Bike models › BMX
Sunday Primer 20: specs, upgrades and what fits
A well-built entry freestyle BMX offered in several top-tube lengths, with sealed mid BB, a 9-tooth sealed cassette hub and an Odyssey U-brake. Best for: Beginner to intermediate street and park riding.
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My take, from the specs
A well-built entry freestyle BMX for street and park riding, with a sealed mid bottom bracket, three-piece chromoly cranks and a sealed 9-tooth cassette hub. At about 11.7 kg it is reasonably light for an entry bike, and the choice of top-tube lengths lets you match the bike to your height. The front hub is loose-ball, so check it for play and keep it adjusted.
Sizes: 20in: 4′10″–5′8″ (147–173 cm) · 20.75in: 5′5″–6′1″ (165–185 cm) · 21in: 5′11″–6′6″ (180–198 cm)
Stock specs
| Type | BMX |
|---|---|
| Year | 2027 |
| Price when new | $510 |
| Sold at | Sunday Bikes shop / BMX shops |
| Wheels | 20" × 61 mm tires |
| Gears | Single speed · 25/9 |
| Brakes | Odyssey Springfield U-brake |
| Fork | Sunday Primer, 2-piece steerer, welded preload |
| Crank | Sunday 3-piece chromoly, 165mm (160 on 20/20.5in, 170 on 21in) |
| Bottom bracket | Sunday Sealed mid, 19mm |
| Axles | Bolt-on |
| Seatpost | 25.4 mm |
| Weight | 25.8 lb (11.7 kg) |
| Sizes | 20in, 20.75in, 21in |
| Stock colors | Gloss Pine Green, Gloss Billiard Green, Matte Midnight Purple, Matte Dark Brown, Gloss Black, Matte Battleship Gray |
Upgrade limits
How far each part can go on this frame, and why. Measure your own bike to confirm the estimated ones.
| Part | Limit | Why |
|---|---|---|
| Widest tire (current wheel size) | 61 mm | Unknown until measured. Your 32 mm internal rims suit roughly 47–83 mm tires. |
| Tubeless | Not recommended | Tubeless needs a rim built to seal (bead hook + channel) and tubeless-ready tires. |
| Valve type | Schrader | Decides which tubes and pump heads fit. Presta tubes fit Schrader rims with a grommet; not the other way. |
| Replacement wheels | Bolt-on · 100/110 mm | Any wheel matching axle type, spacing and brake mount fits. Rear also needs the right freehub. |
| Brake pads (rim) | Threaded-post pads (V-brake / U-brake) | Rim brake pads are sorted by how they mount, which depends on the brake: threaded post with a nut (V-brakes, U-brakes), smooth post in an eye bolt (cantilevers), road cartridges (dual-pivot calipers) or short threaded pads (side-pull calipers). Any compound… |
| Front gears | 1x (25T) | One ring, no front derailleur. Adding a front derailleur needs a mount on the seat tube and a 2x crankset, so most riders change the ring size or cassette instead. |
| Chainring size | Unknown (now 25T) | Estimated from similar frames. Measure the chainring-to-chainstay gap to confirm. Check whether your ring is bolted or riveted. Spindle length (19 mm) sets chainline; a big change in ring size may need a different BB spindle. |
| Gear count upgrades | Single speed | One cog and no derailleur. To change the gearing, swap the sprocket or the rear driver/cog (more teeth on the cog = easier pedaling). |
| Cranks & bottom bracket | Mid BB (BMX) | Match crank spindle to BB type. |
| Pedal thread | 9/16" × 20 | Every adult multi-piece crank uses 9/16". One-piece kids/cruiser cranks use 1/2". |
| Stems & bars | 1-1/8 steerer · 22.2 mm bar clamp | Any stem for a 1-1/8 steerer with a 22.2 mm clamp fits. You can cut a bar narrower but not wider. |
| Seatposts | 25.4 mm | Buy posts in exactly this diameter. |
| Racks, fenders, bottles | No rack · No fender · 0 bottle | Threaded eyelets at the dropouts and seat stays take a rack and fenders. Fork leg mounts take cargo cages. |
| Max load (rider + cargo) | Unknown | Wheels are usually the weak point under heavy loads. Stay under this with rider plus luggage. |
Best upgrades by area
Three options that fit the Sunday Primer 20 as-is in each area, from budget to best. ★ marks the one most worth the money. How we pick. Typical US prices, checked October 2026. They change often: check the price at the store.
Upgrades that fit as-is
Brakes
- Kool-Stop Salmon V-brake pads, threaded post (2 pairs), $$. threaded post pads ↔ your rim brakes
- Shimano Deore cartridge V-brake pads (2 pairs), $$. threaded post pads ↔ your rim brakes
- Shimano S65T V-brake pads, threaded post (2 pairs), $. threaded post pads ↔ your rim brakes
- Kool-Stop threaded V-brake cartridge holders with salmon inserts (2 pairs), $$. threaded post pads ↔ your rim brakes
Control
- Race Face Chester composite flat pedals, $$. Big platform with pins. Feet stay put on bumps and in rain. Install with an 8 mm hex key (no wrench flats).
- ROCKBROS aluminum flat pedals, $$. Budget metal platform with pins. A big step up from stock plastic.
- Shimano PD-M520 SPD clipless pedals (cleats included), $$. Nearly indestructible two-sided SPD pedals. You also need SPD (2-bolt) shoes, about $60–100 more. Set the release tension low and practice unclipping before…
- Crankbrothers Stamp 2 aluminum flat pedals (small or large), $$$. Sized by shoe: small for US men's 5–10, large for 10 and up. Grease the threads and tighten to about 35 Nm.
- OneUp Components Aluminum flat pedals, $$$. Bearings and bushings can be serviced with a cheap kit instead of replacing the pedal. Grease the threads and tighten to about 35 Nm.
