Showing posts with label Steering. Show all posts
Showing posts with label Steering. Show all posts

Friday, 2 November 2012

Vehicle Standards Bulletin 14 (VSB 14)


Vehicle Standards Bulletin 14 (VSB 14)

LINK to VSB Source


National Code of Practice for Light Vehicle Construction and Modification (NCOP)

The National Code of Practice for Light Vehicle Construction and Modification (VSB 14) has been prepared by members of the Australian Motor Vehicle Certification Board Working Party in consultation with industry, user groups, government agencies and individuals with an interest in modifying light vehicles and/or building individually constructed light vehicles (ICVs).
VSB 14 is a "live" document and will continue to be revised and updated as required.
The documents listed below form Version 2 of VSB 14 and are now available for free download in PDF format.
VSB 14 essentially provides the technical requirements that need to be met when modifying or constructing a vehicle. It does not cover the administrative requirements of each State and Territory.
Administrative requirements include, but are not limited to:
  • Registration processes;
  • Fees for processes such as registration, issue of temporary permits, vehicle inspections; applications for approval to modify, applications for exemptions etc.;
  • Determination of the date of manufacture for Individually Constructed Vehicles;
  • Processes for submitting applications; and
  • Administration and management of modification schemes including the administration of signatories.
The Preface and Introduction to VSB 14 provide the necessary background information to assist users in understanding how VSB 14 is administered by the Registration Authorities across Australia. Understanding and following these requirements reduces the likelihood of having a vehicle rejected by a Registration Authority.
Prospective constructors or modifiers should contact the Registration Authority in the jurisdiction in which a vehicle is to be registered or modified, to determine the most up to date information about the administrative arrangements that may be in force.
Where a jurisdiction is unable to nationally recognise an element of VSB 14, the individual difference/s are highlighted within VSB 14. In these instances, users should contact the responsible Registration Authority for further advice.

VSB 14 Documents

  • NCOP1 Preface V2 01Jan2011 [PDFPDF: 83 KB]
  • NCOP2 Introduction V2 01Jan2011 [PDFPDF: 142 KB]
  • NCOP3 Section LA Engine V2 01Jan2011 [PDFPDF: 218 KB]
  • NCOP4 Section LB Transmission V2 01Jan2011 [PDFPDF: 131 KB]
  • NCOP5 Section LG Brakes V2 01Jan2011 [PDFPDF: 180 KB]
  • NCOP6 Section LH Body Modifications V2 01Jan2011 [PDFPDF: 993 KB]
  • NCOP7 Section LK Seating and Occupant Protection V2 01Jan2011 [PDFPDF: 1729 KB]
  • NCOP8 Section LL Motorcycles V2 01Jan2011 [PDFPDF: 281 KB]
  • NCOP9 Section LM Fuel Systems V2 01Jan2011 [PDFPDF: 243 KB]
  • NCOP10 Section LO ADRS ICVs V2 01Jan2011 [PDFPDF: 814 KB]
  • NCOP10A LO1-3 ICV Checklist V2 01Jan2011 [PDFPDF: 144 KB]
  • NCOP10B LO1-4 ICV Checklist V2 01Jan2011 [PDFPDF: 122 KB]
  • NCOP10C LO7 ICV Motorcycle Checklist V2 01Jan2011 [PDFPDF: 193 KB]
  • NCOP10D LO1-2 Second Edition ADRs Checklist V2 01Jan2011 [PDFPDF: 127 KB]
  • NCOP11 Section LS Suspension and Steering V2 01Jan2011 [PDFPDF: 1319 KB]
  • NCOP12 Section LT Test Procedures V2 01Jan2011 [PDFPDF: 564 KB]
  • NCOP13 Section LV Alternative Power Units V2 01Jan2011 [PDFPDF: 90 KB]
  • NCOP14 Guidelines Electric Drive V2 01Jan2011 [PDFPDF: 307 KB]
  • NCOP15 Trike Guidelines V2 01Jan2011 [PDFPDF: 781 KB]
  • NCOP15A LEM Trike Checklist V2 01Jan2011 [PDFPDF: 139 KB]
  • NCOP15B LEP Trike Checklist V2 01Jan2011 [PDFPDF: 146 KB]
  • NCOP16 Section LZ Appendices V2 01Jan2011 [PDFPDF: 437 KB]
  • NCOPC1 Cover Page VSB14 V2 01Jan2011 [PDFPDF: 357 KB]
  • NCOPC2 Cover Page Guidelines Electric Drive V2 01Jan2011 [PDFPDF: 972 KB]
  • NCOPC3 Cover Page Trike Guidelines V2 01Jan2011 [PDFPDF: 386 KB]

