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Bike FAQ's

Components | Wheels | Electronics | Pedals/Cleats/Shoes | General


  1. Bottom Brackets
  2. Chainrings
  3. Brakes
  4. Brake Pads
  5. Chains
  6. Derailleurs
  7. Stems/Headsets
  8. Handlebars
  9. Saddles/Seatpost

1. Bottom Brackets

How to measure a bottom bracket?
Bottom brackets (BB) are designated by 2 pieces of information: BB shell width and spindle length.
Bottom bracket shell width: The BB shell is the part of the frame into which the BB threads. It will be 73 mm, 70 mm or 68 mm. Measuring the shell is easy. With a metric ruler measure on a line parallel to the BB spindle. Don't measure any of the old BB if it protrudes beyond the shell.
Spindle length: The spindle is the axle that supports the crank arms. If you are using your old cranks, you'll want the same length that was installed initially. Pull the cranks and measure from one side of the spindle to the other in millimeters. If the cranks are secured with nuts as opposed to bolts, do not measure the extended threaded portion. If buying a BB for a new crank, follow the crank manufacturer's recommended lengths. Tech has that info.

2. Chainrings: - Back to Top

What replacement chainring do I need?
Chainrings are available in different sizes. To select the correct one, you'll need to know three things:

  1. The number of chainring mounting bolts, either 4 or 5.
  2. The number of teeth on the chainring.
  3. The Bolt Circle Diameter (BCD). The BCD is the diameter of the circle running thru the mounting bolts.
The first two are easy. Just count the bolts attaching the chainring to the crank and count the number of teeth on the ring. The chainring may be stamped with the number of teeth. For the BCD the charts below will help. Measure the distance between the centers of adjacent bolt holes, then refer to the appropriate chart.

For 5-Bolt Chainrings:

Bolt Circle Diameter Bolt To Bolt (center to center)
56mm 32.9mm
58mm 34.3mm
74mm 43.5mm
94mm 55.4mm
110mm 64.7mm
130mm 76.4mm
135mm 79.5mm
144mm 84.6mm

For 4-Bolt Chainrings:

Bolt Circle Diameter Bolt To Bolt (center to center)
58mm 41.0mm
64mm 45.3mm
68mm 48.1mm
104mm 73.6mm
112mm 79.2mm

3. Brakes: - Back to Top

Can I put disc brakes on my bike?
Disc brakes require that a frame or fork have special mounts, called disc brake tabs (also called bosses). Each mount has two holes. Fork disc mounts are located on the back of the left leg near the dropout. On frames they are braised or welded near the back left dropout. There are two common standards that dictate the placement and spacing of the brake tabs, the Hayes Standard and the International Standard (IS). Here are descriptions of the different mounts:

International Standard Fork Mount: Drilling: 2 threaded 6mm holes, parallel to the fork legs and spaced 51mm apart.
Forks: Rock Shox, Marzocchi, RST, Fox
Compatible brakes: Shimano, Grimeca, Magura, Hayes and Avid (with included adapter).

Hayes Standard Fork Mount:
Drilling: 2 unthreaded holes, perpendicular to the fork leg and spaced 74mm apart.
Forks: Manitou (2001 and newer). Adapters are available to convert these to IS brakes.
Compatible brakes: Avid and Hayes.

International Standard Frame Mount:
Drilling: 2 threaded 6mm holes spaced 51mm apart, perpendicular to the left seatstay above the dropout.
Compatible brakes: Shimano, Avid, Hayes (International Standard), Grimeca and Magura.

Hayes Standard Frame Mount
Drilling: 2 threaded holes spaced 22mm apart, usually on top and parallel to the left chain stay near the dropout.
Compatible brakes: Hayes, adapters are available for other brake systems.

4. Brake Pads - Back to Top

What brake pads do I need?
It depends on the type of brake.

Road: Pads are generally shorter than mountain bike pads. They attach to the brake arm by a threaded post that extends from the back of the pad. Any road pad can be used on any road brake. Shimano's newest road brakes (Dura-Ace and Ultegra) have brake shoes with replaceable cartridge type pads rather than a pad that is permanently bonded to a medal holder. The benefit of this that holders don't have to be replaced nor do they have to be readjusted to the rim.

