Are you trying to find the ideal BMX top tube length for your riding style?
I have been searching for the perfect frame size for over two decades.
Yes, REALLY.
I started on a 20.5″ frame, but year after year, my frame’s top tube (TT) has slowly gotten longer.
Right now, I ride Devon Smillie‘s Cult Biggie frame in 21.5″ TT (by the way, I’m 5’11”).
Yup, this goes ENTIRELY against the grain of all the frame sizing charts you see other websites having (find an example below), aiming at helping you pick the correct frame size.
But these charts might not be as helpful as you’d think, which you’ll see why shortly.
This post covers:
- BMX Top Tube Length Guide
- What Size BMX Frame Do Pros Ride?
- Conclusion: Pick The Right BMX Top Tube Length
- FAQs About BMX Top Tube Length
If following the traditional frame size recommendation, I’d either need a 20.75″ or a 21″ frame.
I’m grateful that I tried both sizes, including 21.25″, but the one I ride now feels GREAT. The best, to be honest.
It was around three or four years ago when I began paying more attention to the frame sizes BMX pros ride.
Why?
Because I noticed that many of the top pros ride pretty large frames – after carefully observing their videos and IG posts.
Note that I find a rider with a slightly “larger” frame to look a lot more stylish. However, that’s just my look at it – of course, I enjoy watching everyone shred.
At the end of the day, there’s no right or wrong in BMX – it’s all about finding what works and feels best for YOU.
Anyway, back to the TT.
After examining the pros, I did a relatively simple calculation, comparing the riders’ heights and the frame sizes they ride.
This helped me answer a common question:
BMX Top Tube Length Guide With Rider Heights
Okay, let’s look at a traditional BMX frame sizing guide for a 20″ bike.
Attention: Almost no BMX pro out there rides a frame according to these standard sizing recommendations, but most ride a longer one.
| Rider height | Top tube length |
| 4’8″ to 5’2″ | 18.5″ – 20″ |
| 5′ to 5’4″ | 20″ |
| 5’2″ to 5’6″ | 20.25″ |
| 5’4″ to 5’8″ | 20.5″ |
| 5’6″ to 6′ | 20.75″ |
| 5’8″ to 6’2″ | 21″ |
| 6’+ | 21.25″+ |
What I will say is this: Don’t be afraid to go with a 0.25″ (or even more) longer TT frame.
I picked a MUCH longer frame for my height, which suits my riding style perfectly.
BUT!
Yup, there’s always a but.
You first need to look closely at your riding style.
- Do you prefer to go super technical?
- Do you like to ride trails and transitions?
- Or do you like a bit of everything?
For instance, if you pick a frame with a longer TT (something I recommend) but also has a long chainstay length, it’d be slightly more challenging to do super technical stuff (unless you’re a taller rider).
Note: Check out my complete BMX bike size chart guide.
BMX TT Length For A 6+ Foot Rider
If checking the above table, a 6-foot-tall rider would need a frame with a 21.25″ top tube.
However, if you’re anything above 6′, I recommend you go with a 21.5″ TT frame.
But if you’re really tall, I’d then pick a 22″ BMX bike (which is something I haven’t said out loud yet – but that’s exactly what I’d do).
Note: Don’t miss my ultimate tips for tall BMX riders.
How To Measure BMX Top Tube Length
If you have a bike you’re unsure what top tube length it has, measure it from the center of the head tube to the center of the seat tube.
That’s it.
What Size BMX Frame Do Pros Ride?
Garrett Reynolds is 5’7″ and rides a 20.75″ top tube frame. According to his TT, I’d need a 21.9″!
And according to Chad Kerley, I’d need a 22″!
Have you ever even noticed how large Chad’s bike is, particularly if he’s sitting on it or standing beside it? Also, the front end – his bar is around navel height.
But it wasn’t like this always. He had a much smaller frame size and lower front end height if you watch some of his older videos and bike check.