Queries regarding VSB 14 should be directed to your local Registration Authority.

Motor Bike ICV

Some take outs for ICV Bikes:
The procedure for ICV bike certification is the following:

Consult VASS Signatory (Engineer) regarding your ICV project (fill the vehicle details form)
Perform complete ADR’s inspection of the completed bike.
Perform brake test (as per section LG of VSB14)
Perform noise test (limit 94 dB(A))
Upon completion of inspections & testing, an engineer report will be issued and send to VicRoads in order to obtain a VIN.
VIN issued and stamped on bike
Bike registered with engineer report.

The list of ADR’s applicable to 2012 ICV bike (LC Category):

ADR 6/00 Direction Indicators 
ADR 14/02 Rear Vision Mirrors
ADR 18/03 Instrumentation
ADR 19/02 Installation of Lighting and Light Signalling Devices on L-Group Vehicles
ADR 33/00 Brake Systems for Motor Cycles and Mopeds
ADR 42/04 General Safety Requirements
ADR 43/04 Vehicle Configuration & Dimensions
ADR 47/00 Retro reflectors
ADR 51/00 Filament Lamps
ADR 53/00 Front and Rear Position Lamps, Stop Lamps, Direction Indicators and Rear Registration Plate Lamps for L-Group Vehicles
ADR 55/00 Headlamps for Motor Cycles
ADR 57/00 Special Requirements for L-Group Vehicles 
ADR 61/02 Vehicle Marking
ADR 83/00 External Noise


Definitions:
VSB 14 definition:
‘An ICV is not a production vehicle; rather it is manufactured as a one-off vehicle. If 3 or more ICVs are manufactured by a person in a 12 month period VSB 14 does not apply to these vehicles. These vehicles are subject to the vehicle certification procedures under the Motor Vehicle Standards Act. Vehicles manufactured on a commercial basis are not ICVs.
An ICV may be composed of parts from one or more Production Vehicles. The parts do not
need to be new.
ICVs include certain kit cars and certain production vehicle replicas that have been assembled in accordance with the production limitations mentioned above.
An ICV should comply with the ADRs applicable to its date of manufacture. Each Registration Authority will determine the date of manufacture of an ICV. It is important that prospective builders discuss this issue with the appropriate jurisdiction before commencing a project.’
VicRoads definition:
‘An ICV means a vehicle based on a floor pan or chassis which is neither taken from, nor an original replacement part for, a Recognised Production Vehicle. An ICV is considered to be a new vehicle even if some of the components used in its construction may have been derived from Recognised Production Vehicles’
‘In Victoria, one ICV per individual may be approved per calendar year. A turn key motor vehicle cannot be treated as an ICV’
Date of Manufacture:
‘The construction of an ICV is often a long term project. In Victoria, an ICV’s date of manufacture (Month/Year) may be dated back to the date construction actually commenced up to a maximum of 3 years before the date of issue of the VASS certificate provided by the VASS Signatory retains documentary evidence of the date construction commenced’.

