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That thingo with a pin

Posted: Sun Dec 30, 2012 11:31 pm
by Mulger bill
It started out as just a chain clean on the commuter :roll:

After servicing the bearings on the rear hub, clean and lube of the jockey wheels and a new shift cable on the rear, I pulled the crank out to give the BB area a good clean and decrud the rings.

Anyhoo, after loosening off the pinch bolts on the LH crankarm this little bugger...
Image
decided to flip out of the way minus the half loop on the left.

Things seemed to go back together fine and the round the block test ride felt OK but I gots to know...

Is this going to cause problems down the line unless replaced as a matter of urgency? The little pin stayed with the main part and dropped OK into its hole in the spindle.

Thanks in advance.

Shaun

Re: That thingo with a pin

Posted: Sun Dec 30, 2012 11:55 pm
by drubie
I don't know what its for other than to help align the pinch bolts mulger bill. Personally I'd put it back even if it's damaged as the other function I guessed at when I saw mine was that it acts like a washer and stops the bolts from loosening over time. The stupid things seem over complicated but some shimano engineer somewhere thinks they are important.

Re: That thingo with a pin

Posted: Mon Dec 31, 2012 4:56 am
by toolonglegs
It's a little safety device I think, Personally I find it annoying and chuck it away... Running 4 different cranksets with out an issue.
Most important thing is that you put ZERO pressure on the star nut on the end of the crank when doing it up before locking the two Allen bolts up.

Re: That thingo with a pin

Posted: Mon Dec 31, 2012 9:38 am
by sturmey archer
My assumption is that the "Stopper Plate" has no function other than to indicate that the left crank is in the correct position on the axle - well that and prevent law suits when incorrectly installed cranks fall off. That plastic and pin is not going to hold ANYTHING.

TLL when you say zero pressure on the star nut, Ive always done it up with the the tool with my fingers until I feel some resistance. I would have thought the plastic would strip before you cold put too much side load on the bearings?

Re: That thingo with a pin

Posted: Mon Dec 31, 2012 9:45 am
by toolonglegs
Mtb ones are alloy aren't they?... Some people do them up with grips :-) . A tiny bit of pressure won't hurt I'm sure... My bearings never last long anyway so not that big an issue.

Re: That thingo with a pin

Posted: Mon Dec 31, 2012 10:01 am
by Mulger bill
Thanks lads :) Looks like the allegedly important bit is there so I'll just keep an eye on it.

Toolong, it's very good to know that YOU can live without them, if your left cranks don't fall off because of the lack of them then this 60watt bulb faces zero risk :mrgreen:

As to the star nut thingy, I thought its purpose was the same as the top cap in a threadless headset, there to preload the bearings before locking the system together with the pinch bolts? I've always done it up enough to remove any play in the crank then loosened it a micron once I've torqued the bolts. Wouldn't be surprised if I've got this wrong :?

Thanks again.

Shaun

Re: That thingo with a pin

Posted: Mon Dec 31, 2012 11:19 am
by Nobody
According to a Hope mechanic, it is tighten the star thingy, then loosen it until it is just not rattling. Anything more will load the bearings and make more wear.

There was a video somewhere on replacing BB...

As for the tab thingy, I've broken some of mine. As long as you keep the bolts tight and the plastic cap thingy in the end, it shouldn't be a problem. Also you should be able to tell when the cranks are becoming loose, before they fly off.

Re: That thingo with a pin

Posted: Mon Dec 31, 2012 9:44 pm
by DarrylH
The tab thingy is not broken - that is how they are made.

Re: That thingo with a pin

Posted: Wed Jan 02, 2013 9:20 am
by Jean
Mulger bill wrote:As to the star nut thingy, I thought its purpose was the same as the top cap in a threadless headset, there to preload the bearings before locking the system together with the pinch bolts? I've always done it up enough to remove any play in the crank then loosened it a micron once I've torqued the bolts. Wouldn't be surprised if I've got this wrong :?

Thanks again.

Shaun


Yep, it's a pre-load widget. Do it up finger tight with the proper tool and then do up the pinch screws.

Re: That thingo with a pin

Posted: Fri Jan 04, 2013 1:49 pm
by jules21
the BB bearings are cartridge bearings - i wouldn't have thought you could cause them to bind by overtightening the star nut. it's primary purpose is to ensure there is no lateral slack in crank axle. if you do it up finger tight, you can't go wrong. i always give the drive side cranks a gentle tap with hammer handle to ensure it butts up against the drive side bearings - it can easily bind and let you tighten the LH crank bolts with slack still there (i.e. tightening the star bolt won't always overcome the binding force).

Re: That thingo with a pin

Posted: Fri Jan 04, 2013 2:09 pm
by jasonc
Jean wrote:Yep, it's a pre-load widget. Do it up finger tight with the proper tool and then do up the pinch screws.


that's what i do.

and i do keep that plastic tab in the pedal arm.

Re: That thingo with a pin

Posted: Sun Jan 06, 2013 4:07 pm
by Stepr
may be a bit late on this..... but the "thingo with the pin' I am pretty sure is to keep the crank in place (stop it coming off) if the bolts get lose and there's no star nut - you have to flip it up and out of the groove so the crank can come off.

Re: That thingo with a pin

Posted: Sun Jan 06, 2013 5:28 pm
by Mulger bill
More reassurance then protection methinks. I did the flip outta the way thing but must've been a touch enthusiastic and broke it off left of the pin in the pic shown.

Re: That thingo with a pin

Posted: Sun Jan 06, 2013 7:39 pm
by twizzle
I hope you had a good torque wrench for doing up the pinch bolts. They are not the usual low-quality low-torque junk used for most bike parts.

Sent from my iThingy...

Re: That thingo with a pin

Posted: Sun Jan 06, 2013 7:54 pm
by Mulger bill
Yep, wouldn't be without it now.

Re: That thingo with a pin

Posted: Mon Jan 07, 2013 7:18 am
by toolonglegs
Meh... Never torqued one of them up, I will stick with my 5mm t bar :p