Cobra 20

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Cobra 20

The Cobra 20 is a kids mountain bike designed to grow along with your little rider. With a durable steel frame, it can handle the abuse that comes with more adventurous rides and inexperienced riders. Equipped with cool features like a suspension fork, powerful brakes, and a 6-speed drivetrain, the Cobra 20 is a great bike to start exploring beyond the confines of the neighborhood. Its big tires are suited for pavement or dirt, and touches like a rear derailleur guard mean this bike will be a reliable adventure partner for a long time to come.

Highlights

  • High tensile steel frame is super durable
  • Suspension fork soaks up bumps
  • Linear pull brakes are simple and strong
  • Shimano 6-speed drivetrain gives a wide range of gears
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Size Guide
Size Boys/20"
Seat Tube Length ** 279.0mm
Standover Height 495.0mm
Top Tube Length * 406.0mm
Head Tube Length 101.6mm
Head Angle 70.0°
Seat Angle 74.0°
Chain Stay Length 381.0mm
Fork Offset 0.0mm
BB Height 322.58mm
BB Drop 12.7mm
Stem Length 0.0mm
Handlebar Width 584.2mm
Crank Length 140.0mm
Seat Post Length 0.0mm
* Measured Horizontally ** Measured from Center
Specs
Sizes Boys/20" 
Frame DB Hi-Ten Jr Boy's 20" Mountain Frame
Fork HL Zoom 20" Suspension, 40mm Travel
Headset Threaded 1"
Cranks 140mm One-piece Steel, 40 Tooth w/ Double Guard
Bottom Bracket Square Taper - 5pc
F. Derailleur
R. Derailleur Shimano TZ-20, 6 Speed
Shifter Shimano RS25 Revo Grip Shift, 6 Speed
Cogset Shimano TZ20, 6 Speed Freewheel, 14-28T
Chain KMC Z51, 6 Speed
Brakes Alloy Linear Pull
Brake Levers Alloy Linear Pull w/ Reach Adjust
Front Hub 36h Steel Nutted
Rear Hub 36h Steel Nutted, Freewheel
Spokes 14g Steel
Rims 36h 20" R-1000 Alloy
Tires Jr ATB Knobby, 20x2.0"
Handlebar Steel Jr Riser
Grips DB Kraton
Stem Steel Quill
Seatpost Steel Pillar, 25.4mm
Seat JR ATB 2-panel
Colors Orange
Extras Owners Manual, Assembly Guide, Tool Kit*
Note Specifications Subject to Change
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Unpacking and Assembling Your Diamondback Mountain Bike (Cantilever brakes)

1

Begin by carefully opening the box. Be aware of the sharp staples that may have been used to secure the box and be mindful not to cut yourself on them. For assembly you will need: cutters/scissors; #2 Philips head screwdriver; a 4,5,6mm allen keys.

If for any reason, you do not have the proper tools or are not confident to safely assemble the bike yourself, it is recommended that you take your bike to a local bike shop for assistance or to have them assemble it. We recommend taking all bikes in for a safety check before riding. They may charge you a fee to do any of these services.

Any damage caused by improper assembly is not considered a manufacturer defect and will not be covered under warranty.

2

Once you have the bike box opened:

  1. Remove the saddle and seatpost.
  2. Remove the small parts box.
  3. Remove the bike.

Before proceeding, be sure that all parts and material are now removed from the box.

  • 2aRemove the saddle and seatpost
  • 2bRemove the small parts box
  • 2cRemove the bike
  • 2cRemove the bike
3

Now that your bike is out of the box:

  1. Begin by detaching the wheel and removing all of the packing material from the frame
  2. Unpack the handlebar by cutting all zipties/ removing any packaging that may be holding parts together.
  • 3aBegin by detaching the wheel and removing all of the packing material from the frame
  • 3aBegin by detaching the wheel and removing all of the packing material from the frame
  • 3aBegin by detaching the wheel and removing all of the packing material from the frame
  • 3aBegin by detaching the wheel and removing all of the packing material from the frame
  • 3bUnpack the handlebar by cutting all zipties and removing any packaging that may be holding parts together
  • 3bUnpack the handlebar by cutting all zipties and removing any packaging that may be holding parts together
4

Install seat post to frame:

  1. Loosen the seat clamp
  2. Insert the seatpost into the seat tube. If you have bike grease you can apply a small amount to the seatpost before inserting it. Make sure that you have inserted the post past the minimum insertion/maximum extension line (printed on post near bottom).
  3. Finish by either clamping down the quick release lever or using a hex wrench to tighten (depending on which style you have). QR Seatpost clamp should have some resistance when closing, but not so much that it takes a lot of force to get it to the closed position. DO NOT OVERTIGHTEN.
  4. When the bike is fully assembled you will then be able to fine tune the saddle adjustment based on your height. Refer to the Saddle Position section on page 12 in the DB Owner’s Manual for guidance.
  • 4aLoosen the seat clamp
  • 4aLoosen the seat clamp
  • 4bInsert the seatpost into the seat tube
  • 4cFinish by either clamping down the quick release lever or using a hex wrench to tighten
  • 4cFinish by either clamping down the quick release lever or using a hex wrench to tighten
  • 4cFinish by either clamping down the quick release lever or using a hex wrench to tighten
5

Position your bike in a comfortable working position. If you have a bike stand, that’s your best bet.

  • Position your bike in a comfortable working position
6

It’s now time to install your handlebar to the stem.

  1. Do so by removing the stem bolts and faceplate,
  2. Place the bar in the stem. Be sure that your cable routing is suitable and that there are no harsh bends or kinks in the cable. When the handlebars are in the stem the right hand side should control the rear brake and rear derailleur while the left hand side should control the front brake and front derailleur.
  3. Loosely re-secure the faceplate to the stem.
  • 6aInstall handlebar to stem by first removing the stem bolts and faceplate
  • 6aInstall handlebar to stem by first removing the stem bolts and faceplate
  • 6bPlace the bar in the stem, making sure that your cable routing is suitable
  • 6bPlace the bar in the stem, making sure that your cable routing is suitable
7

Once the handlebar is loosely placed in the stem, make sure that it is positioned symmetrically before tightening the faceplate bolts. When tightening the bolts, tighten them alternately and equally to ensure that the faceplate is equally tight on every side. The gap opening between the faceplate and the stem should be equal both on the top and on the bottom. Use an “X” pattern when tightening the bolts.
NOTE: stem bolts are typically tightened to 4nm.

  • Once the handlebar is loosely placed in the stem, make sure that it is positioned symmetrically before tightening the faceplate bolts
  • Once the handlebar is loosely placed in the stem, make sure that it is positioned symmetrically before tightening the faceplate bolts
  • Once the handlebar is loosely placed in the stem, make sure that it is positioned symmetrically before tightening the faceplate bolts

Some bikes may arrive without a front/rear brake cable installed. Use the following steps if this applies to your bike.

8

To connect linear pull brakes, set adjusting barrel at the lever so slots line up with slot opening in lever.

  • To connect linear pull brakes, set adjusting barrel at the lever so slots line up with slot opening in lever
  • To connect linear pull brakes, set adjusting barrel at the lever so slots line up with slot opening in lever
9

For the rear brake, you’ll need to release tension on the cable. Start by squeezing the brake arms together in order to release the cable noodle. Next take the the other end of the rear cable and begin connecting to brake lever (the right hand side lever when sitting on the bike). Pull the brake lever to the grip exposing the juncture where the cable enters the lever. Insert the round cable narp (cable end) into lever and guide cable through the designated cable slot on handle. Then place end of cable housing into barrel adjuster. Turn the barrel adjuster so that slots no longer line up with lever slot.

  • Squeeze the brake arms together in order to release the cable noodle
  • Squeeze the brake arms together in order to release the cable noodle
  • Squeeze the brake arms together in order to release the cable noodle
  • Take the the other end of the rear cable and begin connecting to brake lever
  • Take the the other end of the rear cable and begin connecting to brake lever
  • Take the the other end of the rear cable and begin connecting to brake lever
  • Insert the round cable narp into lever and guide cable through the designated cable slot on handle
  • Insert the round cable narp into lever and guide cable through the designated cable slot on handle
10

Your brake pads may need adjusting once brake is assembled. Release the spring from brake lever arm. Next, grasp brake pad with one hand and loosen brake pad bolt. Align pad to be parallel with rim surface and retighten brake bolt. You do not want the brake pad to come into contact with the tire. Check to make sure pad is hitting squarely in center of rim braking surface. Reconnect the lever spring prior to reconnecting the rear brake cable noodle.