VSB14 SECTION LL


Note these are really mostly written and focussed on cars etc and are attempted to be interpreted and applied to bikes.

http://www.infrastructure.gov.au/roads/vehicle_regulation/bulletin/pdf/NCOP5_Section_LG_Brakes_V2_01Jan2011.pdf
http://www.infrastructure.gov.au/roads/vehicle_regulation/bulletin/pdf/NCOP10C_lO7_ICV_Motorcycle_Checklist_V2.0_01Jan2011.pdf
http://www.infrastructure.gov.au/roads/vehicle_regulation/bulletin/pdf/NCOP12_Section_LT_Test_Procedures_1Jan2011_v2.pdf
http://www.infrastructure.gov.au/roads/vehicle_regulation/bulletin/pdf/NCOP11_Section_LS_Tyres_Suspension_Steering_V2_1Jan_2011%20v3.pdf
http://www.infrastructure.gov.au/roads/vehicle_regulation/bulletin/pdf/NCOP8_Section_LL_Motor-Cycles_and_3WheelVehicles_01Jan2011_v2.pdf


VSB14 SECTION LL
MOTOR CYCLES & THREE WHEELED VEHICLES


1.1 BASIC MODIFICATIONS NOT REQUIRING CERTIFICATION


The following are Basic Modifications that may be performed without certification provided they are carried out in compliance with the requirements detailed in sub-section 2 General
Requirements:

  • Fitting a manufacturer’s optional component such as an engine, transmission, exhaust system or fuel tank for the particular make/model of the vehicle in question. (Note that replacing parts or components of a motor cycle with the manufacturer’s parts or equivalent components does not fall into the category of modifications and as a consequence no approvals are necessary for repair work);


  •  Conversion of a two-seat motor cycle to a single seater; and
  •  Conversion of a modified motor cycle to original seating configuration.

Note: The underlying design installation and fabrication requirements for all of the above
modifications are contained in sub-section 2 General Requirements.



2.1 DESIGN

2.1.1 Dimensional Requirements - Motor Cycles Without a Sidecar

The maximum width including the load and equipment must not exceed 1 metre.
The load or equipment must not project more than 150mm beyond the extreme outer portion of
the motor cycle on either side.
The maximum longitudinal projection beyond the outer extremity of the tyres of any part of the
motor cycle and loading or equipment thereon must not exceed 150mm in the case of the front
tyre and 300mm in the case of the rear tyre.
If the motor cycle is fitted with a sissy bar it must not have any sharp points or edges or be of a
design that interferes with the safe operation of the motor cycle.

2.1.2 Ground Clearance

When laden, the ground clearance must not be less than 100mm, measured from a horizontal
road surface to any point on the underside of the motor cycle or sidecar excluding tyres wheels
and hubs.

2.1.6 Stand

Any stand fitted to a motor cycle must be maintained in an efficient and safe condition and must
be equipped with a spring or other device capable of holding it securely in the up position at all
times when the stand is not in use.
For all LA and LC group motor cycles manufactured after 1 July 1998, a stand must be fitted
that is capable of holding the motor cycle in a substantially upright position. The stand may be
of the side or centre type and must be equipped with a spring or other device capable of
securely holding it clear of the road at all times when the stand is not in use. A side stand must
be designed so that it does not remain in the down position when the vehicle is moving or about
to move.


2.1.7 Foot Rests or Foot Pegs

Every motor cycle must be fitted with adequate foot rests or foot pegs for the rider and, in the
case where a pillion seating position is provided, foot rests for the pillion passenger.

2.1.8 Rear Vision Mirrors

A motor cycle and motor tricycle built before July 1975 must have at least one mirror on the
right hand side.
A motor cycle or motor tricycle with one front wheel, built after July 1975, must be equipped
with two rear vision mirrors symmetrically placed relative to the centre of the handlebars.
The rear vision mirror or mirrors must be fitted so as to allow the rider to clearly see, by
reflection, the road behind the vehicle and any following or overtaking vehicles. For circular
mirrors the reflective surface area must have a minimum diameter of 94mm and for non-circular
mirrors the reflective surface must be not less than 78mm in diameter and at least 120mm by
200mm.
If a mirror has a convex surface it must have a radius of curvature not less than 1200mm.
Motor cycles and motor tricycles may be fitted with additional mirrors that are flat or convex or a
combination of these surfaces.

