Bicycle Archive · Specification report

1999 DirtMaster Big Bertha

Velopedia Archive ID 83493

Overview

Model year	1999
Brand	DirtMaster
Model	Big Bertha
Bicycle type	Freestyle/jumping
Archive ID	83493
Original MSRP	$569.99
Colors	Black, Chrome-Plated, Red, Yellow
Sizes	Pro XL
Weight	34 lb

Frameset

Frame construction	TIG-welded
Frame material	4130 chromoly
Fork	Dirtmaster Street Fork
Fork material	4130 chromoly, unicrown crown
Rear shock	N/A

Drivetrain

Component group	N/A
Shifters	N/A
Front derailleur	N/A
Rear derailleur	N/A
Crankset	1-piece chromoly 180mm, 44 teeth
Bottom bracket	YST BB 621
BB shell width	American 24tpi
Rear cogs	1-speed, 16 teeth
Chain	KMC 410H, 1/2 x 1/8"
Pedals	Wellgo LU-313U

Brakes

Brakes	Dia-Compe 990 brakes, Dia-Compe Tech 99 levers

Cockpit & contact points

Headset	1 1/8" threadless Aheadset SE-1 F/S w/Odyssey Gyro detangler
Handlebar	Dirtmaster Hoochie
Handlebar extensions	N/A
Stem	Odyssey Bang
Saddle	Team Products embroidered
Seatpost	Primo Rod, 25.4mm diameter

Wheels & tires

Hubs	Joy Tech Jy A085SBT
Rims	Alex Supra, 48-hole
Spokes	Da-Sen stainless steel, 2.0mm straight gauge
Spoke nipples	Brass nipples
Front tire	20 x 2.25" Kenda K-841
Wheel size	20" wheels

Geometry · Legacy reference

Top tube	552.4 mm
Head-tube angle	75°
Seat-tube angle	72°
Chainstay / rear center	406.4 mm
Wheelbase	984.2 mm
Fork offset / rake	38.1 mm

Manufacturer-published archive data. Confirm exact standards and dimensions before ordering parts or performing service. Generated by Velopedia on September 30, 2026.