Road Pads:
Road pads w/ holders:

  1. Shimano Road Thrd, 53-0128

Cartridge Rd Pads (no holder):
  1. 7700/6600, 00-5441

Mountain: There are 3 types of ATB brakes: V-brake, cantilever and disc brake. V-brakes (also called linear-pull brakes or long arm sidepulls) are activated from the side by a single cable. Most V-brakes come with brake shoes that have replaceable cartridge pads (i.e. the braking material can be replaced independently of the holder). The shoe attaches to the brake with a threaded post and nut. MTB cartridge pads are longer than road pads and more curved. They are secured in the shoe with a pin. There is only ONE standard for replacement ATB cartridge pads.
Non-replaceable Pads: Some earlier V-brakes (e.g. 2001 & earlier Shimano LX and Avid) came with pads with integral holders (non-replaceable pads). The entire pad/holder needs to be replaced and can be replaced by the cartridge type.

V-Brake Cartridge Pads:
ATB Cartridge Pads (no holder):

  1. Shimano XTR/XT V, 00-1762
  2. Ritchey V-Brake, 00-2769

ATB Threaded Shoes w non-replaceable pads:
  1. Aztec LX V-Brake, 00-6353

Are found on older mountain bikes plus on modern cyclocross and touring bikes. Unlike V-brakes, cantilevers have two cables, a straddle cable that runs over the wheel from one brake arm to the other and a second that pulls the straddle cable to activate the brake. Some cantilevers uses pads with threaded posts. Others require a shoe with an unthreaded post. Threaded and unthreaded pads can NOT be interchanged.

Cantilever Pads:
ATB Threaded Pad/shoe (non-replaceable pads):

  1. Aztec LX V-Brake, 00-6353
  2. Kool Stop E2 Thrd, 00-6511

ATB Unthreaded Pad/shoe (non-replaceable pads):
  1. Kool Stop E2 Canti, 00-6527

Each manufacturer (e.g. Hayes, Shimano, Avid, etc.) has brake-specific pads. With one exception they do NOT interchange.

Disc Pads:
Disc Brake Pads:

  1. Aztec Replacement Disc Pads, 50-1584

5. Chains - Back to Top

What chain will work on my 7-speed system (7 speeds in the rear)?
Any 8 speed or 9-speed chain will work. The same 8 speed chain will also work with 6, 7 or 8 speed freewheels and freehubs. For 9 speed systems ONLY a 9 speed chains will work. Campy's new 10-speed system requires special 10 speed chains. Both Wipperman and Campy make them.

Can I use a SRAM chain on my SHIMANO or CAMPY drivetrain?
YES, SRAM chains will work with both Campy and Shimano systems, however the correct one must be chosen.

  • For a 9 speed Shimano or Campy system, ONLY a 9-speed SRAM chain will work.
  • For older Campagnolo or Shimano 7 or 8 speed systems, either the 8spd or 9spd SRAM chains can be used.
  • For very old 6-speed systems, the 8-speed chain works.
  • SRAM does NOT make a chain for Campy's 10-spd systems, but both Wipperman and Campy do.

6. Derailleurs: - Back to Top

What size front derailleur clamp do I need?
Typical front derailleur clamp sizes are 1 1/8", 1 ¼" or 1 3/8". To determine the size you need, measure the diameter of the frame tube where your front derailleur clamps. You can use a micrometer, a Vernier caliper or a large adjustable wrench. To use the adjustable wrench tighten it on the tube- careful not to damage the paint- and then measure the gap between the jaws in inches.

What's the difference between Top Pull and Bottom Pull front derailleurs? Which one do I need?
The difference is how the cable is routed to the front derailleur:

  • If the cable goes down to the derailleur from the top, you need a top pull.
  • If the cable goes up to the derailleur from the bottom bracket, you need a bottom pull.

7. Headsets/Stems/Handlebars: - Back to Top

What type and size stem or headset do I need?
Getting the correct stem or headset for your bike or frame depends on matching it to your fork's steerer tube. First a definition: the steerer tube is the extension of the fork that connects it by means of the headset to the frame and the handlebars & stem. Headsets and stems are sized according to the outside diameter (OD) of the steerer. They are further defined by whether the steerer is threaded or not. In ordering a stem or headset you'll need to specify a size (fork steerer's OD) and whether it is threaded r threaded.

