Shimano Hollowtech II Bottom Brackets Make No Sense | An In-Depth Rant

[@watertankhikes]

Here's some good info I grabbed off a forum awhile ago. Sorry I can't credit the author; I can't remember where I got it from: SHIMANO BB DIFFERENCES Here's a rough guide to BSA Hollowtech II BBs that are in production today. "Large" BBs, with the 44mm OD, 16-notch spline that's also used on external-spline centerlock brake rotor lockrings. Nowadays these are the "lowest tier" BBs. They use an uncommon-but-not-proprietary 37x25x6 6805N bearing that is semi-sealed. Some of the wattweensters claim they have fractionally less drag than the more expensive BBs, but they are a few grams heavier, and they don't last as long when used in harsh weather. Road: BB-RS500 MTB: SM-BB52, BB-MT500, BB-MT501, SM-BB80 Additionally, pretty much every discontinued older Road or MTB threaded Hollowtech II BB, aside from SM-BB9000. With the older ones, there may be some better seals on the "higher tier" Ultegra/Dura Ace/XT/XTR models (and the Saint SM-BB80 that's still sold today) but it's not really a huge difference. "Medium" BBs, that have a 41mm OD, 16-notch spline. These are the "mid tier" Ultegra- and XT-level BBs. They use a very proprietary bearing with a 35mm OD outer race and a 25mm ID inner race. 6mm wide overall on the inner race, but the outer race is only 4mm wide, and the 2mm difference in depth between them is taken up by a rubber seal. Much better sealed than above, which seems to more than make up for the smaller bearing. Road: SM-BBR60 MTB: BB-MT800 "Small" BBs, that have a 39mm OD, 16-notch spline. These are the "top tier" Dura Ace and XTR-level BBs. The 39mm OD is the same OD as your typical steel BB shell, which is kind of cute, I guess? I have yet to see someone punch the bearings out of one to see what's in there; I have an R9100 that's developing a slight tick after 5k miles that I'm planning to replace relatively soon and tear down to see for myself... That said they don't seem to be any less durable than the mid-tier BBs above; my suspicion is they have the same bearing and Shimano just cut a little bit of weight out of the cups. Road: BB-R9100 (and the discontinued SM-BB9000) MTB: SM-BB93 FYI the difference between the Road and MTB BBs is that the MTB models have cups that are 1mm narrower than the road BBs. An alternative to BB-52 which does work is BB-MT501. It's basically the same BB but in black, which in my opinion looks better if you have a black crankset.

[@Bikes-with-Ben]

This is huge, thanks for posting this!

[@paradisedot50]

I had a brand new Shimano slx m7100 bottom bracket put in my bike (replaced the drive train with the SLX 7100) AND, right off the bat it "has a tick" when I stop cranking hard. It just "clicks and slips backwards." Oh well...

[@paradisedot50]

I guess I should say the bottom bracket is the BB-MT800 one. It was installed at a bike shop...and correctly. It, apparently, has a "bad bearing" (I'm told) and just was a lemon. The derailleur was thoroughly checked out (yes, the B tension screw is set properly). It just is what it is...

[@tomekborucki1120]

The bottom brackets you are talking about are from different product range. The oldest is sm bb52, there was bb70 and 90. Then shimano moved to smaller cups for road and mtb. But bb52 was still offered over all geberations. They still manufacture it, but it was replaced by 3 digit one, mt501. It's the same bb as 52 but with different finish. The main difference between the bb's is sealing and bearing quality, bb52 is just cheap crap , worth considering only if you need a new bb and have no money for something else. It has no seal on the inside of the bearing, what kills them quickly.

[@MisterCOM]

I thought i was smart by getting a bb80 for 20 bucks but now im just confused

[@paultrial]

most annoying difference in my opinion is that you need a different tool for each of the three bottom brackets on yout table. 3 tools to do the exact same thing.

[@paultrial]

... and you get in the video to this particular aspect.

[@smithandshortdogs]

the different BBs use different size bearings. As they cannot change the diameter of the inner race (due to all hollowtech 2 cranks having a 24mm spindle) they had to make the outer race and therefore the overall diameter different. Hope that helps.

[@madyogi6164]

And if you buy the plastic Shimano insert, for their dedicated wrench. it will snap, 100% guaranteed.

[@coastalhillbilly3419]

Only good thing, there are cheap aftermarket sockets and tools available, also Park tools are reasonably priced . Just bought 4 new aftermarket tools for about $50 for my new trail bike, XT cranks preload tool, chainring removal socket, XT chainring removal socket, MT 8100 BB socket and center-lock rotors socket.

