Why are Hollowtech II bearings so terrible?

Don’t want to bitch about Shimano as most of their stuff I’ve used over the years has been great but the lameness of Hollowtech bearings baffles me. Why are they so terrible? Is it purely financial (designed to be a consumable that needs replacing every few months) or is there an engineering reason for making them out of cheese?

They’re only a tenner at the moment. Stop moaning. 😀

Lack of grease from the factory?

Before fitting new ones ,I now take them apart and pack with marine grease.
Get 2-3 years out of them ,and a lot,lot longer on the road bike sets.

They’re failing through their exposure to shite and insufficient sealing.

Stiffness, strength, capacity, simplicity… yeah, great. However the Evolution to HT2 sacrificed the sealing and longevity. In dry, contamination free conditions HT2 would likely last longer, bu that’s not the real world.

Before fitting new ones ,I now take them apart and pack with marine grease.
Get 2-3 years out of them ,and a lot,lot longer on the road bike sets.

Sounds good Fasthaggis. How do you disassemble them, is it something that can be done with readily available tools? I’ve read online that the bearings are a non-standard size so I suspect the 2x pairs Ive got that need replacing are goners.

Directly in the line of fire from crap from the front wheel. Small bearings, high load. Little space for seals. Design is conducive to numpty over tightening.

The first couple of sets I had were awful but they are pretty good these days I generally get well over a year/2500km per BB.

BUT I don’t jetwash my bike.

I throw the Shimano ones away and use the same Chris King BB I’ve been running for 5 years.

2004 called, they want their rant back.

I get about 2000miles off road, mostly muddy from XTR bearings (£12 from germany).

Even my cheap X5 cranks BB is putting in a good showing, and old GXP cranks really did deserve their reputation.

The bearings are fine, they’re just not as well aligned as they were in cartridge BB’s. Old square taper BB’s weren’t even threaded, they sat in the frame and two slightly wedge shaped threaded cups went in either side to hold it. Then shimano started putting one of the threads into the cartridge. But because the bearings were in the cartridge not the frame they were perfectly aligned with each other and the axle (until it bent which they were prone to do), they lasted a fair while. Then when HT2 came along it seemed to take a few years for frame QC to catch up and frames to come out perfectly aligned, and some bearings were just woefull (race face and truvative GXP being by far and away the worst offenders) which compounded the problem.

Having said that, I just fitted a new square taper BB to my road bike at the weekend, felt like getting re-acquainted with an old friend, and they really do feel smoother when you can flick them round with your finger and they just keep spinning.

Thought they were impossible to over-tighten as they’ve sat in cups separated from the threaded part. Not sure how you’d apply enough torque with the plastic crank installation tool or find anything with decent enough purchase.

Not sure how you’d apply enough torque with the plastic crank installation tool or find anything with decent enough purchase.

You’d be surprised, the cups aren’t supposed to be “throw all your weight on the spanner” tight, and they will deform if over-tightened. And the pre-load tool should be no tension at all, just push the crank on, and take out the play. The proliferation of CNC’d versions with hex heads doesn’t help.

Thought they were impossible to over-tighten as they’ve sat in cups separated from the threaded part

My thoughts too, but you could over-tighten the cranks onto them I guess by goong nuts with the preload.

Are you a bit free and easy with the jetwash, be honest now.

2004 called, they want their rant back.[/quote

For sure but no ones really come up with a viable explanation as to why they don’t do something about making them last.

Definitely think GXP goes someway to help them last longer with the over tightening issue being eliminated. Hope ones being slightly larger bearings as well mine are lasting well.

For sure but no ones really come up with a viable explanation as to why they don’t do something about making them last.

Well they do last, any I’ve fitted in the last 8 years or so have lasted at least what I’d class as an acceptable time.

There are plenty of reasons they don’t last:
1) Frames were out of alignment, which was never an issue before HT2, but suddenly was.
2) Some of the early BB’s were rubbish.
3) Over tightened cups deform.
4) Over preloaded bearings wear out
5) Washing; jet washes, bike wash solutions, WD-40/GT-85, etc, all kill the seals and bearings.

174 miles is my record.

At first, I was getting about a year from new.
Went through three in less than 1000 miles a couple of winters ago, almost exclusively in North Manchester/Bury grinding paste.

Switched bike shops after moving, they suggested drilling the bottom bracket or making sure I stored the bike upside down, which hadn’t been practical for a few years.

I no longer ride mostly in grinding paste, just a different kind of mud.
Try and dry my bike out a bit more, now getting about 1000 miles, which seems OK.

Wonder if I should get the BB alignment checked?

Going back to square taper on the new bike.

There are loads of long-lasting alternatives.

£25: Gusset ext 24, mine is seemingly indestructible*, and extremely well sealed. uses standard bearings.

£35: Uberbike, similar to the Gusset, just a little bit ‘nicer’.

£80: Hope, not as well sealed as the Gusset/Uberbike, but, y’know, it’s Hope…

BB’s for every budget, all of them really good.

(*over 15,000 km, on my commuter/off-road tourer. certainly not a dry-weather sunday-best)

I do as above- I take the shields off and pack them with grease. They last me a years riding through all weather- way over 2,500m. Even then some have been saved by repacking them.

Swap to PF30, then you can complain.

Frames were out of alignment, which was never an issue before HT2, but suddenly was.

That’s to do with the BB shell face being perfectly square with the threaded shell body. With old, self contained cartridge type BBs this didn’t matter so much. Maybe Shimano Hollotech IIs have lower tolerances to compensate for this.

Maybe Shimano Hollotech IIs have lower tolerances to compensate for this.

They have no ‘tolerance’ for it at all, if the shell isn’t perfect the bearings last no time at all.

