Brake Bleeder Screw Size Chart
A brake bleeder screw size is set by the thread and length of the fitting in your caliper or wheel cylinder, and this guide lists the common metric and SAE sizes so you can match the old screw before ordering.
On this page
A brake job can go sideways over a part smaller than a fingertip: the bleeder screw. When that little valve rounds off, snaps, or will not seal, a routine fluid change turns into a caliper swap. Brake bleeder screw size is the thread diameter, thread pitch, and overall length of that valve, and matching thread, pitch, and length to the caliper or wheel cylinder is what keeps the job simple.
As an Amazon Associate I earn from qualifying purchases. GarageToolHQ earns a commission when you buy through links on our product pages, at no extra cost to you. Read our affiliate disclosure.
Below: the common metric and SAE sizes, how to read a bleeder screw size, and how to match the old screw before ordering.
Brake Bleeder Screw Size: The Common Sizes
Most bleeder screws in the kits sold for home garages fall into a small set of metric and SAE threads. The metric sizes use M7, M8, and M10 threads, and the SAE sizes use 1/4-inch, 5/16-inch, 3/8-inch, and 7/16-inch threads. A screw that matches on diameter but not on pitch will not thread in cleanly, so each number matters.
| Thread | Lengths stated |
|---|---|
| M10x1.0 | 29mm, 29.2mm, 32.1mm, 32.80mm, 35.1mm, 35.8mm |
| M10x1.5 | 29.2mm |
| M10x1.25 | 33.1mm |
| M8x1.0 | 29.7mm, 37.3mm |
| M8x1.25 | 25.1mm, 28mm, 30.2mm |
| M7x1.0 | 31.5mm |
| 1/4"-28 | 0.92" |
| 5/16"-24 | 1.01", 1.11" |
| 3/8"-24 | 1.18", 1.49" |
| 7/16"-20 | 1.37" |
| 7/16"-24 | 1.1", 1.47" |
A 54-piece kit lists 36 valves in 18 sizes, covering 11 metric and 7 SAE options, with dust caps included. Other kits hold 48 pieces in 8 sizes, 6 pieces of each size, or 36 pieces in 6 sizes, 6 pieces of each size. Some kits ship with dust caps, and some ship without caps, so check the cap count before ordering.
How to Read a Brake Bleeder Screw Size
A metric size reads as diameter, pitch, and length. M10x1.0-35.1mm means a 10 mm thread diameter, a 1.0 mm pitch, and a 35.1 mm length. The pitch is the distance between one thread and the next, so a finer pitch packs more threads along the same length.
An SAE size reads the same way in inches. 3/8"-24×1.18" means a 3/8-inch thread, 24 threads per inch, and a 1.18-inch length. The thread count after the dash is threads per inch, which is the SAE way of stating pitch.
Length is the overall length of the screw, and it matters as much as the thread: the valve must seat in the caliper bore and seal when closed. A screw that is too short may not reach the seat, and a screw that is too long may bottom out before it seals.
How to Match the Old Screw Before Ordering
The surest match is the old screw itself. Pull it, clean it, and compare it against the sizes in the chart above before ordering.
- Read the size off the old screw or match it with a thread gauge, checking diameter, pitch, and length.
- Match the thread first. A screw with the right diameter and the wrong pitch will not thread in cleanly, even when it looks right at a glance.
- Match the length. The valve has to seat and seal in the caliper, so a length far from the old screw can leave it sitting wrong.
- Check the part number. H9402-6, H9403-6, H9404-6, H9406-6, H9407-6, H9410-6, H9497-5, and 30300 cover the common replacement screws in these kits, and the part number ties a screw to the caliper or wheel cylinder it fits.
- When the old screw is too damaged to read, a multi-size kit covers the common threads: a 36-piece kit in 6 sizes, or a 48-piece kit in 8 sizes, holds the sizes most home garages meet.
The kits that state a material use iron. Kits that include a case keep each size in its own compartment in a clear partitioned box. One brass set uses 1/8"-27 threads with a 1/4"-28 bleeder screw, made for aftermarket calipers. Keep the dust cap on the new screw: the cap blocks dust and grit from the valve opening, and a cap with a connecting ring stays attached to the screw while you work.
What Comes in a Bleeder Screw Kit
A bleeder screw kit is a box of spare valves, not a bleeding tool. The valves are the wear part: the small screw that opens to let fluid and air out of the caliper and closes to seal it again. Kits that include a case hold the valves in a clear partitioned box, with each size in its own compartment, so the size you need is easy to find.
Counts run from a 4-piece set of one size, M10x1.0-32.1mm with 4 caps, up to a 90-piece assortment in 18 types. The middle ground is a 36-piece or 48-piece kit in 6 or 8 sizes. Larger kits suit a garage that works on more than one car, while a 4-piece set suits a garage that already knows the size it needs.
Use the kit with the bleeding method you already use: a kit of screws does not bleed brakes on its own. The guide to how to use a brake bleeding kit walks through the steps and adapters.
Read the manual before first use, wear eye protection, keep the work area clear and ventilated, and stay within every stated rating. Read our Safety Disclaimer.
FAQ: garage tools
What size is a brake bleeder screw?
There is no one size. Common metric sizes are M10x1.0, M10x1.5, M10x1.25, M8x1.0, M8x1.25, and M7x1.0, with lengths from 25.1mm to 37.3mm. Common SAE sizes are 1/4"-28, 5/16"-24, 3/8"-24, 7/16"-20, and 7/16"-24, with lengths from 0.92" to 1.49". Match the old screw or its part number.
Are brake bleeder screws metric or SAE?
Either one. Calipers and wheel cylinders use metric or SAE threads, and a metric screw will not fit an SAE hole. Read the old screw or its part number to find which system your caliper uses, and order in that system.
How do I know which bleeder screw fits my caliper?
Match the old screw on diameter, pitch, and length, or match its part number: H9402-6, H9403-6, H9404-6, H9406-6, H9407-6, H9410-6, H9497-5, and 30300 cover the common replacement screws. When the old screw is unreadable, a multi-size kit in 6 or 8 sizes covers the common threads.
What does M10x1.0 mean on a bleeder screw?
M10 is the thread diameter in millimeters, and 1.0 is the pitch in millimeters. The length follows after a dash, as in M10x1.0-35.1mm, which is a 35.1 mm screw. The full size is diameter, pitch, and length together.
Can I use a longer bleeder screw than the old one?
Match the stated length. A screw that is too long may bottom out before it seals, and a screw that is too short may not reach the seat. The length in the size, such as 35.1mm in M10x1.0-35.1mm, is part of the fit, not a rough guide.
Do bleeder screw kits include dust caps?
Some do and some do not. Kits marked with caps include them, and the 4-piece M10x1.0-32.1mm set includes 4 caps. A kit marked without caps ships the valves only, so check the cap count before ordering.
Related: brake bleeder tubing size, how to do a brake fluid flush, brake line size chart, and the engine and shop equipment hub.
