Critical Cycles - Harper Single-Speed / Fixie Matte Black / 43cm / xs, Critical Cycles - 3

Harper Single-Speed / Fixie

$ 329.99 $ 199.99
Matte Black
Sage Green
Graphite and Orange
White and Black
Sky Blue
Suggested Height:
4'9" - 5'2"
Suggested Height:
5'2" - 5'6"
Suggested Height:
5'6" - 5'9"
Suggested Height:
5'9" - 6'0"
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The Harper single-speed fixed-gear is the next generation of commuter bike. It’s built around a tig-welded steel frame and fork and top shelf componentry and is equipped with front and rear brakes. The hand-built track frame has bar-spin clearance, a flat top tube, no toe overlap, and horizontal dropouts. This is a bike designed for you and your city street adventures.



The Harper Single-Speed / Fixed-Gear comes standard with a flip-flop hub. This means you can choose how you ride, whether it’s single-speed with a freewheel or fixed gear. The Harper SS comes with the freewheel single-speed side installed. A freewheel allows you to cruise without pedaling, as you would on a traditional bicycle.

You can also ride fixed with an easy switcheroo. All you need to do is remove the rear wheel, flip it around, and then remount it. With a fixed cog, the movements of your bike directly correlate to your pedaling. The faster and harder you ride, the faster and harder you’ll go. The motion of the rear wheel relies on the motion of your feet. But remember, riding fixed is a choice you can make or reject.


A single-speed / fixed-gear bicycle is simple, lightweight, and requires almost no maintenance. There are fewer parts that make up this kind of bike, which means there are fewer parts to potentially damage. Riding fixed is also an efficient workout because you’re always in motion and, therefore, always exercising. When you ride fixed, you are most at one with your bicycle. It doesn’t move unless you move with it. One of the best parts about having a flip-flop hub on a bike is that you can choose which way you want to ride anytime. Riding fixed is a choice you can always say no to.


Riser handlebars encourage a relaxed, upright riding position. This posture is more comfortable and ultimately better for your back.


The Harper single-speed / fixie is designed for longevity. The high-tensile strength steel diamond frame is hand-built and tig-welded for the commuter’s lifestyle. Rest assured you’ll be riding on your Critical Cycles frame for a long, long time.


Your safety is very important to us. We’ve equipped the Harper SS with dual braking. You’ll have more control over your commute and your stopping with a front and a rear braking system. The rims have machined braking surfaces for safer stopping.


We wouldn’t say we’re control freaks exactly, but we do like to be in control of our rides. That’s why we put so much effort into making every part of our bikes the best it can be. VP freestyle pedals and KMC chain are long-lasting and hard-wearing while the 30mm Deep-V rims and thick, stable Wanda tires make for a softer ride.


*All of our bikes have a weight limit of 220 lbs.
Hand-built steel track frame
Bar spin clearance & no toe overlap
Horizontal drop-outs
30mm Super Deep-V Double Wall Rims with Braking Surface
Flip Flop Hub with Single-Speed 16T Freewheel & Fixed-Gear 16T Cog
Wanda City Tires 700x23C
KMC 1/8”
1 1/8" Threaded
Promax Alloy 25.4mm clamp size diameter
25.4mm Riser Handlebars
Kraton Rubber Track Grips
Front & Rear Promax Brakes with 22.2mm brake lever clamp diameter
Bottom Bracket
NECO 68x110 Cartridge Sealed
9/16” Plastic Pedals
Critical Cycles Pista Saddle
All the tools you need to build and maintain your own bicycle including three metric Allen wrenches and a flat wrench.


What we give you: 3 Allen Wrenches (4mm, 5mm, & 6mm), a 10-function multi-tool

What you need: Scissors, Phillips Screwdriver, 15mm wrench or crescent wrench.



1 – Cut the white shipping straps on the outside of the box.

2 – Remove the box staples as these are sharp and can cut you as you access the bike.

Open up the cardboard flaps, affectionately eye your new bike, and lift it out of its box.

3 – Rotate the fork so that it is facing forward of the bike. Place the bike on the ground, so it’s standing upright on the fork dropouts and rear tire.

4 – Cut all of the zip ties.