[@Yoyoyoitsdatboi]

My uncle works at Shimano, I'll tell him to update the website.

[@scottbailey5644]

Thanks matey. So I'm pleased it's not just me that's confused. Helpful, cheers.

[@EnthusiastsGarage]

Agreed, shimano’s website does a terrible job explaining and comparing the different components.

[@shanewade5654]

The middle tier BB comes with an adapter in the box to install it (plastic ring with correct notches). It adapts to the hollow tech 2 bb tool.

[@NonLegitNation2]

maybe. Mine didn't come with one. i had to buy one off Aamzon, i ended up buying an aluminum adaptor. I recently switched to a SRAM GX Eagle crankset so I also had to switch to a SRAM Dub BB, which also uses a different tool then all shimano BBs.

[@Bikes-with-Ben]

Interesting, I didn’t see one in my box, I’ll have to double check.

[@ktse87]

I bought one that did include one and another one that did not.

[@philipcaldwell3187]

Thank you for taking this one on! Not much out there for the non-ball bearing expert. I have been sucked into the Cane Creek marketing story on their sealed and intrinsically self lubricating assembly. The really useful analysis can only come from “testing it in the rain”. My appreciation for the under valued service to the OCD bicycle community for the therapeutic value of your KZbin series, everyone needs to be able to be with their people to maintain their mental health. Hard to tell how many marriages and relationships have been saved. Keep up the good cause!

[@nicolo003]

From what I have read online, I think the BB-MT800 USED to come with an adapter that fit on the bracket, and the other side fit with the standard Hollowtech II tool. My LBS had a drawer full of adapters and tossed me one for free. I ran into the same frustrations with tooling after ordering one for my bike. I believe the part number from Shimano is TL-FC25

[@jayeff4457]

Thanks for posting! I have been researching cranksets and bottom brackets for my Siskiu T8. It gets a bit confusing with all the different part numbers.

[@martincantwell2557]

All I know is that the cheap Shimano bottom brackets are way more reliable than the more expensive sram bottom brackets I used to use. (I ride in muddy conditions mostly). No need to spend money on the more expensive versions.

[@Alaakso]

If you have a tool for shimano 12s mtb direct mount chainring, you have the tool that fits the mt800 bb. Also manuals tell you wich tool to use. But I agree that the info should be easier to find.

[@johnlesoudeur3653]

I have noticed that their higher end bearings feel a little smoother on installation (including pedals). They used to include the correct (non-metal) fitting in the box for the weight reducing deviations from the original Hollow Tech 2 but they have seem to have cut back on including fittings (including their cranks). I recently replaced a shot Race Face BB92 Ø30mm / Double Row with a Shimano XTR (SM-BB94-41A) and XTR cranks and although it is working well, the naming system and instructions could be a lot better to say the least. They seem to be losing their way...gone fishing?

[@danbertcredo7404]

Is it good to put shimano m6100 crankset into BB-MT801?

[@mjojrjr6231]

Have you got a video on shorter crank arms that will work on hallowtech II apart from Shimano brands?

[@Bikes-with-Ben]

@@mjojrjr6231 I don’t know much about crank arms, but I’ll add it to the list and maybe I’ll make something down the road!

[@mjojrjr6231]

@@Bikes-with-Ben thanks, hopefully there's more options.

[@lisashiela9137]

I have worked in the powersports, (motorcycle/atv/watercraft) business for over twenty years. With the year make and model information, I can find the specific part# and order that exact part. I have never seen such a variety of bottom bracket variations, dub, hollowtech, etc, required for identical frames by the same manufacturer in all my years of vehicle parts management. Maybe it's just standard operating procedures for the bicycle industry.

[@64x83]

AWESOME!! Thanks for this! Shimano talks so much about their technologies but nothing explaining specs and differences. I ask a lot but if you could do one on brakes I’d appreciate it a ton :)

[@mattx3190]

Man! Really enjoy your videos. Any thoughts about showing how you took the T8 apart and grease the pivot bearings?

[@Bikes-with-Ben]

I was in a hurry getting that back together this weekend and didn’t film any of it. I ended up getting 4 new bearings for the linkage and pressing them in after beating the old ones out. I put a few laps on it at this past Sunday at the shuttle park and everything stayed together so fingers crossed it seems like I did okay.

[@matthewmahoney6529]

So they have loctite on the 1 bb. Do you guys install with loctite?

