, bottom brackets, and drop outs, not sure why that is..

Maybe majority of frames aren't done this way, but it still seems to be a popular (and cheaper, less effective) method of strengthening a frame.
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Refs : SnM An1mal, GThompson121, Chuck8273, blizzbikes, bmxsteve99, kevin.brock.338, zinum, Brian_Griffin, billyhandyjunior, riverM, tomdon
Instagram : @timhankinsbmx


12/30/2017 11:15 AM

HardBMX_Tim wrote: Here is one example.. from Mike Laird himself, "The material I use to build my chromoly frames with is Vari-Wall's BMX ...more

Again, welding will negate any properties attained by heat-treatment prior to the welding. Heat-treatment ensures that no section is more brittle than another and "relaxes" the metal so that it's not trying to pull itself apart.

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My Sunday Soundwave V3 Build
Insta: @p.gibbons

"You can't educate pork"
- grumpySteve

"Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming "Wow! What a Ride!""
- Hunter S. Thompson

12/30/2017 11:28 AM

p1p1092 wrote:

Again, welding will negate any properties attained by heat-treatment prior to the welding. Heat-treatment ensures that no ...more

I'm not disagreeing with you, but your terminology is a bit off..

Heat Treatment does not mean the same thing as Post-weld Heat Treatment, & i went over the differences in my OP..

You are referring to Post-Weld Heat Treatment, which is when the frame or part is treated as a whole, post-production. & yes, this is the only way to ensure the same properties through out the weld.

Heat Treatment in general only refers to the treating of a piece of metal, in the case of non-PWHT BMX frames, the tubes. & yes, the heat of welding will alter the priorities around the weld, likely weakening them. Regardless, this is still a method that is used by even some of the most renound frame builders, such as Mike Laird. The proof is in the puddin.

I did address the differences that you are mentioning in the OP, so I'm not sure what exactly you are disagreeing with..

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Refs : SnM An1mal, GThompson121, Chuck8273, blizzbikes, bmxsteve99, kevin.brock.338, zinum, Brian_Griffin, billyhandyjunior, riverM, tomdon
Instagram : @timhankinsbmx


12/30/2017 11:30 AM

There's some great frames out there in the 21.6"-22" TT range (for those extra tall riders).

I'd maybe change it to:
5'1" - 5'3" / 20.25"
5'4" - 5'6" / 20.5"
5'7" - 5'9" / 20.75"
5'10" - 6'0" / 21"
6'0" - 6'2" / 21.25"
6'3" - 6'5" / 21.5"
6'6"+ / 21.6"-22"


Just a suggestion, Tim. Also, big props on taking the time to do this!

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12/30/2017 11:53 AM

Bryan91 wrote:

There's some great frames out there in the 21.6"-22" TT range (for those extra tall riders).

I'd maybe change it to:
5'1" - ...more

Thanks for the feedback, I added some info about 21.6+ frames.

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Refs : SnM An1mal, GThompson121, Chuck8273, blizzbikes, bmxsteve99, kevin.brock.338, zinum, Brian_Griffin, billyhandyjunior, riverM, tomdon
Instagram : @timhankinsbmx


12/30/2017 12:04 PM
Edited Date/Time: 12/30/2017 12:10 PM

HardBMX_Tim wrote:

I'm not disagreeing with you, but your terminology is a bit off..

Heat Treatment does not mean the same thing as Post-weld ...more

My terminology is fine, I was referring to both pre and post weld heat treatment.

"the heat of welding will alter the priorities around the weld, likely weakening them."
The welding doesn't weaken the area, in fact, it makes it a lot stiffer. We're not talking hardened high-carbon steel kind of stiff but it's enough to make something similar to a shear plane(can't think of the term) between the weld-affected-zone and the surrounding area. Post-weld heat-treatment removes this difference in brittleness and makes the part as close to uniform in properties as is practicable in a given time.

I'm not arguing for no reason, merely ensuring you have all of the information so that this turns out as well as possible. I want this to end up as a very good source of information. I'm not saying you don't know what you're on about, you clearly have a good grasp on it. I just want to ensure that none of the misinformation already spread throughout BMX by people who only have a basic gist of what they're on about, people who haven't a clue and salespeople, ends up in here.

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My Sunday Soundwave V3 Build
Insta: @p.gibbons

"You can't educate pork"
- grumpySteve

"Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming "Wow! What a Ride!""
- Hunter S. Thompson

12/30/2017 12:19 PM

p1p1092 wrote:

My terminology is fine, I was referring to both pre and post weld heat treatment.

"the heat of welding will alter the ...more

Believe me, I know you're not typing for no reason haha. Just a bit confused with what you're saying, as it sounds to me that I have already covered the points made..