  • Your brake pads may need adjusting once brake is assembled
  • Your brake pads may need adjusting once brake is assembled
  • Your brake pads may need adjusting once brake is assembled
  • Your brake pads may need adjusting once brake is assembled
11

To reconnect the rear brake pull on the aluminum cable noodle in one hand while hooking the lower end of the noodle into the slotted link on the brake arm. If it is too difficult to connect the noodle you have to release a little cable tension by loosening the cable anchor bolt and giving the cable a little more slack. Make sure to re-tighten the anchor bolt.

  • To reconnect the rear brake pull on the aluminum cable noodle in one hand while hooking the lower end of the noodle into the slotted link on the brake arm
  • To reconnect the rear brake pull on the aluminum cable noodle in one hand while hooking the lower end of the noodle into the slotted link on the brake arm
  • To reconnect the rear brake pull on the aluminum cable noodle in one hand while hooking the lower end of the noodle into the slotted link on the brake arm
12

If the cable tension needs to be increased for better braking, loosen the cable anchor bolt. Remove excess cable slack and re-tighten the cable anchor bolt.

  • If the cable tension needs to be increased for better braking, loosen the cable anchor bolt
  • If the cable tension needs to be increased for better braking, loosen the cable anchor bolt
  • If the cable tension needs to be increased for better braking, loosen the cable anchor bolt
13

The front brake is set up exactly like the rear. First release the cable noodle from the brake levers by squeezing lever arms together.

  • The front brake is set up exactly like the rear
  • The front brake is set up exactly like the rear
  • The front brake is set up exactly like the rear
14

Lineup barrel adjustor slots with the slot in the front brake lever (the left hand side lever when sitting on the bike). Pull lever to expose juncture where cable connects to lever. Insert the round cable narp (cable end) into lever and guide cable through the designated cable slot on handle. Then place end of cable housing into barrel adjuster. Turn the barrel adjuster so that slots no longer line up with lever slot.

  • Lineup barrel adjustor slots with the slot in the front brake lever
  • Pull lever to expose juncture where cable connects to lever
  • Insert the round cable narp into lever and guide cable through the designated cable slot on handle
  • Then place end of cable housing into barrel adjuster
  • Then place end of cable housing into barrel adjuster
  • Then place end of cable housing into barrel adjuster
  • Then place end of cable housing into barrel adjuster
15

Your brake pads will need adjusting following the installation of the front wheel (next step). Prior to placing wheel in fork, pre-adjust pads for when you are ready to correctly adjust.

Note:

For wheel removal: the noodle may be unhooked from the arm link. This will allow the brake to open up wide enough to clear a wider width tire. First, pull the boot away from the end of the noodle. Then squeeze the brake arms together with one hand while unhooking the lower end of the noodle from the keyhole-shaped slot in the arm link.

  • Prior to placing wheel in fork, pre-adjust pads for when you are ready to correctly adjust
  • Prior to placing wheel in fork, pre-adjust pads for when you are ready to correctly adjust
16

Now it’s time to get your front wheel ready for installation. Start by pulling the plastic protective caps off of the axle. Please note that some hubs have little spacers which are pressed loosely onto the axle. Be sure not to throw these spacers away with the safety caps.

  • Get your front wheel ready for installation by pulling the plastic protective caps off of the axle
  • Get your front wheel ready for installation by pulling the plastic protective caps off of the axle
  • Get your front wheel ready for installation by pulling the plastic protective caps off of the axle
17

Now install the skewer through the axle of the front wheel. Remove the non-lever side of skewer as well as one spring and proceed to insert the skewer through front wheel axle. Put the spring back on the skewer and thread the skewer nut back on a few turns. Please note the correct positioning of the springs on the skewer when mounting (smaller part of the spring points in towards hub and spokes).

  • Now install the skewer through the axle of the front wheel
  • Remove the non-lever side of skewer as well as one spring and proceed to insert the skewer through front wheel axle
  • Remove the non-lever side of skewer as well as one spring and proceed to insert the skewer through front wheel axle
  • Remove the non-lever side of skewer as well as one spring and proceed to insert the skewer through front wheel axle
  • Put the spring back on the skewer and thread the skewer nut back on a few turns
  • Put the spring back on the skewer and thread the skewer nut back on a few turns
  • Put the spring back on the skewer and thread the skewer nut back on a few turns
18

You can now mount the front wheel on the fork. Make sure that the fork is pointing in the correct direction (the brake should be at the front of the fork, not behind it). Note that the quick release lever should be on the non-drive side of the bike (the left hand side when you’re sitting on the bike). Make sure the wheel is centered in fork.

