Bicycle Adjustment and Fit

Earlier this week, some colleagues had been asking about adjusting a bicycle saddle to avoid pain. I dug through some notes that I had prepared for a commuter cycling workshop and have reproduced them here. Since this information is meant to complement a workshop, it’s not as detailed as some might like. Pictures would help, of course, but in the workshop we have access to actual bikes. I’ll work on getting some photos or other illustrations, but for now, I’ll just present this information.

 

Frame size

Frame size is the most important consideration in buying a bike.

Frame size is the length of the seat tube, measured from the centre of the bottom bracket to the centre of the top tube, in either inches or centimetres.  Sizing is always done according to “diamond” frame dimensions, regardless of the type of frame desired.  There are complex fitting systems in use at quality bike shops, using body measurements, which are mainly for those wanting to order a custom-built or a more expensive bicycle.  For an off-the-shelf bike, the bike fits if the rider can straddle the top tube and clear the top tube by one or two inches.  If your crotch touches the top tube, the bike is too big and becomes a hazard. Mountain bikes will have more clearance than road bikes.

Other dimensions of the frame affect the fit, especially top tube length.  Women often find the top tube too long because they tend to have shorter torsos than men of the same height.

Saddle

Men’s saddles are longer and narrower; women’s saddles are shorter and wider.  New styles attempt to provide increased comfort for the rider (e.g. anatomical and gel saddles).

Seat height

With the ball of your foot over the pedal spindle, there should be a slight bend in your knee when your foot is at the bottom of the stroke.  With your heel on the pedal, your leg should be straight.  Your hips should not wobble and you should be able to put both feet on the ground when in the saddle.

Seat angle

Generally, the nose of the saddle should be level with the rear of the saddle.

Seat fore and aft

Slide the saddle rails on the seat post clamp until the forward knee, with the pedal at the three o’clock position, is directly over the pedal spindle.  A plumb line dropped from the centre of the knee cap, at the side of the bone, should intersect the pedal spindle.

Handlebar height

For touring, the handlebar should be even with or slightly below the saddle height.  For racing, as low as is comfortable (often, about two inches below seat height).  The lower the handlebars, the more aerodynamic the riding position.

Handlebar tilt

On a road bike, the flats (bottom ends) of the bars should be parallel with the ground.  Some riders prefer a slight angle, with the bar ends “pointing” down at about a 10-degree angle.  On flat handlebars, brake levers should be approximately 30 degrees below horizontal, so hands rest easily on the brake lever.

Brake hoods

On road bikes, the brake levers should be positioned so that they follow the line of the down tube.  This is a starting point – racers prefer a lower position, recreational riders a higher one.

Handlebar stem

Stems are available in different extensions and risers, to increase or decrease “reach”.

Handlebars

Different widths of bars are available, to fit different shoulder widths.  Various shapes and styles are available – drop, flat, bar-end extensions and “aero” bars, among others.

Cranks

Crankarm lengths vary to suit different leg lengths and riding styles.  Chainring combinations can be custom built.