2.1.9 Mudguards

Mudguards must be fitted to all wheels, including sidecar wheels (refer to Figure LL1 for details
of mudguard construction and location). Each mudguard must be at least as wide, over its entire length, as its respective wheel and tyre.

A front wheel mudguard must cover the rearward section of the wheel through the area
between two lines, one vertical and the other horizontal, both drawn through the centre of the
wheel. If suitable protection is afforded by the frame or construction of the motor cycle, the
front mudguard need only cover the area that is unprotected.
A rear wheel or sidecar wheel mudguard must extend at least from a point vertically above the
front of the tyre to a point vertically above the rear of the tyre.






2.1.10 Foot and Hand Controls

The controls for motor cycles are standardised, therefore the position and operation of foot and
hand controls must be kept, as far as practicable, to the manufacturer’s original specification.
For example, if the rider’s footrests are moved rearwards (that is, converted to rear seats) the
gear lever must not be reversed or inverted. For safety reasons, the only acceptable method
for this conversion is to fit a linkage, which keeps the gear change pattern the same as the
original. Riders should always be able to operate the brake pedal without lifting their foot from
the footrest.

2.1.11 Drive Guards (Refer to Figure LL2)
If the motor cycle is chain or belt driven and the construction of the frame is not sufficient to
protect the rider and/or the pillion passenger from the driving sprocket and the upper run of the
chain or belt, the motor cycle must be fitted with a guard. The guard must extend at least
300mm rearward of the rearmost footrest or to the vertical centre of the rear sprocket,
whichever is the lesser.
Primary drives must also be similarly protected.







2.1.12 Frame or Suspension Modifications

Motor cycle design is a complex task. Modifications made to a motor cycle’s frame or
suspension, can adversely affect the structural integrity of the frame, steering head, front forks
and suspension increasing the risk of component failure. Similarly, braking and wheel loading
may be adversely affected.
Motor cycles with custom frames, extended forks or structural modifications require an
engineering report.
When forks are extended, without modifications to the frame, care must be taken to ensure the
vehicle continues to comply with ADR57 with respect to special requirements for L-group
vehicles. The horizontal distance between the mid-point of the steering yoke bearings and a
point vertically above the centre of the front wheel must not exceed 550mm.
A motor cycle with a specially designed and constructed frame will be considered to be an
Individually Constructed Vehicle.
Note: Section LO provides information on the construction of ICVs for:

  • motor cycles ADR category LA, LB, LC and LD; and
  • guidelines together with checklists for LEM1 and LEP1, ADR Category Tricycles.




NOT MENTIONED HERE BUT I WAS TOLD PRE 1976 THERE IS A DIFFERENT REQUIREMENT FOR HANDLE BARS

2.1.13 Handlebars

The handlebar must have the same shape and be of the same length on either side of the front
wheel and steering head assembly.
Handlebar dimensions have to be limited to ensure that the rider has adequate control over the
motor cycle at all times.
Motor cycles manufactured before 1 July 1988 (Figure LL5):
The distance between the extreme ends of the handlebar (V) must not be less than 550mm.
The highest point on the handlebar must not be more than 380mm (W) above the top of the steering yoke.
Where the highest point of the handlebar is more than 205mm vertically above the top of the steering yoke (W), the distance between the extreme ends of the handle bar (V) must not be less than 660mm.



Dimension (V) must not be less than 500mm and not more than 900mm.
Dimension (W) must not be greater than 380mm.
Note: If (W) is greater than 205mm then (V) must not be less than 660mm.