  • You can now mount the front wheel on the fork
  • You can now mount the front wheel on the fork
  • You can now mount the front wheel on the fork
19

Next tighten the skewer nut until it touches the fork lightly. Then start to close the skewer lever. Once tightened, make sure that the QR lever is tucked up to avoid snags. The QR lever should close with some resistance, but not too much so that it is hard to close or open.

  • Tighten the skewer nut until it touches the fork lightly
  • Start to close the skewer lever
  • Once tightened, make sure that the QR lever is tucked up to avoid snags
  • The QR lever should close with some resistance, but not too much so that it is hard to close or open
20

Now it’s time to adjust the front brakes. Release the spring from brake lever arm. Next, grasp brake pad with one hand and loosen brake pad bolt. Align pad to be parallel with rim surface and retighten brake bolt. You do not want the pad to come into contact with the tire. Check to make sure pad is hitting squarely in center of rim braking surface.

  • Release the spring from brake lever arm
  • Grasp brake pad with one hand and loosen brake pad bolt
  • Grasp brake pad with one hand and loosen brake pad bolt
  • Align pad to be parallel with rim surface and retighten brake bolt
  • Align pad to be parallel with rim surface and retighten brake bolt
21

Reconnect the lever spring prior to reconnecting the front brake cable noodle.

  • Reconnect the lever spring prior to reconnecting the front brake cable noodle
  • Reconnect the lever spring prior to reconnecting the front brake cable noodle
  • Reconnect the lever spring prior to reconnecting the front brake cable noodle
  • Reconnect the lever spring prior to reconnecting the front brake cable noodle
  • Reconnect the lever spring prior to reconnecting the front brake cable noodle
22

If the front or rear brake pads are not hitting the braking surface of the rim evenly – one pad is hitting the rim braking surface before the other – use the cantilever spring tension screws to adjust. For example, if the left brake pad is hitting the rim brake-surface sooner than that of the brake pad on the right, give the spring tension adjustment screw on the right side lever a turn or two to increase spring tension.

  • If the front or rear brake pads are not hitting the braking surface of the rim evenly, one pad is hitting the rim braking surface before the other
  • If the front or rear brake pads are not hitting the braking surface of the rim evenly, one pad is hitting the rim braking surface before the other
23

For pedal installation, your pedals will show what side they are meant to go on with an “L” or “R” on the end of the spindle or axle (depending on the pedal). We recommend applying a small amount of grease to each pedals thread before installing.

  • For pedal installation, your pedals will show what side they are meant to go on
  • We recommend applying a small amount of grease to each pedals thread before installing
  • We recommend applying a small amount of grease to each pedals thread before installing
24

Start by hand threading in the left (when seated on the bike), non-drive side pedal. The left pedal will be indicated by an L on either the spindle or the axle (depending on the pedal). Tighten by turning your 15mm to the left. (counter-clockwise)

  • Start by hand threading in the left, non-drive side pedal
  • Start by hand threading in the left, non-drive side pedal
  • Start by hand threading in the left, non-drive side pedal
  • Tighten by turning your 15mm to the left
25

Take the right pedal (this should be indicated by an R on the pedal which can be seen on the end of the spindle or on the axle depending on the pedal) and thread into the drive side crank arm (right side when facing forward on bike). Tighten by turning your 15mm pedal wrench to the right. (clockwise)

Do not force a pedal that will not thread on easily or you can cross thread the crank arm which will result in a damaged product. Damage caused by improper pedal installation will not be covered under warranty.

  • Take the right pedal and thread into the drive side crank arm
  • Take the right pedal and thread into the drive side crank arm
  • Take the right pedal and thread into the drive side crank arm
  • Tighten by turning your 15mm pedal wrench to the right
26

Now it is time to make sure the front and rear derailleurs are set properly. While pedaling bike, shift rear derailleur to lowest gear (largest cog) in the rear.

  • Make sure the front and rear derailleurs are set properly
27

Make sure that low adjustment screw (“L” stamped on derailleur) is set so to ensure it hits the stop and the derailleur cannot shift past the lowest gear and into the spokes of the rear wheel.

