Shimano 105 LH crank

[Dave W]

Filthy weather today and my left hand crank starts creaking badly. Could be the pedal - unlikely it's fairly new and feels smooth, could be the external bearing - maybe.
Check the crank first. The crank has a bearing pre-tensioner, two bolts in opposing directions, a strange plastic spacer thing and a washer with rubber seal attached .
Ok. greased everything up and re-assembled.

My questions are as follows.

Which way round should the washer face? (i've fitted it with the rubber side to crank).

What is the purpose of the plastic spacer thing that fits in the slot in the crank and which way round should it face? It has a tiny metal post on the underside.

Thanks.

[Brucey]

http://techdocs.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/FC/EV-FC-5703-3004B_v1_m56577569830745701.pdf

and

http://techdocs.shimano.com/media/techdocs/content/cycle/SI/SI_1M30A/SI-1M30A-003-ENG_v1_m56577569830702207.pdf

are worth a look. I think the rubber widget orientation is clear enough; I think it is just meant to deter muck from getting in the joint. I also think that where the spacer bears against the bearing shield it should be a small diameter spacer or a shoulder that is in contact with it, else it could deform the bearing shield and degrade the sealing.

Shimano say to use grease on the spline 'if the connection becomes noisy'. I wonder.... not all greases are made equal; I would suggest that ones containing EP additives and/or solid lubricants may just allow some movement for ever, ultimately to the detriment of the assembly.

Definitely a place to use the torque wrench, those pinch bolts.

cheers

[Dave W]

Cheers,
the plastic spacer thingy is in fact a stopper plate presumably to hold the crank on as a last resort. I also hadn't realised how important the plastic tensioner would be.

http://bennosblogandmore.blogspot.co.uk ... imano.html

[Brucey]

Cheers,
the plastic spacer thingy is in fact a stopper plate presumably to hold the crank on as a last resort.

yes indeed. You shouldn't need it for that purpose.... things would have to have gone badly wrong before then, but I guess it does no harm and might do some good...

I also hadn't realised how important the plastic tensioner would be.

goodness yes, it controls the bearing preload. The shimano specs give a torque figure; the blog you link to is OK but misleading; just like A-Head headsets you can apply too much preload to the bearings and they will feel fine (at first) but will then fail in short order.

cheers

[Revolution]

I also hadn't realised how important the plastic tensioner would be.


goodness yes, it controls the bearing preload. The shimano specs give a torque figure;

The plastic tool is I think, designed so it is not possible to attach any kind of torque wrench - also, I can't imagine that you could get one that goes as low as 0.7 Nm. I think it is designed so you do it up 'finger tight' though its difficult to know exactly what that should be.

In regard to the original post - and the creaking: Always assuming it isn't arthritis I have suffered an infuriating clicking noise recently which I was sure was pedals, then crank, then bottom bracket. It turned out to be the Freehub - again due to the bike having spent the last 2 months in seemingly continuous rain.

[Brucey]

I have several torque wrenches that go as low as 0.7Nm ( which is about 6 in-lbs). A decent 1/4" drive one will do this. The preload part (which is sometimes replaced by a plastic cap after the LH crank is tightened) is designed to accept this torque and to fail if an excessive torque is applied. [ 6 in-lbs is plenty in some jobs; there are fasteners used in some applications (not on bikes...) that will shear off at around this kind of torque. ]

Having said that, I do wonder if torque to measure preload is the best method here; variations in sllding friction of the assembled parts will cause significant variations in preload. IIRC some other versions of OBB systems use wave washers to provide a controlled bearing preload instead.

cheers