BPR Geometry

BikePRO Geometry Explanation

Contrary to what can only be described as ‘popular belief,’ there is no PERFECT or MIRACLE bike geometry. Geometry calculation involves a complex balancing of variables. The BPR geometry is drawn upon Andy Choy’s knowledge base of over 25 years industry and racing experience, stemming from his Olympic and World Championship training and coaching. Andy’s rich experience has allowed the Geometry of the BPR to be entirely designed ground up for the Australian market. Below is a break down of the BPR geometry:

Head Angle

BPR frames have incorporated differing head angles for their frames to allow for an optimum wheel base length, while maintaining cornering agility and high-speed stability. 73^o is the optimum head angle for road racing, and thus is the base figure for our BPR geometry.

Fork Rake

Fork rake is vital to stability and maneuverability of the bike. Many brands adopt a 41mm rake, however, this criterium geometry is far too ‘twitchy' for road racing. At the other end of the scale some brands adopt a 45mm rake, while being more stable, is far too slow at corning and maneuvering. Therefore, BRP has adopted a 43mmfork rake, allowing for the best balance of high-speed stability and well and agility in cornering.

Theoretical Top Tube

BPR do not fabricate any frames under 525cm theoretical top tubes for the simple reason that a 650 wheel would be required. The largest size BPR production frame features a 585mm theoretical top tube, which would suit cyclist up to 6’4.” Riders taller that this should look at a custom frame to suit their requirements.

Seat Angle

As all BPR geometry has been designed for the Australian market, the seat angle is no exception. While ‘Italian’ frames generally feature a steeper seat angle to be aimed at overseas riders with shorter legs, the BPR design takes into consideration the needs of Australian cyclists and thus features a slightly slacker seat angle.

Bottom Bracket Drop

When designing bottom bracket drop many companies do not take into consideration the differing crank lengths applied to the frames sizes. In actual fact bottom bracket drops should take into consideration whether the bike build is using a 170mm, 172.5mm or 175mm crank length. BPR has carefully incorporated an allowance for different cranks lengths into our frames, allowing for consistent ground clearance across all sizes.

 Chain Stay length

BPR frames adopt a 405mm chain stay length, which allows for optimum wheel to seat tube spacing. This has been chosen to allow for clearance to protect the carbon seat tube from stone and debris damage as well as catering for tyres up to 25c, while maintaining short wheel base.