Technical Reference Guides
Essential charts and standards for identifying and sourcing the correct parts for your vintage bicycle project.
Common Compatibility "Gotchas"
1. The French Connection
Peugeot, Motobecane, Gitane
Older French bikes used metric threading (35mm x 1mm) for bottom brackets and 25.0mm for seatposts. Standard English parts (1.37" x 24 TPI) will feel like they fit for the first few turns before stripping the threads.
Watch for: Left-hand threaded fixed cups on both sides.
2. Raleigh's 26 TPI Proprietary
Pre-1977 Nottingham Raleighs
Most of the world used 24 threads-per-inch (TPI). Raleigh used 26 TPI for their bottom brackets and headsets. A standard 24 TPI cup will physically not thread into a 26 TPI shell.
Solution: Source original Raleigh parts or use a threadless BB.
3. The Schwinn Ashtabula
Varsity, Continental, Suburban
American-made Schwinns used a heavy, one-piece "Ashtabula" crank. The bottom bracket shell is unthreaded and much larger than a standard BB.
Tip: Use an "American to Euro" adapter to run modern 3-piece cranks.
4. Hub Spacing (O.L.D.)
120mm vs 126mm vs 130mm
As the number of gears increased, so did the width of the rear hub. 5-speed bikes are 120mm, 6/7-speed are 126mm, and 8+ speed are 130mm.
Note: Steel frames can often be "cold set" (stretched) to fit wider hubs.
Bottom Bracket Threading Standards
| Standard | Thread Type | Shell Width | Commonly Found On |
|---|---|---|---|
| British (ISO/BSC) | 1.37" x 24 TPI | 68mm / 73mm | Most modern bikes, Raleigh (post-1970s), Japanese bikes. |
| Italian | 36mm x 24 TPI | 70mm | Classic Italian road bikes (Campagnolo). |
| French | 35mm x 1 TPI | 68mm | Older French bicycles (Peugeot, Motobecane). |
| Schwinn Ashtabula | 1.375" x 24 TPI | N/A | American-made Schwinn cruisers, balloon tire bikes. |
Always measure your specific frame to confirm.
Crankset Bolt Circle Diameter (BCD)
The BCD is the diameter of the circle that passes through the center of the chainring mounting bolts. This determines which chainrings are compatible with your crankset.
| BCD | Common Name(s) | Examples of Use |
|---|---|---|
| 130mm | Road (Standard) | Most traditional 5-arm road cranksets (Shimano 600, 105, Ultegra). |
| 144mm | Campagnolo (Standard) | Older, classic Campagnolo 5-arm road cranksets. |
| 110mm | Compact (Road) | Modern compact road cranksets, also common on 'touring' style cranksets. |
| 94mm | Compact (MTB) | Older 5-arm mountain bike cranksets for smaller chainrings. |
| 74mm | Granny Ring (MTB) | The small inner chainring on many 3x mountain bike cranksets. |
| Ashtabula | 1-Piece | American Schwinn cruisers and other 1-piece crank systems. |
Headset Standards
The headset type and fork steerer size are critical for finding a compatible replacement. Most vintage bikes use a threaded system.
| Standard | Steerer Diameter | Commonly Found On |
|---|---|---|
| ISO / JIS (Threaded) | 1" (25.4mm) | The vast majority of vintage and modern road bikes with threaded forks. |
| Campagnolo (Threaded) | 1" (25.4mm) | Older high-end Italian bikes with Campagnolo headsets. |
| French (Threaded) | 1" (25.0mm) | Older French bicycles (Peugeot, Motobecane). |
| 1-inch Threadless | 1" (25.4mm) | Found on some early American mountain bikes and 90s road bikes. |
| 1 1/8" Threadless | 1 1/8" (28.6mm) | The modern standard for virtually all quality bikes since the late 1990s. |
Measure your fork's steerer tube with calipers for an accurate fit.
Rear Hub Spacing & Axle Type
The rear hub spacing (or Over Locknut Dimension, OLD) determines the width of the rear dropouts on your frame. This is critical for ensuring a new wheel will fit.
| Spacing (OLD) | Common Use | Axle Type | Notes |
|---|---|---|---|
| 120mm | Road 5-Speed Freewheel | Solid | Found on classic track bikes and very old road bikes. |
| 126mm | Road 6/7-Speed Freewheel | Hollow (Q/R) | Standard for most steel road bikes from the 1970s and 80s. |
| 130mm | Road 8/9/10/11-Speed | Hollow (Q/R) | The modern standard for road bikes. |
| 135mm | Mountain Bike | Hollow (Q/R) | The universal standard for modern mountain bikes. |
| Ashtabula | 1-Piece Crank | Solid | Found on American cruisers (Schwinn, etc.). |
Common Seatpost Diameters
Using the wrong size seatpost can instantly damage your frame. It is critical to use the correct diameter. When in doubt, measure inside the seat tube with calipers for accuracy.
| Diameter (mm) | Fractional Approx. | Commonly Found On |
|---|---|---|
| 25.0 | ~31/64" | Older French bicycles (Peugeot, Motobecane). |
| 25.4 | 1 inch | Classic American and Japanese road bikes (Schwinn, Fuji, Miyata). |
| 26.2 | ~1.03" | Common on older Italian road bikes (Campagnolo). |
| 26.6 | ~1.046" | Found on many classic Raleigh and other English bikes. |
| 26.8 | ~1.055" | Common on some older Specialized and other modern steel frames. |
| 27.0 | 1.06" | Found on many high-end racing bikes from the 80s/90s. |
| 27.2 | ~1.07" | Very common standard for many modern and vintage steel road bikes. |
| 30.9 | ~1.216" | Common on many modern mountain and gravel bikes. |
| 31.6 | ~1.244" | Common standard for many modern oversized frames. |