  1. Incorrect Chain line
  2. Correct chain line
  • Make sure that low adjustment screw is set so to ensure it hits the stop
  • 27aIncorrect Chain line
  • 27bCorrect chain line
28
  1. Incorrect Chain Line
  2. Correct Chain Line

For proper rear derailleur alignment and adjustment, please refer to the manufacturer’s instructions for your specific derailleur model. Shimano the derailleur jockey wheel should line up directly below smallest cog. On SRAM, the jockey wheel should line up just to the right of the smallest cog

Parktool Rear Derailleur

  • For proper rear derailleur alignment and adjustment, please refer to the manufacturer instructions for your specific derailleur model
29

Now it’s time to make sure the rear derailleur will shift appropriately up and down the rear cog set. Proper shifting is all related to cable tension. Begin by pedaling bike with the chain in the highest gear (smallest cog). Each “click” of the shifter lever should correspond to the chain moving up the gear one cog at a time. To adjust the cable’s tension, use the adjusting barrel at the derailleur/or at the shifter to tune the shifting. If the chain shifts past the desired gear, the cable tension is too high. Turn the adjusting barrel clockwise to ease cable tension. If chain is not shifting to desired gear, turn adjusting barrel counterclockwise to increase tension on cable until chain shifts to desired gear.

Parktool Rear Derailleur

  • Make sure the rear derailleur will shift appropriately up and down the rear cog set
  • Make sure the rear derailleur will shift appropriately up and down the rear cog set
  • Make sure the rear derailleur will shift appropriately up and down the rear cog set
  • Make sure the rear derailleur will shift appropriately up and down the rear cog set
  • Make sure the rear derailleur will shift appropriately up and down the rear cog set
30

Next, adjust the front derailleur. Check to make sure front derailleur height and alignment is correct.

  1. Set derailleur angle so outside plate lines up with large chain ring. Make sure that the chain is sitting on the smallest chainring (if there are only two) or the middle chainring (if there are three).
  2. Check height of derailleur using guide sticker on derailleur. If there is not a guide sticker, the outside front derailleur plate should sit about 2mm above larger chain ring on crank.
31

Now it’s time to set front derailleur adjustment screws. To start this step, shift the rear derailleur so that the bike is in its lowest gear (largest cog) in the back. Make sure the front derailleur is set so that the chain is in the lowest gear (smallest chainring) in the front.

  1. Check the distance of chain to inner plate of front derailleur
  2. Set front Low set screw so that inner plate is approx. 1-2mm from chain. (“L” stamped on Derailleur)
  • Set front derailleur adjustment screws
32

Next, shift the rear derailleur so that the bike is in its highest gear (smallest cog) in the rear and the shift the front derailleur so the chain is in the highest gear (largest chainring).

  1. Check the distance of chain to outer plate of front derailleur
  2. Set the High limit Screw so that the outer Front Derailleur plate is approximately 1-2mm from chain. (“H” stamped on Derailleur)

HELPFUL LINK:

Parktool Front Derailleur

As a last step, shift through the rear gears starting out in the smaller chain ring on the cranks and then in the larger to make sure that the shifting runs smoothly.

  • Shift the rear derailleur so that the bike is in its highest gear in the rear and the shift the front derailleur so the chain is in the highest gear
  • 32aCheck the distance of chain to outer plate of front derailleur
  • 32bSet the High limit Screw so that the outer Front Derailleur plate is approximately 1-2mm from chain
33

Align your bars to the front wheel.

  • Align your bars to the front wheel
34

Tighten stem cap bolt.

  • Tighten stem cap bolt
35

While the handlebars are still aligned with the front wheel tighten stem bolts. Most stems have a 4nm maximum torque setting.

  • While the handlebars are still aligned with the front wheel tighten stem bolts
  • While the handlebars are still aligned with the front wheel tighten stem bolts
36

Inflate your tires. Each tire will have a recommended air pressure (measured in PSI) on the sidewall. Please follow the recommended inflation setting.

  1. Take off valve cap
  2. Pump up tire to recommended tire pressure.
  • Take off valve cap
  • Pump up tire to recommended tire pressure
37

The final step is to go through the entire bike one more time to make sure that:

-every bolt is tight

-your wheels are secured in place

-your front and rear brakes are functioning properly, that the handle bars are tight and don’t move when you hold the front wheel between your legs and twist them, and that your suspension has been adjusted to the proper recommended settings.

If, for any reason, you do not have the proper tools or are not confident to safely assemble the bike yourself it is recommended that you take your bike to a local bike shop for assistance or to have them assemble it. We highly recommend taking any bike to a local bike shop for a safety check and regular tune ups. The bike shop may charge a fee to do any work on your bike.

Please note: Any damaged caused by improper assembly is not considered a manufacturer defect and will not be covered under warranty.

Make sure to register your bike by simply filling out form found in the back of your owner’s manual and mail it in, OR you can register your bike online at Diamondback’s webpage: here for Diamondback.

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