My Moulton has a Stronglight chainset and external BB and I've just spent a few minutes measuring up the sizes of them, then looked them up at SimplyBearings. 14mm wide 21.5mm inside diameter 31mm outside diameter
There's nothing wrong with the existing ones. Let's get his straight. I don't need new ones ................ yet. Moulton has done 2,600miles from new.
From what I've read on here, I find that folk generally don't think much of external BBs. I have no real experience of them, so can't comment. I get the impression however, that the one's that folk have a problem with, aren't double row bearings, but thin single row bearings ............. or am I wrong?
Could it be that mine will be ok for quite some years? .................. or not?
Most of the external bearings for chainsets use single-row bearings, which are fairly resistant in terms of load. Is the contamination that kills them: larger diameter = more chances of moisture to leak in.
IIRC, that chainset fitted on Moultons does use an odd spindle, smaller than most external-cups style cranks. Shimano, Sram, Campagnolo, etc., they all use 24 or 25mm OD axle, so you have a common #6805 (25x37x7) bearing, or a less common 2437 (24x37x7). The #6805 are used by Campagnolo Power Torque, and the "old" Shimano HT2 cups and some FSA cranks too; altogether with the last two, some other manufacturers do use this size by adding a plastic sleeve, to reduce the ID of the bearing to 24mm. The #6805 size is widely available. And is this plastic sleeve that often gives problems for replacing the bearings, being difficult to remove without cracking it; also to reinstall it, as it's often arranged in a way that makes a labyrinth with another seal pressed in the cup.
Long story short, some BB cranks are easier to keep up running due to widely available bearings, some other aren't. For all, keeping the bike clean and dry after riding in the rain always helps.
It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are...
The cups come out easily enough. Remove the self-extracting chainset off the RH side, then with a soft mallet knock out the LH crank and axle as it's in one piece. The cups unscrew using a outboard BB cup tool. The RH side has a ring to undo first, and that exposes the RH bearing. You need to undo that first (RH thread) before undoing the RH cup (LH thread).
With both cups out, the bearings can be pressed out, though I didn't get that far, just measured them up for future reference. They are quite chunky, and I think that's a Good Thing.
No issues at all, and I'm very happy with the chainset and BB. Just a query regarding complaints on here about external BB bearings and lack of longevity.
They all seem fragile and flimsy in comparison to the Stronglight Activ stuff.
As far as I could work out, Activ Link was a reference to a system where you did not fully screw in the LH cup. See Fig.3 and the term 'functioning space':-
Thanks for the pdf, but I've already got a copy on my computer.
Both cups tight as a tight thing, and were from new. They also had threadlock on them, but I've cleaned that off and used copper grease. I understand that the cups tend to unscrew, but as I take off the chainset periodically, I'll be checking for security. Although Moulton used threadlock, the Stronglight pdf doesn't mention it.
There's a spacer on the RH side behind the chainset, but nothing else except a sleeve through the middle inside the tube connected by O rings to the insides of the cups.
By the time it's all assembled and tightened down, there's plenty "functioning space" between crank arm and cup.
Dunno what they mean by 'active link'. Nowt active except for my legs furiously turning the cranks!
IIRC, those cranks work in a similar way to Sram's GXP? The Lh BB cup ought to have a smaller ID (or a small sleeve) bearing so to engage a reduction of the OD that is on the Lh end of the crank axle. In practice, the Lh BB bearing holds the crank axle captive.
I cannot see any reason why the BB cups would unscrew if the BB sheel is correctly chased&faced to the correct width, and the cups tightened to a correct value (usually 35-45nm).
It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are...
Gattonero wrote:I cannot see any reason why the BB cups would unscrew if the BB sheel is correctly chased&faced to the correct width, and the cups tightened to a correct value (usually 35-45nm).
Precession is different in external BBs than internal ones I understand. I read it on here somewhere and how they tend to undo. Hence Moulton using threadlock.
The whole rotating assembly is held together by the RH nut. Remove the RH side, and knock the axle and LH crank out with a soft-faced mallet.
From what I can tell, the axle is the same diameter throughout, so the bearings are identical - as I would expect. Next time I have it out, Ill check, but I doubt there's any difference. I reckon that you could put the whole thing on back-to-front, and have the chainwheels on the left.
Gattonero wrote:I cannot see any reason why the BB cups would unscrew if the BB sheel is correctly chased&faced to the correct width, and the cups tightened to a correct value (usually 35-45nm).
Precession is different in external BBs than internal ones I understand. I read it on here somewhere and how they tend to undo. Hence Moulton using threadlock...
Lots of component manufacturers do use dry-threadlock factory applied in the cups, it is however not useful unless there is some real damage to the threads. Even Italian-threaded bb's won;t come loose if properly done.
It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are...
I'll have to take your word for that, but it's not what I've read on here before. I have no real practical experiences on this subject, and can only say what I've read ............... but I couldn't tell you where or when.
Mick F wrote:Precession is different in external BBs than internal ones I understand. I read it on here somewhere and how they tend to undo.
Precession is the same for external BBs as for internal, since the threading is the same (BB threads inside BB shell threads) and the pedalling loads are the same.
10,550 miles out of my shimano 105 EBBs so far. Fitted 2012 so 5 winters worth of inclement weather. Mind I do have mudguards on this bike which help protect it. I did have a BB cup come loose but don't remember which side. Tightened it up and still working fine. I have just ordered a couple of spare EBBs as playing safe & just in case. If I do come to change them I will see if I can just fit new bearings in the old cups.
SimonCelsa wrote:Despite the doom mongers predictions of rapidly failing EBB bearings my Deore EBB fitted in 2011 is still going well after 12,000 miles.
I've packed grease into the bearings annually by gently prising off the quite brittle plastic seals but they've had no particular maintenance as such.
No doubt they'll fail spectacularly now!!
All the best, Simon
I've got bikes with square taper and the bottom brackets have lasted 23 years (so far) without any problem.
However, I do rate Hope EBB's as I've had one on my Pearson touring bike since 2009, lots of miles, carrying lots of heavy panniers, and running as good as the day I bought it. It might be a different story with other EBB's but I've never used them. Hope kit does have a good reputation.
Raleigh Randonneur 708 (Magura hydraulic brakes); Blue Raleigh Randonneur 708 dynamo; Pearson Compass 631 tourer; Dawes One Down 631 dynamo winter bike;Raleigh Travelogue 708 tourer dynamo; Kona Sutra; Trek 920 disc Sram Force.
