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Promax Disc Brake Caliper Mounting Bolts - Flat Mount M5x21mm

Promax Disc Brake Caliper Mounting Bolts - Flat Mount M5x21mm

Best price now

$3.30at Velo MineChecked 1 h ago

Compared across 20 stores. Prices are checked against each store and labelled with when.

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Price facts

  • Best price today: $3.30 at Velo Mine (checked Nov 12, 2026).
  • Checked at 20 stores.

Our take on the Promax Disc Brake Caliper Mounting Bolts - Flat Mount M5x21mm

These are Promax replacement mounting bolts for flat-mount disc brake calipers, sized M5x21mm. They are a small hardware part, not a brake upgrade: they fix a caliper to a flat-mount frame or fork. They suit riders replacing lost, stripped or corroded caliper bolts, or anyone building up a flat-mount bike who needs the correct short bolt length. Generic stainless hardware can work, but these are sold as a matched pair for the caliper mount.

Best forReplacing lost or damaged flat-mount caliper boltsBike builds and frame swaps needing M5x21mm boltsRiders servicing their own disc brakes
Pros
  • Correct M5x21mm length for flat-mount calipers
  • Promax brand part made for brake mounting
  • Simple, low-cost hardware fix
  • Small and light to keep as a spare
Cons
  • Only one thread size, so no fit for other mounts
  • No washers or threadlocker mentioned
  • Length must match your frame and caliper exactly
  • Not a performance part; no upgrade over stock bolts

Promax Disc Brake Caliper Mounting Bolts - Flat Mount M5x21mm prices at every store

  • Velo MineNew

    In stockReturn policy

    $3.30Checked 1 h ago
    Visit Velo Mine
  • Pro Bike SupplyNew

    In stock

    $3.49Checked 1 h ago
    Visit Pro Bike Supply
  • Voltaire Cycles of Central OregonNew

    In stockReturn policy

    $3.49Checked 1 h ago
    Visit Voltaire Cycles of Central Oregon
  • Stealth TahoeNew

    In stockReturn policy

    $3.49Checked 1 h ago
    Visit Stealth Tahoe
  • Lenny's Bike ShopNew

    In stockReturn policy

    $3.49Checked 1 h ago
    Visit Lenny's Bike Shop
  • 365 CyclesNew

    In stockReturn policy

    $6.44Checked 1 h ago
    Visit 365 Cycles
  • Modern BikeNew

    In stock

    $3.30+ $8.99 shippingChecked 1 h ago
    Visit Modern Bike
  • Send It BikesNew

    In stockReturn policy

    $12.50Checked 1 h ago
    Visit Send It Bikes
  • Colorado CyclistNew

    In stock

    $3.49+ $9.95 shippingChecked 1 h ago
    Visit Colorado Cyclist
  • Gio's OutdoorsNew

    In stock

    $3.49+ $15.00 shippingChecked 1 h ago
    Visit Gio's Outdoors
  • Northwest BikeNew

    In stock

    $2.97+ $17.50 shippingChecked 1 h ago
    Visit Northwest Bike
  • BikeParts.comNew

    Availability unknown

    $3.49Checked 1 h ago
    Visit BikeParts.com
  • Sierra Bicycle SupplyNew

    Availability unknown

    $3.49Checked 1 h ago
    Visit Sierra Bicycle Supply
  • Universal CyclesNew

    Availability unknown

    $3.49Checked 1 h ago
    Visit Universal Cycles
  • Trek Bicycle Stores of FloridaNew

    Availability unknown

    $3.49Checked 1 h ago
    Visit Trek Bicycle Stores of Florida
  • Newbury Park Bike ShopNew

    Availability unknown

    $3.49Checked 1 h ago
    Visit Newbury Park Bike Shop
  • The Bike House, Bike ShopNew

    Availability unknown

    $3.49Checked 1 h ago
    Visit The Bike House, Bike Shop
  • eBayNew

    Availability unknown

    $4.00Checked 1 h ago
    Visit eBay
  • luxbmx.comNew

    Availability unknown

    $11.00Checked 1 h ago
    Visit luxbmx.com
  • WalmartNew

    Availability unknownSold by 365 Cycles

    $13.02Checked 1 h ago
    Visit Walmart

Also available at

  • Pro Bike SupplyCheck price at Pro Bike Supply
  • Northwest BicycleCheck price at Northwest Bicycle
  • Colorado CyclistCheck price at Colorado Cyclist
  • Gio's OutdoorsCheck price at Gio's Outdoors

Store links may earn us a commission.

Promax Disc Brake Caliper Mounting Bolts - Flat Mount M5x21mm price history

Lowest price we've seen: $2.97 on Nov 12 at Northwest Bike. Tracked across 14 stores since Nov 12.

About the Promax Disc Brake Caliper Mounting Bolts - Flat Mount M5x21mm

Promax mounting bolts for disc brake calipers.

Thread Size

M5x21mm

Questions and answers

Will these fit my flat-mount caliper?
They fit flat-mount calipers that take M5 bolts of 21mm length. Check your frame or fork mount and caliper spec before buying, since post-mount and other setups use different bolts.
How many bolts come with it?
The listing does not state a pack count. Confirm the quantity with the seller before ordering, since a caliper mount needs two bolts.
Do I need washers or threadlocker?
Neither is mentioned as included. Most flat-mount installs use the bolts with the caliper's own mounting hardware, and a threadlocker is commonly applied at installation.
Are these stock replacements or an upgrade?
They are replacement mounting hardware, not a performance upgrade. They match the original bolt size rather than changing brake feel.
Can I use them on a post-mount brake?
No. These are M5x21mm flat-mount bolts; post-mount calipers use different bolt lengths and often different hardware.
Where is the Promax Disc Brake Caliper Mounting Bolts - Flat Mount M5x21mm cheapest?
At Velo Mine, for $3.30, as of our latest check.
Where can I buy the Promax Disc Brake Caliper Mounting Bolts - Flat Mount M5x21mm?
20 stores we checked sell it, including Pro Bike Supply, Gio's Outdoors, Colorado Cyclist, Velo Mine, Send It Bikes.

Stores we've priced the Promax Disc Brake Caliper Mounting Bolts - Flat Mount M5x21mm at

  • Sierra Bicycle Supply deals and prices
  • Walmart deals and prices

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