Motor cycles manufactured after 30 June 1988 (Figure LL6):
The distance between the extreme ends of the handlebar (X) must not be less than 500mm and
not more than 900mm.
The height of the lowest part of the handgrip must not be more than 380mm above the lowest part of the upper surface of the rider’s seat (Y).
The horizontal distance between the mid-point of the steering yoke bearing and a point vertically above the centre of the front wheel must not exceed 550mm.
Dimension (X) not less than 500mm and not more than 900mm.
Dimension (Y) not greater than 380mm.
Dimension (Z) not greater 550mm.








2.1.14 Tyres and Rims
Each tyre and rim must be strong enough to support the machine when it is fully loaded.

2.1.15 Noise
Motor cycles manufactured from 1 July 1975 are subject to strict design requirements for noise
emissions. Components affecting noise emissions (especially exhaust systems) must not be
modified and must be maintained in a serviceable condition. Any replacement component must
be as near as practical to the original component specification.

The AVSR sets stationary noise limits for all motor vehicles including motor cycles. The
stationary noise level for a motor cycle or a motor trike, built after February 1985, is 94 dB(A) or
for any other motor cycles or motor trikes, 100 dB(A). Refer to Section LT Test Procedures for
details about the stationary noise test.
Exhaust system should therefore not be replaced or modified if this is likely to increase the
vehicle’s noise output beyond that of the unmodified system when in good condition.
Motor cycles manufactured from 1 July 1988 have all components of the Silencing System
marked with the name or trade name of the manufacturer. Every motor cycle manufactured
after 1 July 1988 carries details of the ADRs 39/… and 83/... stationary noise test in a format
similar to that shown in Figure LL7.

STATIONARY NOISE TEST INFORMATION
Tested at ..................dB(A) at ..................r/min
Silencing System: (manufacturer’s name)
Identification: (silencer trade description)

Figure LL7 Stationary Noise Test Information Decal

Any replacement part of the system must show the trademark or the name of the manufacturer
of the system.


2.1.16 Horn

An efficient horn or other device must be fitted that is capable of warning other road users of
the presence or position of the motor cycle. Horns, sirens or other devices that emit a sound
like a siren, exhaust whistle, compression whistle or repeater horn must not be fitted.

2.1.17 Speedometer

Motor cycles manufactured after 30 June 1988 must have an accurate speedometer calibrated
in km/h.

2.2 FABRICATION

All work must be performed in accordance with recognised engineering standards. Cutting,
heating, welding or bending of components should be avoided by choosing unmodified
production components wherever possible.
2.2.1 Welding, Fasteners and Electroplating
Mandatory requirements and guidance on the above items are contained in Section
LZ Appendices.
 For the use of fasteners refer to Appendix A Fasteners;
 For welding techniques and procedures refer to Appendix C Heating and Welding of
Steering Components; and
 For electroplating refer to Appendix D Electroplating.


3 AUSTRALIAN DESIGN RULES


A modified vehicle must continue to comply with the ADRs to which it was originally
constructed, except as allowed for in the AVSR.

Outlined in Table LL1 below are requirements and/or components of the vehicle that may be
affected by the modifications and that may require re-certification, testing and/or data to show
continuing compliance for the modified vehicle. This is not an exhaustive list and other
modifications may also affect ADR compliance.

Table LL1 Summary of items that if modified, may detrimentally affect
compliance with applicable ADRs
ADRS DETAILS
ADR 7, 7/... Hydraulic Brake Hoses
ADR 28x, 28/... Motor Vehicle Noise
ADR 33x, 33/... Motor cycle Braking Systems
ADR 39x, 39/... Motor cycle Noise
ADR 42/... General Safety Requirements
ADR 57/… Special Provisions for L-group Vehicles
ADR 83/... External Noise

To determine the ADRs that apply to the vehicle in question, refer to the applicability tables in
Section LO. Vehicles manufactured on or after 1 January 1969 and prior to 1 July 1988 need to
comply with the Second Edition ADRs whilst vehicles manufactured after this date need to
comply with the Third Edition ADRs. Section LO has separate applicability tables for each
edition.
Alternatively, ADR applicability tables for individual vehicle categories may be referenced on the
Department of Infrastructure and Transport RVCS website at the following address and under
the section titled ADR Applicability Tables:
http://rvcs.dotars.gov.au/






4 NON-CERTIFIED MODIFICATIONS

The following modifications may be carried out provided they do not affect compliance with
ADRs and provided they meet the general safety requirements specified in Subsection 2
General Requirements, and in the case of seat conversions, the additional requirements
specified in Subsection 5 Specific Requirement for Seat Conversions.


