Bearing life Eccentric BB

[Cyclewala]

Hello,

I have Shimano Alfine 8 on the commuter. The chain tension is managed by an eccentric bottom bracket (EBB). The BB itself is the Hollowtech 2 type and I've always used Shimano's mid-range offerings: Tiagra or 105.

Over the last 10 years of running this bike, I've found the BBs last from 800 miles to as much as 2200 miles.

Whilst the bike is ridden in all weathers, I run full mudguards with an extended flap. After each wet commute (like the ones we've been getting of late) I'll dismantle the BB and repack with fresh grease.

Two things bother me:
1. BBs mileage on this bike is low. Other bikes with Hollowtech BB (not EBB), the mileage is upwards of 5k miles.
2. It's always the left bearings that start squeaking and making death noises. The right are usually smooth. This goes against conventional thinking as one would expect the driveside bearings to wear quicker and suffer from water ingress from roadspray.

Is it just a case of getting the EBB threads re-faced or could there be other factors?

[reohn2]

FWIW,I had the same problem with a new MTB with same Shimano Deore BB,it lasted 500miles even though from new I removed the chainset and top hats and bearing seals,topped up the bearings with adequate Shimano gease then torqued up the preload as per Shimano specs on reassembly.
I searched around and thought at £20 I'd give the Token make from Taiwan a shot.
I haven't regretted it,from day one with the chain off it the chainset spun like a Square Taper chainset does ie;smooth and for a long time with the flick of a crank arm,unlike the Shimano unit it replaced that did about two turns then stopped dead.That was almost 5 years ago an whilst the bike doesn't do a lot miles,it does do a lot of riding time with a lot of low gear in that,and that time is mostly in a mucky environment.
The other plus with the Token BB and another reason I bought it was that the bearings are a standard size that can be pressed out and new ones easily pressed in,though there's no signs of wear yet.Only week before last on a major service I checked the bearings which I found were still as good as new

[PH]

I've never used a Hollowtech BB, but have plenty of miles with a square taper BB in various designs of EBB, they last as well as the same BB does in a standard shell. I can't think of anything that would contribute to it not doing so. What sort of EBB is it? The surfaces not being manufactured square may be an issue, others will know better, I thought the need for it on a frame was to correct the slight distortion when the tubes were welded together, which I wouldn't expect to be the case on the EBB inserts I've used, though with ST id doesn't matter so haven't had the need to test it.

[rjb]

What type of eccentric do you have? One piece eccentrics shouldn't be a problem but if you have separate left and right inserts then any misalignment could cause early failure. A pic would help.

[Cyclewala]

It's a one piece Taiwanese aluminium shell like this.

Pic not working so added link to SJS:

https://www.sjscycles.co.uk/bottom-brac ... ndems-etc/

[reohn2]

It's a one piece Taiwanese aluminium shell like this.

Pic not working so added link to SJS:

https://www.sjscycles.co.uk/bottom-brac ... ndems-etc/

The faces on a unit such as that should square,Idon't think that's your problem.
If you want to check it,remove the EBB shell clean it and stand it on end on a known flat surface such as glass or steel plate then check it's truth with a square,turn it over and check again.

EDITEd to add the word don't

[Brucey]

I can think of two likely/possible reasons why this is happening;

a) the BB alignment is poor

b) the grease you are using is basically no good; what grease do you use?

You can check for one end of the BB shell being cocked to one side by measuring the width of the assembled BB (cups in shell) using digital verniers; variations in width at different points are a sure sign that one or both cups are off line.

In HTII the LHS bearings commonly fail before the RHS because the RHS bearings are protected from road spray to some extent by the chainwheel, and (depending on what lube you use) there tends to be odd splashes of chain lube all around that area. This tends to deter water from getting in.

If the LH bearings are suffering with water ingress it should be obvious when you inspect the failed bearings. That the bearings often start to squeak suggests that whatever regreasing regime you use, it ain't working.

