The Part That Causes More Compatibility Problems Than Anything Else
When we spec a custom build or a groupset upgrade, the first thing we check is the bottom bracket. It's the compatibility chokepoint that trips up more builds than any other component. Here's what you need to know about the main standards in use today.
BSA (British Standard Threaded)
The gold standard. 68mm or 73mm shell width, right-hand thread on both sides. Threaded in, done. You can run any Shimano or SRAM crankset with the correct BB. Replacement is easy. Service life is essentially forever. Most steel frames, many aluminium frames from smaller builders, and some carbon frames use BSA. If you're building a custom frame, we'd recommend BSA for simplicity and longevity.
T47 (Threaded Races, Modern Standard)
Like BSA but with a larger diameter thread and no reverse thread on the non-drive side. Developed by ENVE to replace press fit with something that doesn't creak and doesn't require special tools. Used by many modern carbon frames from Trek, Specialized, and others. T47 is excellent: it threads in like BSA and doesn't creak. If you have a T47 frame, you're in good shape for compatibility.
BB86 / BB92 (Press Fit)
BB86 (road, 86mm shell width) and BB92 (cross country, 92mm) are press-fit standards where the bearings sit directly in the frame shell without threads. Press fit frames are notorious for creaking: the bearings settle, moisture gets in, and the whole system starts making noise. They also require special tools to replace. For service: we can replace press fit bearings, but we always use proper press-fit tools and anti-seize compound.
PF30
Another press fit variant: 30mm spindle diameter, larger shell than BB86. Similar creaking issues and tool requirements. Becoming less common as frame makers move back to threaded standards.
How We Check This
Before we spec any groupset, we measure the bottom bracket shell. We check the type, the width, the spindle compatibility. We tell you what cranksets are compatible with your frame before you buy anything. This check is free: it's part of the consultation before any custom build or groupset upgrade.
The Bottom Line
If you're buying a new frame and the choice is yours: go BSA or T47. They're serviceable, reliable, and don't require specialist tools. If you already have a press fit frame: we can work with it, we just need to know in advance so we can source the right parts.
Ready to get your bike sorted?
Book online or call us on 07951 125 843. Based in Putney and Wimbledon, South West London.
Book a Service →Why bottom bracket standards matter
The bottom bracket is where the crankset runs through the frame. Standards such as BSA, BB86, press-fit and T47 describe how the bearings fit into the frame and what cranksets can be used. The wrong standard means the parts will not fit, or they will fit badly with adapters that may creak or wear quickly.
BSA is threaded and widely trusted. Press-fit systems can be light and clean, but depend heavily on frame tolerance and correct installation. T47 combines a larger shell with threads and is popular on some modern performance and custom frames. BB86 is common on many road frames and can work well when installed properly.
Before ordering parts
- Identify the exact frame shell standard.
- Check crank spindle diameter and length.
- Confirm bearing type and required tools.
- Inspect the frame shell for wear or damage.
- Plan for future servicing, not just initial fit.
Bike Clinique checks the standard before quoting chainsets or groupsets. It prevents expensive compatibility mistakes.
How Bike Clinique would approach it
Our workshop process is diagnosis first. We check the bike in the stand, separate urgent safety work from optional upgrades, then explain what is worth doing before parts are ordered. That means brakes, steering, tyres and wheel security first, then drivetrain wear, bearings, cables and setup. The result should be a bike that is safer, quieter and more predictable on real South West London roads.
If you are unsure which route is right, send clear photos or bring the bike to Unit 1, The Swan Centre, Rosemary Road, SW17 0AR. We can tell you whether the sensible answer is a small adjustment, a service, replacement parts or a properly planned upgrade.
When to book the bike in
Book the bike in when the fault affects safety, reliability or confidence. Brakes that feel weak, gears that skip under load, tyres with cuts, steering play, creaks from the bottom bracket area or a drivetrain that stays noisy after cleaning are all signs that the bike needs a workshop check rather than another quick adjustment at home.
For riders around Wimbledon, SW17 and South West London, the most common pattern is simple: the bike feels fine until it is used more often, ridden in bad weather or pushed on a longer route. That is when hidden wear shows up. A short inspection can prevent a chain from damaging a cassette, a brake fault from becoming dangerous, or a small bearing issue from turning into a bigger repair.
Bike Clinique works from diagnosis first. We check the issue, explain what is urgent, quote the parts and labour before fitting, and keep the recommendation practical for the bike and the way it is ridden.
For service decisions, we also look at value. A small adjustment is right when the bike is fundamentally sound. A deeper service is right when several wear points are showing at once. An upgrade only makes sense when it solves a real riding problem and the frame is worth the investment.
The aim is simple: a bike that is safe, reliable and matched to the rider, without unnecessary parts or guesswork.