4.1 OPTIONAL COMPONENTS OFFERED BY THE MANUFACTURER

The following is a list of typical optional components offered by manufacturers of motor cycles.
 Engine;
 Transmission;
 Front and Rear Suspensions;
 Exhaust;
 Fuel tank;



5 SPECIFIC REQUIREMENTS FOR SEAT CONVERSIONS

The following are specific requirements that need to be followed for seat conversions.
All work must also comply with the general guidelines contained in sub-section 2 General
Requirements.

5.1 CONVERSION FROM TWO SEATER TO SINGLE SEATER

For a two seater motor cycle to be converted to a single seater, it is necessary to shorten the
seat and remove the pillion foot pegs/mounting brackets. For a motor cycle to be classified as a
single seater, it is necessary for the motor cycle to be fitted with only:

  • one seat which has a length less than 500mm; and
  • one pair of foot pegs and mountings.


5.1.1 Reduction in Seat Length

Only the upholstered section of the seat needs to be shortened.
The maximum length of the upholstered section of the seat is 500mm.
The shortened seat must have no sharp edges or protrusions.
Any equipment or fittings exposed by the seat modifications must be protected if they are likely
to cause injury to any person.

5.1.2 Removal of Foot Pegs and Mounting Brackets

The foot pegs must be removed.
There must be no sharp edges, damage to the frame, or damage to the trailing arms.
These modifications must not incorporate oxy-cutting or application of heat.

5.2 CONVERSION FROM A SINGLE SEATER TO A TWO SEATER ORIGINAL

When converting a motor cycle (which has been previously modified to a single seater) to a two
seater, it should be restored as close as possible to the original manufacturer's specifications.

5.2.1 Increase in Seat Length

The seat must be returned to original motor cycle manufacturer's specification or equivalent.
The lengthened seat must have no sharp edges or protrusions.
Any equipment or fittings exposed by the seat modifications must be protected if they are likely
to cause injury to any person.

5.2.2 Fitting of Foot Pegs and Mounting Brackets

Pillion passenger foot pegs must be fitted as close to the motor cycle manufacturer's original
position as possible.
The foot pegs are to be mounted in accordance with good automotive practice.
There must be no sharp edges, damage to the frame, or damage to the trailing arms.
These modifications must not incorporate oxy-cutting or application of heat.


6 CERTIFIED MODIFICATIONS (LL CODES)

There are currently no certified modifications in this Section of VSB 14.

Tuesday, 7 February 2012

Real vs False Trail


Having read this article I may have to go back and recheck my planned steering geometry for  correct trail measurement. I have measured False Trail. Although if everyone has based their recommendations on the same misunderstanding then I may still be good.  Just the same worth checking.




Rake And Trail
From American Suspension, February, 2009 issue of Street Chopper
By Vince Costa



What is rake and trail, and what does it mean to you? Hit a 100mph on a bike with a 1/8-inch of trail and you will wish you knew about rake and trail before you built your bike. Is your new bike going to wobble, or steer like a tank? With a little planning, your bike can be rock solid, yet able to carve through the canyons.

What is rake and trail?

Rake is the angle of your steering neck. Stock Harleys have about 28 to 34 degrees of rake. Choppers have something more than that; usually 40 to 50 degrees of rake in the neck. The raked neck allows them to have a lengthy and low look with long forks. After all, the difference between ordinary motorcycles and a chopper are those long forks.