Other contributory factors might include that

c) the preload on the bearings is not set correctly (Q. is the back of the LH crank perfectly square?)
d) the seals are damaged e.g. when you disassemble the bearings and repack them, or they run dry too soon.
e) water is getting into the bearings at some other time/place, e.g. from inside the frame (if the seal tube is not working properly) and/or when the bike isn't being ridden.

cheers

[andrew_s]

How tight are you setting the chain?
It could be that the chainring isn't properly concentric with the BB axle, and if it gets too tight when you're pushing, it could cause problems.

Hub gears aren't fixed wheel, and a slightly slack chain isn't much of a problem provided it's not so slack it keeps coming off.

[Cyclewala]

I can think of two likely/possible reasons why this is happening;

a) the BB alignment is poor

b) the grease you are using is basically no good; what grease do you use?

cheers

I'm careful with the BB alignment to ensure its even on both sides. Also, preload cap is always finger tight minus quarter turn.

Grease is an all purpose lithium grease from a car parts shop. I always pack well to the point that little bit seeps out when installed. I have an hour's commute one way and in the sort of heavy rain we have today, water tends to find its way into the bearings (usually left). When I open the bearings they're either milky white or mid-brown. The grease in the RH cup is largely intact.

[Cyclewala]

How tight are you setting the chain?

12mm. But this can extend to c. 18mm. There is little risk of the chain coming off as the Alfine chainset has guard on either side of the ring. But once chain tension exceeds 18mm I'll reel it in. A slightly loose chain becomes noisy and feels inefficient.

[Brucey]

I can think of two likely/possible reasons why this is happening;

a) the BB alignment is poor

b) the grease you are using is basically no good; what grease do you use?

cheers

I'm careful with the BB alignment to ensure its even on both sides. Also, preload cap is always finger tight minus quarter turn.

Grease is an all purpose lithium grease from a car parts shop....
.

by alignment I meant squareness of the cups, but I'm glad you mentioned preload;
you could do with more bearing preload than that; the clearance you make by leaving things slack like that means that the seals are less likely to work.

Using cheap car wheel bearing grease is a false economy. There are any number of other greases that are better than that. How many more BB assys are you going to trash before you spend another fiver on better grease?

cheers

[Cyclewala]

I can think of two likely/possible reasons why this is happening;

a) the BB alignment is poor

b) the grease you are using is basically no good; what grease do you use?

cheers

I'm careful with the BB alignment to ensure its even on both sides. Also, preload cap is always finger tight minus quarter turn.

Grease is an all purpose lithium grease from a car parts shop....
.

How many more BB assys are you going to trash before you spend another fiver on better grease?

cheers

It's the Yorkshireman in me. Penny rich, pound poor. I have some good grease bought a few years ago off here when one of the forum members arranged a bulk purchase. Mobil something. I reserve that for the annual Alfine hub servicing.

[tim-b]

Hi
I tend to find that the LH bearing goes first. It's not the whole answer, but a couple of rubber O-rings help; one on the crank near to the axle, and a smaller one on the axle between the crank and bearing. The O-rings divert water to drip off before it causes a problem.
Marine grease is pretty good but don't overpack the bearing because you'll cause additional drag
Regards
tim-b

[Cyril Haearn]

Indeed, it is worth thoyling better grease that costs a bit more

[zenitb]

At the risk of being "Master of the Bleedin Obvious" isn't the Hollowtech 2 the BB that sticks out both sides of the bottom bracket shell straight into the path of water coming up from the front wheel? i.e. The one shimano designed to give racing cyclists slightly stiffer cranks on their sunny race days?

Getting less than 1000 commuting miles from a BB sounds bad. That would mean replacing it every 3 months for me. And servicing it after every wet ride would be out of the question for me. Ok I am not a big gear muncher but my muddy, splashy, all year commute has not killed a BB in 15000 miles/4 years. I use the basic Shimano UN55 square taper BB where the bearings are inside the bb shell.

I may have missed something here ...but I would suspect the "hollowtech" rather than the EBB being the issue?