BSA
| Acronym | Definition |
|---|
| BSA | Boy Scouts of America |
| BSA | Birmingham Small Arms (BSA motorcycles) |
| BSA | Bank Secrecy Act |
| BSA | Bovine Serum Albumin |
BSA bottom brackets are reverse threaded on the driveside to counteract this.
Best Bike Bottom Bracket [Review] in 2021
- Best All Round Bike Bottom Bracket For Cycling.
- Wheels MFG BB86/92 Shimano Bottom Bracket.
- Shimano Dura-Ace BB-R9100 Bottom Bracket.
- Shimano Tourney TX BB-UN100 Cartridge Bottom Bracket 68/122.5mm OEM.
- Shimano BB-UN55.
- SRAM GXP Team Bottom Bracket.
Square taper bottom brackets may seem like anachronisms dating from the last century, and yet they remain the best option for metal cranks. The result is a lighter bottom bracket – but the larger spindle requires more material on the crank.
As for a bottom bracket, on the low end, maybe 5000 miles. The basic Shimano one most people use (UN51/55/similar) can reasonably expect 10k+ miles. But sometimes you get unlucky and get a bottom bracket that lasts maybe 500 miles.
While both standard BSA threaded frames and BB30 frames have 68mm shells for road bikes, the external bearings of the BSA frame when used with an outboard bottom bracket would render a standard BB30 crankset's spindle too short to use with a BSA30 bottom bracket.
The non-drive side (left side) on the English standard is a right hand threading, tightening clockwise. The drive side (right side of the bike) uses a left hand thread, tightening counterclockwise. The term BSA stands for Birmingham Small Arms, a British company that produced bicycles, cars and other durable goods.
“The BB386 EVO cranks are compatible with almost every BB shell standard (BSA, BB30, PF30, BB86),†says Jason Miles of FSA. Frames with BB386 EVO shells should be able to run almost any crank.
ARE PF30 & BB30 the SAME? No they are not the same. But they are also not all that different. 6806 is a number you'll see describing the bearings used for both pf30 and BB30.
The bottom bracket on a bicycle connects the crankset (chainset) to the bicycle and allows the crankset to rotate freely. It contains a spindle to which the crankset attaches, and the bearings that allow the spindle and crankset to rotate. The chainrings and pedals attach to the cranks.
Anyway, the new BB386EVO system is press fit and uses an 86.5mm bottom bracket shell width – the frame is wider down there than currently and the axle is as long as that of an external system. And the axle diameter is 30mm – the same as BB30.
Which crank fits on which frame?
| | Frame BB Shell Standard |
|---|
| | English (BSA) |
|---|
| Crank Spindle Standard (Spindle OD in mm) | SRAM/Truvativ GXP (24mm) | Perfect Fit |
| FSA MegaExo (24mm) | Perfect Fit |
| Campagnolo Power-Torque (25mm) | Perfect Fit |
2 Answers
- Measure the length of the Bottom Bracket shell.
- Count how many chainrings you have.
- Count the teeth on the chainrings, or look for markings that may indicate the number of teeth (e.g..
- Count how many cogs you have at the rear.
- Length of crank arm is less important for me.
According to his website Hambini works as an aerospace engineer and has sidelines in designing and making bottom brackets as well as producing his YouTube videos, with one uploaded recently criticising a Cycling Weekly article regarding testing of aero helmets.
Thus, cranks from Shimano, SRAM, and Campagnolo are freely interchangeable along with those from all aftermarket brands (e.g. FSA, Rotor, Praxis, etc.). Mixing and matching cranksets and bottom brackets is a completely different matter that depends upon the specifications for the frame and the crank axle.
In 2018, SRAM introduced mountain bike cranksets which use a new technology name DUBâ„¢ (Durable Unified Bottom Bracket). Meant to simplify frame BB and crankset compatibility across their product lines, it brought about yet another standard to understand.
HOLLOWTECH technology is an ultra-lightweight hollow crankarm created by SHIMANO with the company's own proprietary forging technology that also maintains rigidity.
There are 4 widths available with BSA bottom brackets; 68mm, 73mm, 83mm or 100mm. For road bikes, a BSA bottom bracket is always 68 mm wide. Other sizes, and particularly the 73 mm width, is commonplace with mountain bikes. The 83 mm and 100 mm dimensions have become rare these days.
(Click here to read BikeRadar's complete guide to bottom brackets.) According to Friction Facts' latest report: “No statistically significant difference exists showing a general advantage or disadvantage of a standard type under similar loading conditions.
The bottom bracket is the bearing system between the cranks. It sits inside the part of the frame called the bottom bracket shell. The bearings are held in the shell by an adaptor or a cup. The spindle connects the two cranks to one another and to the bearings.
To find out the size of bottom bracket needed, measure the inside of the bottom bracket shell in your frame, it will be 73mm, 70mm or 68mm. Some older frames may have Italian threaded bottom brackets, instead of the more modern English.
Is it ok to use a 68mm external (hollowtech II) BB in a 73mm shell? Yep, but ignore the advice above and use one spacer.
Almost anything can be taken apart without proper tools, including bottom brackets. it, but it can be done. The right tool for the job(any job) makes life much easier and will lower your frustration level by leaps and bounds. If it is a Square taper, isis or octalink then no.
In most cases three-and two-piece cranksets are compatible with the same bottom brackets so long as the axle is the same diameter. One-piece: This is where the axle and crank arms are a single piece of steel. Most commonly found on entry-level or kids' bikes.
The critical thing is your spindle length: as long as you can set up the correct chainline you will be good to go. But, again, best never to mix standards if you can at all avoid it. If you are looking to replace a cottered crank setup with a square taper setup, then look no further than a cartridge bottom bracket.
Pull off both crank arms, then measure the spindle of the BB, that's what the Shimano Crank is saying it needs. When you measure spindle length, you need to only measure to the ends of the square taper. Some spindles have threaded bits that extend beyond the square taper. Don't include those in that measurement.
Bottom Bracket Standards
| BB Standard | Frame BB Shell Inner Diameter | Common Shell Width |
|---|
| Specialized OSBB Alloy | 42mm | 68mm (Road) 84.5mm (Mountain) |
| Cannondale BB30a | 42mm | 73mm 83mm (Cannondale BB30A-83) |
| PF30 | 46mm | 61mm (Specialized OSBB/FACT) 68mm (Road) 73mm (Mountain) 83mm (Downhill) 100MM (Fat Bike) |
| BBRight (Press Fit) | 46mm | 79mm |
Chainline is measured from the centerline of the frame to the center of the chain. Simply hold the ruler against the seat tube or down tube and measure the distance from the middle of the seat tube to the middle of the chainring teeth. In the case of triple chainwheel sets, measure to the middle chainring.
Bottom Bracket Height is a measurement taken vertically from the ground up to the center of the bottom bracket.