Image
Figure 1 Steering Axis Tr… 
So if that is rake, what's trail? The next time you are at the supermarket, take a look at the shopping cart wheels as you race around the aisles. As shown in FIGURE 1, the wheels trail behind the steering axis. As you push the cart, the wheels are stable because they trail behind the steering axis. If the wheels flip in front of the steering axis, they will wobble and flop back behind the steering axis until they again trail the steering axis. If you don't believe me, head to the supermarket and try it out. Oh, and while you are out, grab me a pizza and a sixxer of cold ones.

As a general rule, when the wheels trail behind the steering axis, they are stable. When the wheels are in front of the steering axis, they are going to wobble and flop back. It is kind of like putting the cart in front of the horse. The cart needs to trail the horse.

The amount of stability is proportional to the leverage that the tire contact patch has on it. Conversely, the longer the trail, the harder it is to turn the wheels. This is due to the increased leverage the wheel has about the steering axis. It is an easy concept to remember because the longer things are, the harder they are to turn. We can measure the trail on this system as the distance along the ground from the axle to the steering axis.

Image
Figure 2 Rear Trail Steering… 

Now lets look at a motorcycle; both the front wheel and the rear wheel pivot about the steering axis. Both the front and rear wheels trail behind the steering axis. The big difference is that the steering axis is at an angle to the ground. The true trail is still the leverage that the tire has on the steering axis. Since we have tilted the steering axis, the trail tilts along with it.

So, we can measure trail as the perpendicular distance from the point where the tire contacts the ground to the steering axis. We are using the center of the tire contact patch as the tire contact point. In reality, the centroid of the tire contact patch is slightly behind the center of the tire. But that is an entirely different article.

A lot of builders will measure trail from the tire contact point to the point where the steering axis intersects the ground. We call this false trail. To determine vehicle dynamics, you need to measure the leverage that the tire has over the steering axis. The correct measurement is the perpendicular distance from the steering axis to the tire contact point. To clarify things, we often call this measurement true trail.

Image
Different True Trail In this... 

FIGURE 3 shows that two bikes with the same false trail can have very different measurements for true trail.

Is too much trail bad?

Image
Increased Rake Increases ... 
FIGURE 4 shows that as you increase the rake angle of a bike, the trail also increases. Now, is it possible to have too much trail? Yes it is. If you have too much trail, the bike can feel very heavy and sluggish and can be unstable with too much or too little trail. Another common complaint about too much trail is that the bike will flop. This is because the steering axis is inclined (unlike the shopping cart, and by the way, where is my beer and pizza)? The inclination causes the bike to be raised and lowered as the wheel pivots about the steering axis. The long leverage that the wheel has on the steering axis requires big arms to keep the bike from "flopping" over.

What Are The Stability Modes?

Lets talk a little bit about stability. A motorcycle can exhibit three primary modes of instability: the roll mode, the wobble mode, and the weave mode. The roll mode of instability is easy to understand. Just sit on your bike while it is standing still and pick up your feet. Unless your balance is outstanding, you will fall to the ground; a victim of the roll mode of instability.

The wobble mode of instability is where the main portion of the motorcycle stays relatively stable, while the front fork assembly oscillates back and forth. In other words, the main mass of the motorcycle stays steady, while the front fork assembly pivots about the steering axis. Too little trail can cause the bike to wobble. There are also lots of other factors that can make a bike wobble as well. Common culprits are tires, shocks, frame stiffness, stem bearings, and weight distribution, to name a few.

The weave mode of instability is where both the fork assembly and the main portion of the motorcycle oscillate back and forth. The bike will feel as though it weaves. Although there can be a number of causes for this mode of instability, it can sometimes be caused by too much trail. There are also lots of other factors that can make a bike weave as well. Tires, shocks, frame stiffness, stem bearings that are too tight, and weight distribution are often other causes of a weave.

Many riders are unable to tell a wobble from a weave. Either way, your buddies will rocket away from you at high speed no matter how big your motor is.

