Head tube angle determines the angle of your forks. A steeper HT (i.e 75°and higher) will make the bike turn quicker than a mellower angle (i.e 74.5 and lower°). The more responsive the frame, the more twitchy it will feel, especially at highspeed!
The ALVX AF frame by BSD features a super tech invest cast chainstay yoke which gives even more tyre clearance as well as stiffening up the rear triangle. Your wheel can be slammed at an extremely short 12.5" Chainstay length with no worries of your tyre rubbing!
On a frame the highest concentration of stress is at the junctions between the headtube/toptube and headtube/downtube. To handle the pressures of modern riding, the required strength is achieved using a combination of butted tubing and external gussets.
The dropout is cast as one piece, much stronger than a plate welded to a tube, 7mm thick to provide good support for your axle, and the small shape has been designed for grinding meaning there's no overhang to catch on ledges or rails, also the dropout is heat treated before welding making it extra tough. There are integrated chain tensioner bolts to keep the wheel in place.
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NEED SOME HELP UNDERSTANDING FRAME GEOMETRY?
bmx frame geometry can look daunting but thanks to our handy guide below you will have it figured out in no time, and remember we're all bmxers here, so if you have any questions just ask.
Frame Size Chart
Frame Sizing is very much a personal preference, some riders like them longer, others shorter - here's a rough guide - if you have any questions remember we are here to help!
3ft - 4ft - best suited to a 16" or 18" wheeled bike
4ft - 5ft - 18" to 20" top tube
5ft - 5ft 4" - 20" to 20.25" top tube
5ft 4" - 5ft 8" - 20.25" to 21" top tube
5ft 8" - 6ft - 21" to 21.25" top tube
6ft Plus - 21" top tube or longer
Frame Geometry can take a bit of understanding - but here at SourceBMX we are here to help! The first thing to understand is that BMX frame Sizing is best measured by the length of the Top Tube - shown here as TT. Keep reading on to understand how the angles change how your frame will feel and check out our sizing chart below!
Headtube Angle (HT)
Chain Stay Length (CS)
The chain stay is essentially the length of the rear end of the bike. A shorter CS length will make the bike more responsive and a longer one more stable. As a rough guide a 13.5" long chain stay is about average.
Seat Tube Angle (ST)
Seat tube angles don’t vary too much (around 71°) and affect the centre of gravity. The steeper the angle the shorter your bike will feel. Some frames have a mellower seat tube angle (example 69˚) which makes for a longer frame without actually being longer and reduces how fast your frame turns.
Stand Over Height (SO)
Standover height is essentially how high your frame is. A frame with a low standover height is more responsive and easier to ‘throw around’ whilst a high SO height is more stable; particularly useful when going fast.