To me it sounds like you were saying Heat Treated frames are only post-weld treated, which is not true, as there are certainly frames built with pre-treated tubes.

The idea behind using pre-treated tubes is that, although the weld may only be as strong as a frame built without them, the center of the tubes are more dent proof/resistant to breaking. And because of this, in the case of Laird Frames at least, you can get away with using slightly lighter tubing without sacrificing strength compared to a non treated frame with regular tubes.

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Refs : SnM An1mal, GThompson121, Chuck8273, blizzbikes, bmxsteve99, kevin.brock.338, zinum, Brian_Griffin, billyhandyjunior, riverM, tomdon
Instagram : @timhankinsbmx


12/30/2017 12:31 PM

HardBMX_Tim wrote:

Believe me, I know you're not typing for no reason haha. Just a bit confused with what you're saying, as it sounds to me that ...more

Ah, I get what you're saying now. I'd still say pre-weld heat treatment is entirely pointless. What's the point in the center of the tube being as strong as possible if the frame is going to snap at the welds at the first hint of abuse? Frames and any other welded parts for that matter should be post weld heat treated to deal with the weld-affected-zones. You could get whatever properties you want in the center of the tubing with post-weld heat-treatment and deal with the weld-affected-zones in one fell swoop. If you pre and post heat-treat a tube, you're just adding extra cost to the build with no actual benefit.

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My Sunday Soundwave V3 Build
Insta: @p.gibbons

"You can't educate pork"
- grumpySteve

"Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming "Wow! What a Ride!""
- Hunter S. Thompson

12/30/2017 12:48 PM
Edited Date/Time: 12/30/2017 12:54 PM

p1p1092 wrote:

Ah, I get what you're saying now. I'd still say pre-weld heat treatment is entirely pointless. What's the point in the center ...more

S'all good haha.

The main reasons for pre-weld treatment that I can think of are..
A. Cost. Not only is it cheaper to run an oven the size of just 1 tube, but they don't even have to. They usually buy the tubes pre-treated & don't have to worry about heat treating anything at all. A little more material costs & far less manufacturing costs, and they're still able to advertise it as "Heat Treated".
B. Dent resistance in the middle of the tube, so the tube won't dent or even cave in if you hit it really hard. I personally wreck downtubes like it's nothing if they're not oval shaped, so I can totally understand why they'd want to strengthen up at least that part of the tube.

But I totally agree with you. As I concluded in my OP; Post-weld Heat Treatment is a process that consists of heat treating the entire frame post-production so that the properties of the metal are the same through out the weld. This is the most efficient way to strengthen both the tubes and the welds. 

Also, have you heard of WTPs Liquid Treatment?
Instead of cooking the frame in an oven, where the heat works its way in from the outside, they essentially boil the frame at the same temperature to ensure equal properties on both the outside and the inside of the tubes and welds.

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Refs : SnM An1mal, GThompson121, Chuck8273, blizzbikes, bmxsteve99, kevin.brock.338, zinum, Brian_Griffin, billyhandyjunior, riverM, tomdon
Instagram : @timhankinsbmx


12/30/2017 3:46 PM

Thread is finished.silly
Hope you all enjoy and that this will be able to help many generations of riders to come!
If you have any questions or suggestions, leave them in the comments and I'll address them & add to the post.
Thanks for reading!

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12/2/2020 10:29 AM

I have recently started Bmx and I purchased a dk helio 2018 for 100 used when I bought the bike I had no idea that it’s size would affect my riding it has a 21 TT and a chain stay of 13.5 head tube angle of 75 and a seat tube angle of 72 I am around 5,4, 5,5 I think and im still growing. I am looking into purchasing a new frame and wondering what specs I should get with it I like street riding but I also like drops and jumps I am also concerned if my old parts will be compatible with a new frame can someone help me out.

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12/2/2020 2:06 PM

My job might be giving me 680 bucks to spend on bike parts soon , might be time for some new stuff , haven’t looked around at frames latley time to start browsing again this could be exciting

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12/2/2020 5:07 PM

eskimojay wrote:

My job might be giving me 680 bucks to spend on bike parts soon , might be time for some new stuff , haven’t looked around at ...more

Keep us posted on what you’re getting

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smile

12/2/2020 8:14 PM

HardBMX_Tim wrote: Back to the Ultimate BMX Buyer's Guide

In this thread, we're going to go over all the different specifications & features ...more

Nice work throwing this together. It’s always helpful to refresh on the geo. I always have to reread specs like this specifically about HT and ST angles...but I sucked at geometry in school. Got yelled at a lot.

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