[@Bikes-with-Ben]

@@matthewmahoney6529 I don’t use loctite. The BB is threaded reverse on one side to the other to tighten with pedaling. I use just a little bit of anti seize and call it a day.

[@spoonage82]

I had the same issue with their disc brake adapters years ago, they don't explain very well the differences.

[@Bikes-with-Ben]

@@spoonage82 I’m currently doing a bunch of research trying to figure out the best value Shimano brake set and the amount of confusion I’m experiencing is too much.

[@spoonage82]

@@Bikes-with-Ben they make great products as far as drivetrains and brakes but need to get better about product details, uses and comparisons to other models

[@Bikes-with-Ben]

@@spoonage82 yeah, there are just so many variations that it would be so hard to easily spell out the differences. I think so much of it is for OEM too and that adds to the confusion on the straight to consumer side of things.

[@greenhill26]

The other thing I found was weird was how difficult it was to find the mt801. The mt800 is more readily available state-side. Looking at the XT crankset on Shimano's website the recommended BB is now listed as the 801. I also could find NO information!! I took a chance and ordered mine from overseas. Looked legit when it arrived and so far so good. I'm super happy about the 1 gram weight savings ;) Great vids!! I've enjoyed them.

[@MB-ek1ub]

I have BB52 on all my bikes. They last like 7000km (4000? Miles) of off-road sandy muddy use. Cheap as chips. Cannot think of a reason to upgrade.

[@obxarms7685]

yeah but you ball bearing is a too big.

[@tomahoks]

I butchered completely my tapered BB with a rattlegun. The driveside thread was reversed after all. No, I did NOT go to KZbin University beforehand.

[@RC-fp1tl]

I couldn’t find which tool fits the MT800, so i just 3d printed a top lol! It works wonderfully!

[@smithandshortdogs]

Tl-Fc37. Much cheaper your way.

[@ScrappyIndustries]

Cut em apart let’s see some bearings!

[@mickeymouse4897]

Agree. Shimano are no different than most other big engineering brands in that they use the exact same bearings in the lower & upper price component ranges, higher price parts may look a bit fancier externally, internally they will use the exact same bearings/spindles/seals/grease etc.

[@FGIRAFFE]

I was asking to myself exactly this question and found the funniest video ever! Thank you! It was informative! I'll try the cheapest one first. I'll have to buy two or three of them each year. That'll make this part the one that wears out the fastest. How strange...

[@LaurentiusTriarius]

You should look into wheels manufacturing BB's you can service the bearings independently, Shimano uses proprietary bearings in the 52's you can't take them apart.

[@Forthetimebeing72]

Thanks for your super nerd shimano videos. I enjoy them! I bought the 8100 for my bike cause it was $17 on sale, it could not figure out the tools exactly like you said lol.

[@donpalmera]

I had this issue recently. One of my bikes had a prowheel hollowtech II clone BB. I thought it had started creaking after 4000km. Turned out to actually be one of the derailleur jockey wheels... anyhow I knew I needed a BB that can take a 24mm HTII style crank and it needed to be 73mm BSA. The old taper BBs had a spindle length too but I couldn't find that written anywhere on the old BB or the specs for the frame so I guessed that it wasn't a thing for HTII. I could not for the life of me work out really which of the shimano BBs I could get off of Amazon would work. They all seemed identical with no explanation of "this is deore level, this is slx level with better bearings, this is DH level with stronger but higher resistance bearings" on amazon or the shimano site. So I ended up working out which would arrive the next day and wasn't insanely expensive and took a gamble. I ended up with the bb80 and despite the gash looking gold colour it seems to work fine. It's apparently a saint level part which is downhill specific but it says "mountain/bmx" on the plastic tube part so I have no idea. Maybe downhill BMX is a thing? I think if there are any actually differences like better/different bearings in some of the models even shimano doesn't know. It was actually easier buying a prowheel crank/bb set off of aliexpress to convert one of my old bikes from 3x8 to 1x8. I selected the cranks, the chain ring size and BB with a single option and hit order. 🤣

[@smithandshortdogs]

Shimano mtb bbs are designed to work in a housing that is 68/73 mm wide (the metal/carbon part that they are screwed into). The threaded part of the right housing on the gold saint one is much longer which allows it to additionally work in a 10mm wider 83mm bike. This allows a theoretically stiffer frame, a wider chainline for say superboost rear axles etc. Basically you have a little extra material in the thread area which you don't need and is adding a miniscule bit of extra weight. It might look good if you had a black bike with Fox Factory kashima suspension, or maybe a renthal stem. Cheers

[@jamescamry2024]

Your thinking in regards to devices abs parts is just like me. It's like I have another brother. I do this with mobile phones, other tech items. Also anything my wife and I plan to purchase for the home. And holiday parks (Australia). 😊

[@donofthedonmtb]

Looking to the future....are brakes next? I want to see brakes. Did I mention brakes? How about brakes?

