This post will explain bottom bracket compatibility. Which bottom brackets (BBs) can be combined with which crankset standards.
Before you start, to avoid any misunderstanding:
please take the 5 minutes needed to read the compatibility articles use instructions.
If you have any questions (or additions and corrections), please use the BikeGremlin forum’s compatibility section:
https://www.bikegremlin.net/forums/bike-compatibility/
Posts that explain in detail the history and construction of each BB standard can be found here:
1 History and threaded BB standards
2 Threadless (press fit) bb standards
T47 – a new threaded BB standard
Note: crankset for mounting on externally screwed in bearings, with a hollow axle 24 mm in diameter, is compatible whichever manufacturer produces it. So: Race Face X-type, FSA MegaEXO, Truvativ/SRAM Giga X Pipe (GXP), Campagnolo Ultra Torque – they are all compatible with Shimano Hollowtech II standard, so only Hollowtech II will be named in tables and remainder of the post.
1. Compatibility of bottom brackets
Table of BB standard and compatible cranksets of different standard (all the BBs accept the same standard cranksets, of course, others require an adapter, as is explained in chapter 3):
| BB standard | Crankset compatibility |
| Threaded (brit, ital.) | square taper, ISIS, Octalink, Hollowtech II, BB386EVO The first 3 require BB cartridge of their standard to be installed. HTII and BB386EVO require HTII BB shell |
| 1 a) BB30 | Hollowtech II, BB386EVO, |
| 1 b) BB30A | Hollowtech II, BB386EVO, BBright, BB30 if they have spacers on the left side |
| 2. PF30, OSBB | Hollowtech II, BB386EVO, OSBB, BBright, BB30 |
| 3. BB86, BB90, BB92 | Hollowtech II |
| 4. BBright | Hollowtech II, BB386EVO |
| 5. BB386EVO | Hollowtech II, BBright, OSBB, BB30 if the spindle is long enough |
| 6. BB90, BB95 | Hollowtech II |
| 7. PF86, PF92 | Hollowtech II, BB386EVO |
| T47 | All – if the spindle length is appropriate |
2. Compatibility of cranksets and different BBs
Table of crankset standards and compatible BBs (all the cranksets are compatible with the BBs of the same standard, of course, the others needing a special adapter):
| Crankset standard | BB compatibility |
| Square taper | Threaded (british, italian) |
| Octalink | Threaded (british, italian) |
| ISIS | Threaded (british, italian) |
| Hollowtech II | Threaded (british, italian), BB30, BB30A, PF30, OSBB, BB86, BB90, BB92, BB95, BBright, BB386EVO, |
| BB30 | PF30, OSBB, BB386EVO if it matches the spindle length, BB30A if the crankset has spacers on the left side |
| BB30A | BB30 with use of spacers on the crankset |
| PF30 | / |
| OSBB | BB386EVO |
| BB86, BB90, BB92 | / |
| BBright | BB30A, PF30, OSBB, BB386EVO |
| BB386EVO | Also available as threaded (British, Italian), BB30, BB30A, PF30, OSBB, BBright, PF86, PF92 |
| BB90, BB95 | / |
| PF86, PF92 | / |
| T47 | Fits all the BBs – if the spindle length and diameter match the required for the BB used |
3. Combining different standards
There are several adapters made by various independent manufacturers that can match certain BB standards with certain crankset standards. They are usually placed directly into the frame, replacing the “standard” BB bearings. Solutions vary from case to case.
Clicking on the image opens Amazon affiliate link with a bottom bracked adapter search.
Amazon.com search of bottom bracket adapters (as an Amazon Associate, I earn from qualifying purchases).
4. What to pay attention to when buying bicycle, cranksets, or BBs?
In terms of both BBs and cranksets, of course. There are so many (in)compatible standards and how not to get confused or get mismatching equipment? Just follow these simple steps:
- Always check for the frame you have, or are planning to buy, what standard of BB does it’s BB shell have. Pay attention to all the details.
