Bicycle saddle
A bicycle saddle, sometimes called a bicycle seat, is one of five contact points on an upright bicycle, the others being the two pedals and the two handles on the handlebars.
The bicycle saddle has been known as such since the bicycle evolved from the draisine, a forerunner of the bicycle. It performs a similar role as a horse's saddle, not bearing all the weight of the rider as the other contact points also take some of the load.
A bicycle saddle is commonly attached to the seatpost and the height of the saddle can usually be adjusted by the seatpost telescoping in and out of the seat tube.
Components
Typical saddles are composed of a few identifiable components.Shell
The shell creates the shape of the saddle. The nose of the saddle is the forward most part. It is usually rounded. The shell can be made from several materials.Most modern saddles have a hard shell made from a moulded piece of plastic, such as nylon. Carbon fiber may also be used.
Leather saddles do not have a hard shell. Instead a moulded piece of thick leather is stretched, like a taut hammock, between the front and rear ends of the rails. Traditional leather saddles such as those made by Brooks have been used for many years. Such a saddle is generally more comfortable after a break-in period during which it conforms to the shape of the rider, so long as the basic shape is right to start with.
Cover
Most saddles use some form of padding on top of the hard shell followed by an outer cover consisting of spandex, vinyl, artificial leather, or leather.Saddles designed for hard use e.g. mountain bike or BMX style riding, may have additional cover reinforcements such as Kevlar sewn to the cover to withstand abrasion on those areas most prone to abrasion.
Rails
The rails of a saddle are the connection point to the rest of the bike. They run along the underside of the saddle from the nose to the rear. Most saddles have two parallel rails that the seatpost clamps to, but designs vary from one to four rails. Rails provide fore and aft adjustment of the saddle, usually about 2-3 cm or so. They can be made of solid or hollow steel, titanium, aluminum, manganese, or carbon fiber, typically trading off cost, weight, strength, and flexibility. A recent innovation, used with carbon shells and rails, is for the rails to be integrated into the shell for their entire length.Rail configurations include:
- 2-rail "standard" round 7 mm diameter
- 2-rail oversize
- * Round 8 mm diameter
- * Round 9 mm diameter
- 2-rail carbon fiber
- * 7 mm round
- * 7 mm × 9 mm oval
- * 7 mm × 10 mm oval
- * 8.5 mm round
- * 9.6 mm round
- Single-rail I-beam
- 4-rail
- Proprietary systems
Saddle clamp
The most common type of sold-separate clamp has a single horizontal bolt-with-nut which goes behind the top of the seatpost. Tightening this bolt brings together four pieces of metal which have round slots to grab and hold standard-size rails. The inner rail grabbing pieces have interlocking grooves on the other side that interface into disc shapes on the outer sides of the central post-grabbing piece. Continued tightening of the bolt causes the central piece to close very slightly around the top of the post. To adjust the saddle's position, loosening the bolt allows the rails to slide forward and backward and to tilt up and down around the axis of the bolt.
There are two common types of built-in saddle clamps for standard rails, both associated with genericized trademarks:
- "Campagnolo" seatposts use two vertical bolts to hold the two rail-grabbing pieces together. Loosening one bolt allows forward-and-back adjustment of the saddle; loosening one and tightening the other adjusts up/down tilt. In some cases, there is a separate bolt that controls tilt around a dedicated pivot. Because these systems do not rely on grooves, the tilt adjustment is continuous rather than stepped, and these are known as microadjust seatposts.
- "Laprade" seatposts use a single vertical bolt which when tightened pushes two rail-grabbing pieces together. The lower surface of the lower rail-grabbing piece is convex and grooved, matching a concave groove on the top of the seatpost. The curve allows the up/down angle of the saddle to be adjusted when the bolt is loosened, and loosening also allows the rails to slide forward and back. Depending on the saddle angle, the vertical bolt is not perpendicular to the angle of the rails, but the grooves prevent the interface from slipping and adopting a completely horizontal angle. This angular adjustment mechanism is known as pivotal and is common on BMX bikes. Because the grooves are finer than the grooved discs in the sold-separately saddle clamp, sometimes Laprade-style posts are also marketed as "microadjustable" even though the adjustment is not continuous as with the Campagnolo style.