So what is the right true trail?

Not enough trail will make your bike wobble and too much trail can make it steer like a tank. Too much trail can even make the bike unstable in the weave mode. How do we make sure our trail is going to work for our bike? While there are a number of variables involved, we have seen that as a general rule if the true trail is between 1-1/2 to 5 inches, your bike should be good. Bikes with less trail steer quicker and are more agile, and often more fun to ride. Bikes with longer trail tend to take more muscle to make them change direction. It is really a matter of personal preference.

Now saying that it is a matter of rider preference may make many of you unsettled. I hear people everyday telling me that exactly 4.1 inches is right. This is especially comical because typically they are measuring false trail anyway. In addition, there are errors in determining true trail due to tire deflection, pneumatic trail, and other factors.

I have to admit that I used to think there was a perfect set up myself. But my experiences as a racing suspension tuner changed my mind. While it is not quite the freestyle spirit of anything is possible and everything is OK, there is a lot more flexibility in what the riders want and what we can give them. Now I will tell you a story to illustrate that when someone says that they are exactly right, they are almost certainly wrong.

Years ago, I use to set up race bikes for a living and I was working with two particular riders. The two riders were on nearly identical bikes (except for steering geometry) and were within hundredths of a second of each other during practice. Each rider had dramatically different steering geometries. I was thinking of how to make them faster. I assumed one must have the right set up and the other had the wrong set up. The one rider must just be better and able to ride past the shortcomings of his inferior set up. But how to tell which rider had the best set up? Both riders were former national champions and equals. Just for fun, I swapped settings on them. I figured that one rider was just so good, he's able to ride with the handicap of his terrible set up! Whoever got faster after the swap would now have the better setting. Neither rider was aware of the changes when they went out to practice. Then I sent them out, same time, and same practice. When they came back in, they were both ready to kill me. Both riders said that the new set up was unrideable and just plain terrible. They both hated each others set up. So I changed it back and they each got their own set up. When it came time to race, both riders were within a wheel of each other, and they changed lead about 20 times. It came down to the last turn of the last lap. One rider squeezed past the other at the finish line.

I learned a valuable lesson that day. It changed my thinking about right and wrong.

Personally, I run very little trail. I used to race Superbikes back in the days when a good handling bike was one that did not spit you off immediately. So, I am comfortable trading a little stability for nimble handling.

Female riders are lighter and tend not to muscle the bike around. I will set them up with a very light trail as well. Heavier riders or inexperienced riders often need more trail to keep them in check. A lot of riders can make an otherwise good handling bike wobble. But how your riding can upset the bikes handling is yet another article.

How can we change trail?

Lets take a close look at the bike in FIGURE 2 . The bike has a 45 degree neck and zero degree trees. So it ends up with true trail of almost 7 inches. That bike is going to steer like a tank.

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Figure 5 Steering Axis 45... 

It is raked trees to the rescue. Oddly enough, if adding rake in the neck increases trail, adding rake to the trees reduces trail. Take a look at FIGURE 5 -it is the same bike-but with 6 degree raked trees. The true trail on that bike is 2-1/2 inches; perfect. The bike even looks tougher too. As a good rule of thumb, if your neck rake is less than 38 degrees, use zero degree trees. If your neck rake is more than 36 degrees, but less than 42 degrees, you can use 3 degree trees. If your neck rake is more than 40 degrees, but less than 50 degrees, you can use 6 degree trees. If there is more than 48 degrees in the neck, you can consider 9 degree trees.

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Wheel moves forward due to... 

We can also change trail with the rocker on a springer. FIGURE 6 shows the same bike, but this time with a springer front end. The rocker kicks out the wheel so that the trail is about 1-3/4-inch. That will give us a quick and nimble bike with the look of an old school chopper. The best of all worlds.

I hope this article helps keep your new bike as fun to ride through the twisted canyons, as it is on the lonesome highway.



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