- If buying a BB, make sure it fits the frame BB shell (as determined in step 1).
- If changing cranksets
BB30 and PF30 cranksets won’t fit frames with different BB shell standard, because their spindle will be too short.
Cranksets with 30 mm wide spindles won’t fit into frames with BB86, or BB90 BBs, but with correct BB some can be made to fit into threaded frames.
Cranksets with 24 mm spindle diameter are the most versatile and, with the right BB, or adapters, can fit almost any frame. - Cranksets with 24 mm spindle diameter are not all the same! SRAM and some other manufacturers make spindles that are 24 mm wide at one end, and 22 mm wide on the other, so the correct matching BB needs to be acquired.
- If the frame has a press-fit BB shell (without threads, threadless), then you need quite expensive, special tools to install and remove/change BBs. If not using such tools (like a bearing press), bicycle frame can be damaged.
On the other hand, threaded BBs allow the use of simple, inexpensive tools. - When it is all set up correctly, differences between different BBs (e.g. stifness) are never perceivable when riding the bike – basically they are unimportant. So there is really no need to buy a frame with a certain BB standard because it is marketed as stiffer, better. Just see what kind of frame you like, or what components you already have, and go for the simplest, easiest, cheapest solution to make it all work.
5. Author’s personal opinion
For ease of installation and replacement, threaded BBs rule! 🙂
Square tappr and Octalink BBs are by far the most durable, long lasting ones.
New T47 standard looks promising, but still not enough first hand experience data to confirm durability and ease of maintenance.
Help BikeGremlin
stay online & independent
This website is educational, free, objective, and not commercial
(sponsors don’t enjoy paying if you mention all the product downsides that you notice 🙂 ).
How much does a WordPress website cost?
If you find this site to be good and helpful,
and if $5 per month is what you can afford to set aside,
please consider supporting my work with a Patreon donation:
Related post – Bicycle cranks (“crankset”) compatibility:
Compatibility posts are also available in eBook (printable and Kindle) and paperback editions on Amazon:
If you have any questions (or additions and corrections), please use the BikeGremlin forum’s compatibility section:
https://www.bikegremlin.net/forums/bike-compatibility/
The existing comments posted under this article (questions and answers) have been moved to this BikeGremlin forum thread:
https://www.bikegremlin.net/threads/compatibility-10-bottom-brackets-article-comments.134/
Hi There I am riding a Specialized Sirrus X 5.0, and the current bottom bracket is a Praxis 68-0201B , 68mm BSA , with Praxis Alba Crankset 1 X 11.
I have purchased a Shimano GRX 810 Gravel 1 X 11 that runs on Hollowtech 11 bottom bracket.
Looking at changing BB to XT MT800 sized 68/73mm – English Thread – 24mm or the SHIMANO XTR M9000/9020/980 THREADED BOTTOM BRACKET.
Question i’m asking, does either of these BB fit my current frame and are compatible with the GRX Crankset
Or what Bottom Bracket do i need to fit the Sprcialized frame, as the current bottom bracket has not much detail stamped on it, i believe it is a Praxis one though.
Any advice on this would be greatly received.
Regards
Kevin Taylor
Hi Kevin,
Short answer: yes, either should work.
Long answer:
In terms of the BB fitting the frame:
You have a 68 mm BSA bottom bracket, so your frame uses the British standard threaded bottom brackets (and is most probably 68 mm wide).
Hence – any BB that has the British standard thread should screw in without problems.
Now, many BBs are designed to work with both 68 and 73 mm wide frames, but not all – check before buying.
In terms of the BB fitting the cranks:
Any Shimano Hollowtech II compatible BB should work.
A budget option is Shimano Tiagra BB-RS500.