Suspension
A saddle may contain one or more suspension components to improve rider comfort by absorbing or deadening vibration and shock transmitted by the frame and seatpost.Saddles may incorporate gel, gel-foam, and/or multiple-density foam padding or lining to cushion impacts from the roadway, while integrated saddle rails may be designed with added length in order to flex vertically, providing limited shock and bump absorption.
Another method encountered on recreational, comfort, or 'cruiser' saddles is to attach a pair of steel coil springs to the rear terminus of the saddle rails, affixed at their other end to the rear of the saddle. Some newer suspension designs replace the twin coil springs with four or more elastomer donut-type springs. By using interchangeable elastomers with variable densities the suspension saddle can be tuned to the rider's weight and riding style.
Yet another method of suspension utilizes a web-spring platform made of eight or more coil springs mounted horizontally beneath the saddle shell. These springs are connected to each other at the approximate center of the saddle, with the ends connected radially to the perimeter of the saddle frame, forming a spider's web. A shock transmitted to the seat is partially absorbed by this web-spring platform. In an effort to cut cost and weight, some suspension saddles utilize a skeletonized, flexible nylon frame in lieu of the steel web-spring.
Saddles may incorporate two or more of these suspension designs in an effort to provide additional comfort and shock absorption, as they have since cycling first became popular in the 1880s.
Adjustment
The position of the saddle should be adjusted relative to the bottom bracket, not to the ground or handlebars. For example, if the reach to the handlebars is too far, it is better to get a shorter stem than to move the saddle forward of its ideal location. More accurately, saddle height should be adjusted relative to the position of the pedals as fitting different pedals or different length cranks would also mean the saddle needs to be re-adjusted. In practice, the distance from the top of the saddle to the center of the bottom bracket is used as the saddle height, e.g., setting up a new bicycle using measurements from another, as this is easier to measure. Other methods and calculations are used for determining seat height, such as LeMond's formula. Some saddles now provide an even greater level of adjustment by making the front and rear width adjustable to properly fit a cyclist's anatomy.Height
The saddle height should be set so that when pedaling, the legs have a slight bend even when the pedals are at their furthest distance. This means that if the saddle height is properly adjusted, on bikes with traditional geometry, the rider cannot place both feet flat on the ground when seated on the saddle. If they can, their saddle is too low, unless the bike is a recumbent bicycle, crank-forward, BMX or other form of special bicycle.Tilt
The saddle should be nearly level, although the height of the handlebars and style of cycling will cause this to vary. In professional bicycle racing, UCI rules require that the saddle be within 3° of level.Fore and aft
Conventional wisdom dictates that the saddle should be positioned so that when the crankarms are horizontal and the feet are on the pedals the head of fibula of the forward leg is approximately above the pedal spindle in a vertical line. However, several authors argue that there is no anatomical basis for this. Furthermore, the relative position of saddle and bottom bracket varies between road racing, track and triathlon bicycles.The range of adjustment differs for each saddle, and the comparison of saddles for increased ranges of adjustment can be confusing owing to their different shapes. In comparing them, it is the range of adjustment of their comfort points that need considered, and because the matter is largely subjective, giving it proper attention is difficult to do. The range of fore-aft adjustment for double-rail saddles rarely exceeds 2-3 cm or so, but advertisers claim that I-beam saddle designs can give up to 200% more adjustment range than some of these.
When the fore-aft adjustment range of the saddle needs further extension than the clamp affords, it may be possible to add a saddle adjuster. One such adjuster mounts on the existing saddle clamp and allows up to 40 mm of increase or decrease in the fore-aft position of the saddle. Another method for increasing the fore-aft adjustment is the swept-back seatpost, where the seatpost has a curve in it over the or so before the saddle. Because of the gentle sweep of the tube, the top part of the seatpost cannot fit within the seat tube, so this solution is useful only for high seat positions.