For a complete bike (as opposed to just a frame), the secret is in examining your existing stem. The most common sizes are 1" and 1 1/8". If the stem fits down into the steerer, the bike has a threaded headset, stem and steerer. To size a threaded steerer, measure the diameter of the stem's quill (i.e. the part of the stem that slides into the fork) and add 1/8th of an inch.
Stem or Headset for Threaded steerer = quill diameter + 1/8" = steerer O.D.
If the stem clamps to the steerer, the bike has a threadless headset, stem and steerer. To size a threadless steerer, remove the stem's top cap and measure the inside diameter of the stem where it clamps to the steerer.
Stem or Headset for Threadless steerer = stem/steerer clamp I.D. = steerer O.D
For unbuilt frames with no fork, measure the inside diameter of the head tube:

  • ~30 mm = 1" steerer
  • ~34 mm = 1 1/8" steerer
  • ~37 mm = 1 ¼" steerer

How do I measure the length or extension of my stem?
Extension is the length along the top of the stem. It is measured in millimeters from the center of the handlebars to the center of the fork steerer tube.

How do I measure the rise or angle of my stem?
Rise is the stem's angle in degrees. It is measured relative to the fork steerer tube or frame head tube (steering axis). A stem that is at a right angle to the steerer has a 0° rise and will angle up. On most road bikes a stem with -17° rise will be parallel to the ground while a -10° will angle up 7°.

Can I use this mountain stem with my road bars?
Use. Mountain bike and road stems are different and they should not be interchanged. Good quality road handlebars are generally 26.0 mm in the center where they are clamped by the stem. Mountain bars are 25.4 mm. This silly .6 millimeter is enough to keep a road stem from securely holding an ATB bar and enough to damage an ATB stem trying to grasp a road bar.

How can I tell if my stem is a threaded or threadless type? A bike's headset (bearings), stem, bike frame and fork connect together as part of a system. To be compatible each has to assemble using the same standard and be the correct size. The 2 standards are threaded and threadless. For the threaded type, the stem has a cylindrical shaft called a quill that inserts into the fork steerer tube and is held in place with a wedge nut. The steerer tube is threaded to accept the upper parts of the headset. In a threadless (also called Aheadset®) system the headset slides on--- it doesn't thread on--- and the stem clamps to the steerer tube.

8. Handlebars: - Back to Top

How do I know what size road handlebar I need?
Road handlebars are produced in various widths. Handlebar width is measured in centimeters across the drops (this is the bottom of the curved portion of the bars, pointing toward the rider). Most companies measure their bars center to center but others, TTT's bars for example, measure outside to outside.

As a general rule, the size of your handlebars should be equal to the width of your shoulders at a line up from the armpit. Some riders prefer wider handlebars for easier breathing while other riders prefer narrower handlebars for greater aerodynamics and maneuverability. A properly sized bar should strike a balance between comfort, aerodynamics and your particular riding style.

9. Saddles/Seatposts: - Back to Top

What saddle should I order?
Saddle preference is very much a personal matter. It depends on what type of riding you'll be doing and how much padding you like and your anatomy. There is NO way to GUARANTEE a successful mating of butt and saddle.

How do I know what size seatpost I need?
Most good quality posts have the size stamped under the "Minimum Insertion" line. The size corresponds to the outside diameter of the post in tenths of millimeters (e.g. 26.8 mm, 27.2 mm, 32.4mm, etc). If there is no stamp or no post, then it's time to break out the calipers. To prevent damage to the frame, a very precise measurement is needed. Using a Vernier caliper or micrometer, measure either the inside diameter of the seat tube of the frame or the O.D. of the seatpost in tenths of millimeters. No calipers? Call the manufacturer or take the frame to a professional. Wheels/Tires: - Back to Top

    1. Tires

    What is the 700c tire size conversion for a 27 x 1 1/8 tire?
    They do NOT convert! 27" and 700c are different sizes and they are NOT interchangeable.

    What is TPI? If a tire has a higher TPI does that mean it's a better tire? Does TPI affect the ride in any way?
    TPI is an acronym for Threads Per Inch and describes how fine the threads are in a tire's casing. A tire with a high TPI (e.g. 127 TPI) will have a thinner, suppler sidewall. This enhances performance (rolling resistance, acceleration and handling), makes the tire lighter, but also makes it less durable and more costly. Most high quality, high performance tires have a higher TPI.

    "Is higher better?" It depends on what you want or need.
    If you are a competitive athlete who wants speed regardless of the cost, then the answer is an unqualified "YES". Generally a tire with a soft, thin, tread compound and super high TPI will stick like crazy in the corners and accelerate like a rocket. There is a downside. Thin light tires usually will not last very long.
    If you are a rider on a budget then the answer is probably "no". A cheaper tire with lower TPI and a thicker tread will be more puncture resistant and last longer but it will be heavier, it won't roll as fast nor will it handle as well.