Relja
Enjoying reading your site…very informative. I have the following BB Compatibility question. I’m updating the BB’s (tapered steel spindles w/ caged bearings) on two of my 1980’s steel frame rides, one a two-chainring road bike & one a 3-chainring tour bike. I want to replace with the more current threaded, tapered spindle, cartridge/sealed bearings. The two spindles are “eccentric”…each has a longer dimension(on the right/drive side) from the bearing surface than the left side. From all the info/specs I’m finding, none of the offerings spec an eccentric spacing, just the overall length (such as Shimano UN300). I think the original idea was to allow for specific chainline alignment. Will any of these products work without chainline “problems”. Thanks for your input.
Hi Steve,
In my experience, the first thing to pay attention to is the frame’s BB shell threading standard. Making sure which one it is, before trying to screw anything in. I know it may sound silly, but I think it’s worth stressing for anyone reading this.
The article “Vintage bicycle frames with modern parts” deals with this in great detail.
As for the cartridge bottom brackets – all the spindle eccentricity is dealt with within the enclosed mechanism, so it is less plain to see, but it still exists.
Unfortunately, it’s difficult to know upfront which length will be the optimal choice. For all I could try, it still boils down to trial and error. I make sure to always have the entire range of lengths in the shop and am happy to do test-mounting to confirm, starting with the length I expect to be the optimal choice first.
At the end of my bicycle chainline article, there’s a chart that gives some left and right eccentricity data, but it won’t help much. Many cup and cone axles (spindles) have a slightly different taper compared to Shimano’s cartridge BB square spindles. That’s mentioned in my threaded bottom bracket standards article – chapter 4 (JIS and ISO standards for the taper slope).
So it’s mostly eyeballing and trial and error. Some very rough guide (what I often try with first) would be:
110 mm spindle for singlespeed cranks.
113 to 115 mm spindle for double cranks.
120 to 128 mm spindle for triple cranks.
Maybe this isn’t much of a help, but it’s the best I can do. Coming up with a system to know upfront which spindle length fits best would save me a lot of time and hassle, but I still haven’t managed to do that. I get it right from the first time about 50% of the time, and from the 2nd try (with a longer spindle most often) about 40% of the time. But sometimes it takes 3 tries to get it right. On the upside – it is quite a Zen-like procedure, no-hassle once the old BB has been removed. 🙂
Relja
Relja…thanks for your prompt & thoughtful reply, very helpful. I never thought that BB’s would be such a problem…but eventually I think I’ll be able to work out a solution. IRD does list a spindle selection that includes the cups and 1/4″ caged bearings and shows the asymmetrical spindle with left/right “offsets”… that may be the best solution, although more expensive than their cartridge bearing alternative. Thanks again…your site is very helpful!
Hi i have a road bike with BB72-41B road bike BOttom bracket. I believe this is an ultegra
My question is can I install a BB71-41A (deore) or a mt800 (xt) BB on a 105 crank? Seems like they have same specifications except the inner sleeve width? Will they fit if i dont use the inner sleeve? (sealed frame)
Both press fit
Hi Vendmerc,
Based on Shimano’s specs, the BB71-41A is too wide – designed for 89.5mm and 92mm wide frame bottom bracket shells.
Road bike cranks generally work with 68 to 73 mm wide frames.
The Deore BB, model BB-MT800 (XT M8000 Series) should fit road frames and cranks fine.
Generally speaking – for the 105 cranks, it is important that BB is for Hollowtech II, and that its width matches the frame (probably 68 mm, but, as I like to say: “one good measurement is better than a thousand expert opinions”). 🙂
Relja
Hey, I have a road bike with a BB30 Bottom Bracket I was wondering if Hollowtech II Cranksets. The bike is a Specialized Allez Sprint
Hi Rust,
There is enough room for a 24 mm in diameter Hollowtech II axle inside the BB30 brackets and bearings. But you need an adapter.
Here’s an Amazon affiliate link for a BB30-Hollowtech II adapter.
I suggest you look for an adapter in a local bicycle shop – keeping them in business and keeping a good relationship with LBS-s is priceless.