[@bthomas518]

For the 4 piston calipers, Deore are the heaviest and do not have a banjo on the hose (SLX and up do, you can adjust angle of hose going into caliper), SLX and XT are quite a bit lighter and they are same exact thing with different paint, XTR are an even lighter alloy. They all have similar stopping power. You can run the same fin-less pads on all four, but I don't think that the finned pads that come with SLX, XT and XTR will fit in Deore. Brake levers: Deore heaviest, SLX lighter but no extra "features", XT same weight as SLX but gets dimples on the lever and a screw that adjusts the bite point (most people don't think it works, I notice a difference slightly if I adjust it while gently squeezing. SLX actually has this in it, just doesn't have the screw), XTR same features as XT but lighter still (there is an even lighter XTR lever option that loses the adjustability, but I think it only works with the 2 piston calipers)

[@max-eb9vi]

You didn't take em apart. The main differences are the tolerance of the bearings and different ends that match up to different cranks. Some are a bit inset to take xtr and certain grx cranks, then theres road and mtb differences. I cant remember all the differences cos so many but when shopping for one find out which one matches your crankset properly, saying that they will pretty much all work on any shimano crankset just find out which exact bb came on the bike from factory

[@CPWaite83]

I ran into the "which tool fits" issue back when rebuildnig my bike. I got an MT800 because it was 1) black and 2) slightly higher end than the MT500 for only $5 more. I bought the larger MT500 tool because there was no indication there was a difference, and wasn't able to install it and had to go buy the right tool. Its stupid they can't just list the outer diameter and link to the right tool on Shimano's website. Totally stupid...

[@Bikes-with-Ben]

I agree 100%. I understand that parts change and a new tool may be required. It’s annoying, but it is what it is. They should at least tell you what tool is compatible.

[@craigellis680]

My understanding is that 0 or 00 is black and any other end number is silver. Also the tool for a direct mount chainring is also the tool for the bb800/801 as the xt class bb is intended for higher end cranks. I also believe the correct size bb is not just the 68-73 shell width but also the diameter so slim bb shell means slim bb IE mt800 and fat bb shell meant bb52/500

[@johndef5075]

Im using an MT501 with my new XT crank. Working fine so far.

[@mat6713]

i found that mess out the hard way when i wanted to install a mt 800 in my gravel bike frame and my tools didnt work. thanks shimano for cheapening out and not including 10 cent plastic adapter in the box.

[@krollpeter]

The website leaves me more confused than before I looked through it. Lifestyle, Recreational, MTB, Road, etc. ... and then everything with overlapping products lines, plus cryptic names and numbers. And no much info what fits to what. There could be three categories, travel+urban, MTB and road race bikes. Each category may have 3 lines, standard, mid-level, pro. Then they could add to each line special components, if deemed necessary. For example for travel a maintenance free and extra solid derailleur, for race an extra lightweight cassette. All shifters should have the same pull. The chains also could have only three categories, standard, high quality, and light. Etc. etc. As well, there are not so many different gear categories needed. 6 for the casual rider, 9 and 12 for more ambitions, and these all available also with 2 or 3 chain rings. Square tapered cranks should be scraped, and only hollowtech sold for all lines. These are not anymore relevantly more expensive in the market. That would be a good start.

[@smithandshortdogs]

I suspect shimano doesn't really want you buying their parts directly. Either get it on a complete bike or go to a retailer. I don't know if that is a great stance from a customer service perspective but hey... I suspect their info is also driven by their being an asian company. It has been forever since I lived in Asia but my recolection is that they highly value the personal touch and are probably only providing the information that they grudgingly are as a nod to western mores.

[@krollpeter]

@@smithandshortdogs They are not too keen end-users buying their products. I came to the same conclusion. But I am still puzzled about the confusing number of product lines, and even inside these lines various products, with seemingly no apparent differences.

