Velopedia Bicycle Archive
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Compare published geometry, gearing and specifications for up to three bicycles.
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1 of 2 bicycles
At a glance
Key differences
Supported differences are shown below. Data limitations are labeled separately.
- Data limitation
No geometry is recorded for 2001 GT Thumper and 2004 GT Thumper.
- Identity & price
2004 GT Thumper had an original MSRP $250 lower than 2001 GT Thumper.
Original MSRP is the published list price when new, not today’s used-bike value.
Gearing comparison
Lower gears help on climbs. Higher gears suit higher speeds.
RPM
RPM = pedal turns per minute.
Ratio2.75:1
Estimated speed at 90 RPMGear
Uses front tire 20×2.1; rear size isn’t listed.
Ratio2.79:1
Estimated speed at 90 RPMGear
Rear tire: 20×2.1.
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.
Complete specification tableShows different published values and gaps where a bicycle lacks data. Different wording reflects source language, not necessarily different components. Swipe for more columns.
Specification
2001 GT Thumper
2004 GT Thumper
Overview
Model Year
2001
2004
Brand
GT
GT
Model
Thumper
Thumper
Bicycle Type
Freestyle/jumping
Freestyle/jumping
Original MSRP
$549.99
$299.99
Colors
Martian Green, Starlight Blue
Blue
Sizes
Pro
One
Weight
—
—
Frameset
Frame Construction
TIG-welded
TIG-welded
Frame Material
Chromoly
Chromoly
Fork
GT
GT
Fork Material
Chromoly, unicrown crown
Chromoly, unicrown crown
Drivetrain
Crankset
GT 3-piece chromoly, 44 teeth
GT 3-piece chromoly, 39 teeth
Bottom Bracket
Sealed cartridge
—
BB Shell Width
—
American
Rear Cogs
1-speed, 16 teeth
1-speed, 14 teeth
Chain
KMC, 1/2 x 1/8"
KMC Z510H, 1/2 x 3/16"
Pedals
GT aluminum platform
GT BMX Design Aluminum
Brakes
Brakes
Tektro FX-20 U brake rear brakes, Tektro 270-AX rear levers
Tektro FX-11 U-brake rear brakes, Tektro 273A rear levers
Cockpit & Contact Points
Headset
1 1/8" threadless Tange Seiki STE
1 1/8" threadless Tien Hsin w/SST Oryg
Handlebar
GT F.U.B.a.R.
GT BMX
Handlebar Extensions
Not included
—
Stem
GT Johnson
GT Piston
Saddle
GT
GT Launch Pad
Seatpost
GT aluminum micro-adjust
Steel micro-adjust
Wheels & Tires
Hubs
GT Mohawk
Aluminum, 14mm axle
Rims
Alex AL-MX22, 48-hole
Alex DX-2418, 36-hole
Spokes
14g
Stainless steel, 14ga. (2.0mm) straight gauge
Spoke Nipples
Brass nipples
Brass nipples
Front Tire
20 X 2.10" GT LP-III
20 x 2.20" GT 1453
Rear Tire
—
20 x 2.10" GT LP-4
Wheel Size
20" wheels
20" wheels
Historical specifications are presented as an archival reference. Components may have varied by market, size, or production run.