Velopedia Bicycle Archive

2003 Diamondback RM20

Original specifications: 20" wheels · legacy reference geometry.

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At a glance

Archive #39410

Model year: 2003
Category: BMX
Original MSRP: $499.99
Sizes: Pro
Colors: Fast Black/Silver/Black
Geometry: Legacy reference
In this record: 22 specifications · archived image · original MSRP · geometry

Model history 3 other years

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Identification clues

2003 archived details

Published colors: Fast Black/Silver/Black
Frame: 7005 aluminum
Original equipment: N/A

Clues, not proof of model year. Colors vary and components may have been replaced.

Original build7005 aluminum · 20" wheels

Manufacturer catalog

Published sizes and colors

1 size · 1 color

Manufacturer-published sizes and colors; availability and exact size/color pairings may vary by market or production run.

Published sizes

Pro

Published colors

Fast Black/Silver/Black

Frameset

Frame Construction	TIG-welded
Frame Material	7005 aluminum
Fork Material	Carbon fiber composite w/chromoly steerer, unicrown crown

Drivetrain

Crankset	AC Race 16 3pc, 44 teeth
Bottom Bracket	AC Euro Sealed Bearing
BB Shell Width	68mm English
Rear Cogs	1-speed, 16 teeth
Chain	KMC HP20NP, 1/2 X 3/32"
Pedals	Aluminum

Brakes

Brakes	Tektro BX-20 linear-pull rear brakes, Tektro Sabre rear levers

Cockpit & Contact Points

Headset	1 1/8" threadless aluminum
Handlebar	Chromoly BMX
Stem	Aluminum
Saddle	Diamondback BMX
Seatpost	Aluminum, 27.0mm diameter

Wheels & Tires

Hubs	Aluminum
Rims	Alex DM-24, 36-hole
Spokes	Stainless steel, straight gauge
Spoke Nipples	Brass nipples
Front Tire	20 x 2.125" Tioga Comp III
Rear Tire	20 x 1.75" Tioga Comp III
Wheel Size	20" wheels

Geometry

Legacy reference · 6 measurements

Historical measurements. Frame size unknown.

All geometry measurementsLegacy reference · 6 measurements

Measurement	Legacy reference
Top tube	539.8 mm
Head-tube angle	73.5°
Seat-tube angle	71°
Chainstay / rear center	393.7 mm
Wheelbase	985.5 mm
Fork offset / rake	30.5 mm

Frame size not recorded.

Gearing

Lower gears help on climbs. Higher gears suit higher speeds.

Pedal cadence

RPM

Speed units

RPM = pedal turns per minute.

Published build44T · 16T · 1-speed

Ratio2.75:1

Estimated speed At 90 RPM Gear14.4 mph

Rear tire: 20×1.75.

How it works

Ratio = front teeth ÷ rear teeth. Hub gears also include the hub’s internal ratio. A 400% range means the highest ratio is four times the lowest.

Speeds are estimates from tire size and pedal cadence. Actual speeds vary.

Try other gearing

Try your current gearingChanged tires or gears? Calculate your setup.

Your changes apply to this calculation. The archived build stays unchanged.

Gears Drivetrain

Front teeth Smallest rear teeth Largest rear teeth

Use up to three front tooth counts, separated by /. For one rear sprocket, enter the same count twice.

Rear tire

Rear tire marking

Apply the marking on your rear tire or edit its dimensions below. Older or fractional inch sizes need the ISO marking (e.g. 37-590).

Rim diameter (BSD, mm) Tire width (mm)

For 32-622, width is 32 mm and rim diameter is 622 mm. Use the rear tire on mixed-wheel bikes. Leave both fields empty to compare ratios only.

Cadence (RPM) Speed units

Gear, dimension and cadence changes update results automatically.

Gearing comparison
Measure	Original	Your setup
Lowest ratio	—	—
Highest ratio	—	—
Total range	—	—
Lowest-gear speed	—	—
Highest-gear speed	—	—

Speeds are estimates. These calculations do not establish component compatibility or available tire clearance.

Parts & serviceability

Find replacement parts

Original specifications

Brake pads · Original

Tektro BX-20 linear-pull rear brakes

Tektro Sabre rear levers

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Seatpost · Original

Aluminum

27.0mm diameter

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Rims · Original

Alex DM-24

36-hole

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Parts and service referenceQuick reference before buying parts

Archived specifications for reference. Check the fitted parts before ordering.

Front tire: Front: 20 x 2.125" Tioga Comp III, Rear: 20 x 1.75" Tioga Comp III
Drivetrain: 1-speed
Seatpost diameter: 27 mm
Bottom bracket / shell: AC Euro Sealed Bearing · 68mm English

Equipment inspection checks 9 checks based on 5 archived component groups Open equipment checksClose equipment checks

Checks selected from the archived equipment. Confirm what is fitted today. This is not a complete safety inspection; use the full inspection guide before test riding.

Full used-bike inspection guide →

Frame and fork

Inspect the frame and fork →

Archived: Frame: TIG-welded · Fork: · Carbon fiber composite w/chromoly steerer, unicrown crown

Look for dents or shape changes and inspect the edges of welds around the head tube, bottom bracket, seat cluster and suspension mounts for hairline cracks.

Drivetrain

Check drivetrain wear →

Archived: Crankset: AC Race 16 3pc, 44 teeth · Bottom bracket: AC Euro Sealed Bearing · Rear cogs: 1-speed, 16 teeth · Chain: KMC HP20NP, 1/2 x 3/32"

Check chain tension and chainline, rotate the drivetrain through a full revolution and confirm the rear axle or tensioning hardware cannot slip.
Measure chain wear with a compatible gauge and inspect chainring, cassette or freewheel teeth. A new chain does not rule out wear in the remaining drivetrain.
Turn the cranks slowly, feel for rough bearings and check for side-to-side play. Inspect crank arms, chainring bolts and pedal threads for looseness or damage.

Brakes

Inspect the brakes →

Archived: Brakes: Tektro BX-20 linear-pull rear brakes, Tektro Sabre rear levers

Inspect pads, cables and housings, then examine both rim braking surfaces for concavity, cracking or heavy wear. Confirm each caliper returns and centers correctly.

Wheels and tires

Check wheels and tires →

Archived: Wheel size: 20" wheels · Rims: Alex DM-24, 36-hole · Hubs: Aluminum · Front tire: Front: 20 x 2.125" Tioga Comp III, Rear: 20 x 1.75" Tioga Comp III

Spin both wheels and watch for side-to-side and vertical movement. Check spoke tension, rim condition and hub play.
Inspect both tire casings for cuts, cracking, plugs, bulges or exposed threads and confirm the installed sizes are safe for the rims and available frame and fork clearance.

Controls and contact points

Archived: Headset: 1 1/8" threadless aluminum · Handlebar: Chromoly BMX · Stem: Aluminum · Seatpost: Aluminum, 27.0mm diameter · Saddle: Diamondback BMX · Pedals: Aluminum

Apply the front brake and rock the bike to check for headset play or notchiness. Inspect the stem, handlebar and clamp zones, then confirm every fastener and control is secure.
Check that the seatpost moves for adjustment and that the saddle, post and clamp hold securely without cracks, severe corrosion or damaged hardware.

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Specifications are presented as a reference. Components may vary by market, size, production run, or later manufacturer revisions.

2003 Diamondback RM20