Replacement crank arm cover bolt / dust cap - how to identify serial number / exact size?

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jimster99
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Replacement crank arm cover bolt / dust cap - how to identify serial number / exact size?

Post by jimster99 »

Hi all,

I was cycling along today and discovered that the dust cap / bolt cover on the non-drive crank arm of my bike had fallen off unnoticed (the pedal suddenly became wobbly). I tightened up the inner bolt but now I need to order a replacement outer bolt / dust cap. Any ideas how I found out the exact spec and model number so I can order a replacement?

It was a Truativ crank with a square taper (although I stripped the threads when changing the pedals a few months ago so had to replace it with a generic arm - I probably didn't tighten it up enough). It's from a 2008 Decathlon bike purchased in France and they don't have any details of the specs (which is slightly annoying!).

I have taken photos of the crank here, both of the side where the bolt is missing (the non-drive side) and the other side in case that helps.

Thanks!!!

Side with the missing bolt / dust cap on the non-drive side:

Image

Image Image Image Image

Other side of the crank (nothing missing)

Image Image Image Image

Image Image Image Image

Image
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531colin
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Re: Replacement crank arm cover bolt / dust cap - how to identify serial number / exact size?

Post by 531colin »

This is the sort of thing you have on the chainwheel side https://www.bikeparts.co.uk/products/sh ... 20Strategy

Widely available.
rjb
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Re: Replacement crank arm cover bolt / dust cap - how to identify serial number / exact size?

Post by rjb »

The bolt is still there, just tighten it up with an allen key The plastic collar acts as a dust and dirt seal and is not necessary for holding the crank attached. Your local cycle shop may have a collar in their scrap bin. :wink:
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
jimster99
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Re: Replacement crank arm cover bolt / dust cap - how to identify serial number / exact size?

Post by jimster99 »

Thanks rjb - the inner bolt is still there but I believe the outer bolt acts not just as a dust cap but also as a keep-tight & also is capable of extracting the crank without a special tool due to it's special shape. It's definitely not just a dust cap as it required tightening with an allen key.

531colin - it's not that type of bolt unfortunately, I think there are two bolts on each crank (an outer one and an inner one). The one you have shown is an all-in-one jobby.
Jdsk
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Re: Replacement crank arm cover bolt / dust cap - how to identify serial number / exact size?

Post by Jdsk »

jimster99 wrote: 26 Sep 2021, 12:20pmthe inner bolt is still there but I believe the outer bolt acts not just as a dust cap but also as a keep-tight & also is capable of extracting the crank without a special tool due to it's special shape. It's definitely not just a dust cap as it required tightening with an allen key.
Is the aperture around the bolt internally threaded?

Jonathan
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Re: Replacement crank arm cover bolt / dust cap - how to identify serial number / exact size?

Post by Paulatic »

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slowster
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Re: Replacement crank arm cover bolt / dust cap - how to identify serial number / exact size?

Post by slowster »

I have a Truvativ cartridge bottom bracket with crank bolts incorporating a similar plastic collar bearing the torque settings. The collar is not threaded and is not a self extractor.
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531colin
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Re: Replacement crank arm cover bolt / dust cap - how to identify serial number / exact size?

Post by 531colin »

531colin wrote: 25 Sep 2021, 6:54pm This is the sort of thing you have on the chainwheel side https://www.bikeparts.co.uk/products/sh ... 20Strategy

Widely available.
jimster99 wrote: 26 Sep 2021, 12:20pm ...............
531colin - it's not that type of bolt unfortunately, I think there are two bolts on each crank (an outer one and an inner one). The one you have shown is an all-in-one jobby.
Just undo the chainwheel side bolt.
If it comes out with a black plastic donut on top of it, I'm right.
If it pulls the chainwheel off the axle taper, you are right, and its a self-extracting jobbie.
If it turns out to be a self-extractor, they are also widely available and will fit both your square taper axle and the extractor thread in the crank (provided you get ones for square taper, not for one of the other "standards".) eg https://www.ebay.co.uk/itm/402819849670 ... 2d6e42b7ab
Note the self extracting type all have peg spanner holes so you can tighten the extractor collar.
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