It’s not just the faces of the shell being parallel either, the threads can be cut at an angle too. If you you get the shell faced they have to align the tool in the BB using the threads, and it’s never going to to be perfect because (in steel frames at least) the threads are cut into the shell before the frame is made, so the heat of welding distorts the shell. So when facing/chasing the BB the best you can get is an average of the two threads.

Sounds good Fasthaggis. How do you disassemble them, is it something that can be done with readily available tools?

Take a stanley knife or similar very thin tool and insert under the plastic shield ease up gently working your way round. The shield then pops off, you insert a shedload more grease and then press the shield back into place. you can repeat this next December if you like, but I ride 2-3 times per week in all types of slop and since doing this I have not had an HT BB fail.

GXP are definitely better nowaday after they put a 3rd “O” ring seal on the plastic pipe between the cups.

They’re one of the few things I’ve never really had problems with. Currently running a Saint bb on my SLX cranks with no grief.

The plastic PF30 in my Stumpjumper was literally the most infuriating bike part I’ve ever had.

thisisnotaspoon – Member
Old square taper BB’s weren’t even threaded, they sat in the frame and two slightly wedge shaped threaded cups went in either side to hold it.

Old square taper BB’s were effectively cup and cone, so of course they were threaded. You must be talking about the ones you could get that could be fitted to a BB shell with stripped threads, although I seem to recall Mavic also making a similar item?

the axle pre-load cap is only tightened 1-2nm

very easy to overload, and often overloaded by mechanics both at home and in bike workshop

especially with companies making metal tools to tighten this cap

this drastically shortens bearing life

Old square taper BB’s weren’t even threaded, they sat in the frame and two slightly wedge shaped threaded cups went in either side to hold it.

I think he’s referring to the original Shimano BB cartridges from the 90s- with the cup centering the cartridge in the frame.

especially with companies making metal tools to tighten this cap

Yeah that’s pretty stupid.

*Just for the record, I never pressure wash my bike.

My chuck it in the shed, never clean it, treat it like crap winter bike is still on its original XT bottom bracket. Which i nicked from another bike. Must be 8-10 years old.

Frame was faced when i bought it.

All of them are.

There’s an equation somewhere equating bearing life reduction to axial alignment of the bore…… it’s not an insignificant effect.

Old square taper BB’s were effectively cup and cone, so of course they were threaded. You must be talking about the ones you could get that could be fitted to a BB shell with stripped threads, although I seem to recall Mavic also making a similar item?

Not the cup and cone ones.

UN-72 definitely didn’t have any threads on the cartridge itself. It just came with what looked like (from later versions) two none drive side cups, so you threaded the DS one in, inserted the cartridge which was a plain cylinder, then tightened up the NDS one.

Phil wood used a similar system, as did race-face taperlock BB’s.

thisisnotaspoon – Member

UN-72 definitely didn’t have any threads on the cartridge itself.

I’m going to have to disagree with this – I’ve got a 68 x113mm UN72 here and the drive side of the cartridge body is threaded and screws directly into the BB shell, the NDS is then supported by a threaded sleeve which screws into the other side of the BB shell and is a close fit over the body of the cartridge – as supplied, they have a non-hardening compound inside the NDS sleeve to prevent fretting.

garlic – Member

Thought they were impossible to over-tighten as they’ve sat in cups separated from the threaded part. Not sure how you’d apply enough torque with the plastic crank installation tool or find anything with decent enough purchase.
This nicely explains why there are some many issues with HT2 bearing longevity.
You wouldn’t horse up your headset with an allen key would you? No you just gently tighten it up until there is no slack. Apply the same principle to HT2 BBs. You’re merely removing the slack from the system. The bearings die quite quickly if overloaded because they’re rotating fully all the time. You get away with it on a headset because the bearings rarely move more than 90 deg in any one direction.

The conical BB’s are for use when you’ve mullered the frame threads, actually quite good IME. Hollowtech are shit because theres no money in BB’s that last ten years.

Bottom LH

The early ones were DS and NDS loose cups. Later ones had fixed DS, can’t remember when they changed though.

I’m going to have to disagree with this – I’ve got a 68 x113mm UN72 here and the drive side of the cartridge body is threaded and screws directly into the BB shell

I’ve got a few old UN72’s in the garage. Some are threaded on the driveside body and some have a push on threaded cap.
So you’re both right/wrong. 🙂

Just fit stainless steel bearings in their place, or Hope ceramic ones from CRC.
Standard size (37 x 24 x 7 if I recall)

Do people not get their threaded bottom brackets faced anymore?
It’s not expensive for an LBS to do (although a decent tool can be costly) and along with not overtighteningbthe cranks it pretty much eliminates poor performance of HT2.

Tom KP

I’ve fitted 2 hollowtechs to my road bike in the past year and there’s play in it again, so I’ll soon be on number 3. Tempted to go back to internal BB, but I suppose I can live with it given they cost a tenner. It just seems a bit of a flawed design if they need changing every six months. Yes, you can expect some wear, but internal BBs in comparison last years. They could at least make them serviceable.

I’ve got a few old UN72’s in the garage. Some are threaded on the driveside body and some have a push on threaded cap. So you’re both right/wrong.

Think I remember the early sealed Shimano BBs being a cart contained and centred by two threaded caps.

I was having to replace Deore ht2 bbs frequently (weeks) sometimes after one wet ride they would be filled with rusty water. The XT bbs different story, getting months, always clean inside. Don’t know what makes them better but the bearings are definitely bigger. Sometimes sold cheaper than Deore too.

Some Deore leave the factory with little or no grease in them, had no issues with XT.