================================================================ iBOB HANDLING VOCABULARY - Compiled by Dave Mann based on discussions and input from the iBOB mail list LAST UPDATED: 10/02/2008 ================================================================ CONTENTS -------- + STABILITY AND STEERING CHARACTERISTICS - Initial & Secondary Stability - Responsiveness + TOLERANCE TO LOADS - Handlebar Load Tolerance - Saddle Bag Load Tolerance - Front Pannier Load Tolerance - Rear Pannier Load Tolerance - Front & Rear Pannier Load Tolerance + PEDALING RESPONSE - Planing - Snap STABILITY AND STEERING CHARACTERISTICS -------------------------------------- INITIAL & SECONDARY STABILITY - There are two kinds of stability that should be understood in contrast to each other - initial stability and secondary stability. A bike with high initial stability maintains a straight, predictable line despite small perturbations in steering and lean, such as those caused by shifting, pedaling or eating. Bikes with high initial stability feel as though there is a strong self-centering effect despite these small perturbations. Bikes with little initial stability wobble slightly when there are small perturbations in steering and lean. These wobbles may present themselves as slight movements of the handlebar or latteral movements of the headset. However, these small wobbles may or may not translate into significant changes in direction depending on the steering quickness. (See: responsiveness) Bikes with high initial stability might be described as feeling precise in their handling while bikes with low initial stability might be described as feeling vaque or loose. A bike with high secondary stability has a noticable self-centering effect when there are moderate perturbations in steering or lean. A bike with high secondary stability can be said to be one that naturally seeks to "go down the road" or to "follow the fog line". In contrast, bikes with low secondary stability will veer off course when receiving moderate steering inputs. Bikes with very poor secondary stability will increasingly turn off course as the bike begins to turn, an effect sometimes called "diving into a turn". The difference between bike with high and low secondary stability can be especially noticed on bumpy sections of road. A bike with low secondary stability will begin to veer off course due to the bumps while a bike with high secondary stability will continue on course. Initial and secondary stability can be inversely related. Some bikes have high initial stability (feel solid) but low secondary stability (can veer off course). Others have low initial stability (wobble) but high secondary stability (stay on course). RESPONSIVENESS - Responsiveness is the ease with which a bike can be put into or taken out of a steering lean. A bike with a high amount of responsiveness will lean into a turn relatively sharply for a given amount of steering input while a bike with less responsiveness will lean into turn less. Putting it another way, given the same amount of rider input, a more responsive bike will lean more deeply into a turn than a less responsive bike. Bikes with a high amount of responsiveness may be described as being "quick", or in extreme cases as "twitchy". Bike with a low amount of responsiveness may be desribed as being "slow", or in extreme cases as "sluggish". The difference between quick and slow bikes can especially be felt on S-turns or chicanes on descents. A quick bike will roll right over into a lean without requiring yanking or counter-steering. Then when it rolls out of the turn, it will come right up to vertical, then smoothly going past vertical into the other side lean without hesitation. On a slow handling bike the chicane turns feel like they have components rather than a smooth fluid rolling. It feels like the rider has to make one movement to get it to lean, another movement to get it to arrest the lean (as it feels like it wants to dive into too deep a lean), another movement to get it to start going upright again (where it stops at top and wants to go straight), and then the rider must do all those component movements on the other side. There may be a corellation between secondary stability (see: stability) and responsiveness. It may be the case that bikes that are quick will tend to have low secondary stability, contributing to the effect of the bike veering off course when there are moderate perturbation in steering and lean. And it may be the case that bikes that are slow will tend to have high secondary stability, contributing to the effect of the bike being able to stay on course. TOLERANCE TO LOADS ------------------ On all bikes, the handling of the bike is changed when luggage and other weight loads are added to the bike. The following characteristics attempt to describe how predictable these handling changes are as different kinds of loads are added. The issue is not whether or not a bike's handling is affected under load. Rather, the issue is are these changes predictable and manageable by the rider. HANDLEBAR LOAD TOLERANCE - The degree to which handling is affected by small to moderate loads near the handlebar including: loads in small to moderate handlebar bags, changes in bars or brake levers and lighting systems. SADDLE BAG LOAD TOLERANCE - The degree to which handling is affected by small to moderate loads near the saddle including: loads in small to moderate saddle bags or loads in small to moderate rack trunks. FRONT PANNIER LOAD TOLERANCE - The degree to which handling is affected by moderate to heavy loads carried in front panniers or a on a front rack. REAR PANNIER LOAD TOLERANCE - The degree to which handling is affected by moderate to heavy loads carried in rear panniers or on a rear rack. FRONT & REAR PANNIER LOAD TOLERANCE - The degree to which handling is affected by moderate to heavy loads carried in both front and rear panniers and/or on front and rear racks. PEDALING RESPONSE ----------------- The following characteristics describe the rider's perception of how the bike responds to pedaling. These characteristics may or may not correspond to actual differences in speed, acceleration, climbing efficiency or endurance. PLANING - The perception that the bike harmonizes with the riders regular cadence in a way that the rider feels as though they can maintain their cadence for a longer duration of time. This is typically felt on flat to rolling terrain and is commonly associated with frames that are perceived to have some degree of lateral deflection (i.e. a flexible frame). SNAP - The perception the bike efficiently and immediately converts the rider's power to the pedal into acceleration. This is typically felt on hard climbs and sprints and is commonly associated with frames that are perceived to have little to no lateral deflection (i.e. a laterally stiff frame).