Quick Bike Fit and Function Checkup for
Getting the best results with what you’ve got!
Author's Note: This page describes an
efficient system for fitting and trouble-shooting the bikes of any large riding
group such as a Boy Scout troop. It assumes you won't be upgrading parts or
sawing off pieces of bicycle. Fitting and checkup should take less than 5
minutes per bike. Full details for fitting a bike are found on the Fitting
a Bike page, where you'll also find photos that illustrate the process. I suggest you print the single-page
reference for the group bike checkup (a condensed version of this web page
in MS Word format) for your assistants to use during "bike checkout
night." The Troubleshooting Guide may be
useful to quickly diagnose problems you discover during this Fit and Function
checkup, and is also available as a single-page
troubleshooting quick reference in MS Word format for on-trail use. A laptop
with the web browser set to the Fix-it section of UtahMountainBiking.com will
help your Repair and Tuneup team. - Bruce Argyle
You will need:
Trainer (24 and
29-inch wheeled bikes may not fit)
to check handlebar height, seat level
hard-cover book to check seat
board (1x2 OK) to check handlebar height, and as vertical marker for derailleur
for inseam measurement, starting position for seat
Metal measuring ruler for chain-stretch checkup
Plumb line to check seat front-to-back position
Set of bike tools
stand (consider also: wheel-truing stand)
supplies: degreaser and buckets/brushes, chain lube, paper towels, tubes,
high-capacity patch kit, extra tire, rim-brake pads (V-brake and cantilever), derailleur
cables and cable housing, brake cables and housing, 7-speed and 8/9-speed
chain, extra threadless-headset spacing rings, and maybe a broken bike or
two to cannibalize.
or laptop with internet access
persons, 2 of whom have bike-repair expertise):
(Wrangler) - coordinates movement of bikes and scouts, records required
parts, supplies, and repairs
Fit and Function
specialist (Fitter) - does an efficient bike checkup on the trainer as
specialist (Wrench) - expert half of two-person team with a full set of tools,
repair stand, and spare parts
Repair helper -
Each rider brings
his clean bicycle and supplies, including helmet, backpack, bottles, and riding
clothing to "checkout night."
scout's helmet, clothing, and supplies. Is he ready for the trip?
scout and bike to Fitter.
Scout pedals bike
in trainer, gets off and on again as Fitter makes adjustments.
Wrangler records any required repairs.
If problems are
found, Wrangler takes bike and owner to Wrench, while
Fitter continues with another scout.
problems are repaired, Wrangler routes scout back to Fitter where the Fit
and Function process starts anew.
Does the rider
have a helmet, and is it fitted properly?
Are the rider's
shoes appropriate to the activity? Is the clothing appropriate? (Trouser
"cutoff" shorts have a seam that will chafe the upper thighs.)
Riding gloves highly recommended.
should have a backpack. If the backpack doesn't have a hydration bladder,
the rider must have water bottles (and bottle cages on the bike frame)!
pack or backpack should contain: spare tube of correct size, patch kit with
glue that's still liquid, multi-tool, plastic rain slicker. Consider also:
individual sunscreen/insect repellant packet, chain "quick-link".
have individual mini-pump, either attached to bike frame or in the backpack.
rides: add mini-flashlight, small first aid kit, and small lube bottle to
backpack. Extra set of bike-specific brake pads and any supplies that are
unique to the individual's bike (tubeless setups, 24-inch or 29-inch tubes
and tires, etc) are labeled with the scout's name and added to the main supply cache (to go in the
If it's a
multi-day ride, confirm adequate group supplies: Full tool kit, chain lube,
paper towels, floor pump, shock pump, 7 and 8/9-speed chains, quick-link for
7 and 9-speed chains, tubes, spare tire, large tube-and-tire patch kit, rim-brake
pads (V-brake and cantilever), derailleur cables and cable housing, brake
cables and housing, full first
aid kit, big bottle of sunscreen. Consider: bleed kit for hydraulic disc
brakes, tire liners, Flat Attack or other sealant, repair stand (a trunk or
hitch bike rack that lets the bicycle hang down can function as a field
repair stand). Add individual supplies purchased by riders with unique
bicycle setups (for example Stan's sealant and extra tubeless valve, 29-inch tubes and
bike size: (Does it look like a "borrowed bike?") Frame = 2/3 x
inseam. (example, 24x30-inch trouser size = 2/3 x 30 = 20 inches, which
would usually be a medium (19 inch) frame size, but could get by with a large (21).