[@smithandshortdogs]

@@krollpeter couple of theories on that... Shimano's product lines aren't actually that confusing if you have been dealing with them for a few decades. On the MTB side in their main lines you have XTR (racers) XT (premium) SLX (mainstream) Deore (budget). I theorise that everything below that is a way to provide parts to people who are using defunt products (9 speed 8 speed etc) As to why duplicate products in the same level: I think this is often due to what other companies might ship out as a rolling change; you find a cheaper supplier who makes a better seal that costs less, but you have to change a spec by 1mm to make it fit.... ok well this mt-800 bb is now an mt-801. The military would call it an mt-800a1, ovther companis might call it a mark or v2, software companies would say release 1.01...

[@krollpeter]

@@smithandshortdogs "Shimano's product lines aren't actually that confusing if you have been dealing with them for a few decades." Sure, if you are a dealer you will be probably very familiar with all the lines. I believe the number of products with partially insignificant differences is hindering in the market. There is a (Chinese) company, that works similar to this: Derailleur X3 for 6 and 7 gears, X5 for 8 -11 gears, X7 for 12 and 13 gears.

[@tom.mcf.]

Even more confusing is if you have a gravel bike like i do, that has no information on the BB. Like if it is road or mtb. I bought a Saint for my mtb but ended up on the gravel bike instead, and that is what I'm still using. Yes the alien spider eggs, I mean grease is kind of cool looking.

[@reinholdachleitner2069]

Still the best style and system Hollowtech 2.

[@mrk1075]

I just cruise around on my 26 inch mountain bike with a ebike kit on it so I’ll buy the cheaper hollow tech 2 BB.

[@davidpottage6402]

I think the reason that XTR, SLX etc does not appear anywhere on the box is because like chains, Bottom brackets are shared with road groupsets, so the 9xxx prefix is both XTR and Dura-Ace, 8xxx is for XT and Ultegra *AND* GRX (gravel).

[@jaro6985]

There is a Mountain and Road BB52 version. Supposedly the MTB version has slightly longer thread length on the drive side.

[@smithandshortdogs]

MTB and Road BBs are not shared. I mean they are basically identical, other than the length of the plastic sleeve between the cups, the engraving on the cups and the number of shims in the box, but they are not particularly inter-compatible. I suspect it is more of a way that customers not getting mad when their full xtr bike has a BB marked slx on it.

[@F_youtube_rassist_cencure]

the difference is in the resource 801- 20k+ km 501- 8k+ km also 801 will not die quickly among fans of mud rides)

[@growingup4487]

only diffrence is price

[@kipcc3918]

They definitely mastered the cash grab opportunity and the magical placebo effect, And Yes, I like shimano, It’s the slight/marginal discrepancies between models is what I hate. It’s annoying for budget minded people who builds their own bikes. But it’s always an easy cash grab for rich people.

[@zorro324]

none of them last long....just replace with a wheels manufacturing one with angular bearings...they last much longer and are rebuildable.

[@smithandshortdogs]

I am still running the stock shimano "series" bb that came with my 2009 stumpie.... I must have 25k miles on that bike.

[@christeschke9844]

The information on shimanos website can be....not the best :) If you checked how much chain slack a shortcage vs longcage 105 derailleur could handle for teeth difference, you will not find an answer. Shimano's website will only tell you the Cassette variation , but if you use a road or gravel crank, that will change the amount of chain slack needed, making the shimano information incorrect.

[@NerdyFurry]

Incase you still haven't figured out what tool to use for the smallest dura ace bottom bracket you need a parktool BBT-47-16. It goes on a ratchet wrench. The bike coop i wirk on my bike in ran into this issue recently specifically with the "higher end" hollow tec 2 bbs. I had one put on my bike and none of the bottom bracket tools fit. They had the tool above but its in a special spot and now im the only person there besides the shop lead that knows how to deal with these things. Ill also note that the bike shop I bought the bb from was mildly confused by the uniformity as well Apparently theres 3 sizes of housings and tbh i genuinely don't understand why either. HT2 has the potential to be an incredibly easy and modular technology to deal with but Shimano seems to have completely buggard it up My best guess is that they have to make extra money somehow, particularly with how durable even cheap modern bearings actually are, and that this is also yet another example of "save grams at all costs" Imo shimano has significantly overbloated the ht2 lineup, and should only be making 3 versions: The one with the bigger cups for budget/hobby/commuter riders The high end one for pros (apparently what my ramshackle gravel bike ended up with) And one for enduro/downhill (reading comments they make one of these in gold and its called a saint) Ironically i found this video because my bike is having chain line issues and I was wondering if i used the wrong bb. After seeing this im now assuming i either got the wrong crankset, or need to tinker with it more.

[@anthonycordero5733]

I bought the middle tall box fory old hardtails no problems ever for forty five bucks is great but I don't know about the others