Thursday, December 18, 2008

Reach and stack based sizing

It has finally happened! Some of the bigger players have joined up and suggested a new standard in bike sizing, which means that we can finally leave behind the old fashioned standard that is irrelevent for most mountain bike frames. I have never believed in using the seat tube length as the guage for frame size, as for a lot of freeride or downhill bikes this just doen't make sense, as you are not in the saddle much of the time when really riding.

The new standrad of reach and stack being proposed makes more sense to me. So we are going to add these values to our geomery tables in the near future. I still feel the need to include the old style geometry, as angles are also very important, and for some riders so is the seat tube length. It will just be another tool in addition to more exact geometry to help people choose the right sized frame for them.

The reason why reach and stack dimensions are important to any bike where you standing out of the saddle... because essentially these are your 2 points of contact with the bike... pedals and handle bars. Therefore the geometrical relationship between the 2 kind of gives you the 'feel' of the geometry of the bike. sure it excludes inportant informaion like head angle and seat angle, but it can be used as a guage to select the size of frame best suited to you after you have looked at the overall frame geometries to choose the best frame for your needs.

A step in the right direction!


Bog said...

Good call Keith, there's some major confusion on mtbr about this. These measurements only serve to complement the current frame measurements and are especially useful for DH, FR and DJ frames.


perttime said...

Oh I think the Reach and Stack measurements can be very useful with XC or Trail bikes too.

Seat tube lengths only tell me how high or low I can get the seat. Horizontal top tube measurements depend on seat tube angles too.

Keith Scott said...

You're asolutely right perttime, I was thinking about that yesterday. it is a good system to find the right size of any frame when combined with looking at other geometry.
Reach is definately the important factor for getting the size right, where as stack is more about the feel of the ride (how low the front is!)