Angles and clearances. Getting the design right for a custom built bike

Simon Darby, a keen bike packer and Devon cyclist came to us last week for a “Power-Fit” bike fitting and to discuss his requirements for a bespoke hand-made steel bike . We like Simon, he loves bikes as much as we do, has an eye for clever design and was keen to have his steel bike built locally, here in Devon.

Once the measurements we had captured from the bike fitting were entered into our BikeCAD software , we spent some time fine-tuning angles and clearances before asking Simon to come back to the workshop and discuss progress. BikeCAD software facilitates the creation of super-accurate technical drawings of custom bikes and their components, as well as allowing for smart modification as the design progresses. With the important first design steps in place, we needed to ask Simon a few questions about his preferences and requirements. These included,

  • Tyre width and tread type
  • Stand over height
  • Bottom bracket drop and height
  • Length of exposed seat post

Having a shorter frame, Simon has, in the past, experienced issues with top tube induced discomfort. His decision to opt for a custom-made bike allowed us to set up the frame dimensions with bespoke measurements, using Simon’s other bikes as a reference.

BikeCAD showing lots of dimension detail

Choosing the correct tube angles and lengths is a vital stage in custom bike design as these need to provide the perfect fit as well as customer-pleasing aesthetics. We trialed a few combinations until we were happy with both these aspects and we could tell by Simon’s response, that he was excited about the forthcoming look and feel of his new bike. Simon has opted for a sloping tube that will keep stand over at a maximum but still allow enough room in the main triangle for two bottle cages. We are also going to fit extra bosses on the underside of the down tube for a crud catcher mudguard, to help protect his bottles from mud and anything else he might encounter on his Welsh bike packing trips.

We have suggested a slightly lower than usual bottom bracket to improve handling, as this will lower the bike’s overall centre of gravity. The main triangle will be made from Reynolds 853 steel tubes  and the rear triangle from Columbus steel tubes, with swept or bent seat stays for added tyre clearance.

The next step will be to order the tubing and then the assembly process can begin. It is fair to say that we are as excited as Simon about his new custom-built bike.

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