Consider bike swaps for gross mismatches.
bike in trainer. Use front wheel block to make bike level.
Horizontal to trace upslope. Use book and level.
Starting point = middle of crank bolt to top of seat, directly along seat
post = 0.88 x inseam length.
Knee angle should be 155 degrees when the pedal is extended. Rules of thumb:
Put seat about an inch lower than where you begin to see tilting of hips
with pedaling; Scout can barely touch ball of ONE foot to ground while
seat (while starting to ride -- not while bike is in trainer). Most scout
will arrive with bike seats that are way too low for efficient pedaling.
Pedal until comfortable. Have scout stop pedaling with cranks horizontal.
Use your plumb line. Move the seat forward or back until the bump just below
the knee tendon (tibial tubercle) on the forward leg falls directly over the
height: Starting position = handlebar grip height is 2 inches lower than top of
seat (use board and level). Put scout on bike, pedal briefly to get into
riding position. Raise or lower the handlebar so the scout's view of the
front axle is blocked. (You
may need extra spacing rings for threadless headsets.)
(rotation that controls the angle of the grips on curved handlebars): Rotate
so the grip is comfortable with the elbows hanging slightly away from body,
forearms straight forward, wrists straight (not bent side-to-side).
position: Scout grasps handlebar grip so that the middle of the handlebar,
the space between
thumb and index finger, the middle of the wrist, and middle of the elbow are all in a straight line. Scout
now loosens thumb and index finger. The outer two fingers maintain grip on
handlebar. Loosen attachment of brake lever. Slide and rotate brake lever so
that the crook in the curve of the lever falls under last joint of index finger. If
the lever is beyond the finger's reach, use the small adjusting screw to move
the lever closer to the handlebar.
position: While maintaining the grip and with the index finger on the brake lever, loosen
the shifter attachment. Move the shifters so the thumb/finger can contact
the shifting paddles without releasing the grip on the handlebar.
Chain: 1 foot =
exactly 12 links. Lubed. No twisted links. No rust. Rolls around rings and
derailleur pulleys smoothly.
Spaces between teeth perfectly round semi-circles, no bent or missing teeth, no
“dolphin fin” teeth. (Note: chainring teeth are NOT normally perfectly
in line; the slight side-to-side wandering of the teeth assists in chain
Teeth of cogs in good condition as above. Cassette doesn't tilt back and
forth on freewheel mechanism.
hanger: Quick visual = straight with vertical axis of bike frame (not bent
inward) and straight along forward axis of bike (not twisted). Put board onto frame
for vertical axis, sight on cage between pulleys to see if it lines up with
edge of board.
Cage straight, both pulley wheels turn easily, teeth intact? No excess
“play?” Moves when cable pulled.
Cage intact and unbent? No excess "play" in mechanism? Firmly
attached to frame? Moves when cable pulled.
Cable caps in place. No fraying. No obvious sharp bends in cable housing. No
"floppy" connections of cable housing to receiver in shifter or
Any broken spokes or cracks in the rim? Any bulges, exposed cord, or obvious problems with
Enough left for a long, long brake-intensive downhill ride?
Have scout shift rear derailleur into the middle cog of cassette. While
pedaling, shift up and down through all rings on the front. Chain should
drop into smaller ring quickly. Should take up on large ring without hitting
derailleur cage. Make sure it's not possible to drop chain rightward off of the biggest
ring onto the pedal when over-pushing shifter.
Rear shifter: Shift the front into the middle ring. Have the scout
shift the rear (right hand) as follows. Drop all the way to the smallest cog.
Now shift up 1 and back down. Now shift up 2, then back 1. Repeat the up-2,
back-1 up to the biggest cog. Make sure it's impossible to drop the chain
leftward off the biggest cog into the spokes when over-pushing the shifter. Walk back
down to small cog. Refer problems to the repair team.
Levers shouldn't hit fingers when pulled hard. (Use barrel-adjuster to
adjust.) Cables slide easily without noise? Rim brakes pads hit rim and ONLY
rim. No rubbing of pads (lift front of bike and spin wheel; disengage roller
in trailer to spin rear wheel).
Pedal bike hard uphill in different gears. This will bring out any problems
with shifting, chain, and rings. Make quick stop with brakes.
Now. Where do you take your boys to ride? See our
arbitrary Scout Trail Recommendations.