5 – Separate the loose front wheel from the bike by carefully slipping it away from the crank arm, which is resting within the spokes.

6 – Remove the accessory box and set it aside.

7 – Examine your new bike for any visible damage that may have occurred during shipping and make sure you have all of its bits and pieces.

8 – Special Note: For tightening all fasteners, please refer to Appendix D in the back of your owner’s manual for all fastener torque specifications.



1 – Remove the plastic shipping plug from the top of the seat tube.

2 – Use the included Allen wrench to loosen the seat clamp at the top of the frame.

3 – RECOMMENDED; Apply a thin layer of grease to either the end of the seat post or inside the seat tube

4 – Insert the seat with the seat post into the seat tube of the frame to at least the minimum insertion line on the shaft of the seat post.

NOTE: The minimum insertion line must NOT show above the seat tube.

5 – Using the Allen wrench, tighten the seat clamp once it is at the correct height.

NOTE: This is how you will adjust the height of the seat as needed in the future.


WARNING! Using the bike with the minimum insertion line on the lower portion of the seat post showing above the frame could result in a failure of the seat post and/or the frame causing a loss of control with potential injury to rider. Such failures are not covered by warranty as it is improper use of the product.



1 – Loosen the stem bolt at the top of the stem, remove the plastic packing cap from the bottom of the stem.

RECOMMENDED: Apply a thin layer of grease to the end of the stem shaft by the wedge.

2 – Untwist the handlebars and control cables and insert the quill end of the stem into the fork steer tube. You may have to loosen the bolt and wedge a small amount to allow the quill to fit into the steer tube.

3 – Make sure that the fork is facing forward and the handlebars are lined up with the fork dropouts.

4 – Adjust the height of the stem to your desired level and tighten the stem bolt using a 6mm wrench. NOTE: Be sure that the minimum insertion mark on the shaft of the stem is inside the frame, it must not be visible outside of the frame.


Installing the stem with the minimum insertion mark showing outside of the frame could create a dangerous condition allowing the stem to break causing the rider to lose control resulting in serious injuries to the rider.



1 – Flip the bike over so it’s resting on the saddle and handlebars.

2 – Remove the small black plastic protector from the fork dropouts.

3 – Loosen the axle nuts on the front unattached wheel.

4 – Place the front wheel into the fork dropouts and insert the safety washers into the small holes on either side of the wheel on the outside of the fork.

5 – Begin tightening the axle nuts on each side of the wheel by hand.

6 – Inspect the wheel to make sure it is centered in the fork. To do this, stand the bike up on its wheels and check to see that the axle is fully in the drop out. Then tighten each axle nut with the wrench, alternating between sides, until each axle nut is properly tightened.

7 – Now, turn your attention to the back wheel and make sure it is also centered within the frame. Adjust as needed.

8 – Be sure to tighten the cog and the lock-ring on the fixed side of the wheel. You will need a chain whip and lock-ring tool to do so. We HIGHLY recommend visiting a bike shop in order to have professional bike mechanic do this for you.



1 – Locate the pedal labeled “R” on the spindle. This is your RIGHT pedal.

2 – RECOMMENDED; Apply some grease to the threads of the crank and then insert your right pedal into the right side crank arm (the side with the chain) and thread it clockwise. You should be able to thread this with ease. If it seems difficult, stop, realign the pedal threads and try again.

3 – Tighten the pedal with a 15mm or adjustable wrench until the pedal is securely attached to the crank arm.

4 – Locate the pedal labeled “L” (this is your LEFT pedal), apply some grease to the left crank, and insert your left pedal into the left side crank arm.

5 – Thread it counterclockwise and tighten with a 15mm or adjustable wrench.

NOTE: Be sure to tighten both pedals with an adjustable wrench or 15mm open end wrench to the recommended torque specification otherwise they will unscrew while riding causing an unsafe condition for the rider and damaging the threads in the crank.



We HIGHLY recommend taking your bike to a local bike shop to have your brakes set up by a professional mechanic.


