Friday, September 11, 2009

Determining Saddle Width

What is the minimum saddle width necessary to ensure a reasonable amount of comfort on those long rides? Conversely, is the saddle you ride now too wide?

Recently a friend expressed displeasure with his current saddle and concern about the potential cost of going through a number of saddles before he found something good or at least sucked a lot less. He currently rides a Terry Fly Cromoly Gel which has a width of about 140mm. I suspect the saddle is way too narrow for him, but other than trial and error how can I prove it?

Even though two Specialized BF saddles I have tried in the past didn't suit me, I do appreciate their efforts to properly size saddles to riders with their trademark Body Geometry Saddle Fit System and multiple saddle widths. As with their system that measures "sit-bone" width I needed to come up with a cheap and easy DIY method of doing the same while the rider is on his or her bike.

After giving it considerable though, forgetting about it for a few months, and then finally getting sufficiently bored today to take action, I used the following method:
  1. Cut a simple saddle form out of 1/2 or 3/4 plywood or MDF using a jigsaw
  2. Sacrifice an old saddle and attach its bare undercarriage to the wooden saddle form with flat head wood screws
  3. Place the rider's bike on a trainer
  4. Loosely mount the makeshift saddle on the rider's bike
  5. Cover the top of the saddle form with modeling clay
  6. Using a 1-inch dia or larger. 3ft hardwood dowel roll the clay to a smooth consistent 10mm thickness
  7. Trim off the excess clay hanging over the edges of the saddle form with a knife
  8. Cover the top of the saddle with a sheet of clear plastic wrap.
  9. Make any necessary saddle and seat post adjustments for setback, angle, seat height, and proper bolt torque.
  10. Place the rider on the bike in his or her normal riding position and have him/her pedal for a few minutes
  11. Have the rider get off the bike and then remove the saddle
  12. Remove the clear plastic wrap from the saddle and carefully highlight the ridges and indentations in the clay with a marking pen
  13. With a metric ruler take the necessary measurements to determine "sit bone" spacing

The Saddle
(Click on this picture to enlarge)

The Measurements (Click on the picture to enlarge)

The results show my "sit bones" spacing at 110mm when measured center-to-center. Also measuring from the outer edge of the right "sit-bone" indentation to the outer edge of the left is about 155mm. I am saying "about 155mm" because I am estimated this measurement because the saddle form was not quite wide enough.

These measurements give me some confidence my method works since I know from many years and many saddles worth of trial and error that a saddle width of about 155mm is good for me. Not suprisingly this also explains why my favorite saddle remains the Brooks Team Pro given that amongst its several outstanding attributes is its 160mm width, albeit its usable width is closer to 150mm. However, the measurements put this saddle in the category of being just barely wide enough and suggests I should consider a bit wider model like the Brooks B17 Special with a width of 170mm.

While correct saddle width is just one factor in finding a saddle that meets a rider's needs, it is a very important one. With this metric riders shopping for a new saddle can quickly eliminate saddles that are unnecessarily wide or too narrow from the list of possibilities.

This weekend I will be providing my DIY saddle fitting system to my friend mentioned at the start of this post to him in his selection of a new saddle. My guess is that will show a wider saddle is warranted which will also significantly reduce the list of choices.

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