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 2011 GT Bump and 2008 GT Bump.
- Data limitation
Only 2011 GT Bump has enough published drivetrain data for gearing calculations.
Gearing comparison
Lower gears help on climbs. Higher gears suit higher speeds.
RPM
RPM = pedal turns per minute.
Ratio2.78:1
Estimated speed at 90 RPMGear
Rear tire: 20×2.1.
Gearing unavailable for this size.
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
2011 GT Bump
2008 GT Bump
Overview
Model Year
2011
2008
Brand
GT
GT
Model
Bump
Bump
Bicycle Type
BMX
BMX
Original MSRP
Not documented
$279.99
Colors
White, Matte Green
Off White/Orange, Navy/White
Sizes
—
One size fits all
Weight
—
—
Frameset
Frame Construction
Steel
TIG-welded
Frame Material
CroMo
GT cro-moly BMX dirt/street design
Fork
Cromo
GT BMX design
Fork Material
Steel
Chromoly, unicrown crown
Drivetrain
Component Group
BMX Mix
BMX
Crankset
CroMO 3 piece, 25t teeth
GT Tubular Cr-Mo 3pc.
Bottom Bracket
Sealed Bearing
Ball type with 8 spline Cr-Mo axle
Cassette
Cassette cog
—
Rear Cogs
9 teeth
1-speed, 12 teeth
Chain
KMC Z510
KMC Z410
Pedals
GT Dirt/Street platform
GT Dirt/Street platform
Brakes
Brakes
—
N/A front/Tektro 907A rear brakes, Tektro 274A rear levers
Cockpit & Contact Points
Headset
1 1/8" integrated
1 1/8" Tange Seiki Fatty 22
Handlebar
GT Pro Steel
GT dirt/street Cr-mo
Handlebar Extensions
Not included
Not included
Stem
GT freestyle drop
GT FS design
Saddle
Pivotal Street Design
BMX mini street
Seatpost
Pivotal, 25.4mm diameter
Aluminum micro-adjust
Wheels & Tires
Hubs
Front: GT Aluminum, Rear: GT Alloy
Front: GT aluminum sealed, Rear: GT sealed cassette
Rims
Alienation PBR, 32-hole/36-hole
36-hole
Spokes
14ga. (2.0mm)
14ga. (2.0mm)
Spoke Nipples
Brass
Brass nipples
Front Tire
20 x 2.125" Kenda K-Rad
20" Kenda K-Rad
Rear Tire
20 x 2.1" Kenda Ko-Rolla
20" Kenda Konxsion
Wheel Size
20" wheels
20" wheels
Historical specifications are presented as an archival reference. Components may have varied by market, size, or production run.