If you decide to attempt to adjust the brakes yourself:

1 – Be sure that the brake pads are aligned with the curve of the rim and that they contact the rim surface flat and evenly. The brake shoe angle and height can be adjusted by loosening the Allen bolt attaching the brake shoe to the brake arm. Notice that the brake shoe can articulate a certain amount up and down and side to side.

2 – Loosen the brake cable anchor at the brake arm held by an Allen bolt allowing the brake cable to freely glide through its anchor.

3 – Depending on how the factory attached the cable, you may have to pull out the brake cable core from the housing and feed it through the brake lever anchor point, then back through the cable housing and the anchor on the brake arm. If the cable is already attached to the brake lever, proceed to step 4.

4 – Squeeze the brake arms together until the brake shoes contact the rim surface. Be sure that the black release lever at the brake arm anchor is in the down position. Pull the cable taught through its anchor and tighten the cable anchor bolt.

5 – Squeeze the brake lever hard several times to take the stretch out of the cable and make sure that it does not slip through its anchor. If the cable tension is too tight to allow the brake shoes to retract and clear the rim surface, loosen the anchor bolt and give the cable some slack. If the cable has too much slack and you cannot apply enough stopping force to the rim, repeat procedure “4” to take the slack out of the cable.



1 – Attach the plastic brackets to the handlebar and seat post.

2 – Slide the reflectors onto the brackets (white in the front, red in the back).

3 – Attach the wheel reflectors onto the spokes of the wheels (If not already installed at the factory).


FLIP-FLOP HUB - Switching between the fixed cog and the freewheel cog

1 – Loosen the nut on the rear wheel chain tensioner until it is loose enough to swing out of the way of the frame dropout.

2 – Loosen the axle nuts.

4 – Push the wheel towards the front of the bike to loosen the chain and slip the chain off of the cog.

5 – Remove the rear wheel, remove the axle nuts and washers, switch the chain tensioner to the opposite side of the axle and replace the axle washers and nuts.

6 – Flip the wheel around and place it back into the frame.

7 – Replace the chain on the cog.

8 – Pull the tire back slightly so the chain is taut and tighten the nut on the end of the chain tensioner to adjust chain tension. Do not over tighten the chain. There should be approximately ¼” of chain slack up and down when properly adjusted.

9 – While holding the wheel centered in the frame, tighten the axle nuts a little at a time alternating between each one until the axle nuts a tight holding the rear wheel securely in the frame.



  • Locate the tire manufacturer’s recommended inflation pressure found on the tire sidewall (listed as “PSI”).
  • Using a hand or floor pump with a gauge, begin to inflate the tire to half its recommended inflation pressure and check to see that the tire is properly seated on the rim. Be sure to inspect both sides of the tire for proper fit.
  • If the tire is seated unevenly or bulges out along the rim, let some air out of the tire and reposition the tire by hand so that it sits evenly on the rim.
  • Continue to inflate the tire to the manufacturer’s recommended pressure.
  • Do not exceed the recommended pressure as this will cause an unsafe condition potentially causing the tire to unexpectedly explode.
  • Do not use a compressed air device to inflate your tires as the rapid inflation of the tire can cause it to blow off the rim.
  • Tires and tubes are not warranted against damage caused by over-inflation or punctures from road hazards.


We strongly recommend you take your bike to a professional bike shop and have them check your work and fine tune the bike to ensure your bike is safe to ride.


Shipping on all orders over $65 heading anywhere within the contiguous U.S. is free. Shipping on orders under $65 will cost a flat rate of $7.98. You can also choose to have signature required when your products are delivered for an additional $5.98.

We try really hard to ship all orders within 1 business day, but sometimes we're backed up. Most orders will go out within 3 business. Your order will be delivered within 1-5 business days.

We ship most of our orders out through FedEx. Keep this in mind when you're choosing a shipping method. If you don't request a signature and you're not home when FedEx arrives, it is left up to the driver's discretion to leave the package or not. Sometimes we send smaller orders out through USPS.

Check out more information about our shipping policies here.

Returns Policy

Great news! We offer a 50 day return policy! Returns are accepted for the full product credit if received at our warehouse within 50 days of the date of purchase in the original packaging that is still in retail condition.

Please bear in mind that our refunds do not include reimbursement of shipping fees.

Check out more information regarding our return policy here.

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