- Shimano PD-EH500 dual-sided SPD / flat pedals (cleats included), $$$. Comes with SM-SH56 multi-release cleats, which are easier to get out of in a panic. You still need 2-bolt SPD shoes to clip in.
- Shimano Deore XT PD-M8100 SPD pedals (cleats included), $$$. Cup-and-cone bearings are fully serviceable and last for years. Shoes with a 2-bolt SPD cleat sold separately.
- Salt Pro 2-piece BMX bars 22.2, 9" rise, $$. Made for bmx bars ↔ your bmx bar
- Cult Crew BMX bars 22.2, 9.35" or 9.65" rise (heat-treated chromoly), $$$. Made for bmx bars ↔ your bmx bar
- Odyssey Broc BMX bars 22.2, 9.8" rise (multi-butted, heat-treated chromoly), $$$. Made for bmx bars ↔ your bmx bar
Utility
- USB rechargeable front + rear light set, $$. Daytime flashing lights cut collisions. Required by law at night.
- Pletscher adjustable kickstand, $$. Handy for errands. Check it clears the rotor and chainstay.
- Lisen clamp-style handlebar phone mount, $. Cheap and tool-free for maps on paved rides. On rough gravel or trails a locking mount (Quad Lock or Peak Design, about $45–70 plus a case) is much safer.
- Topeak TopLoader top tube bag (0.75 L), $$. Keeps snacks, keys and a multi-tool within reach. Straps on, with a rain cover. Check your knees do not rub it when you stand up.
- Knog Oi Classic bell, $. Slim ring bell that wraps the bar. Large fits 23.8–31.8 mm bars; Small fits 22.2 mm kids and BMX bars. Required by law in some places.
- Planet Bike Beamer 200 + Blinky Squared USB light set, $$. USB rechargeable, tool-free mounts. Use flash mode in daylight. Rear light is 30 lumens: good for town, modest on fast roads.
- Cygolite Metro Plus 800 + Hotshot Pro 150 USB light set, $$$. Nine headlight modes including a daytime flash. Aim the beam slightly down so you do not blind oncoming riders.
- Trek (Bontrager) Ion Pro RT + Flare RT light set, $$$. Daytime-running flash modes on both lights. ANT+ lets a Garmin or Wahoo show battery and switch them. Full power runs about 1.5 hours; medium lasts much longer.
Tires
- Odyssey Path Pro 20x2.4 BMX (pair), $$. 61 mm tire ↔ your ~61 mm clearance
- Salt Tracer 20x2.35 BMX (pair), $$. 60 mm tire ↔ your ~61 mm clearance
- Cult x Vans 20x2.4 BMX (pair), $$$. 61 mm tire ↔ your ~61 mm clearance
- Kenda Small Block Eight 20x1.75 (pair), $$. 50 mm tire ↔ your ~61 mm clearance
- Schwalbe Big Apple 20x2.0 (50-406) (pair), $$$. 50 mm tire ↔ your ~61 mm clearance
- Schwalbe Marathon Plus 20x1.75 (47-406) (pair), $$$. 47 mm tire ↔ your ~61 mm clearance
Tubes
- Slime self-sealing tubes 20 x 1.75–2.3 Schrader (pair), $$. 20" wheel size matches
- Schwalbe AV7 20 x 1.5–2.4 Schrader tubes (pair), $. 20" wheel size matches · Schrader valve ↔ your Schrader rims
Drivetrain
- KMC Z410 1/8" single-speed chain (112 links), $. 1-speed chain ↔ your 1-speed drivetrain
- KMC Z1 Wide EPT 1/8" anti-rust single-speed chain, $. 1-speed chain ↔ your 1-speed drivetrain
- KMC K710 Kool Chain 1/8" (BMX / single-speed), $$. 1-speed chain ↔ your 1-speed drivetrain
Comfort
- Odyssey Keyboard v2 flangeless BMX grips, $. Made for bmx bars ↔ your bmx bar
- ODI Longneck SLX flangeless BMX grips (160 mm), $. Made for bmx bars ↔ your bmx bar
Fits with small changes (3)
- Stan's NoTubes tire sealant 16 oz, $. In tubes: needs tubes with removable valve cores (Presta or Schrader to match your rims).
- Orange Seal Endurance tubeless sealant 16 oz, $. In tubes: needs tubes with removable valve cores (Presta or Schrader to match your rims).
- SILCA Ultimate Tubeless Sealant 16 oz, $. In tubes: needs tubes with removable valve cores (Presta or Schrader to match your rims).
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Buying one used? Fair prices
Worked out from the price new ($510), age and condition, not live market data. If it needs tires, a chain or brakes, take off what fixing them would cost.
| Condition | 1 year old | 3 years old | 5 years old |
|---|---|---|---|
| Like new | $290–$380 | $235–$305 | $190–$250 |
| Good | $255–$335 | $205–$270 | $165–$220 |
| Fair | $205–$275 | $170–$220 | $135–$180 |
| Needs work | $160–$210 | $130–$170 | $105–$135 |
See what these really sold for on eBay · Other used bike prices
Geometry (size 20.75in)
| Head angle | 75° |
|---|---|
| Seat angle | 71° |
| Chainstay | 339° |
Compare with
- Hyper Bicycles Jet Fuel 20 BMX · compare frames side by side
- Mongoose Legion L20 · compare frames side by side
- Haro Downtown 20 · compare frames side by side
- Kink Curb 20" · compare frames side by side
Sources: Sunday Bikes shop: Primer Gloss Pine Green 20.75 TT specs · Sunday Bikes shop: Primer lineup + prices · Source BMX EU: Primer 2027 sizes, colors, size guide · Kunstform: Primer 2027 announcement (crank length by size)