position & frame design considerations

 

Once you position dimensions have been determined, there are a number of other factors that need to be considered when deciding on the suitability of a particular frame, or to allow some accurate frame dimensions to be determined in the case of a custom built frame.

Not only does the position on your new bike need to be set, but ideally your bike needs to look in proportion, so once your position dimensions are determined a suitable frame (off the peg) or frame dimensions (cutom built) can be decided on. The first list covers the various items that need to be taken into account when determining the rider position and the second list are other items that can be specified in the case of a custom built frame. 

Items that influence the setting of the rider position.

So that the effects of the following can be taken into account, it is reccommended that these items are fitted to the jig prior to the measuring process. 

  • Type of saddle - There are two aspects to this, firstly the amount you sink in to the saddle when you sit on it varies from saddle to saddle, and as the saddle height dimension can only be taken when you aren't sat on the saddle, the saddle you are going to use on the bike needs to be used in the measuring process. Secondly,with reference to saddle set-back,  where you sit on the saddle relative to where a dimension for  the saddle set-back can be taken can vary from saddle to saddle, again this can't be measured when you are sat on the saddle so it is best again, to use the saddle on the jig that you are going to use on the completed bike, this way a dimension easily taken from the front of the saddle (horizontally behind the bottom bracket centre) will be just as accurate as a dimension from the back of the saddle or 120mm from the back in the case of some fitting systems.
  • Shoes - The thickness of  the sole of the shoe needs to be taken into account, as does the shoe plate position., it is therefore best to use your cycling shoes during the measuring process, this way, not only the sole thickness can be allowed for but also the shoe plate position can be checked and altered if need be. 
  • Handlebars - Most handlebars, with the exception of a straight handlebar have a number of different hand positions, ideally all of the various hand positions need to be comfortable, useable and allow you to stretch out (but not too stretched) when you need to, sit more upright (but not too upright) when you want to and have the drops in a useable and comfortable position.

Items that need to be considered in order to determin accurate frame dimensions. 

  • Stem length -
  • Stem clamp depth -
  • Spacing required under the stem required -
  • Saddle -
  • Amount of exposed seat post required -
  • Seat post set back -
  • Pedals -
  • Handlebars -