    How do I determine how narrow or wide of tire I can use on my rim?
    You can go as narrow as the inside width of the rim. Measure between the walls of the rim. For road rims and tires use millimeters and for ATB rims measure in inches. For example if a 700C road rim has an inside width of 19 mm, then you can safely go down to a 700x20 tire.

    For width, you can normally go up to 2 times the inside width for a road tire or 3 times the inside width for ATB tires as long as the tire will fit through the brake calipers, the crown of the fork or the frame stays.

    • How Narrow = not < inside rim width
    • How Wide (ATB) = not > 3 X inside rim width
    • How Wide (Road) = not > 2 X inside rim width

    What's the difference between a Kevlar bead and a wire bead? What are the benefits of both?
    The tire bead is one of two strong, non-stretchy loops of material enclosed within the inside edges of a clincher tire. They keep the inflated tire (even very high pressure road tires) from blowing off the rim. Tires with steel cable beads are called wire bead tires. The steel makes them heavier and relatively stiff. They are not foldable. When high-tech lightweight flexible Kevlar® is used the resulting tires is lighter and foldable. Most fancy, expensive tires have Kevlar® beads.

    2. Wheels

    Can I use a new 8/9-speed wheel on my old 7 speed bike?
    There are 2 concerns in using an 8/9-speed wheel with an older 7-speed bike:

    1. rear triangle spacing and
    2. cassette compatibility.

    Rear triangle spacing (also called "over lock nut spacing") is the width in millimeters between the bike's rear dropouts. Because 8 and 9 speed bikes, wheels and hubs share the same rear spacing, we can treat them as one size, 8/9. Their cassettes and wheels can be freely interchanged. The modern standard for 8 or 9 speed road bikes is 130 mm. For mountain bikes it is 135 mm. Some 7speed bikes have this spacing but most don't. It is usually narrower. You can easily determine the width of your bike. Remove the rear wheel from the frame and measure the distance with a metric ruler.

    If the bike has narrower spacing and is made of carbon fiber or aluminum, then a 8/9-speed wheel CAN NOT be used. However if the bike is made of steel, the frame can be cold set (that is spread and realigned) to the wider standard. Only a professional mechanic with the correct tools should do this.

    Cassette compatibility: 7 speed cassettes are narrower than their 8 or 9 speed counterparts, nonetheless they can be used w an 8/9 wheel. To make up the width difference a spacer must be installed before the cassette. The spacer is item 00-8179.

Electronics: - Back to Top

    1. Cyclocomputers

    I need a cyclocomputer, which one should I get?
    That depends entirely on what functions you want.

    2. Heart Rate Monitors

    I need a HRM, which one should I get?
    That depends entirely on what functions you want.

Pedals/Cleats/Shoes: - Back to Top

    I have SPD compatible shoes, which cleats do I need?
    Cleats are unique to the pedals NOT the shoes. What type of pedals do you have? Select the cleats that are compatible with your pedals.

    SPD compatible shoes have 2 or 4 threaded holes in parallel slots (1 or 2 holes/slot) under the ball of the foot. The slots are ~1/2" apart and run front to rear. Many different brands and shapes of cleat attach using this bolt pattern. For example Speedplay Frogs, Crank Bros. Eggbeaters, Time ATAC and Shimano SPDs are all require the SPD bolt pattern but none of their cleats interchange.

    Why didn't I get cleats with my shoes?
    (See question above.) Cleats come with the pedals, not with the shoes.

General: - Back to Top

    How do you convert mm to inches?
    To convert inches to millimeters, multiply the measurement in inches times 25.4 (1" = 25.4 mm). For more conversions, click on

    What's the difference between the $20 helmet and the $100? one?
    Generally more expensive helmets are 1) lighter for their type, 2) have more sophisticated retention systems that are more adjustable, 3) offer better ventilation with more and larger vents and 4) have a more stylish appearance. Additionally the $100+ helmet's outer shell is usually bonded to the foam core in the molding process. Cheaper ones have outer shells that are glued and taped.

    What's the difference between 105 and Ultegra or LX and XT? Is it worth the price difference?
    FIT, FINISH, FEATURES AND MATERIALS. With Shimano, as with most manufacturers, as you go up the line (e.g. from 105 to Ultegra or from LX to XT), the parts generally get lighter, more durable and reliable, and they provide better performance.

    Is it worth it? A highly competitive athlete will appreciate the performance enhancement. Someone wanting the very best will appreciate the quality.