Moreover, if we take Nathan Williams as another example, he is 5’10” and rides a 21.25″ TT frame. So according to Nathan, my frame size would need to be 21.5″ – you see, I almost nailed it with a 21.6″ TT frame (because Nathan is one of my favorite riders).
But this frame-to-height comparison isn’t always the case. If comparing some other pros, I’d need a lot smaller TT (to my current 21.6″) – still, it’s different from the traditional frame size charts.
Note: Don’t miss my extensive table on what size BMX do pros ride.
Conclusion: Pick The Right BMX Top Tube Length
Even though I recommend doing your own thing and picking a larger frame than the TT size charts suggest, I’m sure that might be daunting for some.
Making a switch was easier for me because I tried and tested multiple TTs to find the ideal one.
Remember, you don’t have to buy multiple frames to determine your best size.
Borrow bikes from your riding buddies for a few laps. And don’t do it just once. Instead, do it over the course of a few sessions, just to get the grip of it.
Also, pay attention to the chainstay – does your friend have it slammed or not? (Because it can greatly affect how the frame feels.)
My final words: Don’t be afraid to pick a frame with a longer TT!
I did it, and it works. AND so did many of the top pros.
FAQs About BMX Top Tube Length
What is the top tube on a BMX bike?
The top tube is the horizontal bar/tube that connects the head tube (front, where your bars go) to the seat tube (where the seat post slides in).
It’s the main part of the frame that determines how big the bike feels and how much room you have when riding.
In BMX, frame size = top tube length — that’s what riders mean when they say “I ride a 21.5” frame.”
What size BMX frame top tube length do I need?
It depends on your height and riding style. Here’s a quick guide:
| Rider Height | Top Tube Length |
|---|---|
| Under 5’2″ (157cm) | 20.0″ or less |
| 5’2″ –5’6″ (157–168cm) | 20.25″ – 20.5″ |
| 5’6″ –5’10” (168–178cm) | 20.5″ – 21.0″ |
| 5’10″+ (178cm+) | 21.0″ – 21.5″+ |
Also:
- Go shorter for tech, spins, and tighter control.
- Go longer for stability, flow, and taller rider comfort.
Does a shorter top tube help with spins and tricks?
Yes, a shorter top tube makes the bike more responsive. It’s easier to throw spins (180s, 360s, 540s), tailwhips.
Why? There’s less “bike” under you, so it whips and turns faster.
But keep in mind: too short might feel cramped or unstable if you’re tall or ride fast.
What’s the difference between a 20.5″ and a 21.25″ top tube?
The 0.75″ difference is HUGE in BMX geometry.
- 20.5″ feels tighter and flickier – great for younger or tech-focused riders.
- 21.25″ feels roomier and more stable – ideal for taller riders or those who need more stability when riding transitions and going fast.
Can I ride a long top tube if I’m a smaller rider?
Yes, you can – but it depends on your preferences.
- A longer TT gives you more legroom and a smoother feel.
- You might lose some quickness and feel “stretched out” at first.
Some shorter riders go long on purpose for more control at higher speeds or to match a certain style. Just expect a short adjustment period.
How does top tube length affect barspins and tailwhips?
- Longer top tubes (21”+) = more room for the bars to spin and easier clearance during tailwhips.
- Shorter top tubes = faster tricks but higher chance of your knees hitting the bars.
If you’re hitting your knees on whips or bars feel too close during barspins, consider sizing up your frame.
Will a longer top tube help with nose manuals?
Yes. A longer TT gives you more balance and control on the front wheel. Your weight shifts are more spread out, making it feel less twitchy.
Is the top tube length the same as the BMX frame size?
Yes. 100%.
In BMX, when someone says, “I ride a 21” frame,” they mean the top tube is 21 inches.
Unlike MTB or road bikes, BMX doesn’t size by seat tube length or standover height.
Top tube = frame size in BMX lingo.
Further reading:
